Some "inside info" from user with experience. I noticed that most audi's get not so good 60ft time, i mean , even with full slicks, and vht on track, they get 1.4x - 1.5x (speeding60, dutter racing, amp s2, and so on), only one does 1.2x , and that is old paavola coupe , is there any thing special with his setup ? ussualy a 0.1 decrease in 60ft , will get a 0.2 better time on 400m, so is worth investigating.
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Jyrki is the one to answer about Paavola's setup if it's ECU related, which i think it is.
That's more than setting up the ecu to the desired settings such as optimum launch rpm and antilag to have max torque on clutch dump, but having a good transition between launch controller and base cal as well. (like an ideal traction controller, how to react on RPM dropping by timing & fuel control)
So partly the calibration setup, but influence of the ECU's controllers & software setup as well.
I mean, with the same tires and a "slipless" clutch dump there should be the same amount of grip/traction, only the electronics are there to counteract and overcome the inertia of the car. -
i think there is more to it.
Jyrki told me once a while ago while we were chatting about a center diff spool. but he mentioned setting the rear subframe up at an angle, like i think the rear of the subframe further from the body. for just this reason. dont quote me, as that is what i "think" i recall.
i run a 24.5" tire, i know Paavloa was running a 26".
but me, i slip the clutch to launch i dont just dump it, i have tried that method and it isnt so great for me.
some more of it could be the suspension setup too. i am now going to start playing with spring rates and dampening rates.... but i think that might also get that last-level type stuff.
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exactly
any movement that is not in a forward direction...ie rear end dropping, the front lifting, or even any drivetrain slop is all lost energy in the wrong directions = lost time
The driver was quite upset of the amount of lift when i showed him a series of photos '68 camaro 1Khp c16 w/200hp shot
after the 1st bounce
then some rod knock near the 1/4 line....7.xx dont rember. it used to run high 6.8's
his other car had no lift...but only ran 7's due to having shifting issues
'91 Pearl 3.6 V8 CQ - building
'13.5 Jetta GLI - toy
'15 Subaru Imprezzzza - work daily
hausofdub.comComment
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for instance.
mine has 900 lb/in rear springs and 650 lb/in front springs. i am going to lower the front ratio some as it still lifts about an inch plus on the launch. i ran 9.55 two weeks ago. last weekend, i raised the rear 5 turns (~1/2") and the front 3 turns (little >1/4") and i ran a best of 9.34!!!!
when i align the car, which is about every two track days, i have them lift the front about 1" with me in the car, just as it is on the track. i am right at the level where i need to start playing with rebound and compression settings, as well as spring rates. but i dunno where to start. so i will start at the simple, the springs. and i gotta corner balnace too, to see exactly what is up.
i have been really lucky i feel, with how the car reacts and responds. it is really doing well. never in my wildest dreams did i think it could perform as well as it does! not too shabby for a dumb construction worker who has a badass racecar as a hobby!!!!!!
and my car still wants to peel that front pass side (right) up on the launch!!!! it has been twisting less lately, though.
Last edited by speeding-g60; 5 August 2012, 12:53.Comment
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Oh yes, i overlooked the geometry part and was pure thinking engine-wise
Sounds to me as a kind of anti lift geometry like the Works rally cars use these days.
Should work indeed, matching bound/rebound for front/rear to stop body motion as well. FWD draggers use it up front.
http://www.turbo-mopar.com/forums/sh...ive-discussion
The IC compared to your Center of Gravity will decide if it jacks up or pulls down the chassis. Look at RWD Volvo's where the rear geometry reaction is to pull the body down of lift off.
Anyone tried to alter the static stance? For instance raising the rear by lets say 2" to have a leveled car on full body tilt?Comment
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i can next month.Comment
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I've been thinking this, and lifting the rear will not work well, and why Paavola switched to 4-link suspension.
To do it right asks for altering the rear suspension big time.
On acceleration the entire body pitch is dicated by weight transfer and controlled by the springs, the amount of weight transferred onto the springs and their spring rates make the pitch angle.
A way to get the body stable is to increase spring rate to reduce deflection of the spring, but this can lead to negative effects in terms of tire load distribution.
So, in order to run the springrates you want to get maximum traction as a normal mass/spring system the load transfer has to be altered.
Now, here comes the funky bit. The amount of force projected on the springs is a function of the height difference between Center of Gravity of the car itself, and the Instant Center of the wheel geometry. The wheelbase makes the arm on with the reaction forces are acting. To make it easy, once CG and IC are on the same spot it makes zero dive/lift. Of course this is impossible to reach, but it possible to tune! That's why a 4-link geometry is so easy. Altering the rod angles make it easy to play with the IC height.
Showing multilink for dive under braking, but it's lift (inverted) for acceleration.
So, much more work to raise/tune it with McPh strut. Means to move the top mount back and tilt the lower wishbone (like suggested by Jyrki)
Some math showing the relation.
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