Steering Tightens When Acceleration During Turn

Hi,

I have noticed a momentary increase in steering effort while brisk acceleration getting onto a main road. In AZ the traffic on our main roads moves at 50mph or so. One has to accelerate quickly to get on the main road when stopped at a side (perpendicular street). I have noticed that when quickly acelerating to 50mph or so, when I am at 40 mph ? or so the steering seems to tighten and get resistive. I am wondering if this is caused by the speed sensitive steering response or maybe the Vehicle Stability Control? I am wondering if anyone else noticed this and/or if you know what maybe causing this.

Dave

I never noticed it, but I wouldn't be surprised if they do that to help combat torque steer.

It could also be torque steer, is it equally hard to turn in both directions?

If it is they could probably fix it with an EPS remapping.

I rarely make left turns under similar conditions so I do not know if it happens when turning left. But turning right, it is quite noticeable, steering almost seems to lock. If this problem seem unique to my car, I will probably take it in to have it checked out.

Dave

I notice something similar. The overall steering feel on the Leaf does have some issues, particularly when accelerating and cornering.

This is not uncommon behavior on some front wheel drive cars. How do I say this ... the better ones have tuned this out but the Leaf is a very basic front wheel drive car so I'm not surprised that it exhibits some of this as I've also noted torque steer under some circumstances as well. It's certainly not bad and generally well in check, but still not up to the standards of some others...

myleaf said:

I have noticed a momentary increase in steering effort while brisk acceleration getting onto a main road. In AZ the traffic on our main roads moves at 50mph or so. One has to accelerate quickly to get on the main road when stopped at a side (perpendicular street). I have noticed that when quickly acelerating to 50mph or so, when I am at 40 mph ? or so the steering seems to tighten and get resistive. I am wondering if this is caused by the speed sensitive steering response or maybe the Vehicle Stability Control? I am wondering if anyone else noticed this and/or if you know what maybe causing this.

Click to expand...

Torque Steer is the result of a lot of torque on the front wheels.
And what does the Leaf have? Lots of torque!

How many other small FWD sedans have 280 Nm (207 lb-ft) basically right off the line?

Actually, the Leaf doesn't have maximum torque right of the line. If you watch the power meter and/or use a Valentine G Meter, you can see that it is dialed down some by the VCM from a standing start. And, actually, there are a lot of high performance cars out there with more torque than the Leaf from a standing start and no torque steer. It does require a more sophisticated front end and drive-line however...

TEG said:

Torque Steer is the result of a lot of torque on the front wheels.
And what does the Leaf have? Lots of torque!

How many other small FWD sedans have 280 Nm (207 lb-ft) basically right off the line?

Click to expand...

I think many FWD cars have the heavy gas engine on top of or even in front of the front wheels for a strong forward weight bias.

Leaf, on the other hand, has the bulk of weight (battery pack) in the middle, so doesn't have as much of a weight bias on the front wheels.
This probably has many positive benefits, but could also result in some traction limitations on the front wheels.

http://en.wikipedia.org/wiki/Torque_steering

Torque steering is the influence of engine torque on the steering for some front-wheel drive vehicles. For example, during heavy acceleration the steering may pull to one side, which may be disturbing to the driver. The effect is manifested either as a tugging sensation in the steering wheel, or a veering of the vehicle from the intended path. Torque steer is directly related to differences in the forces in the contact patches of the left and right drive wheels. The effect becomes more evident when high torques are applied to the drive wheels either because of low transmission gearing, high engine torque, or some combination of the two....

Click to expand...

One "root cause" listed:

# Unequal driveshaft length or diameter

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(Does the Leaf have unequal length driveshafts?)

mogur said:

Actually, the Leaf doesn't have maximum torque right of the line. If you watch the power meter and/or use a Valentine G Meter, you can see that it is dialed down some by the VCM from a standing start.

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( "horsepower equals torque (in ft-pounds) times RPM divided by 5250" )
So, I would expect lower power at lower RPMs even with high torque.

But in any case, I notice the steering pull at slightly higher speeds (not right off the line), so I still think abundance of eMotor torque has a hand in what we notice.

There is probably a lot of output turning (shaping) in the inverter firmware to make the performance safe and comfortable but still allow some "kick" for around town passing. It seems with full pedal around a corner as you go past 10MPH it can do something that messes with the steering a bit.

It doesn't feel unsafe, just more of a slightly annoying curiosity.

http://www.modified.com/editors/technobabble/9909scc_technobabble/index.html#

...In most cases, the point where the steering axis intersects the ground is slightly inboard and slightly in front of the center of the contact patch. The distance between these two points is called the scrub radius because it defines how far the contact patch has to be scrubbed across the pavement when the steering wheel is turned... The higher the scrub radius, the more steering torque will be generated, and the more pissed off you will be...

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I've felt a pull in either direction at full power depending on whether you were turning right or left. It feels like torque steer but it's not (since it swings both ways), it's something to do with the front suspension and steering, maybe scrub, but you won't feel it unless you're doing full "go pedal" in the right conditions (turning left or right and hit full power at 20+ mph).