parabolica

Hi,

Yesterday, I came upon the cloverleaf entrance to our local N-S highway. It being a bright day I couldn't resist take the turn hard (5AT TL) and soon had the Pilot Sports squelling in this RH turn. As I came about through approx. 180 degrees of turn, still pulling hard, the TL suddenly lurched to the right, that is to the INSIDE of the turn.
It was apparent that this was due to some mechnical/electronic feature kicking in.

My question is one of, do you folks think this was the VSA doing its job, or something else? I've read somewhere that the TL may have some steering function that causes it to turn the steering tighter in the direction of a turn if it senses slippage, but have no documentation of this (perhaps this is a TL urban legend).

Any opinions would be welcome......

qali

I believe this is what's called "torque steer"... The TL is front wheel drive, and has 270hp... is the road perfectly smooth? This happens a lot to me when I am on the on ramp of a highway, and I just launch... if the road is even slightly impefect (uneven, cracks, etc), I will get a sudden jerk (in the direction I am turning)... I think it has to due with the fact that the wheels that are used to steer are also the wheels that the power is going to (as opposed to rear wheel drive cars)

alin2

Two possibilities:

1. (most likely): Torque steer. It occurs because of FWD. One tire looses traction, but since the front wheels are also steering, the car jerks towards the wheel maintaining traction.

2. (less likely) VSA detected understeer as you were turning and reduced power to correct for it causing the car to suddenly turn in to its true turning circle where the front wheels were pointed. What you describe is sudden oversteer which is very unlikely with VSA or any form of stability control systems. If it was VSA, you would have also felt sudden decrease in power and the car slowing a fraction.

cpurick

Doesn't sound like torque steer to me. Torque steer is a steering input felt while advancing the throttle. Feels like the steering wheel "kicks" a little when you're giving it gas.

Sounds more like VSA: computer detected differential wheelspin consistent with loss of control and applied a correction. Stuff like that gets corrected before you even sense the original condition.

alin2

Umm, "advancing the throttle"="giving it gas"

The only reason that torque steer ocurs is because the wheels propelling the car are also turning and losing grip. Torque steer never occurs with RWD. What he is describing while accelerating into a turn is probably torque steer. This is a sudden jerk of the steering wheel towards the tire that is maintaining grip. VSA will reduce power to or brake the wheels if understeer is detected. This will also quickly put the car back on its steering path, but with a reduction in power. It should not cause the steering wheel to jerk. In addition, the direction he relates is sudden tightening of the turning radius. This would be oversteer. This is really hard if not impossible to do with FWD. That is why FWD is considered better for the masses. Understeer is a lot easier to deal with. If your turning radius starts to widen due to understeer, the natural reaction is to let off the gas which leads to a return of the intended steering turning radius.

Oversteer is potentially more dangerous. It really is only a problem with RWD and rear weight biased cars. The classic is older Porsche 911's. The problem with oversteer is that as soon as the turning radius is tightening, the reaction of letting off the gas is potentially diastrous as the oversteer will worsen dramatically. You have to throttle up with oversteer in order to correct it. If you ever get a chance, drive a older 911 (can you believe that the new 996 has stability control!). The twitchy super tuned steering is a joy and the sensation of oversteer is pretty cool, sphincter tightening to be sure, but pretty cool. Try it at a driving school or at least in an empty parking lot.

Just my

alin2

Oops...my bad...I misread the original post. I agree if the steering wheel did not jerk in his hand, it is not torque steer.

bluenose

My guess would be the VSA doing its job. When the vehicle is in a state of understeer (not turning as much as the driver wants) VSA will not only reduce engine torque but apply braking to the inside wheels - in this case the right wheels. This will cause the vehicle to tighten it turning radius.