Clutch tuning.

Hi All,

After a bit of a base for tuning our clutch now we're making the power we want.

The setup is;

511ci Rodeck Chevy on alky
BacMan heads
14/71 Littlefield hi-helix @25%
Enderle 110 pump flowed by Spud Miller.
34degrees advance
2 disc AFT 11" clutch, 4 turns of base on medium springs, 21grams on the fingers, .430 finger height
Lenco CS2 with 2.01 1st
9.5" Toploader with 4.56 gears
36" new generation fuel tyres. Non beadlock wheels with liners, 6psi outers and 40psi inners

Our first two passes of the year this weekend, first run soft launch from idle. 1.30 60ft, 7.79@178mph (new PB on speed, and picking up 10mph from 1000ft)

Second run, launched off around 3500-4000rpm and blazed the tyres, pedalled and it kept spinning, pedalled again, shook for around 100ft then picked up. Incrementals are fairly worthless, 1.75 to 60ft, 8.30@177. This time picking up 12mph from 1000ft (leaned the main return from 80 to 86).

The track was a little cold, and burnout didn't really smoke the tyres heavily but the two previous altereds down the track ran 6.35 and 6.50 respectively so it can't have been too bad.

Sorry if it's all a little vauge, I'm just looking for what direction to be going with the clutch.

Videos of the runs
http://vimeo.com/40067511

 

weight

what does the car weigh? I am assuming it is an altered? Sounds like a lot of gear. I would try a lower first gear? Maybe something in the middle to high 1.80s area? Dave Germain

 

You virtually the same power train I have. I use a 2.07 1st and a 4.30 gear (right now) and I'm 2800lbs (door car). I imagine you are almost 1000lbs lighter and using the same ratio's I am. I agree that your gearing is not helping you, I don't think you will be able to take enough clutch out to get it launch good. Just my uneducated observation.

Maybe email Lenco they were very helpful when I was choosing my ratio's. They will also get you pointed in the right direction.

 

Changed the ratios at the end of last year, we were advised between 2.00 and 2.10 to get wheel speed up.

Car is an altered, ~1900-2000lbs

Read a bit about increasing tyre pressures .25 to .50 PSI to increase contact patch? When it does hook it pulls really well, just the first 60ft we need to perfect.

 

I believe Dave is about right you need a taller gear to help pull the motor down (calm it) a bit, that or you need a tall rear gear 4.10-4.30. They main thing I am reading is you either need more grip at the tires or you need to calm it down for the hit in the clutch and out to 100feet...does your wheelie bar play any factor into this..?? does it smack the ground during the intial sqaut/hit of the tire..if it does raise wheelie bar 1/2 if it is, also try the tire psi at 7 for more grip and take a turn of base out of it so it doesnt grab as hard.

 

I'm thinking more grip, more psi and a bit less base could be the answer. It doesn't squat overly much and doesn't smack the wheelie bar. On the idle launch it came out the hole fairly tame then pulled the front wheels 2" and carried to 300ft

Not a great shot but shows what I'm on about
http://www.facebook.com/photo.php?f...0640810396561.391167.665961560&type=3&theater

Will have better ones to show later this week inc a sequence from launch, spin, pedal, spin, pedal, shake

 

wheel speed

Do you have a Racepak or other data recorder on the car? Wheel speed can be a very important tuning clue but without a racepak to look at wheel speed at 1/2 sec and 1 sec everything else is just a guess. But my guess is that you have lots of wheel speed now. Typical 2300 lb TAFC in the states is running a low gear ratio somewhere close to 6.708-7.224. That is low gear ratio multiplied by the rearend ratio. It gives you a total low gear ratio. Yours is 9.165. So a lighter car than most TAFCs, a ton more gear, and I am assuming you ran at Santa Pod on a cold track last weekend? And you are surprised it spun the tires when you left hard? Dave Germain PS. Was your slower wheel speed because the motor was down on power? It sounds like you have fixed that problem.

 

We don't but are fitting one asap, just ran out of time with doing bodywork. Obviously this will give us a much better idea of what is going on for tuning. And being on a cold track doesn't help but other people had hooked up, in fuel and alky cars.

We struggled last year with wheel speed due to bad Lenco gearing and compared to you guys we get hardly any track time so just trying to make the most of what we do get and try to get ahead of the game a bit. The motor is making the power, just that first tricky 60ft! Running 36" tyres doesn't make it easy for us but they look better and we aren't trying to rotate the Earth with the car, 6.7s consistantly would be perfect.

 

fuel cars and A fuel cars use a totaly different clutch set up to what your using which is why they got off the startline
no pm or tafc rub good numbers early on
if you have the power you should have with that combo your gear will cause you problems for sure...your ratios are the same as we ran in the cuda @ 2700lbs if you need gear like that to get wheels peed you have engine problems,
with a 4.56 rear theres no reason you cant get down to 1.6/1.7 low gears the 36 tires wont hurt a lot they dont grip as well as the alky tyres as the shape is different
i know cause i run them on the pro mod,
who advised you that gear ratio??
the two 25% ratios you have for sale would be way better in your lenco, giving around a 7.1 startline ratio without a logger you are pissing in the wind when guessing wheel speed lack of wheelspeed if you have the right gear ratios either clutch or horsepower will be the problem, you should be leaving from 5000 plus to launch the car driving from idle wont ever work it just plain dosnt load the car ...launching too low id say from what you said is your problem, in a converter car you get away with it ...not with a clutch
i have some ratios available i think 25 and 41 in the lenco would be a good baseline
so you can move up or down from there,

 

Mike Canter http://www.insidetopalcohol.com/showthread.php?33185-Lenco-CS2-ratios&highlight= and Luke Robinson advised on Lenco ratios. With the 1.25 in first and second it was flat shit, drove through the clutch no matter what.

Now got a 1.44 in first and 1.39 second. Sure we don't have a power issue, Steve Turner is advising on the fuel and ignition tuning side and all seems well.

Launch RPM will be coming up when I'm confident it'll hook, but until then there's no point giving it hell

 

yes ok well im thinking maybe mike missed the fact its an altered,
with all due respect why wouldnt you ask nick davies as they run a similar combo and run fast
what luke has said is based on doorcar info.... with 36 inch tyres i ran a 4.30 and 2.10 low and always went between 1.02 and 0.98 in a 2700 door car,
we currently run approx 7.1 startline ratio in the superbird at over 2700lbs
with turner tuning why dont you ask him what low gear and rear they tun in the tafc

if it was flat with the low ratio maybe you had a power issue then maybe it was a bit too low but in my honest opinion (and almost everyone else here)your miles away now

 

hi Mike
don't you think a 2.01 low with a 4.56 is going to be real aggressive in a 1900lb altered
with a 14/71 blown rodeck bearing in mind there is no 6 shooter or retard system or data logging ability (yet)
wouldn't driving through the clutch with the lower (numerically) gear be more lightly to have been caused from launching too low causing the cf weight to not be effective assuming there is no clutch fault??

that sounds like a ton of gear for a lightweight blown car with decent power
and with the Turner family tuning they have decades of experience in TAD and know their stuff

Adam you run in a class of blown alky altereds with Joe running in the 6.3s now the ICE

car has been in the 6s for a long time using nothing fancy there are guys who know what you need ....dont you help each other

 

it wasnt in the original post mike but earlier in this thread he says there is no logger and i know the car there is no timing controll (that i have seen) on the car of any kind im sure Adam will clarify this

 

Hi Mike, it was the 1.25 first and second combination it drove through the clutch. Gearbox side we're sorted now - much appreciated.

Data logger will be going on before we run again.

Graham, I 've spoken to a few guys about gearing with altereds but none of them are running a 36" tyre, except the Bennett's (who have run 6.4s on them) but I never asked Luke to be honest.

Appreciate the advice guys, datalogger and better conditions will give me much more idea than one run on a cold track I guess.

 

What does the tire patch look like off the starting line? Is it waffling the tire at the hit or is the tire patch tight? Back in the day we ran that same combo and we ran a 2.08 low gear and up to a 2.25.

 

adam do you have a logger already i have a v300 that just has the two rpm channels and pick ups avaiable soon it works good and it can be expanded as far as you wantbut with those channels and the associated maths channels you get Engine rpm input shaft rpm/driveshaft rpm/clutch slip/engine,driveshaft ratio/trans slip/and trans ratio,
it can be expanded with any analog and v net stuff you want and works perfectly