I remember reading in a motorcycle magazine a long time ago that one of the top race teams was investigating an odd firing order, to get most of the power pulses closer together, and to leave a longer period of no power. I guess the theory was that the tire could recover from the power pulse if it had enough time, but that four evenly spaced pulses wouldn't allow the tire to recover.

I'd seriously doubt this without seeing any data. Wouldn't you need a dynamic model of the entire powertrain, plus tire frequency data as Kevin mentioned?

About the torque curve and gear selection, we tune our engine to be driven from 6000 to 12000 rpm on course. There is enough gear overlap that some of our fastest drivers choose different gears on certain sections of each course. So, that's not the territory of singles only.

I also have serious doubts about that Ashley, but wouldn't dismiss it entirely. I'd also like to see where you got that from and/or if you have other support for the theory.

Like Kevin (and a whole lot of other people I'm sure) I'm not too familiar with how tires dampen and respond to frequencies, but my instinct tells me that pulsing the tire harder but less frequently would result in worse tire dynamics. Seems to me that you would look at the peak of longitudinal loading to determine how much capability the tire has. Unless your driver can correct every pulse to get the most out of the tire I don't quite buy it. But that's my opinion without much to back it up.

Like Denny I'd compare our torque curve to a single's anyday.

(taking another dig)

i'd rather listen to, god forbid, rotary's than singles

I read a neat article back in the day about engine transient response. The editior was talking of how a motor with less overall power output can be quicker in a race than one with more power and less response. I always had a contention, after seeing fsae cars in person and in videos that the engines spend a lot of time getting to the power band than actually driving on it. That combined with the weight/power, I think is where some of the true on track speeds of these cars is can really be derived from. This is obvious to some of the senior guys on the site here but I felt it was worth mentioning to the discussion if people werent thinking it.

After re-reading that article. I wonder how many teams out there "recalibrate" a tach for sound testing. I guess it doesnt matter anyway because I hear all about how a lot of top teams cars get a lot louder on the track than they were at sound testing. Different maps? Conditioning tach signal?

Hey Frank,
I was at a vintage car race once. That had a bunch of group whatever prototype cars. Stuff like lola-judd and such. The kudzu-mazdas sounding like sticky ass sweat when they got off throttle in braking zones. Sounding like they were just breaking into little pieces.

http://www.theoldone.com/archive/world-according1whatishp.htm

quote:

I wonder how many teams out there "recalibrate" a tach for sound testing.

never heard of anyone doing that
***cough, cough***

The fancier tachs have "divider" options. Makes meeting sound regs a lot easier.

But I've never seen/heard of anyone doing that
***cough, cough***

the Kudzu's are all either 2 or 3 rotors (usually turbo, always with the 2 Rotors). They sound terrible.

but a 4 rotor sounds GREAT, IMO.

not ferarri V12, merlin or Gt-40/Cobra 427 great, but great.

Here's the story about the "big bang" theory of tyre grip, as I heard it.

The team was Honda GP500 (they were quite succesful).

The engineers got some riders to test two bikes. The bikes were identical except for their engines. After some laps on each bike all the riders gave pretty much the same report - "One bike screams and the other bike makes a droning sound. The droner vibrates more and it has less power".

The engineers checked their time sheets and scratched their heads. The riders were of varying ability so their times varied a bit, but each rider's time on the droner was about two seconds faster than on the screamer!

The engineers knew that the droner would vibrate more. The engines were 2-stroke V4s. The screamer had power pulses on 0/90/180/270/360 (ie. even), and was reasonably well balanced dynamically. The droner had power pulses on 0/45/90/135/.../360 etc., (ie. a bit like a big single), and was less well balanced. But on the dyno both engines gave the same power.

The time sheets (or data logging?) showed that both bikes had the same top speed, but the droner was faster through corners. Because of the faster exit speed the riders on the droner were reaching top speed earlier in the straight, whereas the screamer would keep accelerating further down the straight. Hence the misconception that the screamer had more power. So far (supposedly) this was all measurable fact. Now for the conjecture.

As the rider on the screamer opened the throttles at mid-corner the rear tyre would approach its peak force and then exceed it. Once over the peak the engine would increase speed (less resistance), the tyre would slide more, and the rider would have to quickly back off the throttles. However, the droner acted a bit like a pulse-width modulated power supply. The rear tyre would repeatedly pass its peak, but just as quickly come back to the "safe side"
of the hill. This rounded off the droner's tyre force hill, compared with the much sharper peak of the screamer.

The screamer could probably sustain a higher peak force than the droner, but no rider could get to the top of that peak and stay there. The droner had a gentler hill, possibly lower, but the riders could easily stay at the top of it.

Well that's the argument as I heard it. Sounds reasonable? Could work in FSAE? Would possibly work better with a 600cc thumper than a 400cc screamer (both singles)? Or with a supercharged 600cc single redlining (or choking) at 6000rpm (no need for gears)?

quote:

Originally posted by Frank:
(taking another dig)

i'd rather listen to, god forbid, rotary's than singles

I'd rather listen to Rotor than you, Frank....

As for the tyre "peaking" and then "recovering" debate, it is probably a point of idle conjecture. I don't necessarily believe that we here on this forum would have access to the right answer on that front, but one thing i would say is beware of slick salesman talk.

The Honda 500 GP scenario revolved around Mick Doohan, who was not only a damn good rider, but with the help of his Chief Engineer Jerry Burgess (?? memory ??) was a master tactician as well. Honda was supplying NSR500's to a number of top GP teams during the 90's, with Mick being the centre of HRC's development focus (with a supposed trickle-down to the other teams). At the start of 1995 (I think it was), everyone in the paddock noticed that the bike HRC wheeled out for Doohan for pre-season testing had a really flat sound - the droner. No-one else had one. Mick won lots of races that year, and suddenly all the other Honda teams were moaning that they were being fed second rate stuff. Championship to Mick and Jerry , dummy spits from the other riders.

Mick continued to win races on the droner over the next few years, with a few of these bikes filtering down to other teams - with little effect. All the while there were odd theories being bandied around, initially as to why the droner was so good (tyre peaking / recovering), and then later to why it suited Mick better than the other riders (Mick's dirt track background as opposed to the junior asphalt classes of most of his opponents, blah blah blah). More Doohan championships, more head scratching and soul searching in the other pit garages - some because they couldn't get a droner, others because they had droners and still couldn't win.

When it got to the point that most of their rivals had droners - Mick and Jerry got HRC to build them a screamer again. Suddenly Mick's bike sounded different again, and because he was still beating everyone the tables turned. The screamer apparently better suited Mick's developing riding style, suited the tyres of the time better, enabled him to slide easier - due of course to the contact patch not being able to recover between pulses.....

After Mick retired, he said that he couldn't have given a flying fish whether he was riding a screamer or a droner, they were just as fast. It was all just a bit of a mind game they were playing on the other riders. Touche.

Moral? Probably don't sweat over things that we have no way of knowing an answer. Fun to think about, but ultimately time-wasting. And also note that these were mind games being played where hundredths of a second make a big difference - we have a long way to go with driver consistency and reliability before our comp gets anything like that.

I could carp on for hours about the relative merits of singles and multis - and I have previously. And I'm sure if dyno charts of various singles were put up here, I'm sure any number of teams could argue that their engines are "better". I guess it depends under what criteria you choose an engine. It seems that some (most?) teams only choose/develop their engines relating to how they can maximize longitudinal acceleration - which is effective on, what, 15% of a typical Enduro/AutoX track?? We spent more time thinking about what all that engine size and weight was doing the other 85% of the time, (and if you think hard you'll realize that is not measured by the oft-quoted powerto weight ratio - more like braking power to weight ratio, cornering power to weight ratio....).

And did i mention the fuel economy event......

I'd been sort of hoping that with a few singles starting to do well, people would start thinking about their engine choices a little more laterally than just how they push the car forward. But engine-heads will be engine-heads....

Cheers all

"big bang" isn't a theory but fact of life for MotoGP teams, attempting to put 250+ bhp through one tyre.
Vale Rossi tested the 360 and 180 deg engine early 2004 and even though the 1st Yamaha Big Bang in-line 4 was down on power it made faster lap times. Yamaha did find the HP and Vale won the world title!
One point missed in "Z"'s excell. post is that the instant. torque peak at the tyre is doubled in the 360deg engine.
And given that torque is almost entirely a function of swept volume a 450cc single has 3 times the instant. torque peak of a 600/4, much less rotating inertia and 540 deg crank rotation for the contact patch to recover.
Yes, 5 valves versus 16+ means less peak power, but power to weight for a good single is 6lb/hp.

In the 1960's Stan Wallis in Adelaide built a "Big Bang" inline 6cyl for speedcar racing. I saw it in pieces so can't tell Frank how fast it was/crappy it sounded.
When I raced karts (remember the good old days Pat?) I noticed that the guys running twins spent a lot of time syncro-ing the engines to fire at exactly the same time. They said that any other setting was slower.
If the suprisingly ignorant senior citizens of this forum want tyre data, find info on why ABS brake systems are calibrated to do what they do.(to the tyre contact patch)

Oh Halfast, what did you go and do that for. I'd only had one minute of glory and you've shot me down in flames already. Hey, it is the middle of the day. Haven't you gots lawns to mow or something??

Cheers old stick

Sorry buddy, I was crapping on at the same time you were putting yours together! I'm watching the 1st round of the world superbike champs. If I am not very much mistaken 1/2 the field sound like big bang engines!
Last week at the GP while not perving, was saying to Rotor that some sort of ready to run engine package would be a huge help to many fsae teams, allowing them to concentrate on designing, building, testing a car, instead of spending huge amounts of their time just getting the thing running/tuned/staying together.
There was a Briggs&Strat 300cc drag engine on display. Owner quoted 34bhp @8,500 (but only for 12 sec) and a cost of A$15000!
But Frank, it sounded like a top fuel car at idle.

Crikey, this thread has taken off since i was last logged in......Thanks to all especially Geoff, halfast and z (whoever you are) who replied and probably explained the theory better than i could have anyway! and to the data question earlier.....No i have no data to support my claims on the tyre pulsing debate but i do know that i have seen how the power is put to the ground in our single cyl (most obvious during wheel spin at launch) with my own eyes and the theory certainly makes some sense to me but i do agree with geoff that the benefit is probably insignificant in the competition but then again each decision has to be backed up so hey the big bang theory for lateral accelaration is one extra tick in the box.

Ash

quote:

When I raced karts (remember the good old days Pat?)

Haha, I have to make one of my rare responses here =]
When I raced twin engined karts, I tested them with both engines firing together, 180 degrees apart, 90 degrees apart 45 degrees apart etc etc.
The method I finally settled on was this...
When I bolted the engines on the chassis, I simply put the chains on! Where the engines were relative to each other seemed to make no real difference apart from moving the vibration band to a different RPM.
What hurt the rear tyres on those karts (And boy, did we hurt the tyres!) was more to do with the lousy weight distribution we were forced to use and the 'band aid' chassis solutions employed to overcome understeer!
But you are right about the 'good old days' we sure had fun!
Pat

[QUOTE]Originally posted by Halfast:

Last week at the GP while not perving, was saying to Rotor that some sort of ready to run engine package would be a huge help to many fsae teams, allowing them to concentrate on designing, building, testing a car, instead of spending huge amounts of their time just getting the thing running/tuned/staying together.
QUOTE]

Agreed completely there Mr. Halfast. Would save a lot of headaches for many teams. I know that many would argue that such an arrangement would remove part of the learning outcome of the project, specifically for those who want to learn engine theory. But by removing a lot of unnecessary complication you might see more teams making it to the finish line (or in a lot of cases, to the start line....).

Might also lessen such oddities as when a team (such as one dear to us both) loses points in Design because it's engine package is "not complex enough". (Given that I see good design as achieving an end with minimal complexity, maybe we can take that as a begrudging compliment ).

And just in case I seemed a bit dismissive in the whole tyre response debate above. It is something that interests me greatly, and I've spent more than a bit of time wondering about it over the years. I was more commenting that the effect wouldn't be as pronounced given our amateur drivers and the higher emphasis on just getting the project completed rather than outright vehicle performance.

Cheers all

The latest (April 05) issue of Race Engine Technology (Ian Bamsey's sister mag. to RaceTech) has an article by Gordon Blair & Assoc. on big-bang MotoGP engines. Its more to do with intake pulsing in the airbox effecting engine power than with rear tyre grip.

The bottom line is that you just have to buy his Virtual Engine software if you want to be competitive...

It wouldn't be a single cylinder thread without Big Bird's contributions

Oh, and Frank... roll your sleeves up

I mentioned a while ago on this thread that I'd post how heavy the singles are

2004 Yamaha WR450 - 29kg

hey guys, i dont think i agree with your engine package ideas! In my humble opinion FSAE is what it is cause it needs a team to be one and integrate subsystems/designs/personalities to have any significant impact.
The option of an engine package in my eyes takes alot of the integration away. I do understand where your comming from, but maybe if its so hard to get right we should have standard suspension packages too!! If it was a racing series it would be a great idea, the last time i checked it was all about an engineering exercise.

Cheers

It seems that an ebay purchased F4i with stock injectors and Motec or PE Controller with a junkyard throttle, average diffuser section, ~3L intake and long runners practically is and engine package capable of 60+hp, 70+ if you get it right!