Battling rear-wheelspin, 944 chassis, open-diff...
08-12-2003, 10:00 AM
#1
Drifting
Thread Starter
Battling rear-wheelspin, 944 chassis, open-diff...
Hey you track guys, have any of you figured out how to minimize wheelspin on the 944 without going to a LSD?
I've got my car pretty nuetral now, although the front end is a tad lower than I'd like, and I am running stock Mo3o stuff all around. I'm on A032Rs with 9" rears. I've got the rear Konis dialed back considerably on rebound (the only adjustment).
Is this an inherent chassis problem, spinning the inside rear?
Any thoughts would be appreciated - it's killing our autocross efforts...
I've got my car pretty nuetral now, although the front end is a tad lower than I'd like, and I am running stock Mo3o stuff all around. I'm on A032Rs with 9" rears. I've got the rear Konis dialed back considerably on rebound (the only adjustment).
Is this an inherent chassis problem, spinning the inside rear?
Any thoughts would be appreciated - it's killing our autocross efforts...
08-12-2003, 11:34 AM
#2
Addict
Rennlist Member
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Minimize rear shock setting, reduce rear swaybar size, those help... probably need more rear torsion bar. You'll still get wheelspin though, unless you go to a LSD. I can get it in my dinky little 924! Just installed a 951 LSD, looking forward to trying it out...
08-12-2003, 12:45 PM
#3
Drifting
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Just go with an LSD. I know that's not what you're asking for, but any proper racing/track car should have one unless the rules specify otherwise. Especially for auto-x where transitions are much more sudden and upsetting to the car. Otherwise, you are going to be making concessions in the rest of your setup to battle a problem that is much easier and more effectively solved with an LSD.
If you must go without an LSD, try disconnecting the rear sway all together. That's something we do on BMW's, even with a built LSD, to put power down better out of the corners.
BTW, I'm in Charlotte as well.
If you must go without an LSD, try disconnecting the rear sway all together. That's something we do on BMW's, even with a built LSD, to put power down better out of the corners.
BTW, I'm in Charlotte as well.
08-12-2003, 01:28 PM
#4
Race Director
Well an LSD is the Ideal situation. Everything else is a compromise.
Here is what happend on my 944 NA.
I had 350lbs front springs, 28 mm wetl swaybar in front and 28 mm t-bars in 22mm rear weltwsway bar in the rear with fresh koni's on all corners.
I was getting inside rear wheel lifting and wheel spin out of tight corners. The answer without an LSD was torsion bars.
I had my front end too stiff and had the crank the rear sway bar full stiff. The sway bar acted to take weight off the inside rear wheel and cause wheel spin. When I softened the rear bar I got too much understeer. So I did what I could to manualy limit wheelspin by limiting power. It was my only option as wheel spin only happend in 1 corner, but the understeer would impact all corners. This was on a race track (PIR), I could get wheel spin in autocrosses too. I just did not care too much about optimizing my car for autocross.
Anyway I when to 30 mm t-bars and much of this went away. What this did was to allow me to reduce the stiffness of the rear sway bar and keep an accptable balance of understeer/oversteer. It is still not perfect as I have am still trying induce more oversteer, but maintain traction in the rear. It is balanceing act with the sway bars.
Stiff in front & softer in rear means more rear traction, but also more understeer.
Soft in front & stiffer in the rear means less understeer, but less rear traction.
The other thing is rear camber. I was running -1 neg rear camber with my 28 mm bars after -2.5 rear burned the inside rear tire. Reducing the camber created a better traction profile in the rear. Now I went back to -2.5 in the rear and the car handles much better overall.
Bottomline:
You can fool around with the stuff above like I did, but it will compromise handling elsewhere. The best way to minimize the negative impact on conering is to use an LSD. It is the right tool for the job. Everything else is band-aid.
Here is what happend on my 944 NA.
I had 350lbs front springs, 28 mm wetl swaybar in front and 28 mm t-bars in 22mm rear weltwsway bar in the rear with fresh koni's on all corners.
I was getting inside rear wheel lifting and wheel spin out of tight corners. The answer without an LSD was torsion bars.
I had my front end too stiff and had the crank the rear sway bar full stiff. The sway bar acted to take weight off the inside rear wheel and cause wheel spin. When I softened the rear bar I got too much understeer. So I did what I could to manualy limit wheelspin by limiting power. It was my only option as wheel spin only happend in 1 corner, but the understeer would impact all corners. This was on a race track (PIR), I could get wheel spin in autocrosses too. I just did not care too much about optimizing my car for autocross.
Anyway I when to 30 mm t-bars and much of this went away. What this did was to allow me to reduce the stiffness of the rear sway bar and keep an accptable balance of understeer/oversteer. It is still not perfect as I have am still trying induce more oversteer, but maintain traction in the rear. It is balanceing act with the sway bars.
Stiff in front & softer in rear means more rear traction, but also more understeer.
Soft in front & stiffer in the rear means less understeer, but less rear traction.
The other thing is rear camber. I was running -1 neg rear camber with my 28 mm bars after -2.5 rear burned the inside rear tire. Reducing the camber created a better traction profile in the rear. Now I went back to -2.5 in the rear and the car handles much better overall.
Bottomline:
You can fool around with the stuff above like I did, but it will compromise handling elsewhere. The best way to minimize the negative impact on conering is to use an LSD. It is the right tool for the job. Everything else is band-aid.
08-12-2003, 09:06 PM
#5
Drifting
Thread Starter
This is good stuff, and echoes what we were thinking!
I am trying desperately to source a cheap factory diff to throw in the transaxle before the necxt evet (end of the month) - however, if I can't get one by then, I'll certainly try detaching the rear swaybar altogether! (just removing the lower bolt from one droplink would do it, correct?)
I am trying desperately to source a cheap factory diff to throw in the transaxle before the necxt evet (end of the month) - however, if I can't get one by then, I'll certainly try detaching the rear swaybar altogether! (just removing the lower bolt from one droplink would do it, correct?)
08-12-2003, 09:15 PM
#6
Drifting
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Originally posted by keith
if I can't get one by then, I'll certainly try detaching the rear swaybar altogether! (just removing the lower bolt from one droplink would do it, correct?)
if I can't get one by then, I'll certainly try detaching the rear swaybar altogether! (just removing the lower bolt from one droplink would do it, correct?)
Is the next auto-x event in Charlotte? It's been years since I've auto-xed, but I wouldn't mind going out to watch if I'm going to be in town. Heck, I may even try entering my Quadrasteer truck for comic relief.
08-12-2003, 09:39 PM
#7
Drifting
Thread Starter
Yessir! The next event is the 24 hr. event at Knights Stadium (just south of Charlotte on 77) - Aug. 30th and 31st (noon until noon)
Come on out, I'l be abusing the 951 there.
Come on out, I'l be abusing the 951 there.
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08-12-2003, 10:57 PM
#8
Drifting
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Excellent...my lease runs out that weekend. I'm supposed to be racing at Summit Point, but I think moving to a new house is going to keep me in Charlotte. I'll try to stop by.
08-13-2003, 04:34 PM
#9
Rennlist Member
stiffer front bar, or stiffer shocks up front. when my sway bar up front broke at laguna, and at Thunderhill, I would get inside turn wheel spin . as soon as it was fixed, no more spin (and that was with a LSD) . However, same thing happed before I went to a LSD. soft springs gave more tight turn 2nd gear wheel spin. all other parts of the track was fine. this was reduced by a stiff front sway bar and a stiffer set of springs.
mk
mk
