I tune and drive RWD cars almost exclusively and have done so for years, first in FH4 and now in FH5. Today I’m trying to do a road racing tune on a Volkswagen Scirocco at D500. Yeah, I know, it’s a weird choice, but there’s some history - my wife drove this car back in the 80’s and loved it, and for some reason I thought it would be fun to campaign it just for the hell of it.
But it’s FWD, and I don’t have much experience there. Stock chassis tuning but powered up to D500, it starts out with bad understeer, its only real problem. I’m a decent tuner on RWD cars, and my usual tools are ARB settings, damping, and as a last resort spring tension. I’ve driven out most of the understeer, but there’s this weird effect that I’m getting from the car. On long high-speed turns, about halfway or a bit more through the turn it takes a dip toward the outboard side of the turn - sometimes it feels almost like a little lurch - and then understeers, even if it’s been doing fine in the first part of the turn.
It felt like it had to be damping kicking in as the car’s weight transitioned, but nothing I’ve done with damping settings has had much effect. Last thing I tried was differential tuning. Stock it was at 13% front acceleration, 5% front deceleration, so I dropped the acceleration to 5% to see if I could move the needle. I don’t think I did, and I’m running out of ideas.
Honestly sounds like a “problem-in-cockpit” issue. FWD will always have some understeer. Just like you have to manage throttle through a turn with a RWD in order to prevent oversteer, you have to manage throttle through a turn in a FWD to prevent understeer.
My second guess based on the symptoms would be a tire heat issue. Raising front tire pressure, as counter-intuitive as this is, could prevent this, especially in relation to the back.
You kind of have to throw out the book of conventional tuning when it comes to hatchbacks.
I know the following doesn’t apply to your specific question, but stick with me. My best advice though is to get used to using understeer to your advantage. Just like oversteer, understeer can be a powerful tool in the right driver’s hands. Hatchbacks, with their short wheelbase and far-forward weight distribution, can really turn in while hitting those apexes. This allows them to get on the gas earlier than other cars, and since they understeer, they can really hammer it to maintain stability. Trying to bash the understeer out of them can really take away from their advantages.
What have you done with the suspension? Springs and dampers or ARBs only? I set it up on rally springs earlier and 1.0 arbs. Softest springs. It barely rolls in corners on stock tires and widths. Tried stock suspension briefly but not with ARBs. Also was locking the rear tires even after upgrading them. The stock bias is probably better for 58% or less front.
@NumberlessMath, starting with stock I dropped the forward ARB way down, my usual strategy for reducing understeer in RWD cars. I’ve also dropped the forward spring tension somewhat, likewise a strategy I use for RWD when I don’t want to drop the forward ARB any more than I’ve already done. For damping, decreasing front rebound and increasing rear bump is supposed to address corner exit understeer, which is exactly where I’m getting it. It turns fine in the corner entry and the first half of the turn.
I understand that FWD and AWD tuning is a lot different from my RWD cars. I’m just trying to learn.
Muchas, muchas gracias to Uber Understeer and SatNiteEduardo ! 100% forward acceleration smoothed out the turn just fine. I can race this thing now without having to worry about driving into the wall when I’m pushing the car hard.
As other people have said max out the Front Accel on the differential.
For a starting point in all my AWD cars, max out both front and rear accel and ARB to F:1.00 and R:65.00. Then dial it back until if feels right for you.