Pulling to left under acceleration

Defcon5 · 13 Dec 2010 at 17:05

Under hard acceleration, if I let go of the wheel, the car pulls strongly to the left. With no throttle, it stays straight if you let go of the wheel. Also stays straight if you hold it straight, but the wheel is trying to turn. More acceleration = more severe pull. Speed makes no difference, only amount of throttle.

What could cause this? I initially assumed geo but why would it only happen under acceleration? Surely not torque steer? Plant the throttle in 6th at 70mph and it still does it.

Tracking is fine, will do a full geo check asap, but as I said, surely anything geo related would make it pull left regardless of throttle input

Car is a Lupo GTI, on height/damping adjustable Koni coilovers. Recently I have replaced the wishbones and ball joints, but this problem has come on more recently.

Thanks

Defcon5 · 13 Dec 2010 at 17:11

Thats my next port of call when I come of day shifts!

Why would that only affect it under acceleration though, thats the bit I cant get my head around

Defcon5 · 13 Dec 2010 at 17:20

Luke said:
Not torque steer from massive power output then?

That would explain pretty much all the symptoms, but I very much doubt it!

Defcon5 · 13 Dec 2010 at 17:51

It has 125bhp, 112ft/lb ,weighs about a ton.

Left drive shaft is shorter than the right. It has an electronic differential to keep the wheels within a certain rpm of each other

I have had the car for 3 years, and never noticed it before. Its not reported amongst other owners as an issue

Defcon5 · 13 Dec 2010 at 18:16

BigglesPiP said:
That'll be a regular diff with ASR then?

VW call it EDL (electronic differential lock) I dont know the specifics of it as id doesnt appear to do anything useful

I beleive it applies the brake to the spinning wheel to send power to the wheel with grip. It doesnt have traction control or anything like that

BigglesPiP said:
Probably uneven tyre wear or tracking then.

Why would that only affect it under acceleration though?

Defcon5 · 13 Dec 2010 at 18:36

sigma said:
I'd get the tracking checked anyway, an ATS will do it for free, my local place is really good they showed me how badly it was out. It was out by 6 degrees IIRC and the car didn't pull at all!

I have been to two different places to check the tracking (jut tracking, not other geo settings checked) and both said it was fine

Ill swap the wheels around and see if anything changes

Defcon5 · 13 Dec 2010 at 18:45

MagicBoy said:
What about the matched tyres?

All the tyres are the same, however I have recently put the rears on the front and new tyres on the rear.

Sigma - I initially thought that, brakes are fine

Defcon5 · 13 Dec 2010 at 19:00

burns said:
Dead wishbone bush? You see the same thing on 205 GTis. If one of the bushes on the wishbone goes then torque to the wheel rotates the hub around the good bush, changing the angle of the wheel. Certainly worth a look.

New wishbones in October, inc all new bushes.

Didnt do the track rod ends though

Defcon5 · 14 Dec 2010 at 16:26

Dogbreath said:
OEM wishbones or pattern? Did you fit polyurethane bushes?

OEM with OEM bushes.

Defcon5 · 14 Dec 2010 at 17:59

Yes, I have just noticed this in the last few days, that work was done months ago

Defcon5 · 18 Feb 2011 at 17:01

Not solved this yet!

Alignment specs are

Front

Camber -2.03 -1.57

Caster 1.37 1.38

Toe -0.01 -0.01

Rear

Camber -1.45 -1.28

Toe -0.04 -0.02

thrust angle -0.01

I have changed the tyres from front to rear which didnt make a difference.

Could the camber differences cause this? I dont think they would.

Any more ideas?

Defcon5 · 18 Feb 2011 at 18:25

MagicBoy said:
Driveshaft or Diff perhaps? Unsure which gearbox is fitted to the Lupo GTI, however other 1.4/1.6 VAG cars around 1998/1999 had a bad batch of diffs which tended to fail within warranty. My Bora was one of them...

Powerful FWD cars with uneven length driveshafts (which is most) can have a tendancy to pull in one direction under hard power. Go find the Top Gear clip of the Astra VXR for an example. If it's a recent problem then it's likely a fault than a design characteristic.

It isnt powerful enough to cause this, nowhere near.

As far as Im aware, no other VAG car uses this 'box, how would a damaged drive shaft cause this? If it were bent it would be undrivable surely?

Defcon5 · 24 Mar 2011 at 17:23

And so the saga continues...

Now changed the front top mounts and bearings (one was split, though I was onto a winner there!) and the track rod ends to no gain.

So, to recap

Changed:

Tyres
Suspension alignment
Track rod ends
wishbones
wishbone bushes
top mounts & bearings

Seem Ok
hubs
wheel bearings

I am going to change the gearbox and engine mounts next. Any other ideas?

Defcon5 · 14 Apr 2011 at 16:46

Well the mounts did naff all.

Im struggling to think of anything left to replace! Could the diff be damaged, so its slipping internally? No noises or anything though.