Quote:
Originally Posted by jts1981
Bill,
Interesting fact about the rear diff, both non M compatible and that you favor it.
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Just to be clear, my preference would be a mechanical locking diff (ie. Quiafe or Wavetrac) but EDL works well enough to make up for the loss of traction in an open diff without EDL that the expense simply isn't justified IMO.
Quote:
Originally Posted by jts1981
I tracked my car a few times with the NYPCA but never felt the handling was up to par. Perhaps with the sway bars to reduce understeer the EDL results would be more noticeable.
We race on some bumpy parking lots, like Nassau colleseum and the power just couldn't get down to the ground. That coupled with too much understeer made for some pretty weak lap times.
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For autocross (especially in bumpy lots and not fully prepared race tracks) I would suggest a lower natural spring frequency than what I am running. On a 28i something like 290lb/in front and 560lb/in rear which is closer to 2Hz. Note, this would be different on a 35i due to the higher weight and different weight distribution.
For reference:
28i Manual Trans: 3263lbs; 47.3/52.7% front/rear weight distribution
28i Auto Trans: 3307lbs; 47.7/52.3% front/rear weight distribution
35i Manual Trans: 3493lbs; 48.6/51.4% front/rear weight distribution
35i DCT Trans: 3527lbs; 49.1/50.9% front/rear weight distribution
For each of these you would potentially have different spring rate setups for street, autocross or track. To determine the spring rate required you have to choose the spring natural frequency based on the application. There are several sources online to help calculate spring rates (Eibach has a good doc available on their website).
Street: < 2Hz
Autocross: 2Hz - 2.5Hz
Track: 2.5Hz - 3Hz
These are just basic numbers you can use as a guideline to get started, it may take several attempts to get it completely dialed in. Given the great weight balance on the Z4 it has a lot of potential... When you get your suspension setup tuned you will find the car has tons of grip available.
Bill