Short wheel-base 4WD = WTF!?

[magburner]

I don't know if anyone has noticed, but short wheel base 4WD cars act strange under certain conditions. They can go from understeer to snap oversteer at the flick of a switch.

I had previously asked a question about the FTO Super Touring Car, and came to the conclusion that my car setup had caused the car to act strange. Which was true to a point, but since then, I have purchased an Alfa 155 Touring Car, and I am again experiencing the same setup problems.

The thing both cars have in common is that they have a short wheel base, are front engined and 4WD. If both cars are raced close to stock setup, then they seem OK. If you do some heavy tuning though, they turn into strange beasts that defy the logic. There may be other cars like this, but so far I have only found these two, What is going on, and has anyone else had similar problems? 👍

 

[budious]

If you click the link in my signature you will find a write up I did investigating the various combination of drivetrain components. I found that many of the nasty problems you are describing actually come from installing semi-race flywheels, and the lighter the car is, generally the more pronounced the problems become. Recommendation, switch down to Sports flywheel and see if you have the same issues. The workaround for cars that won't allow a downgrade from the tune shop is to up the LSD acceleration value, for a 4WD, just generally the rear acceleration value, but the front may help some but it's proportional also to the center differential split.

 

[magburner]

Thanks for your advice budious. I will look over the info in your link, it may well prove useful as I'm strugglingto make those two cars competitive. 👍

 

[Poppins]

the flywheel should have nothing to do with snap oversteer, generally its caused by the anti roll bars being too stiff compared to the spring rate and the dampers or having too much toe

 

[budious]

the flywheel should have nothing to do with snap oversteer, generally its caused by the anti roll bars being too stiff compared to the spring rate and the dampers or having too much toe

It's true that it is amplified by these suspension imbalances but the initial force that causes the snap can be traced back to the semi-race flywheel use, test of course by make and model, but typically lighter cars are more affected. Use of a higher LSD acceleration value will help mitigate it also. I can run the same car without suspension tunes or LSD compensation and notice no adverse effects when equipped with a sports flywheel.

 

[FULL_THROTTLE]

The group b rally cars are 4wd and short wheelbase, they handle fine, the only i've come across that understeers and oversteers like that is a completely untuned FGT, the restore body rigidity in GT auto and the rigidity improvement in tuning shop fixed that though.

 

[uncle_hayley_j]

It's part of the fun although what you're describing is completely different to my experiences >_>

I've noticed it with some of the rally cars, it's good fun with those though.

 

[Poppins]

It's true that it is amplified by these suspension imbalances but the initial force that causes the snap can be traced back to the semi-race flywheel use, test of course by make and model, but typically lighter cars are more affected. Use of a higher LSD acceleration value will help mitigate it also. I can run the same car without suspension tunes or LSD compensation and notice no adverse effects when equipped with a sports flywheel.

i cant notice any difference between the flywheels other than throttle response, and either way if you let off the throttle half way through a drift its going to cause snap oversteer, you gotta keep constant rpms to not catch and snap

 

[onearmbandit]

Never had the problem you've described myself, my 155 handles like it's on rails.

 

[dsgerbc]

I think I experienced this in a few AWD cars. Stock differential seems to help when compared to torsen one you get in the tuning shop. Other than that, I try to fix it with suspension tweaks.

 

[Poppins]

its usually caused by - toe on the front or too stiff anti roll bars like i said.

 

[Sum1s2pid]

Short wheelbase cars sacrifice some stability in favor of maneuverability. They can feel twitchy if pushed hard, and can sometimes be quite unforgiving -- even if it's 4WD. The only things I can suggest are to practice until you get used to it, or try to find a balanced set-up somewhere in the Tuning Forums.

Good luck!

👍

 

[Wolf-M]

I don't know if anyone has noticed, but short wheel base 4WD cars act strange under certain conditions. They can go from understeer to snap oversteer at the flick of a switch.

I had previously asked a question about the FTO Super Touring Car, and came to the conclusion that my car setup had caused the car to act strange. Which was true to a point, but since then, I have purchased an Alfa 155 Touring Car, and I am again experiencing the same setup problems.

The thing both cars have in common is that they have a short wheel base, are front engined and 4WD. If both cars are raced close to stock setup, then they seem OK. If you do some heavy tuning though, they turn into strange beasts that defy the logic. There may be other cars like this, but so far I have only found these two, What is going on, and has anyone else had similar problems? 👍

Doesn't this simply show that your tune is faulty? Why tune if the result is worse than the stock settings?