Lift-Off Oversteer w/ Lightweight Flywheel? (New Bench Racing BS Inside!)
#1
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So as the title states, would having a lighter rotational assembly lessen, worsen, or not affect a cars tendency to transition into oversteer if the drivers lifts a bit mid-corner? Would the transition be more gradual one way or another?
My thinking is this: When you lift mid-corner, you are taking weight off the rears because the car will naturally want to decelerate. On top of that, you are probably at relatively high RPM, and the engine is going to naturally want to decrease revs. You are more or less doing a bit of engine breaking similar to down shifting though not as powerful. So less weight on the rears coupled with engine breaking means they cont hold traction since they are already working for grip to keep the *** end of the car from just plowing ahead.
So if you lower the mass of the rotational assembly (with a lighter flywheel or a cut crank or rods/pistons etc) then you have an engine that will change RPM quicker when free reving, but also be less of a drag in things like down shifting. I noticed on my last car that going from stock 19Lb or so flywheel to a 11Lb unit meant that I did not get quite so much deceleration from down shifting.
So I suspect that this lower inertia means that the engine will actually be less likely to hold revs up against aero and rolling friction forces with 0% throttle. Basically a 30Lb weight spinning will store more energy than a 10Lber. So the 30Lber will hold speed longer against a friction force than the 10Lber.
So (breathes) the car with the lighter rotational assembly will actually decelerate harder without maitenance throttle mid corner and that might actually result in less weight on the rears/more transfer to the fronts.
Does a lighter flywheel make lift-off oversteer more likely as a result?
This is why I shoudl not wake up at 3:30 and drink strong coffee.
My thinking is this: When you lift mid-corner, you are taking weight off the rears because the car will naturally want to decelerate. On top of that, you are probably at relatively high RPM, and the engine is going to naturally want to decrease revs. You are more or less doing a bit of engine breaking similar to down shifting though not as powerful. So less weight on the rears coupled with engine breaking means they cont hold traction since they are already working for grip to keep the *** end of the car from just plowing ahead.
So if you lower the mass of the rotational assembly (with a lighter flywheel or a cut crank or rods/pistons etc) then you have an engine that will change RPM quicker when free reving, but also be less of a drag in things like down shifting. I noticed on my last car that going from stock 19Lb or so flywheel to a 11Lb unit meant that I did not get quite so much deceleration from down shifting.
So I suspect that this lower inertia means that the engine will actually be less likely to hold revs up against aero and rolling friction forces with 0% throttle. Basically a 30Lb weight spinning will store more energy than a 10Lber. So the 30Lber will hold speed longer against a friction force than the 10Lber.
So (breathes) the car with the lighter rotational assembly will actually decelerate harder without maitenance throttle mid corner and that might actually result in less weight on the rears/more transfer to the fronts.
Does a lighter flywheel make lift-off oversteer more likely as a result?
This is why I shoudl not wake up at 3:30 and drink strong coffee.
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#4
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it could be my tune, but i have a bit of a bump in the driving when going from 0 to 5% or the inverse of that when cruising... it seems to be less noticable when driving hard, but its still there.
Everything is tight and new except my trans.
Everything is tight and new except my trans.
#5
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With a lightweight flywheel the engine will be able to change speeds more quickly than before thanks to rotational inertia.
So in theory, the car's deceleration should be greater with a lightened flywheel and thus bring more weight forward upon complete release of the gas pedal.
In theory... I can't say one way or another if there's a real-world difference. I have a lightweight flywheel and the only time I notice it is if I'm shifting lackadaisically and the engine revs drop further than is needed for the next gear
So in theory, the car's deceleration should be greater with a lightened flywheel and thus bring more weight forward upon complete release of the gas pedal.
In theory... I can't say one way or another if there's a real-world difference. I have a lightweight flywheel and the only time I notice it is if I'm shifting lackadaisically and the engine revs drop further than is needed for the next gear
#12
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I think the closed-throttle engine compression has a far stronger braking effect than the lighter flywheel, so the effect on lift-throttle oversteer will be negligible. Maybe in 1st gear it might be noticeable, in the same way acceleration may be noticeably better in 1st.
You are probably right. And too true that liftoff should not be happening anyway. I know I will be getting a lighter flywheel when I do a clutch, so really its more intelectual than anything.
#13
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Have a great day,
Jared
#16
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Thank you for that, how enlightening. I know what throttle steering is. I also know that if you're lifting mid-corner you have already blown the corner because you suck. There's a big difference between making slight throttle corrections throughout the corner to change slip angles and completely lifting off the throttle and inducing oversteer.
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