Why didn't you finish endurance?

[Agent4573]

I didn't get a chance to ask some of the teams but i noticed a couple big names teams got pulled from endurance in the afternoon session and I was wondering what the reasons for it where. The big 3 I remember seeing while in the que where UTA, RMIT, and Texas A&M...

[RacingManiac]

10-32 right-rear pull-rod rodend failure....

curse that bumpy parking lot....

University of Toronto

[Charlie]

The Auburn guys told me the car didn't restart at the driver change. Apparently no RPM signal. It was not overheated (less than 100C) and the battery didn't give up during all the cranking either. When they got back to the trailer it fired right up. Hopefully they are able to track it down and prevent it from coming back!

[tal]

Lehigh had a front roller bearing failure and an engine malfunction. I think it would be nice for people to post pictures of the mechanical failures...

[BeaverGuy]

Oregon State had 1/4-28 rod end failure on the left rear push rod at the a-arm side.

At some point the clearance between the shoulder bolt and the spacers on the a-arm mount became very large. This combined with a last minute ride height adjustment before endurance and very low tolerances between the rod end and a-arm caused the rod end to become lodged against the a-arm and the rod end failed in bending.

[Matt Gignac]

We put a nice big hole in our block and spilled oil all over the track... still trying to figure out exactly what caused the failure... an engine tear-down tomorrow should give us some insight

Matt Gignac
McGill Racing Team

[Jeff The Pyro]

we finished... with a decent time...

and then got four minutes tacked onto our time for using too much fuel... earning us a total of zero points for endurance... our overall standing for FSAE 2005 went from about 30th to 59th place because of this one penalty... i guess sometimes thats how it goes.

Jeff Cortes
UCSD

[GTmule]

Our lower ball joint brackets on our uprights got wanked (over the course of 11 laps), and we got black flagged. I'm glad the stewards noticed it, actually, because I hadn't, and they werne't far from letting go, I suspect.

[Didier Beaudoin]

The right half-shalf broke at the splines and we lost the right rear wheel. It was something I would never have suspected to happen. http://fsae.com/groupee_common/emoticons/icon_frown.gif

[Tidexcab99]

Well after several months of thrashing and breaking everything on the car...UA was 11th after the autocross, so we were proud of that until the first lap of the endurance when a weld broke on our steering arm. We think it fatigued to failure since we had been driving it so much over the past 2.5 months. We will definitely look at this next year to prevent this from happening again!

[bigtoyota9]

We also finished enduracne but by the hair on our teeth. I was the first driver and by my lap 8 the engine was 235F and the oil was 240F. By my 10th lap the oil went over 260F and started to break down and dropped the oil pressure below 20 psi.

At the driver change the car started up and cooled down to 230F before the second driver went out. He had to nurse the car for the whole stint and brought it home turning 66's. when the car rolled of the track the oil was 300F and water temp was 275F. I have to say the Honda, AMSOil and Calico engine coatings worked together to pull our car to a 6th place enduracne finish.

We only used like .9 gal too cause we were nursing the engine. Too bad the briggs took all the fuel economy points.

One of these days we will realize we need a bigger radiator.

[Wray]

Chain fell off. Doh. We're pretty sure that there wasn't enough lateral support on the diff, and it moved to the side while cornering and the chain jumped off. Oh well.. considering we hadn't even driven the car until the braking test, I'm surprised we even made it to endurance! http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Nate Notta]

Our upper control arm mount broke on the upright... with only 2 1/2 laps left in Endurance... ruining our chance to finish endurance for the first time since 2002!!!

Oh the humanity!

I'm still in shock.

[CMURacing - Prometheus]

2002, first year car -- a-arm rod end failure (loaded in bending)

2003, second year -- battery mount failure, battery exited rear of right side pod

2004, third year -- steam escaping from catch can, overheating because fan switch wiring poorly soldered (it would have finished, too, we'd run the engine for longer without water)

2005, fourth year -- almost black flagged at driver change because an oil seal was wet with diff oil, but it was leaking at about 1ml every 10-15 minutes, so when they pulled us in to check on it, it was fine. we're kinda upset there was no most improved team award at the banquet, because it was definitely us. (100th place to 35th)

[B Hise]

Im pretty sure it was the fuel pump that bit the dust, on lap 21 of the enduro. The fuse slow burned and finally let go and the car quit. We were running 65-66s too..

Got back to the shop last night and blew another (higher amp) fuse right away. Tearing down pump tomorrow.

[Kyle Jeffries]

right rear axel broke at a weld as we were going to scrub our tires for endurance, huffed the car back to paddock 99, managed to weld it up, and the other weld broke 4.25 laps in. We knew it was a matter of time, but we're just happy to have gotten there and made it as far as we did!

Kyle Jeffries
University of South Florida SAE

[Dan G]

Too bad the briggs took all the fuel economy points.

You got that right! http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

And that was the briggs that made 16hp at the wheels (according to Land and Sea at least, Sir Newton says ~25 off the accel/weight).

We almost were pulled from the enduro with a loose floorboard. Luckily we actually had two floorboards, so the driver was still protected. And the floorboard that came loose was still rigidly attached on the back half, it just rolled under up front.

UMich-Dearborn... proving a 'Fast and the Furious' floorboard malfunction isn't actually impossible.

[Homemade WRX]

team member threaded out a-arm that was designed to be shimmed...so our tripod popped the c-clip off and the tripod came off of the splines...

[Greg H]

We finished endurance, but upon inspection realized that our half shafts were u-shaped. Turns out it was due to some poor heat treatment and man did we get lucky.

[CMURacing - Prometheus]

dan, did you get a "danger to manifold" warning before the floor got loose?

[Flexicoker]

I'm from UTA... the OEM gear speed sensor on the top of the case cracked and started leaking oil out of it. A little plastic part we don't even screw with knocked us out of endurance. We were gaining on Cornell too.

[The Dudeness]

I'm brand new to FSAE, I went to Detroit this year to see the comp. I couldn't believe how many teams got pulled from the enduro by the tech inspectors. Are their reasons for pulling teams out legitimate?

[Garlic]

How/where did it crack? I can't imagine how that sensor could crack, so it would be interesting if you had some pictures.

We left the o-ring off that sensor one time, but that's the only time we've seen issues with it.

[Jon Huddleston]

I don't believe it cracked. I haven't look at it, but I'm pretty sure the bolts hadn't been checked since we replaced the engine 3 weeks before comp. It was poor preperation that cost us the endurance, if those two bolts had been checked/tightened we would have made it. Too bad, so sad...

[UTA racer rikki]

Jon didn't get to see the part after it came off the engine. The bolts had backed off and the part was cracked right next to the brass insert for the bolt sleeve.

I agree with Jon though, a quick engine change, despite the fact that we did a full endurance run on it, was all it took knock us out. Be sure the nut and bolt checks are insanely thorough guys and gals!

[95M3Racer]

We (RPI) actually finished endurance, somehow only barely made the fuel economy, 15th overall, not too bad, we're very happy.

Sorry to hear about all the weird failures that dropped a lot of bigwig teams out, but thats racing. I think someonme should investigate all these rod end failures though, i think everyone used aurora...

Congrats to everyone, it was a great event, and everyone had a quick car, simply amazing how these cars flew around the endurance course.

[Handles]

bad luck to UTA, ive had troubles with that same sensor in the past, cant remember what problem it was causing, but yeah be careful not to overtighten it cause it can crack fairly easily, especially if the engine has ever been overheated i guess!!

[Cheers!]

Queen's University Car #42

We made a mushroom cloud of smoke 3 stories high. The engine hydrolocked on motor oil that was being sucked pass the oil seal on the compressor side of the Turbo.

Car was black flagged and allowed to idle as teh judges asked is oil suppose to be spraying out of the muffler? Answer, Oh ya! Why not? They let us back on the course and when the driver stood on the gas in second all the oil that normally gets consumed at WOT instead got collected in teh intercooler. So when you mash the gas again all the oil goes into the engine and bang...

Atleast we made the most spectacular and biggest smoke cloud.

Jason
Queen's University
Alumni

[Kirk Feldkamp]

Well, when you have 23 psi of oil pressure at idle, you can't really call it "sucking" past the seal.... it's more like getting pushed past with hurricane-like intensity! You guys gotta find a way to run that pump at different speeds! The oil doesn't come out at higher engine speeds, the pressure differential makes sure of that.

-Kirk

[GSpeedR]

University of Michigan - car wouldn't restart

Either starter got too hot, or a F'ed up alternator/battery means we couldn't get our second driver out there.

We also "smoked" the competition at the Road & Track Triathalon on Sunday. Most of that was from oil on the headers, though... http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

[CMURacing - Prometheus]

we had a pullrod rod-end failure (aurora cm-4) in testing the week before competition, and replaced all the pullrod rod-ends with two-piece teflon lined numbers from mcmaster (they use fk). we've already resolved to bump up to the higher series aurora bearings next year though...

[Greg H]

As a follow up, here is our picture. We definitely got lucky to make it through endurance.
http://www.kengrimes.com/halfshafts.jpg

[Bubba]

We pulled through and finished the endurance for the first time in a few years. When we wheeled the car back to our paddock after, we looked the car over for damage. It turns out that one of our engine coils (F4i) had grown 1 inch longer somehow (???). We knew we were running hot and that is probably what caused this, but we had never heard of such a thing happening.

Dam you CMR! We would be on-deck for the most improved award: 86th to 22nd. Just one less position improved than you guys.

Brent Bell
University of Western Ontario [UWO] FSAE
2005 Drivetrain Manager & Brake Systems Manager

[RagingGrandpa]

Originally posted by DohertyWins!:
University of Michigan - car wouldn't restart

Either starter got too hot, or a F'ed up alternator/battery means we couldn't get our second driver out there. I wonder if that had anything to do with their Data group leader, someone pointed him out to me, what a huge tool.

[MGizzle]

Yeah man, that guy always ran around with a lap top?!?!? Tools...

[Jersey Tom]

We didn't get through the first lap. Either the battery is completely shot or something. Our first driver started fine, then the engine started cutting out, and cut out completely. He coasted off to the side, and the engine wouldn't start again.

Reaaallly sucked. Considering in all the testing we did we had zero problems like that, and while we were in queue and fired up the engine to warm it up there was no problem with it.

Next year we'll be back with a vengeance.

[Wray]

Originally posted by CMURacing - Prometheus:
we had a pullrod rod-end failure (aurora cm-4) in testing the week before competition, and replaced all the pullrod rod-ends with two-piece teflon lined numbers from mcmaster (they use fk). we've already resolved to bump up to the higher series aurora bearings next year though...

This is the first rod-end failure post that's caught my attention. It seems the others were loaded in bending, so I wasn't surprised that the rod ends failed, but you don't often hear of a rod end failing in tension. We were running CM-5's this year and I was planning on going to CM-4's next year, but now I'm having second thoughts..

[GSpeedR]

stop it ya big sillies

[Dan B]

Originally posted by CMURacing - Prometheus:
we had a pullrod rod-end failure (aurora cm-4)...

I don't think you can fault Aurora for a failure of their weakist/cheepist spherical rod end (SRE).

The CM-4 has an ultimate radial static load rating of 2,212# (carbon steel body).

We have always used something more on the line of the AM series. For example an AM-4T SRE has an ultimate radial static load rating of 5,260#.

[Daygo Nighthawk]

UCSD got pulled off after 17 laps- guess it was a lap count error. Went back in, finished off the last few laps without a hitch.

What's this?

0 points in endurance after 4 minute penalty for shitty fuel economy, and 1 minute penalty black flag. great.

[threehondas]

Yeah zero in fuel economy, but dont they make most torque of any team at competition? That setup gets my approval despite fuel economy.

[jaimin]

Wasn't UCSD the team running a supercharger, and the reversed head engine?

[UCBrothers]

Made too much power this year and overheated the car until it wouldn't go anymore. Had an awesome car too..10th in autocross.

Matt
University of Cincinnati
http://www.eng.uc.edu/studorg/sae/fsae/fsae.html

[Jeff The Pyro]

yeah we were the guys with the reversed head/blower. fuel economy was one of the things we never even really payed attention to. we saw that 50 points were allocated to fuel economy, and first had no time to worry about it (we finished the car a week before it left for detroit) and second figured any attempts to boost fuel economy would just cost us more points in other categories. none of us had any idea that you could get a time penalty for using too much fuel. i guess fuel economy is one disadvantage of non load-dependent boost... its on all the time.

on top of that we got the checkered flag 7 laps into the second driver... and then they made us go back in and finish.

[Garlic]

Don't take this the wrong way as I have great respect for all FSAE competitors that make it to competition, but there's no thing as too much power, however poor cooling system designs do exist. http://fsae.com/groupee_common/emoticons/icon_wink.gif

And for the Pyro, well the rules are there for you to read...

[Big Bird]

[QUOTE]Originally posted by Garlic:
...... but there's no thing as too much power, ...

QUOTE]

Disagree completely.

Having the most power doesn't help in any way under the following conditions:
Braking
Corner entry
Mid corner
Most of your corner exit (at least until your overall acceleration vector is as good as pointing straight ahead out of the front of the car)

Given that the above conditions account for 80-85% of your typical autocross/endurance track, you have to make your own decision as to whether the trade offs in weight, fuel economy, cornering speed, development time, financial cost etc are worth it for that tenth of a second or two you will gain on the straight.

FSAE is about finding a nice balance between what works in a straight line and what works elsewhere - with the elsewhere accounting for most of the comp. The rules are written the way they are to make us think about these things. Chasing the holy grail of power is a pretty sure way to spend a lot of money without gettting much quicker.

My two cents worth - as if no-one saw it coming http://fsae.com/groupee_common/emoticons/icon_smile.gif

Cheers all

[vinHonda]

MONASH 2005?!??! it's time to get out of the sport buddy!

But spoken like a true single advocate! I must say it is a convincing argument and I am tempted to believe it.

FStudent was quite the tight track with a LOT of emphasis on corner entry, mid corner and corner exit as well as transient slaloms..... but I believe your 04 car was quite heavy for a single? cuz we produced nearly identical laptimes.

I'm not so sure a single would work in Pontiac though.... that track is mega fast.

Just my 2 cents.

P.S. Geoff...why Monash?!

[jjusb]

I agree with Vinh on this one. The tracks at this year's comp in Pontiac were fast. A lot faster than we anticipated. Of course, the overall balance of the car is what will win the race, but if you have a car with good handling and good brakes, a powerful engine on a track like this would help a lot.

[BryanH]

Saturday morning, Australian GP 1986. Nelson Piquet's Brabham BMW was wheelspinning 3/4 way down Jones straight in top gear. I'd call that sufficient power. Anything less is not enough.

The 2nd thing Rotor said to me after the Detroit enduro "It needs more power and less weight" (I had asked if RO4 was the worlds fastest fsae car)

Geoff, Hoosier tyres and the Detroit carpark have the grip to utilise more power than Aussie tracks. And the "pro" US teams have drivers capable of running their cars 10/10ths.
You talking Monash into going Briggs?

ps Tonight I've been watching the Senna dvd's...excellent but brought back too many memories. After Shui's results so far this season in a not perfect car I'm now certain that Senna was the best.

[Denny Trimble]

Taking this thread even further off-topic, it's really difficult (for me at least) to choose whether to build a car I'd like to autocross at real events (the "intent of the competition"), or a car that's optimized for the FSAE course. And, if you compare the Detroit courses from '03, '04, and '05, they were wildly different. In '04, they were almost open enough to fit a real car through. But in '03, we used 1st gear only in autocross, and got up to 2nd once or twice in '05.

At national level autocrosses, we get up to the top of 4th. And, there's even more grip to be had on concrete surfaces.

So, do we take another couple inches out of the wheelbase and tune for 15mph hairpins? Our car's already a handful getting sideways shifting into 3rd at 60mph...

I guess it depends on what kind of a course they design in California next year.

And, for the record, I need a lot of power to move my big ass around the track http://fsae.com/groupee_common/emoticons/icon_smile.gif

[BryanH]

Originally posted by vinHonda:

. but I believe your 04 car was quite heavy for a single? cuz we produced nearly identical laptimes.
I'm not so sure a single would work in Pontiac though.... that track is mega fast.


Vinny,are you trying to rewrite history? Buy a new stopwatch, yours is 3 sec a lap fast!
btw R04 is 60lb lighter than R03

"RMIT passes Cornell and blows them away"
James Waltman

[kozak]

Now keep in mind that my team has never competed in FSAE before (next year baby)but i say this as a car guy, you can always use more power, always. The key is knowing how and when to use it, second you need to know how to build your car up around that power, bigger brakes, wider tires, different gears. even if you don;t have any straight aways more power can always help.

[BryanH]

Spot on Denny, guess a compromise or just build what you want. Just to clarify things the RMIT single is most disadvantaged pulling out of slow stop/go corners and is at its best on fast transitions and sweepers. Rotor commented that if he were to design another car for detroit it would be longer/wider and probably 600/4! (but he's done with fsae)

[Garlic]

Originally posted by Big Bird:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Garlic:
...... but there's no thing as too much power, ...



Disagree completely.

Having the most power doesn't help in any way under the following conditions:
Braking
Corner entry
Mid corner
Most of your corner exit (at least until your overall acceleration vector is as good as pointing straight ahead out of the front of the car)
</div></BLOCKQUOTE>

Hold on there buddy, you misunderstood my point.

Someone says they made too much power and overheated. Fact is they didn't have a good cooling system, not too much power.

There is, in fact, never too much power. More power doesn't hurt braking or corner entry, only weight does. http://fsae.com/groupee_common/emoticons/icon_wink.gif It was a very abstract statement. I know there are compromises and power isn't everything. But if you can have more power without any other baggage would you ever say 'no I've got too much'? I doubt it..

[Denny Trimble]

Right, I agree that if power is free, there's never enough until you can leave black marks down the longest straight on the course (I think Mark Donohue said that...).

But, if you're designing a car around a power goal instead of, for example, a coursemap, you're probably in for a surprise.

Oh, and I have to say that sitting in line behind the RMIT car for autocross and endurance was pretty annoying... that exhaust kept shaking my internal organs around... http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Jeff The Pyro]

as fast as the track was in detroit 2005, it was still slow compared to the average "real" autocross course. our 2004 car was geared really low and it used to bounce off the rev limiter at local autocross courses.

At some point, too much power might stop being beneficial, but its unlikely it will ever start to be detrimental (aside from some extreme cases). One look at the autocross/enduro courses for 2005 shoots down the argument that 85% of the course was spent off of the gas... nearly every turn had a pretty long strait section right behind it. besides, for what it's worth there's still the acceleration event... which is worth some points (though not that many). Cornell uses the same strategy every year... which is a heavier (compared to many) car with a kickass motor, and they seem to be doing just fine. if you told them they should lose their turbo system to lose a little weight they would probably just laugh at you. our supercharger package added a good 25lbs to our car, but i have no doubt that in the long run it greatly improved our times in just about every event (except for maybe skidpad)

[drivetrainUW-Platt]

bouncing off the rev limiter? depending one what engine your using, and what your actual final drive ratio is, our fsae competition should only be using the first couple of gears, unless you have a different tranny or gutted it, there are prob 2 or 3 more gears in there then you would use in fsae...care to elighten me......

[Big Bird]

Thought I'd get a response with the above http://fsae.com/groupee_common/emoticons/icon_smile.gif No specific offence intended to anyone, (cheers Garlic) just a good opportunity to scratch our heads for a few minutes and truly think about where horsepower helps us - and where it hurts us. I actually started writing a response at home last night - but it started dragging out into a mini-thesis on vehicle dynamics. So when I get a chance over the next few days I'll try to condense it into something readable. I'll post it here, and might copy it into a new thread as well if anyone's interested.

Vinh, good to hear from you sir. Hope all is going well in the outside world. I've moved to Monash for my PhD - logistic reasons, and I also found supervision there for the sort of PhD topic that I'm interested in (design research). A crying shame to finish up at RMIT, I've obviously got a soft spot for the FSAE team and what they are doing. Spewing I missed out on the US trip.

Bryan, I'm assuming Vinh was referring to our times at FStudent - not Mark's. He and I were pretty well level-pegging. As for "more power and less weight" - well, I'd agree every race car could benefit from that. The angle I was aiming at is that you will eventually get to a point where one directly compromises the other. More power helps on straights, less weight helps on corners and transients. I'm starting to stray into the thesis I was writing last night....

Denny, a shame I couldn't get over there and meet you in person. And maybe you've hit upon the single's secret weapon - relative track speed through massive internal bleeding of the opposition.

Jeff, and anyone else who might have the info, I'd love to know a percentage value of full throttle time on the 2005 track. Sounds like it was a good one. And yes, I have no doubt Cornell have hit on a good design solution. But from all accounts the RMIT car was equally as quick. Anyone got a full set of endurance lap times?

Cheers all,

[Jeff The Pyro]

well... our 2004 car was geared absurdly low... i think it maxed out at about 65mph or so in 6th gear. in the autocross/enduro we ran 3rd gear nearly the entire time, but the gearing was so low that i think 3rd allowed for like 55mph... not much spread inbetween.

i dont remember the actual scores but i believe cornell came out just a bit faster in both autocross and endurance compared to rmit.
yeah, rmit was pretty fast around the FSAE courses, but i'm guessing on a full sized scca autocross course a larger, more powerful car like cornell's would begin to pull away. of course... some people would call me crazy for designing for anything other than the actual FSAE competition...

my personal opinion is that going smaller and lighter is the way to go, but at the same time, horsepower shouldn't just be neglected. rmit is one good example (UTA is another). as fast as they were, if they had added 10-15lbs to get another 10-15hp (both teams told me they were running a fully stock motor, so i think this would be a pretty reasonable thing to do) out of their car, their lap times would probably get considerably faster.

unfortunately we didnt do any onboard datalogging in detroit so i couldnt even guess what the percentages are for full throttle times.

[Z]

How much power is too much power?

With the FSAE restrictor any more than ~80hp is too much.

I reckon it is a huge waste of time and money to chase more than 80hp. Even the time/money spent getting the last 5hp from 75hp up might be better spent elsewhere (diminishing returns, etc.). So build a motor that gets ~75 healthy horses - to keep everyone happy - then concentrate on the important stuff! http://fsae.com/groupee_common/emoticons/icon_smile.gif

Big Bird, I eagerly await your dynamics thesis...

Z

[rjwoods77]

This might be stupid but I pay attention to the power to weight ratio. I know it is simplistic to look at it that way but whenever I even think of doing a mod to the car I ask how much is it going to weight and how much more power will it garner. I try to keep the power to weight ratio around 7:1 . Its a really good goal to shoot for that but obviously other factors toss into to that. Some cars that are 8:1 run as fast as cars that are 7:1 and vise versa. I just look at that 7:1 as a healthy goal and try to make informed decisions to keep any extra systems out of the car if the really arent going to help that.

[MikeWaggoner at UW]

Originally posted by Z:
How much power is too much power?

With the FSAE restrictor any more than ~80hp is too much.

I reckon it is a huge waste of time and money to chase more than 80hp. Even the time/money spent getting the last 5hp from 75hp up might be better spent elsewhere (diminishing returns, etc.). So build a motor that gets ~75 healthy horses - to keep everyone happy - then concentrate on the important stuff! http://fsae.com/groupee_common/emoticons/icon_smile.gif

BS... This is an engineering competition, and to divide it into groups, I'd say we've got engine guys, chassis guys, and suspension guys. If the engine guys can pull of something that doesn't add weight, more power to 'em; they're not going to add to other systems because we tell them to give up and use last year's crap because it was 'adequate'. Putting arbitrary labels on stuff is silly. You should always try to do better.

[Jeff The Pyro]

im gonna have to agree with mike on this one... accepting anything as "adequate" is the exact opposite of what this competition is all about.

besides, most teams are divided up into subteams... so if the engine guy just decides he's done well enough already, he's probably just gonna sit on his ass anyways.

[Didier Beaudoin]

Back on topic for a while...

A visual explanation of our retirement.

http://www.etudiants.polymtl.ca/fsae/gallery/albums/Detroit-2005/IMGP1635.sized.jpg

http://img.photobucket.com/albums/v240/Didierf1/roue.jpg

http://www.etudiants.polymtl.ca/fsae/gallery/albums/Detroit-2005/IMGP1628.sized.jpg

http://www.etudiants.polymtl.ca/fsae/gallery/albums/Detroit-2005/IMGP1636.sized.jpg

[drivetrainUW-Platt]

Didier,
was there a threaded stud with a nut on there, what would have caused it to shear like that?

[Didier Beaudoin]

Originally posted by drivetrainUW-Platt:
Didier,
was there a threaded stud with a nut on there, what would have caused it to shear like that?

Yes, in fact the part sheared right across the first thread. We don't precisely know why, but we think it could be a simple fatigue failure as this part had been used for at least 2 years. It could also be because we overtightened the nut. Another reason would be that the two bearings weren't perfectly aligned, which caused more fatigue than it should have. We haven,t proved anything yet, but we should have an upright going onto a CMM soon.

[Didier Beaudoin]

Oh, and another reason would be that we have TOO MUCH power. http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

[threehondas]

We had the exact same outer CV tip failure at competition in 2004, - I'll post a pic soon.

Didier, let me know what you do about the failure. We ended up stepping up the outer CV threads 1-2mm (I cant remember) in diameter and ran a different hardness.

Also, "Oh, and another reason would be that we have TOO MUCH power" That failure is not torque related.

[Didier Beaudoin]

Originally posted by threehondas:
Also, "Oh, and another reason would be that we have TOO MUCH power" That failure is not torque related.

I know, I just thought it fitted well with the discussion going on... http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

I'll let you know about what we do, but for the moment we've replaced all the old CV parts by new ones, changed all bearings and hubs.

Another reason could have been because the splines in the hubs were really worn out and there was a slack in it, so each time we applied power, there was some sort of an impulse on the splines. I know it wouldn't have broken at the threads then, but oh well...

[MikeWaggoner at UW]

Originally posted by Didier Beaudoin:

Another reason could have been because the splines in the hubs were really worn out and there was a slack in it, so each time we applied power, there was some sort of an impulse on the splines. I know it wouldn't have broken at the threads then, but oh well...

The way Nascar gets camber is by tapering their splines, and allowing the spline to shift during driving... But they may oversize their parts to compensate for that. My vote is for overtightening; there's no scalloping like I'd expect from fatigue failure.

[rotor]

we had a throttle pot on the car for the enduro and the result is somewhere between 30 and 40% at max power throttle pos (not going to tell you exact data...) and remember that is from a car that has already has less power. what would be interesting is some throttle data from a fast 600 car (kev/nick, denny??)

what is also interesting is a histogram of lat G will give you an insight into the time spent where you are traction limited and how much is power limited and the results are quite interesting. obviously alot of assumptions there without more study of the tyres but gives an indictation.

still hp is very important and i agree that our car could have another 15hp with a small mass increase from someform of forced induction or larger capacity but given its only the second car with this engine it wouldn't have been a smart move at this stage, if it was the 10th car with the same engine (not mentioning any names..) then it would be a different kettle of fish.

I find it quite funny when people coment on how our car would go on a large autocross track.. do you really think that we would build the same car for a large track?

mark hester
rmit fsae 03,04, 05US

[John Bucknell]

Hmm, maybe I'll go back to school so I can build an engine with too much power for this comp. Then alla you'd be sorry http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Denny Trimble]

John,
Is that a threat, or a promise? http://fsae.com/groupee_common/emoticons/icon_smile.gif

Rotor, I'll find that throttle % for you, it's hiding on a laptop somewhere...

[David Kieke]

I've seen this type of failure before and it looks like you are running a similar setup. It looks like you have the outer CV cup riding in the inner hub bearing and the drive hub riding in the outer hub bearing. Therefore the only way to transmit the bending loads to the inboard bearing is by the female-to-male spline interface, which is never a good idea. This bending load causes the castle nut to be loaded and transmits the bending torque back to the CV cup through the threads, therefore breaking at the smallest diameter (undercut between splines and thread). Look at the cross-section of your hub/upright package and trace the load paths to help visualize this.
The solution - your wheel hub (one piece of metal) should ride in two bearings (or a double row of some sort) and the outer CV cup should only take the axial force required to preload the bearing unit correctly.
I hope this helps.
David

[VFR750R]

Going back to the post on too much power. Most teams including ours come to competiton with not fully tuned engines and there is a lot of wasted hp there. The basic ingredients are there for 80hp, no money need be spent...just time. Tuning should gather more thought then it does, it's pivotal in getting the most of your engine package. One of the reasons we run E85 and a turbo is plenty of power is available with the rest of the package not properly tuned, and the E85 keeps us from blowing up engines due to timing/fuel issues we always have. Anyone watching endurance this year would have noticed our car gasping for fuel on corner exits (the chassis judges did), and us stall after RMIT passed us.

[Z]

Originally posted by John Bucknell:
Hmm, maybe I'll go back to school so I can build an engine with too much power for this comp. Then alla you'd be sorry http://fsae.com/groupee_common/emoticons/icon_smile.gif

More details please John? http://fsae.com/groupee_common/emoticons/icon_smile.gif

Come on, what would the basic specs be? How big would your "too much power" be?

Z

[John Bucknell]

Originally posted by Z:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by John Bucknell:
Hmm, maybe I'll go back to school so I can build an engine with too much power for this comp. Then alla you'd be sorry http://fsae.com/groupee_common/emoticons/icon_smile.gif

More details please John? http://fsae.com/groupee_common/emoticons/icon_smile.gif

Come on, what would the basic specs be? How big would your "too much power" be?

Z </div></BLOCKQUOTE>

Actually, I've got it all designed in my head. But since I'm one of those hotshot powertrain design judges, I'm gonna keep the details to myself - I just wanted to see if anyone would bite on whether I could do it or not (thanks Denny!). However, I will say that I could basically keep the restrictor choked all the time http://fsae.com/groupee_common/emoticons/icon_smile.gif. Oh and friction would be tiny (and I could build it cheap). And so on...

Also, listen to VFR - he's right about a lot of power hiding in calibration...

[Z]

Originally posted by John Bucknell:
However, I will say that I could basically keep the restrictor choked all the time http://fsae.com/groupee_common/emoticons/icon_smile.gif. Oh and friction would be tiny (and I could build it cheap). And so on...


Aww, not fair... Stop teasing! We all know you really want to tell http://fsae.com/groupee_common/emoticons/icon_smile.gif . I gave my suggestions (crazy as they are) back on the "Single cylinder engines" thread (pages 4,5,6).

So, how about just telling us your expected maximum power, and roughly the shape of the torque curve (and rpms)???

Z

[RagingGrandpa]

Originally posted by Big Bird:
[QUOTE]Originally posted by Garlic:
...... but there's no thing as too much power, ...

QUOTE]

Disagree completely.


Well it may be different for you, but I've never met a horsepower I didn't like...

[TA]

Originally posted by Jeff The Pyro:
im gonna have to agree with mike on this one... accepting anything as "adequate" is the exact opposite of what this competition is all about.


Just to play devil's advocate -- there's a lot more to "winning" than max power.

How many teams had to tack cobbled up silencers (destroying any exhaust tuning they may have had) onto to their exhausts to pass tech?

How many teams had stalling issues? With the attendant "fail to re-start" DNF?

Was anyone's car "undrivable" out of tight corners, snap oversteer from spiky powerband?

Did anybody lose endurance points due to fuel mileage?

Maximum power is cool, makes people feel all warm and fuzzy but drivability -- a robust idle, smooth torque curve, "adequate" power, decent fuel mileage -- wins the competition.

And as an added bonus, all the above goals are what you'll be looking for when you get "real-world" jobs as powertrain engineers.

Cheers, Ted

[Z]

Well said Ted,

To your;
1. Robust idle.
2. Smooth torque curve (no holes/spikes)
3. Good fuel mileage.
4. Quite exhaust.

I would also add that instead of 1 - 2 extra "peak" horses the engine guys would be better off working on;
5. Reliability
6. Lighter weight, lower CG, more compact package (incl. radiator and muffler).
7. Smoother throttle linkage.
8. Smoother gearshifting (assuming the "engine guys" also do drivetrain).
9. Better yet - no gearshifting.
10. Lower cost... etc. etc.

It is a no-brainer to say "you should always try to do better". It takes a bit more thought to figure out in what areas you should be spending your scarce resources (and even Ferrari F1, since Todt arrived, accept that they have "scarce resources").

Putting it another way, assume that one day you are running your own company (rather than just playing a game with other peoples money). You have the future of the company, its workers, and of yourself and your dependents, in your hands. The company has three divisions - Engine, Chassis, Suspension - each receiving one third of the budget. For several years one of the divisions, the "Engine guys", have only been bringing in less than 1% of revenue, and things don't look like changing.

Do you say "Well guys, you should keep trying to do better", and let them keep bleeding one third of your resources? Or do you, perhaps, rename that division "Aero" because you can sense an opportunity in that relatively unexplored field?

Z

PS. Apologies for being way off-topic here, but John Bucknell, come on, just a few more details??? (What do you think of my suggestion in "Single" thread?)

[John Bucknell]

PS. Apologies for being way off-topic here, but John Bucknell, come on, just a few more details??? (What do you think of my suggestion in "Single" thread?)

Nope, wouldn't do anything like you described. Wouldn't start or idle for one. Good fuel economy and clean pickup from closed throttle require good low load combustion stability - which low compression doesn't have in spades. And I have a spectacular loathing for anything with only two valves and/or pushrods - both of which are not weight efficient or flow efficient or combustion efficient, rather they are holdouts from the days when nobody could cast or machine worth a darn. Finally, screw compressors - while better than roots blowers - are finicky and difficult to size, but worst of all still have horrible polytropics of compression.

Sorry, you'll have to guess at the rest based upon the above http://fsae.com/groupee_common/emoticons/icon_smile.gif In fact, as a systems engineer I wouldn't do a FSAE car like anyone is currently because of the inherent inefficiencies of off-the-shelf powertrains - but neither would I build a brown go-kart, because I know I can build something small and light but still sophisticated and cheap because it would ultimately be faster. The FSAE powertrain discussion seems to be like american politics - only two choices of philosophy, which is way oversimplified....

[BeaverGuy]

Sounds about like what I figured from your post about "always choked and low friction" a "boosted" engine without poppet valves.

And this talk of good fuel economy, good response from closed throttle, and not low compression makes it sound more like a diesel cycle than an otto cycle.

[Jeff The Pyro]

<pre class="ip-ubbcode-code-pre"> Just to play devil's advocate -- there's a lot more to "winning" than max power.
</pre>

sorry... i wasnt very clear about that... i didnt mean all the power had to be concentrated at one rpm range. if you dont believe me keep in mind i'm from UCSD... the team with the flipped head and the roots blower, clearly that combo wasnt dreamed up for peak hp... (i dont remember the exact results from the land and sea, but on a dynojet our torque was within about 15% of being constant (literally flat) between about 4500rpm and 10,500.

and maybe its not wise to call the bluff of a design judge... but i always understood that off the shelf powertrains were preferable because of millions of dollars of research that companies put into designing them....

as far as the inherant flaws of roots blowers... we're well aware of this but there's only so much you can do in one year...

[kozak]

yes but thoes off the shelf power trains were ment to work with an efficient intake and no restrictor plate.

[Z]

John,

The two valve head (SOHC, not pushrods) was to make it easier to machine a bespoke head (the low revs mean the valve weight is less important). I mentioned somewhere that a 5-valve Yamaha Moto-X head could also be used. The real CR (with S/C) was ~12:1. Also the S/C is the quick option - I mentioned "turbo next year". Nevertheless, I take it you don't like big singles... Ever seen a Lanz Bulldog? Too inefficient??

But since there is so much talk about "too much power", how about just giving us that one number? http://fsae.com/groupee_common/emoticons/icon_smile.gif

85hp? 90hp?? 100hp??? More??? http://fsae.com/groupee_common/emoticons/icon_confused.gif

Z

PS. Oh, and I'm guessing boxer-twin or 90 degree V-twin??

[BryanP]

I think that the Yamaha Raptor head would fit the bill quite nicely. 100-mm. Bore, 5 valves, single overhead cam. Our team, (High school formula sae team) currently uses this engine and we plan to sleeve it to 595 cc. for next year. (I would prefer to de stroke the engine, but was convinced by our engine builder that sleeving it would be vastly easier.) . We are planning to either supercharge or turbo charge it for next year. I prefer to supercharge ( simplicity)but finding a supercharger that was smaller and lighter than the engine has been impossible until I saw this e-bay ad.
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=7976387131
Hopefully it will display for you. It looks sweet. In case it does not it is a small 7.25"� x 5.375"� x4.3"� roots supercharger that displaces 300cc. per rev. I contacted the seller and they come from a 600cc. Diahatsu delivery van that is only sold in Asia. I am concerned that the displacement is too small. The seller told me that he has some larger ones coming in (500 cc. per revolution). I would appreciate any feedback on the suitability, reliability, etc. of this unit. We might just get to see a Z type motor yet.

regards
Bryan

[John Bucknell]

Originally posted by Z:
The real CR (with S/C) was ~12:1. Also the S/C is the quick option - I mentioned "turbo next year".

Actually, I did read all of the posts on the singles thread. I didn't comment then, and probably shouldn't have now. I understand the trade-offs necessary to compete in FSAE (more than most race engineers - working in big business is all about extreme compromise), so finding the time/money/know-how/etc to build a unique powertrain specifically for FSAE is mostly a losing proposition - so I'm not dumping on the single or multi solution cause they are efficient in the resource sense. None of the professors I had (even the ones in grad school - in motown no less), none of the books I read, none of the technical papers I read contained the knowledge I needed to build an optimized engine for FSAE. Ten years in the auto industry barely has, and I tune powertrains for a living. So, yes I could do it now with the know-how I have - and yes I think I could do far better than utilizing an existing powertrain, but that's me - not most of the competitors that I talk to. I'd love to see somebody successfully try to optimize (WWU & their V8 was refreshingly different), but I'm not gonna taint this board with how to get points in my design queue.

But anyhow, to comment on your compression ratio calc - a screw compressor does nothing for you when you only want a little bit of power (read 'idle' or 'mid-corner tip-in'). At low load, your clearance volume is still huge with a low 6:1 geometric compression ratio - and flames don't propogate very well in low pressure/high dilutant environments. It's a driveability/throttle response issue that as a work-around you'd have to left-foot brake all the way around like the turbo F1 or Group B rally cars....

[Kevin Hayward]

This discussion of powertrains is pretty interesting.

I would have said that the biggest problem with the whole single or multi setup has almost nothing to do with the available power. Rather I would say the biggest problems are with the gearbox, engine mounting and differential setup. I don't even think that removing gears etc from the typical 4 cylinder comes close to a decent solution.

We have looked into a few different options for drastically modifying a CBR to suit a race car better. The studies show a massively improved vehicle but at quite a cost in terms of resource allocation. However packaging can be improved out of sight and significant weight can be saved. Up to this point it does not appear that we could accomodate the required program to implement the solutions we have come up with.

The more testing and development we have done has really shown us that the engine and its characteristics have a great affect on the overall vehicle dynamics package. Especially with the differentials and traction control that most teams run. Some of the talks with judges during the competition has also led us to thinking about things like traction control a little differently.

Unfortunately my ignorance in powertrain knowledge is fairly complete. However if I was to develop a powertrain in terms of a full systems approach the big things I would be worrying about would be the ones I mentioned above. Realistically the most efficient form of engine mounting and setup has to be something similar to what F1 has been running for a long time. Tub up front engine down back. The 600cc engines are just 60kg of underutilised aluminium and steel. A well packaged engine solution should be able to eliminate nearly all of the weight associated with differential mounts and packaging, gearbox internals and rear chassis for suspension mountings.

I admire the V8 from Western Washington more for its packaging and overall changes to the vehicle rather than the fact that it was a V8. Hopefully one day the FSAE cars may develop to the point that such powertrain projects are not so rare. However as John mentioned the development costs and the long term nature of the projects may make them almost impossible to implement effectively within the student team environment we all have to work within.

It is a massive ask of any powertrain group. Being able to implement one of the more common solution is a massive ask as it is. To have a half-decent tune, with good throttle response, good fuel economy, bulletproof reliability, simple maintenance, simple construction, decent mounting, lightweight differential setup etc. is a real effort. Especially considering that the teams are not full of professional engine builders.

As a suspension guy I hate having to give any credit to the power people. But I think that the required learning curve for the engine team is much more than what we see on any other area of the car. Then they also have to deal with the most number of reliability headaches. At least with a teflon lined spherical bearing there is no way for oil to leak or for an electrical connection to come loose http://fsae.com/groupee_common/emoticons/icon_smile.gif

Anyway I'm starting to babble.

Cheers,

Kev

Once upon a time FSAE student
UWA Motorsport

[rjwoods77]

First team who blows the cash on that maxim twin is gunna be in hog heaven. The packaging and weight alone are worth it. Who knows how much hp after the restictor but just the packaging alone is incredible. Anyway....

[Z]

Originally posted by John Bucknell:
At low load, your clearance volume is still huge with a low 6:1 geometric compression ratio - and flames don't propogate very well in low pressure/high dilutant environments.

John,

There is obviously a hole in my knowledge here. Perhaps you can help fill it in? http://fsae.com/groupee_common/emoticons/icon_smile.gif

Back in the 1960's & 70's there where many racecars with 8 litre V8s, eg. Can-Am, Ford MkII (7 litre), etc. Many of these had CR of around 10:1, which gives a combustion chamber volume of ~110cc - about what I was suggesting (give or take a bit...). These engines were derived from production car "big block V8s" with even lower CRs, hence even larger chamber volumes. With the throttle just cracked open these engines would have very dilute air-fuel mixtures in the chambers at TDC. (All "throttled" engines, eg. typical SI engines, are "variable CR" in the sense that their power is varied, at given rpm, by varying the mass of air-fuel going into the constant volume combustion chamber.) Furthermore, many of these engines had only a "single 4 barrel Holley" (so quite variable mixture strengths), points & coil ignition, and not a computer in sight. But they still seemed to work ok? Or not???

All the bigger V8's I've had (non-racing) seem to idle well and run smoothly at low load. In fact, that's their strength. What have I got wrong?

(I'm assuming a low overlap cam - 'cos low max. revs. If it needs squish then give it squish. Or is there still something missing?)

Z

[James Waltman]

Z,
Maybe I'm missing what you are saying.
˜Big V8s from the 60's worked alright so they must not be that bad?'

The 7 liter MkII made less than 500hp. I've seen a modern 2 liter race engine that makes (reportedly) over 300hp. There are even production 2 liter engines that are making over 200hp. I'm not sure if that really relates to anything.

I understand that John doesn't want to give too much away. I sure would like to see him prove it though. Just for fun (as long as everyone is bench racing) this is what John does with production engines:
http://dot.etec.wwu.edu/fsae/HostedPics/Junk/wow-srt4.jpg

(The red line way up top is his.) Source (http://www.sportcompactcarweb.com/features/0301scc_under20gs/)
Way off topic now...

[Z]

James,

My point was that big combustion chamber engines with lowish CR's seem to run smoothly (??) at low throttle openings... Or not???

After 40+ yrs engines should be getting better! The MkII 427 was a production block modified to ~500hp so that it could run 48 hrs at Le Mans power levels. (And despite that monstrous cast iron block the MkII was about 300kg lighter than today's all aluminium Ford GT!)

Z

[Ché]

James or John: Correct me if i'm wrong but the Mini numbers are also what John "does with production engines"...and seriously John if you are going to flaunt a badass powertrain without revealing what it is I'm not going to hold my breath and wait for you to show up in Detroit with it. Obviously if we (student engineers) had the knowledge and resources you had then we wouldn't be making formula SAE cars but rather would be working for an OE or race team...My point being that as a design judge you are encouraged to offer advice and direction, bragging about what you would do hardly seems helpful...Anyway I'm a suspension guy and care more about the the cars' IC migration than the torque curve anyway....John you wouldn't be using active exhaust in your secret powertrain would you??? http://fsae.com/groupee_common/emoticons/icon_wink.gif

[Jeff The Pyro]

Z...

i think the low end torque/drivability were due more to the sheer size of the engines than any of their other characteristics.... an advantage a .6 liter fsae motor clearly doesnt have.

regardless, i agree that there's a lot more potential to the 2 valve configuration than a lot of people say... the best example is the ls6/ls1 (possibly the newer gen as well... but i havent seen any specs). its not very often you see a >400hp production motor with a 28mpg epa... and im sure most people would agree that this motor has more than adequate throttle response and low end torque... yet this engine uses the same _basic_ configuration as the small block chevy designed back in the day that everyone swears is so horribly obsolete.

anyways... from the standpoint of the whole "objective" of the competition (according to the rules) that you're supposed to be building a small scale production vehicle to be sold to ameteur autocrossers, i cant imagine that a built-from-scratch engine is a wise choice... aside from the inherent reliability issues, there's forseeable problems with replacement parts, as well as the costs of production (though i cant argue with the coolness factor)

[Denny Trimble]

Originally posted by Jeff The Pyro:

regardless, i agree that there's a lot more potential to the 2 valve configuration than a lot of people say... the best example is the ls6/ls1 (possibly the newer gen as well... but i havent seen any specs). its not very often you see a >400hp production motor with a 28mpg epa... and im sure most people would agree that this motor has more than adequate throttle response and low end torque... yet this engine uses the same _basic_ configuration as the small block chevy designed back in the day that everyone swears is so horribly obsolete.


I spoke with a Corvette engineer in '98, who related one of his pet peeves. People would frequently ask him "What have you guys been doing since 1960-whatever? The corvette engine sitll makes the same horsepower as the muscle cars of my youth... " And his response was, fuel economy and driveability.

So, I wouldn't say that those are inherent characteristics of large 2-valve V8's.

On the topic of "we shouldn't be discussing crazy engine ideas like this", why not? If a team embarks on a major deviation from the norm (WWU V8, Wattard twin, etc), they will certainly learn a lot. In my mind, the "concept of the competition" is less important than learning and/or winning (but that's another debate).

Besides, somebody has to de-throne the Bowlands at the SCCA Nationals in AM some day... http://fsae.com/groupee_common/emoticons/icon_smile.gif Of course, that's another set of constraints, wildly different, and I'll probably never build an AM car ground-up, but one can dream and design...

[Denny Trimble]

Originally posted by rotor:
we had a throttle pot on the car for the enduro and the result is somewhere between 30 and 40% at max power throttle pos (not going to tell you exact data...) and remember that is from a car that has already has less power. what would be interesting is some throttle data from a fast 600 car (kev/nick, denny??)
...

mark hester
rmit fsae 03,04, 05US

Just looked at our data, 30% average TPS for me, 25% average TPS for Mike T. Unfortunately we screwed up logging accelerometers this time, but we have data from testing. Looking at histograms of % time at >80% throttle, and % time at >80% lateral g's, is definitely worthwhile.

[MikeWaggoner at UW]

Re: Denny's comments on Vette's

I'd think the main thing would be emissions. You can't run a that rich anymmore, and have to eliminate most shitty places in the combustion chamber. Getting the same power is impressive.

[Jeff The Pyro]

the other thing you have to realize is that back in the day, the factory horsepower specs were inflated by over 30% in some cases...

its easy to make a lot of horsepower from a small block if you dont have to pass smog anyways...

[Big Bird]

Seems I flared up a bit of debate with my comment about engine power. Sorry to have completely diverted the thread. Anyway, Z, and anyone else interested, I've posted my "thesis" on the matter in a new thread ("Life, the Universe, ...."). I thought it best to justify my position, so you can all decide whether my point has any validity - or whether I have truly dropped all my marbles and they've rolled somewhere behind the fridge.

Cheers all

[John Bucknell]

Fun! Who knew this hijack might turn into an interesting discussion after all? First of all, Che - the reason I'm being obstinate is multi-part, but mostly I love being a design judge. There is no way I am getting tossed by making specific recommendations to make a car significantly faster. Advice & theory yes, how to design a killer engine no. Secondly, I am not a braggart and I hope my tone so far this last year on the forums has born that out - I was just caught by the imp of the perverse and blurted out a challenge to all of you to try new things if you are so inclined. Z can speculate and recommend to his heart's content - I'm bound.

Kevin Hayward is saying the same things I might've (when I say powertrain, I mean driveline as well). Look at the rules, effectively the only limitations are displacement and restrictor - what's limiting making your car faster? We have one thesis now (thanks Geoff!) - I'd love to hear others.

So a few more points to fill in Z's hole. Effective compression ratio is the largest single contributor to charge density at ignition (since once intake valve closes you are effectively driven by the ideal gas law). Looking at valve timing on about any naturally aspirated engine, high or low speed and you find the effective compression ratio that works best is anywhere from 7 to 9:1. So in order to get up to to 9:1 in a high speed engine (with big cams), you have to have a tiny clearance volume (12:1 or better compression rato). If you desire to run at lower speeds, your cam timing isn't as extreme and so your geometric compression ratio can be lower (and no crazy piston top shapes that hinder flame propogation). This is all limited by full load performance, but good engines run well all the way down to effectively no load. A supercharged engine running a tonne of boost necessarily needs lower geometric compression due to knock limits (especially so when fuel rules limit toluene) or piston temp or connecting rod bearing stress. The lower the compression ratio, the greater the residual gas left over from the prior cycle (residual is a function of overlap AND clearance volume AND pressure ratio from intake to exhaust). Way far under the nice 9:1 effective compression ratio (like 6:1) requires a bit of luck to get the flame to light and find other fuel/air molecules to burn when running low manifold pressure (ie when the driver is indicating you don't want much torque, or why it is called a 'throttle' http://fsae.com/groupee_common/emoticons/icon_smile.gif). What ends up happening is you get an engine that makes no torque for some amount of throttle travel and then 'comes alive' with maybe more torque than you want at that instant. This is the problem with nearly all two strokes, and many motorcycle race engines with huge cams (bikes need much finer throttle control because a rear-wheel slide can easily turn into a painful high-side crash). There just aren't any good ways around this physical property of combustion. In conclusion, this property has nothing to do with actual size of the clearance volume, rather the ratio to the trapped volume...

Finally, no offense to SBC lovers - but when in a displacement-limited class you have to talk specific power. Sure, I can make an air pump that moves a lot of air by making it bigger - but making a smaller pump move more air requires reducing the flow restriction of the orifii. And valve area is the name of the game when you want to reduce restriction, four poppet valves are better than three which are better than two in a given bore. Same goes for supercharged applications - air flow equals power, if you choke - power has to come from somewhere to jam more charge through a little hole. Some will argue that a restrictor motor invalidates all of the above, but I point to the dyno results of the multis versus the singles at the silverdome. Who's making more specific power (naturally)? The engines with more valve area is who. The motocross singles are as highly developed as any multi - it's just physics that allows a big heavy multi to breathe better.

[James Waltman]

I think that Ché may have started celebrating the end of classes just before he posted that.

John,
I saw your original comment as a challenge for teams to play with more than the intake and exhaust. There are not many (any?) teams that are really going all out on their engines. I think that there is a lot of room for improvement. Of course Geoff might have just convinced me that we don't even need an engine...

[John Bucknell]

Not to kill this thread any deader than I have already - but I had a few more thoughts that might make what I'm saying be clearer. This comp is all about learning, and no matter what - somebody will attempt what a judge recommends blindly. That's not what we want, we want you to think for yourselves - and tell me I'm full of crud if you've got data saying otherwise.

As far as Geoff's thesis goes - the chassis development exhibited so far I think is showing as much incremental improvement year over year as any other subsystem. Too bad we don't run the same track in endurance, we'd be able to compare what that chassis improvement is worth in lap times. It's just my personal opinion that there is relatively more merit in optimal powertrain development (again, if you've got the resources) - as nothing significant has happened but for the introduction of the 4-stroke motocross engine in the last ten years. I think Univ of Illinois's turbo Sidewinder from 1994-5 was also a good example of outside the box thinking -> Sidewinder (http://dilbert.cen.uiuc.edu/soc/sae/formula/h/sidewinder.html)

[VFR750R]

Wow, this thread is about the deepest I've seen on engines in forever. I agree with what most everyone is saying. Formula 1 engine packaging is an optimization in design, obviously our package would be different but there shouldn't be any frame members anywhere near the engine, and transaxle.

Sometimes I feel like John giving stuff away(but since I'm not a design judge its obviously not as bad). I'll throw this out there though. Cylinder pressure is your friend and you can do stuff with your intake and exhaust cam to up your cylinder pressure and your effective compression ratio. If you understand general camshaft design and think about what is going on in a NA restricted engine on the intake and the speed ranges you see vs the bike you can quickly come up with ideas on the right direction to take.
Since we don't do this anymore I don't mind telling you that we used to run 18:1 compression ratio in restrictor plate races. yes...18:1 and I heard the fords were closer to 19. BE CAREFUL, I don't recommend 18:1 but think about WHY it was soo good in oval track plate racing. Hint: we don't ever lift, and we're running substanial man vac at speed.

[rjwoods77]

But at that high of a compression and rpm you surely must have been running a sick overlap so your dynamic compression was actually alot less right? Around 12:1 dynamic about? But i guess it really doesnt matter because it is a 2 valve piece of junk that is obviously inferior to everything else in the world. http://fsae.com/groupee_common/emoticons/icon_smile.gif Or so the school of though is these days. I can remember back in the day when they ran a pushrod buick in indy and they smoked alot of cars just due to the lower cg of the heretical cam in block engine. Iron block no less. A 4 banger head is actually a weighty piece to have at the back of your neck in these cars. Pushrod motors can actually be an advantage as far as weight and cg. Well... anyway. Different strokes for different folks.

[VFR750R]

Overlap has little to nothing to do with dynamic compression, but intake closing does. To be honest I don't know how our old cam profiles looked like but our current overlap ends up being slightly less then our open engines. I can tell you my gut feeling is our intake cam profile was designed to maximize cylinder filling and was not compromised by compression ratio.

Engine speed at daytona ~7200rpm, not high by any means. Before this years gear rule lots of open cars had a 10500+ rev chip.

[John Bucknell]

Okay, since nobody bit on the Sidewinder post above - it is an ~390 lb, turbo 600/4 (in 1994) with huge rear weight bias (driver practically over the beam rear axle) with the engine next to driver immediately in front of the axle. It was really fast, and would probably still be competitive today...

I think I know where it is, maybe I'll get to drive it this summer...

[rjwoods77]

John,

Its just a 600cc sprint car like the one my buddy races without the top cage supports. But be carefull, if you mention the words sprint car or baja around here you are liable to be critized as someone who couldnt possible engineer something in formula because in this competition , only fsae people know what they are doing. (not even going to bother with a smiley because there is not face to connect this level of sarcasm and distaste toward the status quo around here. Well... maybe my face)

It is interesting to note they are also running a parallel 4 link, solid axle rear suspension with panhard directly from a 600cc sprint car. They said they had problems with understeer but the rear suspensions on those are already set for high understeer reactions. I wonder what would happen with that setup if they got the geometry to have neutral handling with just a tad of understeer. Hmmmmm. Well, its not a double a-arm with a diff that weighs almost 500lbs so i guess it sucks.(not even going to bother with a smiley because there is not face to connect this level of sarcasm and distaste toward the status quo around here. Well... maybe my face)

[rjwoods77]

John,

The UIUC sidewinder(#54) took 7th with 727.66 points when 1st was 856.37 points in 95. In 94 it took 10th with 660.58 points when 1st was 852.96 points. Should have tried to develop it more. Would have been intersting.

[Z]

Originally posted by Rob Woods:
not even going to bother with a smiley because there is not face to connect this level of sarcasm and distaste toward the status quo around here. Well... maybe my face)

Hmmm? A Rob Woods emoticon? Perhaps something like this (!) ?

Hint - its not a face, but it does have two cheeks. http://fsae.com/groupee_common/emoticons/icon_wink.gif

Z

[Denny Trimble]

If not a Rob Woods emoticon, perhaps an avatar (the guy in the back's expression):
http://www.kidanal.com/upload/pics/skanking.jpg

For a good time, click here (http://images.google.com/images?q=moshzilla)

[rjwoods77]

oie! oie! oie!

ahahahahaha

looks like he is about to wail her in the back of her head. I would do something like that.

ahhahahahhahah

[Marshall Grice]

Those farkers always make good avatars.

[James Waltman]

Originally posted by John Bucknell:
...the Sidewinder...I think I know where it is, maybe I'll get to drive it this summer...

Anyone we might know? Ken worked on that right? Does he have it?!

[John Bucknell]

Ken actually got it as a wedding present, but had to give it up because of shop room limitations. One of two other Illini grads in town have it...

[Chris Davin]

Originally posted by John Bucknell:
Fun! Who knew this hijack might turn into an interesting discussion after all? First of all, Che - the reason I'm being obstinate is multi-part, but mostly I love being a design judge. There is no way I am getting tossed by making specific recommendations to make a car significantly faster. Advice & theory yes, how to design a killer engine no. Secondly, I am not a braggart and I hope my tone so far this last year on the forums has born that out - I was just caught by the imp of the perverse and blurted out a challenge to all of you to try new things if you are so inclined. Z can speculate and recommend to his heart's content - I'm bound.

Kevin Hayward is saying the same things I might've (when I say powertrain, I mean driveline as well). Look at the rules, effectively the only limitations are displacement and restrictor - what's limiting making your car faster? We have one thesis now (thanks Geoff!) - I'd love to hear others.

So a few more points to fill in Z's hole. Effective compression ratio is the largest single contributor to charge density at ignition (since once intake valve closes you are effectively driven by the ideal gas law). Looking at valve timing on about any naturally aspirated engine, high or low speed and you find the effective compression ratio that works best is anywhere from 7 to 9:1. So in order to get up to to 9:1 in a high speed engine (with big cams), you have to have a tiny clearance volume (12:1 or better compression rato). If you desire to run at lower speeds, your cam timing isn't as extreme and so your geometric compression ratio can be lower (and no crazy piston top shapes that hinder flame propogation). This is all limited by full load performance, but good engines run well all the way down to effectively no load. A supercharged engine running a tonne of boost necessarily needs lower geometric compression due to knock limits (especially so when fuel rules limit toluene) or piston temp or connecting rod bearing stress. The lower the compression ratio, the greater the residual gas left over from the prior cycle (residual is a function of overlap AND clearance volume AND pressure ratio from intake to exhaust). Way far under the nice 9:1 effective compression ratio (like 6:1) requires a bit of luck to get the flame to light and find other fuel/air molecules to burn when running low manifold pressure (ie when the driver is indicating you don't want much torque, or why it is called a 'throttle' http://fsae.com/groupee_common/emoticons/icon_smile.gif). What ends up happening is you get an engine that makes no torque for some amount of throttle travel and then 'comes alive' with maybe more torque than you want at that instant. This is the problem with nearly all two strokes, and many motorcycle race engines with huge cams (bikes need much finer throttle control because a rear-wheel slide can easily turn into a painful high-side crash). There just aren't any good ways around this physical property of combustion. In conclusion, this property has nothing to do with actual size of the clearance volume, rather the ratio to the trapped volume...

Finally, no offense to SBC lovers - but when in a displacement-limited class you have to talk specific power. Sure, I can make an air pump that moves a lot of air by making it bigger - but making a smaller pump move more air requires reducing the flow restriction of the orifii. And valve area is the name of the game when you want to reduce restriction, four poppet valves are better than three which are better than two in a given bore. Same goes for supercharged applications - air flow equals power, if you choke - power has to come from somewhere to jam more charge through a little hole. Some will argue that a restrictor motor invalidates all of the above, but I point to the dyno results of the multis versus the singles at the silverdome. Who's making more specific power (naturally)? The engines with more valve area is who. The motocross singles are as highly developed as any multi - it's just physics that allows a big heavy multi to breathe better.

John,

I understand "dynamic" or "effective" compression ratio to be related to "geometric" or "static" compression ratio by volumetric efficiency; specifically, (D. C. R) = (eta-v) x (G. C. R.). I also understand that it's not uncommon for a high-revving naturally aspirated racing engine to achieve over 100% volumetric efficiency. This would put the dynamic compression ratios well over the 7-9:1 you quoted. Have I gone wrong somewhere?

Thanks,

[John Bucknell]

Chris,

I created the 'effective' compression ratio term to describe the trapped volume compression ratio. This compression ratio is equal to the clearance volume over the volume in the cylinder at intake valve closing. Effective expansion ratio is by the same method is defined by the end of the polytropic expansion when gas exchange starts (ie when the exhaust valve opens). Therefore 'dynamic' compression ratio is simply the 'static' compression ratio times the ratio of the induced mass of air to reference mass (ie, ambient air density x displacement volume). Thinking in terms of gas pressure at ignition, the ratio of volumes at the start of compression is more relevant.

For example, a high speed engine has a 280 crank degree intake cam duration running at 120 deg ATDC centerline. So intake valve closing occurs at (280 / 2) + 120 - 180 = 80 degrees after bottom dead center on the compression stroke (trapping somewhere in the neighboorhood of 60% of the displacement volume). Effectively, the compression portion of the cycle only begins once the volume is sealed - and using the trapped volume as the reference volume (instead of the geometric displaced volume) some engines can exceed 200% volumetric efficiency. That's real tuning....

[Joji]

I wonder why no post in this topic for last 6 years??
Have all teams started finishing endurance since then?? http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

[The AFX Master]

There's only one answer to such question...

"Because a two dollar part"

[vandit]

couple of teams that i remember from this year's FSG event -

> TU Graz did not finish because of their rear right suspension failure. I think they also did not finish FSG 2010 Endurance because of front right rocker failure.

> Liverpool LJMU did not finish because of welding failure in their Steering column.

> Braunschweig TU did not finish because of oil Leak and resulting fire.

> TU Dortmund did not finish because of failure in throttle mechanism.

> for many teams engine did not start during driver change.

> for electric cars, Tobias posted in thread 'Formula Student Germany 2011 Competition: - Updates, Pictures, Stories, and More'

[df_fsmb]

Am I right that at FSG one of the teams was called to the driver change area for mid-endurance scrutineering because there was too much fire out of the exhaust when running at the RPM limiter on the straights? It is a normaln thing, or was it really that excessive?

[vandit]

yes, one car was called in from the track because there was fire spotted at the back of left side-pod (where the car had exhaust muffler). The fire extinguished itself but the car was declared unsafe primarily for the driver because the heat shield protecting the driver from exhaust was too hot on the driver side. If i am remember correctly, the heat shield was rather a part body-work panel (Carbon fibre !!) with aluminium foil on driver side and the driver was in direct contact with it all the time while driving. The Scrutineer actually made the driver touch the heat shield and i think the driver was also in quick agreement.

[df_fsmb]

Originally posted by vandit:
yes, one car was called in from the track because there was fire spotted at the back of left side-pod (where the car had exhaust muffler). The fire extinguished itself but the car was declared unsafe primarily for the driver because the heat shield protecting the driver from exhaust was too hot on the driver side. If i am remember correctly, the heat shield was rather a part body-work panel (Carbon fibre !!) with aluminium foil on driver side and the driver was in direct contact with it all the time while driving. The Scrutineer actually made the driver touch the heat shield and i think the driver was also in quick agreement.

That explains a lot. Thanks!

[TiTiKo]

Hi Guys;
A lot of time without see the forum. We didnt finish the endurance on FSAE2006 - Michigan (Fsae-LUZ from Venezuela) for the most unusual reason: "fuel tank empty" http://fsae.com/groupee_common/emoticons/icon_confused.gif at 21 lap of 22 lap. That moment was so sad for us since the fuel tank didnt has enough capacity and in the other hand our car ran 100% perfectly without any fault or defect.

That was our sad history on endurance 2006.

Regards,
Aristides Nava

[cvargas]

Originally posted by Agent4573:
I didn't get a chance to ask some of the teams but i noticed a couple big names teams got pulled from endurance in the afternoon session and I was wondering what the reasons for it where. The big 3 I remember seeing while in the que where UTA, RMIT, and Texas A&M...

Because racecar

[vandit]

can anyone tell what happened with TU Graz car in Autocross this year at FSAE Italy. From the couple of pictures i saw it looks like failure of rear right suspension system (again!!). i also remember them, unloading car on Monday morning from their truck, so i am assuming they took it out to repair during night.

i am also interested if any team had failure in tripod joint on track during FSAE Italy 2011. I know that car 56 had tripod joint failure during testing but i am collecting data for DNFs resulting from failure of tripod joint.

also it would be great if someone from Cornell can share what exactly was the failure during FSG 2011 endurance. I remember it was something to do with left driveshaft. Just looking for the word 'Tripod'.

[Jan_Dressler]

We nearly had a DNF because of a tripod joint failure in 2010 in Italy (our fault, the tripod housings were just too short for the amount of camber we run there). Luckily, and because of our drivers driving very cautiously, we got through.
This year, we had an electronic problem (fan not kicking in --> water temp too high --> trail of smoke --> meatball (guess the Marshalls have learned after some other cars caught fire)).

[Bemo]

Cornell did have a tripod failure at FSG this year. One of them told that it literally exploded. If you want to know more details you should contact them directly (there should be contact information on their website).

[TMichaels]

Originally posted by vandit:
couple of teams that i remember from this year's FSG event -

> for many teams engine did not start during driver change.

I just had a look at the timekeeping data: 11 teams made it to the driver change area, but were not able to get out on track again.

Regards,

Tobias

[Nicky]

Our on-board compressor for our shifter stopped working on lap 22 of endurance, FS Italy, 2011. Caused a DNF. Hard luck. Never have guessed that that'd go wrong...