Throttle induced understeer

[ghostnote]

2015 GTPP with BMR lockout, vert springs, and 19x10 inch wheels with 275/40/19 MPSS. On the stock PP alignment.

If I apply throttle at low speed corners, the car acts predictably. Too much throttle, and I'll get oversteer, but just the right amount and it feels like the car is planted and rotating well. But at higher speed corners, if I apply some throttle, the car will push. The wheel will steer towards the outside of the corner with some force and I need to correct. It feels as though there's slack in the drivetrain and suspension that's tightening up under load, and I can feel it clearly in the steering wheel.

I'm not sure whether this is normal or fixable. I mean, it's preferable to snap oversteer, but it's still a bit unsettling to have the car push unpredictably.

Any thoughts?

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[Performance nut]

Throttle understeer in a 400+ HP, RWD sports car... I have taken note of that as things I thought I would never hear/see.

Not sure if it is throttle related as it is you are going too fast for the turn. I would think with more throttle, you will end up with the exact opposite (and it will be quite abrupt change too). Looks to me that you need to look at your components and research what you want to try to counter it.

For example, I noticed tire pressures make a difference. I like more pressure in the front than in the back (usually about 2# more). This creates a small amount of oversteer. I tried the opposite when they rotated my tires and I absolutely hated life.

 

[jbailer]

I agree with Performance nut, To me it sounds like you just carried too much speed into the turn. If there's no understeer if you go into the turn at a manageable speed then it should be ok. Now if you're going into the turn and you feel the speed should be manageable, then I would just consider that understeer, not throttle induced but speed induced. If you let off the throttle it can create oversteer by shifting weight forward, obviously too much gas will bias oversteer as well. Sounds to me like you just need to bias the suspension more to oversteer to hit neutral so you can go into the corner a little quicker then manage it with the pedal.

 

[jasonstang]

Yes when you apply throttle enough but not letting the back loose, you are shifting weight to the back of the car causing from to lose weight and reduce grip.

 

[Grintch]

2015 GTPP with BMR lockout, vert springs, and 19x10 inch wheels with 275/40/19 MPSS. On the stock PP alignment.

If I apply throttle at low speed corners, the car acts predictably. Too much throttle, and I'll get oversteer, but just the right amount and it feels like the car is planted and rotating well. But at higher speed corners, if I apply some throttle, the car will push. The wheel will steer towards the outside of the corner with some force and I need to correct. It feels as though there's slack in the drivetrain and suspension that's tightening up under load, and I can feel it clearly in the steering wheel.

I'm not sure whether this is normal or fixable. I mean, it's preferable to snap oversteer, but it's still a bit unsettling to have the car push unpredictably.

Any thoughts?

Driver technique and physics. At low speed, more throttle easily overloads the rear tires. At high speed, wheelspin is harder to induce, so the weight transfer off the front when you accelerate induces a push. Nothing unpredictable about it with experience.

 

[ghostnote]

There's a detail I inadvertently left out. This happens only when I enter the corner after braking but not on the throttle. So there's a bit of engine braking going on, which transfers weight to the fronts. Once I apply throttle, weight transfers back, and I lose grip in the fronts.

So, am I supposed to brake and reapply throttle to "maintain" rpms through the turn? I'm a novice, so any input would be appreciated.

 

[jasonstang]

There's a detail I inadvertently left out. This happens only when I enter the corner after braking but not on the throttle. So there's a bit of engine braking going on, which transfers weight to the fronts. Once I apply throttle, weight transfers back, and I lose grip in the fronts.

So, am I supposed to brake and reapply throttle to "maintain" rpms through the turn? I'm a novice, so any input would be appreciated.

Yes, you are supposed to have some throttle to balance the weight but not too much to unsettle the front to back weight balance to cause under steer.
Throttle application is a fineness work at the limit.

 

[CrazedAntelope]

There's a detail I inadvertently left out. This happens only when I enter the corner after braking but not on the throttle. So there's a bit of engine braking going on, which transfers weight to the fronts. Once I apply throttle, weight transfers back, and I lose grip in the fronts.

So, am I supposed to brake and reapply throttle to "maintain" rpms through the turn? I'm a novice, so any input would be appreciated.

This reminds me of some time I spent on the skidpad at a BMW CCA Car Control Clinic. They had a circular set of cones with 2 gates to pass through at 180* away from each other. I got the car in a steady state circle around the skidpad and the steering wheel was locked in position (the instructor actually grabbed the wheel and held it in place). The goal was to make it into the gates and to see how throttle affects the car's ability to turn. Also to teach the driver to look well ahead of where you want to go.

To answer your questions, do what feels natural given the setup of your car and your understanding on how it will react. It is recommended to have a light bit of maintenance throttle through the turn, just enough to get rotation going. Slow in fast out is better than fast in slow out.

 

[ghostnote]

Thanks all for the replies.

Maintenance throttle works wonders... I tried it out and the issue is pretty much gone.

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