sp2816

The size of the headers will have an effect, but I found that the length played more of an effect. There are some calculators out there for doing this for the exhaust pulses, but I think that you will want to make sure that your primary tubes are around 32" long. The longer that you can make them, the more it will help on the torque.
I tried shortening the headers once on a 7800rpm 427 with 2 1/4" headers. I lost about 1/10th when I shortened them from 30" to 24".

Bill M

mcracecars

It sounds to me like you want the car to leave hard, but you are handicapping it by trying to limit the top end mph so you dont need to run the chute.
It would seem more logical to me to do what is necessary to use all the power and tork the motor can make at the start, but limit the top end mph with some sort of throttle stop. Until you can get a chute on there of course. There is good reason to use a chute, not only to slow the car down, but it can straighten you out if you start to go sideways at the top end.
Why would you need to remove the body to redo the back of the car?

triniemi

Ed, you should see the car and you would agree with me. It's a very small car and the real chassis ends at the rear shocks. The "chassis" from rear shocks to rear bumper is very weak, only carrying the weight of fuel cell and battery. And the fuel cell fills the cap between the tires, so it has to be relocated too. There is no way I can attach the chute to the existing chassis, is has to be rebuild to handle the chute. And to rebuild the chassis, the body must be removed, believe me. No room to work anywhere.

edvancedengines

Ok, the car does not look bad at all. As has already been mentioned the 60' and the ET are pretty much right on the money as they should be.

I also agree that the front end to me looks too stiff. You could possibly use a touch more of what is now called antisquat but not much. You can likely get that just by loosening the shock a couple of clicks on the extension. That front end does look like too stiff of springs/too stif of shocks/ or no travel with it too much limited by limiters.

You will not like what I see as your main issue though. You are trying to run that thing at too low of rpm. You are severely limiting any horsepower making it wants to do. You are working the engine harder by restritcting the rpm to ranges it is in the highest destructive harmonics ranges, and likely holding it down just when it may want to start running. Turn that baby loose and let it eat dude.

Is that cam advanced much? I would want to retard it some It is not enough cam for your car or engine. It is usable though.

You can mount a good strong cross member at any place in the car where you find frame strength. Then brace it with triangulations. The chute should be tethered (Attached) no higher than the camshaft ht, and no lower than the crankshaft ht at the lowest. Too high will possibly unload front suspension and too low will definetly unload rear suspension. When you do put a chute on it, Keep your foot hard on the pedal when you pull the chute. Only let off the pedal when you feel the chute hit or if it doesn't hit. You will get used to how long it takes to hit after the first two or three pulls. When you get used to it, you will be pulling the chute just before the finish line.

Ed

triniemi

I measured the 4-link settings last weekend and fed them to my friends 4-link calculator. The IC lenght is 37.2" and 8.2" high. I got Jerry Bickel's book (Complete Guide to Chassis Performance) and it suggests for a low hp (under 900hp) and auto. trans car IC lenght 45"-50" and 1"-3". But it also says that weight distribution should be 51% Front, 49% Rear and that's something I can't achieve.

Any ideas where to move the IC or is it ok now?

BTW, thanks for the help with the chute attaching. I measured also the crankshaft height (12.5") and camshaft height (18") so between those numbers will the chuteanchor go someday.

mcracecars

those chassis books are great, but the info they give on settings is kind of generic, gets you in the ball park as they say, but you still need to play around with the settigs to see what the car likes the best.
plot out all the holes and possibilites for the 4 link, then you have some reference points.
try a lower and longer setting, ie drop the front of the lower bars down 1 hole and see it the car likes it. you may need to play with the shock settings to see if there is more improvement or non at all. Write everything down in a log book, you can never have too much information.
a test and tune day at the track is ideal for this kind of stuff as you do not want to do this on a regular race day.
you only need to do 60's or 330's for this, no sense wearing out the motor.

triniemi

Yes, I have measured all the holes in the frame and in the rearend.

If I'd drop the lower bars one hole lower in the frame, the data would change like this:

IC lenght 37.2" -> 43.6"
IC height 8.2" -> 6.1"
Antisquat 146% -> 92%
%Rise 83% -> 53%

How would that sound?

The software I'm using is Performance Trends Inc. 4Link Calculator v2.0

triniemi

Good news from Finland, Alastaro dragstrip! 8.987 @ 147 mph with 6400 max rpms, shifting at 6000! I lowered the launch rpms from 4400 -> 3600, raised the tire pressure from 6.7psi -> 7.0psi and made a big burnout throuht the starting line. Also the throttle wasn't all the way open before but now we got it right.

Here's the 8 second pass video: http://www.youtube.com/watch?v=GF-Rf_4eVXc

We broke the transmission on the next run but I did got a spare trans and we even manage to win the eliminator with it! Next race is 5. July and I think we're going to try the four link setup a mentioned before. It seems that the body rises at the starting line. I want it squat or be neutral.

Also I weighted the car with a full fuel cell and it isn't so bad that I thought. 56.6% front, 43.4% rear, 2410lbs.

Corner weights:

LF: 749 RF: 615
LR: 502 RR: 543

Comments?

Thanks,

Mikko

sp2816

Congratulations on getting your 8 second time slip. I know that it had to feel good to do that and to also come back and win your eliminator.

Bill M

buffjhsn1

welcome to the club! great feeling isn't it? :lol: :lol: