rear diff behavior
peter*g,
I think you are right about the sway bar, I just don't want to get to the point where the sway bar is too stiff, like brian94ht's last experiment. This is why I want to do something like a 3-way adjustable sway bar so I could go back to stock if need be. The problem is, nobody makes one. If you know otherwise, I'd be the first to try it out.
I think you are right about the sway bar, I just don't want to get to the point where the sway bar is too stiff, like brian94ht's last experiment. This is why I want to do something like a 3-way adjustable sway bar so I could go back to stock if need be. The problem is, nobody makes one. If you know otherwise, I'd be the first to try it out.
One thing you can do is actually weld on some extra metal past the point where the current mount is. I've known some fast ProSolo guys who have fabricated their own "adjusters" when front sway bars were not available yet for a new car, and it works pretty darn well. It's also not tremendously difficult, so most reasonable race fab shops can do this for you.
All that said, IMO you won't want to go back to stock. I think this is the right size bar for tarmac.
I think another solution is more rear toe out. My car felt great last year when I added the toe out(only 1/16th"), but this year I think my front tires my have lost a little grip since last year and has overcome my toe setting. I might have to try 1/8th" for the next event. I am also going to experiment with the "Snow" setting.
What does your comment on tires mean? Are you still running a set of tires you ran last year? If so, do you think that you might have heat-cycled them beyond their usable life?
First off, talk to 10 different guys and you'll likely get 10 different answers! 
The guy from Gears is recommending a differential solution? *SHOCKING* Kidding of course, but there is something to be said for focusing on getting the chassis right first and changing diffs later. The driveline will only mask the underlying problem.
What I'm recommending is not in conflict with what was proposed, only offering a different path. I'm basically telling you to drive it more like a FWD car if the rear wheels are getting off the ground (a common sight with FWD racers -- my old VW used to get like 8" under the inside rear tire, and that was on canyon drives!). Easiest way to do that is to tell the diff to not transfer torque to the rear wheels as soon or as aggressively. This definitely requires that you change your driving style a bit, but I think it's a viable option.
IMO, increasing the rear lock-up will help. It will make the one wheel on the ground work harder and take away some of the spin on the other wheels. It will also help push the rear around.
The more I drive my own Evo, the more I wish I had a locked center and rear diffs so that the diff behavior was more consistent. It certainly would make turn-in a little more difficult, but I don't think it's anything you can't drive around. That said, I'd never trade even the most magical diff set-up for a well sorted chassis.
The guy from Gears is recommending a differential solution? *SHOCKING* Kidding of course, but there is something to be said for focusing on getting the chassis right first and changing diffs later. The driveline will only mask the underlying problem.
What I'm recommending is not in conflict with what was proposed, only offering a different path. I'm basically telling you to drive it more like a FWD car if the rear wheels are getting off the ground (a common sight with FWD racers -- my old VW used to get like 8" under the inside rear tire, and that was on canyon drives!). Easiest way to do that is to tell the diff to not transfer torque to the rear wheels as soon or as aggressively. This definitely requires that you change your driving style a bit, but I think it's a viable option.
IMO, increasing the rear lock-up will help. It will make the one wheel on the ground work harder and take away some of the spin on the other wheels. It will also help push the rear around.
The more I drive my own Evo, the more I wish I had a locked center and rear diffs so that the diff behavior was more consistent. It certainly would make turn-in a little more difficult, but I don't think it's anything you can't drive around. That said, I'd never trade even the most magical diff set-up for a well sorted chassis.
Bingo!!!
If the rear inside tire is spinning, you're going to loose out on exit speeds.
If the rear inside tire, which is usually in the air, is locked to the same speed as the outer tire because the rear diff is really clamping down then the car will want to rotate better at the rear because the rear outside tire is doing more work. This is similar to the way that the Super-AYC helps steer the car but not quite as effective because the Super-AYC will put nearly all the power to the rear outside wheel thus improving the steer-by-throttle action.
Plus the suspension can be set-up to work on grip instead of trying to get the thing to rotate.........aaaaaad the ACD unit doesn't get confused from seeing a bunch of wheel speed, unlocking the center diff.
Want it your EVO to carve the exit with more speed? Send a PM.
Jon@TRE
Last edited by GEARS; Jun 26, 2007 at 07:52 AM.
More preload on the clutch pack really has the greatest effect in mid-corner, and more generally equates to more push. What really needs to be altered are the ramp angles. If the car turns in fine and is ok mid-corner, but pushes on corner exit, then the ramp angles need to be altered to produce less exit locking.
Cheers,
Cheers,
Luckily this doesn't add anymore preload to the clutch plates and allows the rear diff to completely unlock when you are off the throttle leaving the car free of influence.
Jon@TRE
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