450 or 600cc??

[JD232]

I was joshing around the sites of Formula SAE teams and I found that some teams prefer a 450cc engine over the conventional Honda cbr600 which seems to be tailor made for Formula sae series. Does anyone have any insights on benefits of using a 450cc engine over 600cc?

(p.s. Being a new member I did search for this discussion, and I apologise if this topic has already been covered.)

[Orion ZyGarian]

I'm new as well and also dont know. I would assume that it just doesnt make as much of a difference as one would think...maybe the weight savings is worth it?

[js10coastr]

There is no right or wrong choice here... choose one based on your design philosophy and have logical reasons to back up your decision.

As a matter of personal preference, I like driving a race car that has some balls when you get on the gas.

[Big Bird]

Hi Silverback,

FSAE is about balancing a number of competing (and conflicting) objectives. Engine output is great, but it comes at the cost of engine and drivetrain weight, cooling capacity and often fuel consumption. Your handling performance through cornering and transients is quite dependant on weight, and physical size (in particular track width) has a big effect through slalom type turns. Your strategy for the dynamic events has to take into account each of the above conflicting needs - basically you are never going to build a car that has the most power, and the least weight, and gets the best fuel consumption.

Your strategy for the event also has to balance your performance desires with your time constraints and your design and manufacturing capabilities. Your analysis and your lapsims might predict that a design "A" will achieve a 45 second lap around your test track, and "B" only will only achieve 45.2 seconds at best. But if design "A" costs takes 20,000 man hours and $40,000 to design and build, but design "B" only requires 2,000 hours and $10,000, then "B" has a good deal of merit.

Remember that in every competition around 60% of teams fail to complete the whole event. The racer in us all wants design A, but it seems too many teams won't step back from that high ground to accept something that might be a little less fancy but is more achievable. Any team of senior level engineering students can build a basic vehicle capable of finishing the event - it is only our own management decisions that prevent us from getting there.

Our choice in this whole 450/600 argument came down to the fact that in 2003, we had the smallest budget and the most inexperienced team in our teams short history, and we had failed to complete either of our previous two events (too much "design A" emphasis). We had to come up with something more achievable, or else risk losing uni support for the whole project. The 450 single would cost us horsepower, but we would gain back some ground in terms of size, weight, and fuel consumption. Being a much simpler engine package we could also get a running, FSAE legal engine on line much quicker, and we had a simple fall-back strategy if things went pear-shaped with the EFI (use carby and stock ignition with a restrictor plate in the intake).

If you are after an even more painfully long-winded philosophy lecture on why we went to a low-powered single, I started a thread on this a couple of years ago called "Life, the universe and our curious obsession with engines" - or something similar. It explains in some more detail where we were coming from.

Hope that helps

Cheers,

[moose]

I'd say at least up in the NE US, its also much easier to source a 600cc sport bike engine than a 450. If you look hard enough, its not difficult to get one for approx 1k, or less. Also - they are a little beefier - so sometimes its less likely you'll blow one up. But from experience, its not that hard.

It really just comes down to availability, and then a design strategy. There are plenty of advantages and disadvantages of each, starting with the obvious two in Power and Weight.

[John Grego]

We've won a 450, a 550, and a 600 and I would say if you are new then it is probably easiest to run a 600. Check out the thread http://fsae.com/eve/forums/a/tpc/f/125607348/m/16010883141/p/1 for more insight.

[rjwoods77]

Geoff,

Can you send me your personal email to rjwoods77@yahoo.com I didnt get it from you before so I can write to you off of here.

[flavorPacket]

one thing that I've never heard from a 450 team is a good counterpoint for the loss of education/experience with multi cylinder engine dynamics. It is a huge part of general IC engine theory that 450/single teams never get to touch on.

While this may not have any consequences in FSAE, I believe that running a 600 can potentially teach someone more about engines than running a 450. There are only a few teams out there, however, that have reached a level where such a difference would be noticeable. It's up to you to determine how important knowledge is to your team, but I can tell you that this is one of several reasons that my team uses a 600 and not a 450.

[Pete M]

I'm sure the RMIT boys will argue that if you don't have to spend the time figuring out multiple cylinders, you can spend that time figuring out something the car's performance is more sensitive to. We run a turbo 600, and we have our reasons, but that we'd learn more isn't really one of them (although you sure do learn a lot if you down that route...).

Following the "what will make us learn the most" path to its logical conclusion leads to an extremely complex car. I believe FSAE is primarily a project management competition. Building a simple car, getting it running early and reliably finishing every event is better management that building an overly complex car for the sake it and not getting it running right in time for comp.

So... unless you have competed several times and finished the enduro, do whatever is quickest and easiest. For some that's a 4 cylinder, for others it's a single. Once you've got that right, you can think a bit harder about what the optimal solution for the competition is (if such a thing existed...).

[Kai69i]

Hi Silverback,
I'll be the first to admit that I am biased on this one due to the recent success of our team with the 450 single, but I honestly believe that both alternatives can be made to work in on-track performance terms.

I have been hanging around Geoff way too long, but whatever the concept you select, you will need to present a clear, well argued and justified case as to why the selection has been made (particularly for the Design Event).

In my few years in FSAE, the limiting factor each and every year has been time. With a workforce of volunteers driving the project while completing their engineering degrees in the limited spare time they have, commitment on the same levels that paid employment would yield is often challenging for the best of us.

Although having said this, I don't personally believe that there is any more complexity in running a 4 cylinder 600 over a 450 single (although let me clarify my standing here before anyone tries to contradict me).

It takes no more time designing around, or getting the 4 running relative to a 450 single (other than in Mr. MoTeC terms for the tune). I understand that it would typically take more time in areas such as induction and exhaust, but I will confirm that we probably spend more time in this area with the single than any teams do running a 4 cylinder engine!

It is just when any problems arise with the 600, it becomes more complex to deal with; more components and hence a higher probability of failure and the likelihood that things can simply go wrong.

As Geoff pointed out, more than half the teams at each competition fail to complete the entire event. With the points structured as they are, a DNF in a single event puts pay to even a decent finish at all competitions around the world today. If risk can be removed in this area by running a single, why wouldn't you do it?

Having said this, I am still a big fan of the 4 cylinders. If I am not mistaken, a 600 won the Detroit competition this year, by placing 1st in Design and 2nd in the Endurance/Fuel Economy Event. Hence, both concepts can be made to work on the track, as well as be properly justified to the judges in the Design Event off the track.

Although I personally believe the tracks are making it more conducive to run a single each and every year, by virtue of the rule changes for 2009 (particularly the cockpit opening), the 600 will remain just as competitive as the single (if not more so in theory). This however needs to be weighed up against Mr. Newton's F=ma, as the additional mass of the 600 is a mere liability on the way into, and in the corners. And lets face it, there are plenty of low speed corners in today's FSAE tracks as well as a lack of high speed straights; mainly due to political and safety reasons.

One thing I would like to point out with the cars that have won the major competitions this year (RMIT and University of Wisconsin – Madison), is that although vastly different in concept (4 cylinder spaceframe to single cylinder carbon fibre monocoque), both are relatively simple cars which merely get the job done. No tricks or allusions: just whatever you turn up with at competition, make sure it can finish all the dynamic events, and you can present a good argument to the judges as to why you have gone with the concept.

I am fairly confident that this is not the technical response you were after when you made this post, but I hope it has given you another perspective of the important areas which must be considered in FSAE Competition.

Cheers,

Kai

[blister]

One thing I would like to point out with the cars that have won the major competitions this year is that although vastly different in concept (4 cylinder spaceframe to single cylinder carbon fibre monocoque), both are relatively simple cars which merely get the job done

We need to add Stuttgart here, who won in Germany with a "simple" car. "simple" is a harder to achieve than "complex"...

[Peter7307]

There are more points to consider besides the technical merits or lack of them pertaining to each engine.

Costs and sponsorship can be a (sometimes THE deciding) factors in any racing team's budget and subsequent plans and desires.

Familiarity with the operating machinery ,as some have already mentioned , can be one point not requiring more resources than necessary. This obviously means those resources can be deployed elsewhere to ensure the team at least manages a finish result of some sort.
Personally speaking motivating a team after several DNF results can be a heart breaking exercise.

An interesting thread.

Pete.

[flavorPacket]

Kai,

great post. I think it essentially sums up this discussion.

BUT, I believe you're mistaken about FSAE courses becoming tighter. At FSAE east this year the average speed for autox was over 37mph, the fastest in several years. The course at FStudent, however, bordered on being illegal in my opinion. There wasn't one corner that could be characterized as 'big radius' by the rules, but this is neither here nor there. I just wish that the various organizers could come together to make a standardized FSAE track style. It's rather difficult to optimize a vehicle when you don't know what course it will run on!

To the original poster,

I hope it's pretty clear by now that your engine choice depends a lot on your team's particular circumstances. Both engines are capable of powering cars to win the competition. It's up to you to determine how to best maximize your resources to meet your goals.

[Hot Rod JayRad]

To answer the original question:

We made our decision based on a many things. A few considerations included
-ease of packaging
-shape of power curve
-cost of parts

As with everything in the competition, its an engineering dilemma. Whichever you choose wont be perfect. My opinion: you are better off not spending too much time deliberating about it. Instead, make a decision, and spend more time making it work the way you want it to.

[VFR750R]

600cc. Why, torque. Regardless of the number of cylinders you choose, any team should consider corner exit accel to be highest priority. It factors into all straightaway lengths. A 600cc engine should and typically will have 30% more torque (assuming all else equal) then a 450 at below choke engine speeds and therefore has more acceleration, and a 600cc single car doesn't weigh 30% more then a 450 single car.

Engine availability aside. If weight was purely a function of displacement it's hard to argue against 600cc. Although real engines that are available require many more things to be taken into account.

[Kai69i]

Engine availability aside. If weight was purely a function of displacement it's hard to argue against 600cc. Although real engines that are available require many more things to be taken into account.

Hi,
I couldn't agree more, so I thought I'd go into the specifics of those things which should be taken into account (as you have indicated).

The weight reduction associated with going for the 450cc would be an absolute waste if it were purely a reduction in the mass of the engine. You would be giving away a significant performance advantage if this was the case; however it is not.

Although closed loop cycles are usually dreadful, the weight reduction one is far from. The reduction in torque from the single means that driveline components can be downsized, which leads to significant weight (and inertia) reduction which in relative terms is more appropriate than purely comparing engine mass and torque figures.

The smaller engine also leads to a far narrower track as a result, and hence a lighter chassis if you know what you are doing. There is also the opportunity to run the minimal wheelbase required by the regulations (if the suspension guys are not protesting!).

A lighter vehicle also means that smaller wheels can be utilised. Hence, gains can also be made in unsprung weight reduction, as well as in the ratio of unsprung to sprung mass (which is one of the most significant factors in FSAE competition)

Less vehicle mass also means that components such as brakes can be downsized (don't forget Mr. Newton's F=ma). This leads to even further gains in weight reduction terms. Smaller uprights and hub dimensions also lead to a substantial weight reduction.

The major benefit of the single within your vehicle is in running all the same components as with the larger engine, but they are all far smaller in size (as mass); drive shafts, chassis, brakes, wheels, uprights, differentials, etc (you name it). Hence, it is not appropriate to only compare the mass of the engines and the torque in which they produce.

My final point is that on a typical endurance lap, the cars would be lucky to spend 20% of their track-time at 100% throttle. Hence, the additional power and weight of a 600 concept vehicle is an absolute hindrance for the remaining 80% of the lap (think of F=ma again through all those corners!).

Having said that, I wouldn't mind the 600 for a couple of acceleration runs at each event!

That's my perspective of the scenario anyway; more than happy to discuss.

Cheers,

Kai

[flavorPacket]

Kai, I don't understand what you're saying about a single giving you the ability to run a 60" wheelbase. Wisconsin runs that comfortably with a 600, and we will also do so in 2008.

[Igor]

Kai, I don't think you can downsize your driveline components when you go to a single cylinder engine.
Peak torque is quite a bit higher, it's not an electromotor....


Igor

[Kai69i]

Hi Walter,

Let me clarify my stance, as a little was lost in the translation on my behalf. I concede that it is possible to run the minimal 60"� wheelbase with the 600, but my argument is that it is far easier to achieve this when using a single (if that is what you want to achieve).

I personally don't believe that running the minimum wheelbase required by the regulations is a good option with the single (and a number of teams running a single don't for a few basic reasons), but I am saying that should it be your choice, it can be implemented using the single with your eyes closed.

I am not sure what the majority of teams are running at the moment, but Cornell for example were running a 64"� wheelbase of late (and may still be). Our team has not used a 600 in more than five years now, so I cannot relate personally to the 600 in this argument.

Can anyone else? Reply to the post....

Other concerns in my opinion- rear weight bias issues with the minimal wheelbase configuration and a 600: most evident with many (not all) cars at Formula Student UK this year on the super grippy circuit.

Thanks for your clarification.

Cheers,

Kai

[Kai69i]

Kai, I don't think you can downsize your driveline components when you go to a single cylinder engine.
Peak torque is quite a bit higher, it's not an electromotor....

Are you serious???

You are not getting confused with shock loading considerations are you??

[-M-]

Driveability is another consideration when deciding between a 450 and 600.

Due to a narrower torque band with a 450, more gear shifting may be required, and due to more serious shock loading through the powertrain with a 450, a slightly less stable rear-end may be detected under acceleration.

Your drivers may well be up to coping with these two issues though...

-M-

[A Richards]

Due to a narrower torque band with a 450, more gear shifting may be required, and due to more serious shock loading through the powertrain with a 450

-M-

Not sure weather you will experience a narrower torque band with a single, our engine, KTM 525, can pull any gear just off idle and because of this we are widening the ratios this year to avoid needing to change gears quite as much. Also not sure why there will be a greater shock loading with a 450, it all makes no sense to me, would like to hear some justification for why this would be the case. I would argue the opposite.

[Kai69i]

Hi,

I'll endeavor to get our diff man to put some more in depth wisdom on this post than what I can offer, but here is a start.

The shock, overload or service factor is associated with acceleration torque in particular in the case of the single; with the total engine torque being the sum of the fuel toque (produced on the power stroke) and the inertia torque (which the crank will contribute to in all cases except if the engine speed is constant, and also the piston, con rod, etc contributing too).

These components will vary with engine speed; with the fuel torque dominating at low engine speed, and inertia torque dominating at higher engine speeds (as would be expected, since it is proportional to the square of the angular velocity of the crank).

Hence, in the case of the single where only one stroke of the four in the cycle is doing work, shock loading needs to be taken into consideration due to large torque variance across the cycle (remember that 4 cycles are not occurring simultaneously such as in the case of the 600).

This occurs even when a flywheel is used on the single, as the variance in torque across the cycle will still be large (particularly at high engine speed).

My thought is that this is the point Igor was trying to get at on the previous page of this post. Although such a shock factor would mean that you would be required to run a slightly more oversized drivetrain configuration than would be required if the shock loading wasn't present, the drivetrain components will still overall be far smaller in size than required for the 600 (say in wall thickness and outer diameter of driveshafts for example). After all, as previously mentioned the 600 will probably be producing about 30% more average torque than the single (basic assumption based on displacement and all other parameters equal).

Have a look at some equations for shaft design- just considering a solid shaft for the moment as it is theoretically far simpler. The diameter will be proportional to the square of the torque- not just a constant multiplied by the torque. Hence, an almost doubling in the torque will result in a shaft four times as thick. This was my initial point when I stated that weight reduction also came from this area when running a single.

Have a look at the following site for shock factor values:

http://www.gearcalc.com/downloads/manual/manualse60.html

I think these values are pretty good. Common design practice for the single will typically be a shock factor of 2.0 to 2.5.

More than happy to discuss anyway (as always!)

Kai

[VFR750R]

kai, If you only consider a 600 single to a 450 single, the wieght loss is minimal. You explain this downsizing displacement allows a substaintial weight loss in other areas and i beg to differ. 10" wheels can be run with 600 or a 450; 4 cylinder or single.

There are many more components that weight loss would be very small and the sum would also be small. For instance a 50lb reduction in mass in a 350lb car with 150lb driver would allow for a 10% reduction in strength of loaded parts like a-arms, uprights, spindles, framework ect. But those parts account for only ~25% of the car's weight. The multiplication factor you speak of has diminishing returns as driver, seat, wheels and tires, engine, cooling system, steering, shocks, intake/exhaust, become even greater percentages of the weight. Plus buckling, stiffness, and availibility of parts makes changes like that never turn out as good as orginially concieved. 10% less strength may not be 10% less weight, and almost certainly will mean more then 10% less stiff. For instance, you could reduce your a-arm tube wall cross section by 10% but reduce stiffness by twice that in bending and run the risk of DNF from a cone.

Not to say you won't be able to downsize, but it's not as straight foward as it appears. Obviously if you have a 600lb car, weightloss should be an easy endevour and most certainly will mean an increase in performance.

And it's much harder to argue the 600cc 4 cylinder over the 600cc single. There is a lot of weight lost for the small change in WOT performance. That's where a turbo comes in. If you're going to run a 4 cylinder, how could you not go ahead and add the ~10lbs for a turbo system. Torque gains are huge, like being a 900cc engine for only 10lbs weight, and with short headers and less muffler the weight gain can become almost negligible. Similar can be said of turbo or blown singles although they have a much harder time handling the extra stress and the manifold dynamics are much more difficult to deal with.

[Kai69i]

That's where a turbo comes in. If you're going to run a 4 cylinder, how could you not go ahead and add the ~10lbs for a turbo system.

Hi mate,
I knew you would manage to sneak the turbo in at some stage!

Your arguments are very good, and coincide well with the law of diminishing gains- as our team has found with sub 150kg (330lbs) cars over the past year or two. I also agree with the fact that some gains never turn out to be as nice as anticipated (as we have also found).

I respect your approach; Cornell as a team obviously have a long and successful history within FSAE in the US, and hence were obviously doing a very good job with wins in '04, '05 and many years previously.

Although the turbo system for 10lbs is a wonderful gain in engine performance to weight terms, I would argue that on the modern FSAE circuits, they push the cars to the limit of being undrivable for about 80% of the lap. There are also so many more tight and twisty sections than was the case as little as 3 years ago- hence it is hard enough to properly get the power down from the single coming out of slow corners, let alone a turbo charged 4 cylinder 600!

You could argue this is where traction control comes in. I argue that this is where simply finishing all events comes in; this is hard enough without introducing unknowns such as turbos and electronic aids. You can also write off the fuel economy event with this approach!

Anyway, I like your arguments and I think they are all quite valid. This is also the beauty of FSAE, whereby any concept/configuration can be competitive at any event.

What is your name by the way? I keep going to refer to you as VFR

Cheers,

Kai

[Biggy72]

Why do you think that turboing a car will kill the fuel economy event?? From what I've seen Wollongong has done pretty well in that event. I'm assuming that they turn their boost way down specifically for that event which hurts power, but for the endurance power isn't as big of an issue as is driving smooth, not hitting cones, and finishing.

[VFR750R]

Kai, my name is Judd. RMIT has proven that the small car/engine can be very fast. Texas A&M and others have proven it as well. I agree that it's too complex of a question to have a single answer at this point.

Many teams maybe right about 80% of the time you're NOT at WOT. With more power, you'd expect to spend even less time there. Since 4 cylinder cars are still ultra competitive, even ones without the added power of turbos leads me back tire linearity. It also brings in load variance, since light cars typically have higher unsprung to sprung ratios, and tire temperature vs weight and it's effect on grip.

Traction control is nice, but it doesn't give you more grip.

My personal opinions with respect to tire load-grip linearity, mean i feel a high CG rear weight bias car will be faster.

Anyone do a study on tire temp/grip vs weight?



This will start something.

http://www.roadandtrack.com/assets/download/0207_FormulaResults2.pdf.pdf

Notice the fastest car 0 to 60 and 0-100ft for east and west were turbo 600cc. Our car gave nothing up in slalom or braking. From 20-40mph(what i'll assume to be majority of straights), it takes turbo cars less time. Do i think that's the end all of fsae performance, no, but it also shows that accel, braking, and slalom don't tell the whole story. It also shows that on two different days on the same course layout a 600cc turbo or a single can be fastest. The devil's in the details.

[Pete M]

Yeah, we used 3.4 L of fuel at our last comp. That's not terrible, but we're still pushing pretty hard to drop it further. 3.4 L was only good enough for 8th. I believe cornell have won fuel economy at least once with a turbo though.

Fuel economy has nothing to do with what boost you run and everything to do with how efficiently you make power and how efficiently the driver uses that power. The other totally massive factor is the weight of the car. If you're hauling around a car that's 50% heavier than the other guy and you've got the same power to weight ratio, you're making a lot more power and using a lot more fuel.

As for VFR's comment, i agree. If you've taken the route of the heavy, powerful engine package, see it to its conclusion. Go for maximum average power to weight over a typical driving rev range. Just also make sure that the points you gain in speed exceed the points you'll lose in fuel due to the heavier car.

[mtg]

Originally posted by Kai69i:
Although the turbo system for 10lbs is a wonderful gain in engine performance to weight terms, I would argue that on the modern FSAE circuits, they push the cars to the limit of being undrivable for about 80% of the lap.


Sounds like somebody needs better driver training. Undriveable for 80% of the lap? I'm pretty sure I could have handled an extra 50 hp without making the car undriveable (as long as the powerband was somewhat linear).

[flavorPacket]

mtg,

you only say that because I think you haven't seen the european or australian tracks. At student this year, we protested the course because it was so tight. The FSAE-Aus course and FStudent courses are not at all similar to the 2007 east course.

[Pete M]

Yeah, that was indeed a problem at Aus last year, and is part of the reason that we did not do as well as we'd have liked (not the biggest part though, mostly we had no testing time). The autocross run that got us third in the event was on no more than 60% throttle (mind you, we see boost at that throttle setting).

It wasn't that the track was overly tight, really. It was more the near total lack of anything resembling a straight. I'm all for having a crazy tight hairpin and a few chicanes that really force you to make an agile car, but when you spend most of the track in near-constant-speed alternating corners, it sucks a lot of the fun out of it.

Quoting rule 5.7.4:

"Course speeds can be estimated by the following course specifications. Average speed should be 48 km/hr (29.8 mph) to 57 km/hr (35.4 mph) with top speeds of approximately 105 km/hr (65.2 mph)."

I really don't see how the track last year was a legal FSAE track. It's not like Aus has always been like that though. It was before my time, but apparently the 2004 track was borderline illegal the other way, consisting of virtually nothing but drag strips. Neither is good. We'd love to see a highly variable track with lots of different stuff in it so it's not just constantly testing one aspect of the car and ignoring the others.

Why don't we make a car more suited to last year's track? Well firstly, i'm hoping that the officials this year will find a few places on the track where they could put in a respectable straight. Higher speeds are not necessarily unsafe. The runoff is grass, but there's plenty of it in places. And if the straight is done sensibly, with a couple of cone chicanes well before the end of the tarmac, the chance of leaving the track is pretty remote. Worst you'd do is plow down a bunch of cones and cop a massive penalty.

The second reason is that our car absolutely loved the 2006 West track and we were extremely competitive there (you better believe the drivers found full throttle and it was drivable). We don't want to make compromises that will affect our performance at future US competitions (we're hoping for detroit next year). If the aus track doesn't change, it puts us in a bit of a tight spot. Do we optimise for our local comp and be less competitive overseas (with the exception of FStudent) or do we gun for the world championship and struggle at Aus? For the teams that have never been to a US competition, basically there are straights where you're full throttle clicking up gears for a good few seconds, often with fast sweepers leading into them.

[Bill_Murray]

I am coming into this a little late, but I don't understand the lighter drivetrain components with the 450. Assuming you have enough power to spin your tires at least at a stop, the strength of your drive train components should mainly be dictated by whatever torque it takes to do that. There can also be additional torque that would be proportional to the inertia of the drivetrain and whatever rate you could accelerate those components in a wheel spin condition, but this is a significantly smaller torque load then the initial torque to spin the tires. So the torque should be similar for either engine given the same tire. (RMIT might run light drivetrain components because they run 10 inch tires that don't put down as much longitudinal force?)

As far as the shock loading from the combustion stroke of a single vs 4. It would seem like if there is a significant shock it would be absorbed by the elasticity of every component in the system, especially the drive shaft. The rotational inertia of the drivetrain up to the drive shaft is the only inertial mass to be accelerated by this 'shock' and the toque required to accelerate those parts seems again somewhat insignificant next to the wheel torque.

Just my thoughts on the subject, be happy to hear contradictions and counterpoints

[rjwoods77]

Getting away from performance for a minute. By running a single you have less injectors, coils, less stainless tubing for headers, less alum/carbon tubing for manifold, smaller lighter cooling system(less fluid in the block at approx 8lbs/gallon) all make up for points on the cost report whih is what we are really designing here which is a consumer vehicle right? On the same note as cost as with weight you lose weight in all the little spots that can add up. Also with better fuel economy due to less BSFC you save on fuel wieght and fuel tank size. You lose frame members trying to support the stock cbr mount locations vs the simple mounts I have seen for the 450wr ala Lehigh. By chocking up the wheelbase in the car due to smaller packaging you dont have to run those frame members way past the front wheels to accomodate the drivers legs. (i.e little overhang unless it is cosmetic/attenuator i.e RMIT)The weight difference between the engines is only really part of the story and to ignore the rest is kinda foolish. Turbo system isnt just the extra 10lbs if that is accurate. Does that count for the weight/cost of an FPR, wastegate/BOV's, intercoolers if run, possibly heavier manifold? What about the cost report side of things? I would have to imaging that a turbo system would add approx 1000 to the report but I could be off since I havent tried to creatively account for fake costs. I would just like to note that I am super impressed by the turbo cars and dont dislike them. Just dont think in the long run they will be as viable as they once were since people are getting smaller packages to work better and better.

[VFR750R]

I am a fan of reducing the front overhang, it makes since if anyone's seen a backhoe go down the road. We've always run a YZF600, but the newer 600's are shorter front to back. How much longer is one then a ktm525 or something.

You can get our turbo from an online retailer for $485 last time i checked, and there is no intercooler or bov in our system. Our intake manifold has always been more prone to buckle from high rpm manifold vacuum then boost. ECM, injectors ect cost the same. Muffler probably costs enough less to offset extra tubing required. The turbo itself weighs just shy of 8 lbs, and the extra intake plumbing (aluminum) weighs in at less then a lb. Exhaust primaries are shorter then many NA teams run, and the muffler is also very small. There are two extra oil lines for the turbo but they don't weigh a lb between them. I'd imagine 10lbs total increase is maximum to be honest, at least for our system. A team could add half that with a variable runner length manifold and actuator, and not have half the increase in performance.

This is where that mahle 3 cylinder comes in. Turbos love 3 cylinders, you can move the transmission behind the rear tires. Less distance from seat back to rear axle line, probably almost as good as a single. Narrow, so turbo can be low on one side, cooling system low on other side. Diff integrated into trans case, less overall weight for driveline system.

In practical terms, the parallel twins out there don't seem like a bad choice either. The v-twins are narrow like a single but seem like they'd have an even longer overall length then the 4 cylinder engines. T A&M care to comment?

Noone seems to want to sleeve a 650 hawk or SV650 either which seems like a shame, although they probably weigh close enough to a 4 cylinder that it's not worth doing.

[rjwoods77]

VFR,

My packaging contention with 4 cylinder bike engines is that the cylinders are leaning the wrong way. They force such a large distance from the main roll hoop plane. Any inline engine mounted transverse and leaned backward 30 degrees with the gearbox and diff underneath it would be a super efficient mounting scheme. Image if the 450wr was leaning the "right" way. I bet RMIT could move their driver/wheelbase offset back at least 6 inches if they so desired. I just dont get it when people longitudal mount engines because it takes up so much room because of how it forces your body away from the rear axle centerline.

V-Twins package real well if you use the right one. I have plenty of reasons to go with the 590cc Briggs and one of them is that since they are a pushrod engine they are really short and that you can put the inboard cylinder right under your back. You can see in this pic I made with some dimensions.

http://i194.photobucket.com/albums/z36/rjwoods77/2007formulacar.jpg

We are able to lean over the engine hence the super short distance from the main roll hoop to the axle centerline (19"). Our rear suspension also contributes to this packaging benefit but a irs rear suspension would only add 1 inch to that assuming you put a gearbox under the inboard cylinder and ran a chain to the diff mounted right under the outboard cylinder. Or if you ran the cvt and ran the chain to the diff. The chain would go between the primary cvt and the engine which makes the side cover of the engine a nice place to put a chain tensioner. There are tons of other benefits to it but the other sweet one is lack of cooling system. A whole ton of weight can be dropped from radiators, mount and bracketry, 1-2 gallons of coolant at 8 lbs a gallon, and whatever bodywork you make to direct air. I guess I am combining this topic and the "ever popular diet" post but they are really one in the same. The briggs will put out 50hp reliably and that is what I intended in the design because it became clear to me when I started that power isnt really needed to finish very well if not win. Dearborn proved that for the last couple years and especially this year(400lbs with 42hp,10:1 power to weight) as if they didnt break they would have finished top 15 with a generator engine. Cal Poly SLO finish 12th in west 2006 with a carbed 450wr a solid axle and infinite rear roll stiffness. (319 lbs with 23 hp,14:1 power to weight). RMIT I dont have to even talk about because we all know. In both cases, and I hope with ours when it gets going, it seems like packaging and weight reduction schemes are really bearing fruit over the other direction which so many teams have copied your teams recipe(turbo or not) over the past 10 years. It really catched my attention to see teams with half the power to weight ratio doing much better than most due to packaging and weight concerns. Point being without talking about drivetrain loads which for the same torque levels have to built just as beefy there are a whole lot of frame members, body work, etc. that can be tossed if innovative engine packaging is used with a motor that allows for it.

[rjwoods77]

Vfr,

Figured I would throw this in the pile as well. I am always talking about using the Jawa 500 air cooled engine on E-85 and making a airshroud and a squirrel cage blower to force air onto the fins. Crank mount or electric whatever. Exhaust out of the back and intake is on the firewall side which has plenty of space to mount a plenum. If you mounted it in this config in our chassis we can shorten up the 19" dimension by 3.5" inches just simply switching motors. If done with an irs it would be laid out a little different but you still can get a choked up diff placement.

http://i194.photobucket.com/albums/z36/rjwoods77/2007formulacar2.jpg

The entire frame structure in the back is replaced with the sketches you see there. Just a 30 degree roll hoop support bars 6" inches from the top of the hoop and the secondary bars need to support those that run 30 degrees toward the car via the rules. The engine would be supported using the same setup Lehigh used to mount their 450wr a couple years back with aluminum plates mounted to the firewall. Rear frame structure basically the same as Cal Poly SLO. I am showing the rear axle articulation but also threw a 4 circle for a torsen diff if an irs was thought about. Again by going the other direction and simplifying and taking a hit on horsepower for super efficient packaging and weight reduction through simply eliminating things that dont need to be there. Less of everything, better cost report score, much less weight has recently shown to be competitive against the monsters out there.

[Pete M]

Really there's two arguments i can see for a 450. The first is weight. Light weight, low power is a design philosophy i don't really agree with, but if the tracks continue to contain increasing amounts of constant speed cornering, then power is not needed anyway. The other big argument is complexity. Your headers become a pipe. Engine manufacturing takes less time so you've got more time for taking weight out of other systems or for more driving. There's a lot to be said for doing something very simple when you've got an inexperienced team.

On the other hand, if the rest of the car is going to be heavy, putting a cookie-cutter 4cyl package on it is going to make the weight less painful. Cars with gutless engines really need to be light or their power to weight is terrible.

As for the engine leaning the wrong way, nah... that's just where you fit your turbo. http://fsae.com/groupee_common/emoticons/icon_wink.gif

[VFR750R]

Pretty cool concepts. Without a gear box and OHC head that briggs looks to be a packaging gem. The jawa 500 look great too. Why not a transaxle mounted to either? Does it just defeat the cost benefits? or were you only considering solid rear axles?

how much does that briggs weigh?

[Kai69i]

The FSAE-Aus course and FStudent courses are not at all similar to the 2007 east course.

Hi Walter,
Thanks for backing me on this one; this is the point I have been trying to make since page 1 of this forum in regards to compromise in vehicle design.

I think that many of the US teams who have never competed abroad don't really understand what other teams face outside the US with track layouts (particularly compared to Detroit). I will choose my words carefully here, but the Australian track last year was not ideal. The FSTU track this year was also far from ideal.

For the record, if we were only competing in the US, I personally believe our car would be vastly different to what it is. But given we compete on 3 continents at the moment, the package has shown itself to work well on different track layouts.

I hear the Detroit autocross track was good this year, with average speeds quite a bit higher than previous years. Here's hoping on behalf of everyone that this is reflected at some more events in the future.

Cheers,

Kai

[rjwoods77]

I must say for how low tech the thing is that it is well build. Says made in Japan on it so I dont know if it was designed for briggs or just manufactured. Tucking stuff under the cylinders is nice to keep it tight. Currently I think it weighs 80 lbs without the exhaust but we still havent bought the aluminum flywheel that will drop 9 lbs more off of it. Not that lightweight but overall it works well. The jawa packages waaaaayyyyy better and is lighter. Most likely more power due to the fact the Briggs is limited to about 8000rpm. Sounds really cool too. The jawa spins to 11k.

http://fsae.com/eve/forums/a/tpc/f/125607348/m/91910406041


Tranaxles while really cool and tight only if you make it stressed doesnt meet the cost and theme of the competition in my eyes. More so that that is the concept of no diff. UQ, WWU and a couple teams have not run diffs in the past with good results. Cal Poly SLO murdered everyone in handling in West on 23 hp with a similar setup to ours. Diffs cost a bunch in weight and money. A set of good halfshafts cost and weighs a bunch of money. My 8 lbs 51" 7075-t6 axle costs 250 bucks and I can get one in a day since it is a 600cc sprint car axle. So on the cost and weight I am really far ahead. Again decisions based off the intent of the comp to provide a cheap, durable consistant car. The packaging is even better because all the rear suspension attaches at the firewall. If done right, Jawa style I can cut the entire rear subframe out. More of that "dont even use it and it wont cost weight or money" thing again. My theory was if you are going to use a spool then why bother with a double a arm. Just going to squat and lose traction and all the other assorted hassel with having all that extra stuff back there. Also I have a hard on for cvt's. No shifting, clutch pedal, clutch lever, cable etc. Less crap. It also allows for a longitudally reverted drivetrain that make packaging really compact. The entire car is an exercise in packaging. It is way overweight (approx 375) since almost nothin was FEA'd and such but it is a first gen car and the team is working hard to finish and also to work on the future stuff. As far as handling tuning time is obviously necessary but Cal Poly SLO is running a similar system, with a different linkage config, and they did really well. I'll send you a couple papers to look at if you are intersted. Send me a PM with your email address.

[rjwoods77]

Kai,

You guys would have most likely ripped it up. University of Applied Sciences - Graz finished 9th in Autocross and I believe that was the highest single cylinder place in Autocross and I think your car is lighter by a bit so...

[Kai69i]

Rob,

We will need to start a new post on the forum: "Keep the FSAE East Autocross Track Intact for 2008!"�

I'll tell Geoff to also have your personal tee-shirts ready to go for the event!

Cheers mate,

Kai

[Superfast Matt McCoy]

Originally posted by Kai69i:
Rob,

We will need to start a new post on the forum: "Keep the FSAE East Autocross Track Intact for 2008!"�

I'll tell Geoff to also have your personal tee-shirts ready to go for the event!

Cheers mate,

Kai

If you're pushing for that track, you'd better be well into your aero package design.

[FryGuy]

Originally posted by Superfast Matt McCoy:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kai69i:
Rob,

We will need to start a new post on the forum: "Keep the FSAE East Autocross Track Intact for 2008!"�

I'll tell Geoff to also have your personal tee-shirts ready to go for the event!

Cheers mate,

Kai

If you're pushing for that track, you'd better be well into your aero package design. </div></BLOCKQUOTE>

That is an extremely good point. If the autocross tracks keep going that route, aero definitely becomes alot more relevant. You guys (Oklahoma) and UTA pretty much had the rest of the field by a full second in the autocross at detroit.

[Kai69i]

If you're pushing for that track, you'd better be well into your aero package design.

Hi Matt,
We are all over it.

Cheers,

Kai