Tips To Prevent Oversteering Under Boost?

[stevechumo]

Does anyone have any tips of how to keep the steering wheel straight when launching the boosted car? I have a turbocharged SC400 (1UZFE)with a single T-67 running at 15 psi, and I keep having the issue with oversteering, which means losing control when launching from the dead stop. There's so much torque at low end that I can't overcome yet. I tried different methods from brake-torque and flooring after that. I also tried to roll a little easy from start for 0.5 second, then flooring it. But the results are all the same.

My tranny is a built auto tranny with a shift kit so it helps with time, but it makes the car shifts so quick to the point that I lose control (I can say badly) when launching every time when the boost kicks in.

I'm running 245/35/19 front and 285/30/19 rear. All tires have very good threads on them. I also have a Supra Torsen LSD. My full coilover is set at mid dampening level, which is a bit firmer than stock. Will increasing the stiffness help with oversteering?

I've been practicing to get ready for the track this Saturday, but I'm still worried because of this issue.

Thanks folks,

 

[WDoherty]

19's low profiles aren't going to be your friend for drag racing. Have you considered some drag radials on some supra 17's?

 

[spf_lexus]

max the stiffness on your coilovers and give it a try. your coils transmit a lot of torque when u launch and can "Man Handle" your car off the line. what brand of coilover? Also, any neg. camber will affect a launch due to the uneven contact patch. My last idea is a bad ball joint could cause the car to mysteriously wander. You obviously have wide rubber, at 285 I would think thats plenty... widest I have seen on SC w/ rolled fenders was a 305/25/19

Any chance your LSD is setup too tight or loose?

 

[stevechumo]

max the stiffness on your coilovers and give it a try. your coils transmit a lot of torque when u launch and can "Man Handle" your car off the line. what brand of coilover? Also, any neg. camber will affect a launch due to the uneven contact patch. My last idea is a bad ball joint could cause the car to mysteriously wander. You obviously have wide rubber, at 285 I would think thats plenty... widest I have seen on SC w/ rolled fenders was a 305/25/19

Any chance your LSD is setup too tight or loose?

Slick tires can help with the hook-up to the ground, but I don't think they help much with oversteering. In my case, the street tires can't hook up yet. I deflated them to 35 psi and they seem to hook up a little better with a slight improvement with oversteering.

I'm running Tein SS coilover and set it at mid level. I think my car has straight camber/caster, and I also have new Supra control arms.

I've been looking for 305 tires with widening the rims from the inside to fit the tires. I just don't want to roll the fenders because it'll cause an uneven flow of the body. Rolling the fenders will require repainting that section also, so it's too much for me.

Imagining on those 800-1000 rwhp cars, how can they be controlled? Damn!

 

[sniper]

The sidewall is really thin on the 285/30/19 you have, which is a really wide tire. Now you need something that is going to hug the track, rather than break loose. With that tire size you have about an overall width of ~11.3" to work with since you don't want to do fender work, and who does anyways! Id rather be driving. Anyhow, if you go to a 18", or even better, a 17" wheel, you should have much better launches. Lets say you chose to use a Nitto NT555R size 275/40-17. The overall width would be 10.9 inches, and if you want a 18" rim you can try a 285/40-18 which will be 11.2 overall wide. Either of these tires aired down are going to keep the power on the pavement and produce much quicker 1/8 miles times, and thus 1/4 mile times. I would first try the 275/40-17 with a 17"X11" wheel. With a wheel that wide, later on you can choose to use a 315/35-17 which is 12.13" wide. Hope that helps some.

If all else fails, use a 15"x10" wheel and a 325/50-15 tire, which is 13.11" wide...

You can try and stiffen it, but you also want the car to transfer the weight over, and then sit on those tires.

 

[spf_lexus]

sniper hit it pretty good. i remember when i first test drove my LS w/ new JIC coilovers dropped 2.5'' to my surprise proved quicker launches. your car cant move until it's suspension and chassis overcome the torque.

steve check out Ikeya Formula control arms for SC, they eliminate a huge amount of suspension play compared 2 stock and are lighter too. Their arm collection is on my wish list lol, they will cost you an arm/leg but will cure a lot of your steering issues. (Forgot how expensive an SC can get)

 

[Lextreme II]

let go the gas pedal....

 

[stevechumo]

I'll try to find some fat tires that can fit over the OEM rims that have 16" diameter when going to the track, and hopefully I'll have some lucks finding and running them.

I'd like to let go of the gas like David said, but my feet are addicted to it.

 

[Cobber]

Traction control.

I have traction control through my Adaptronic ecu, I can adjust it via a pot on the dash or just switch it off. It is infinitely adjustable through the settings and certainly helps keeping the back end at the back.

 

[spf_lexus]

hey cobber,

how hard was the traction control feature to setup inside the softwar?

 

[Cobber]

I just used the suggested settings from their website and trimmed it in from there. It took me about a day to play around with the settings. You can set it up to pull timing and or spark depending on % difference from front to back wheels. You can also set up two setting with a change over road speed. Once it is set up, the pot on the dash effectively goes from maximum intervention to minimum and I can also switch it off if need be.
Nothing replaces skill with the right foot but it helps in a short wheelbase car.
I see you have adaptronic also you will just need to get a front wheel speed signal into the ecu. You can use the ABS signal if you have one or in my case I had to make a chopper disk and proximity switch.

I'm certainly no expert in setting it up so if I can do it so can you.

Go to the Adaptronic forum and look for the traction control thread.

 

[stevechumo]

I have the AEM ecu and I just don't know if it's tuned with traction control or not. And my car doesn't have traction control equipped from the factory, so I think it's not tuned for traction control.

 

[Cobber]

You can get several aftermarket traction control units that can be fitted. Look up racelogic and moretraction, a friend has the racelogic in his LS7 powered cobra and it is also very adjustable. Some units also have launch control as well.
Adaptronic has launch control which I have also got set up on my car.

http://www.racelogic.co.uk/

 

[spf_lexus]

Go adaptronic steve, i swear in the last 8 months there has been a lot of people trying them out and really liking it's virtually infinite features. If all works out It's setup to keep all creature comforts. I just hope David and Tim can get the ball rolling on the two LS400's waiting a tune.

I remember forum member retrodrive had a custom setup on his early LS but it ended up like $1000.


What about limiting boost until certain speed/gear? the new front wheel drive mazdaspeed 3 has it's boost limited all the way through 3rd to keep it in a straight line.

 

[stevechumo]

I wish I have the extra money for the Adaptronic. I already paid $1500 for the AEM, which is already a good deal comparing to $1800 if buying from some other vendors, plus $700 that I paid for tuning.

And the thing is I don't really know how the Adaptronic will work out on the SC400. I haven't seen anyone running it yet. To swap to the Adaptronic, I'd say paying $1000 for wiring, $1000 or more for the unit itself, and about $700 for tuning. That's some pretty money there. The nice thing I like about the AEM is I can take it out and put the stock ECU back in and run it right away. When you go with a universal ECU, you'll have to resolder every wire to put the stock ECU back.

I don't want to limit the boost at any gear because that'll slow down the 1/4 time for sure. We all want it to go at low RPM as soon as possible if we drag. The 3 main things that I think causing the oversteering is too much torque at low end (I've seen many draggers losing control like that), the transsmission that shifts through 1st and 2nd gears so quick. I don't feel any delay in any gear at all (I have a built tranny with the shift kit in it). When I had the stock tranny with the same boost, it didn't really cause oversteering like this. And the last thing is maybe my tires aren't just good enough.

I'm starting to look for some 295 or 305 tires for the rear if there's enough clearance. And I'll widen the rims to accomodate that.