Help me understand traction control

[Justjuice]

For the longest time I always assumed that slight juddering when the traction control light came on meant that my wheels were spinning a bit and then brake force was applied electronically to stop it. To elaborate what I thought is that the judder was the wheels breaking traction.

The other day I decided to turn off the traction control to see how it would feel (I have done this on two occasions and oddly enough on both occasions I was turning while accelerating hard so the car was sliding somewhat, not a true indication of what its all about).

To my surprise the car felt much smoother when changing gears (manual) and overall just a bit nicer even when driving normally. The biggest part that surprised me is that the car felt slower under hard acceleration but looked to have gotten up to speed quicker than normal. I was confused. The more I pushed it the smoother it felt, the judder was no longer there but I'm 100% certain that my wheels would have been spinning (stage 1 with torque arm insert).

So what exactly is going on here? Is that judder Im feeling when the TC light comes on actually the brakes and not the wheels breaking traction? Is there any sort of electronic power cut that takes effect? Is the TC good enough to stop all wheel spin thereby also saving tyre tread wear or do the wheels still spin somewhat?

If thats the case how much does the TC actually slow the car down by and is it potentially possible to get more out of the car by turning the TC off?

Also why does the car feel smoother without the TC on even when driving normally in a way that would never spin the wheels? All in my head perhaps?

Someone please educate me!

[team_v]

What model and year is your car?
Any modifications other than stage 1 and the torque arm insert?

I wouldn't turn off TC on a public road ever, the judder could be fixed by an anti-lift kit if it happens during accelleration.

[Ryan_R]

I once asked a guy from Pedders about that, he said the car had a pretty dim-witted TCS which as you've already said just applies the brakes when the ABS sensor detects a loss of traction. The judder is usually the TCS/ABS (brakes go on/off/on/off/on/off, etc very quickly) instead of just limiting power output.

Don't ever do a fast start with TCS off when the road is wet/slippery, you'll change lanes even with the wheel pointed straight.

[14nce]

Are you guys sure thats how th traction control works?
Maybe on a N/A, but the older 1.8T dumps boost pressure with the "N249" system. I can see this happening on my boost guage when the light is flashing, but it doesnt simply dump all boost. Boost guage jumps up and down constantly, would account for the pulsing feeling.

Would assume the newer TFSIs have a similar system.

[Justjuice]

That's what I was thinking its doing, brakes on/off in rapid succession.

Few more details, it's a 2010 gti. Only engine mods are the stage 1 tune and torque insert. Have PSS tyres on slightly wider than stock @ 235 too.

Just gonna clarify its not axle tramp I'm talkin about as I still get that eventually with traction control on or off.

[tonymy01]

I thought it cut spark and fuel, the use of brakes is for the stability control (car sliding) rather than for breaking of traction under power in a straight line.

[Ryan_R]

That's generally how it works in expensive sports cars (and video games) hence the 'dim-witted' comment above.

MK6 Golf's are TSI not TFSI btw.

[tonymy01]

Certainly in the R (tfsi) you can feel it cutting ignition(and presumably to avoid trashing the cat, fuel). That much power being attempted to be pulled back with brakes alone is guaranteed to shrapnel the driveline pretty quickly.

[Ryan_R]

Might be a difference with having 4motion as well.

[tonymy01]

Possibly, as you said, 2010 GTI=TSI, R=TFSI, different engine and thus different ecu. The R (2012 model anyway) has a 2 stage TC/ECS disable, so they are different features, I am sure the TC is done with engine power cut and ECS done with brakes.

[zoomda]

It is definitely power cut in my R. I don't know if it breaks as well though.

[Justjuice]

Just so we're all on the same page I'm talking about turning off ESP just in front of the gear shifter.

With it off do you guys ever feel your wheels spinning or just know that it occurs at some point?

I seriously don't know if it's just in my head but it really does feel a better drive overall with the ESP off.

[tonymy01]

For the R >=2012, first step is TC off, second step (holding down about 3 or 4 secs) is ECS off.

[BoschAutoShop]

There is a lot of misinformation in this thread. To get the facts straight, no modern Bosch ESP system will apply the brakes when metering traction under hard, straight-line acceleration - this is nonsensical and would only destabilise the vehicle further.

Without explaining the complexities of the system, it is effectively cutting power output when it detects wheelspin coming from excessive acceleration. The effect is basically the same as a soft rev limiter and will be audible out the exhaust.

The instances during which the brakes may be applied via the ABS circuit, however, is when there is an unnatural slip angle found during cornering - such as understeer. An example: if the front left wheel is loaded and losing traction, the system may apply brake pressure to the inside right rear wheel in order to tighten the steering angle.

[Rawcpoppa]

Guys this document may go a long way to explaining traction control systems in VAG vehicles.

https://dl.dropboxusercontent.com/u/88004385/K0028037420-Nr__374__Traction_Control_and_Assist_Systems.pdf

The document is a VAG document under their Self Study Programmes. If you have trouble accessing it let me know.

See page 36.