Differences in Traction control between cars

[PECivil]

ok I have been autoXing for a year now and getting my times down to where I am doing well using street tires so I am told.

When I autoX my M3 I very quickly noticed leaving TC on greatly hurt acceleration out of corners, and I am much faster (5 seconds+) with it turned off.

My elise has TC and after 6 events in it I started experimenting with turning it off and I am not faster with it off at all. Last Sunday I was in a good groove and for my 4 timed runs I got progressively faster
1st run 84.8
2nd run 84.1
3rd run 83.8

I was quite happy with the 3rd run as it put me about 8 seconds behind the experienced peeps with the full on autoX setup cars running hoosiers. TTOD was 75.XXX

so i decided to turn TC off for the last run and got an 87.8????

I thought TC was pretty much the same no matter what car it is on?
In my M3 having it off gives you the ability to put the power down out of corners. It makes the back end looser but definitely controlable.
The only effect I noticed in the lotus is the back end is much more loose and I have to enter corners slower to maintain control.

My elise is non LSS and stock but has TC and LSD.

Is it the M3 is just easier to drive or is there a maj difference in what TC does for different cars?

[fitfan]

traction control is not created equal... in a lot of ways -


your BMW has "stability" control, which is different than just "traction" control...


that data recieved, the action of the system based on data, and the systems that are manipulated.

for example, one manufacture my control each corner of braking, and each drive wheel independantly, and my set those limits very conservation or liberal. another may not employ differentail torq control (lotus does not i believe - only throttle control based on fw speed vs rw speed - hence only "traction" not stability)

the BMW will split torq delivery (i am pretty sure, or uses brake to limit wheel torq) and will brake each corner -also the BMW is very intrusive (conservative) ... brilliant in the snow! anyoing with good grip. BMW system analysis steering yaw vs vehical yaw vessus 4 corner wheel speed.

similar to porsche, but posrche is MUCH better (for agressive driving) BMW is not a stability system for performance driving - it is stability control for foul weather driving. - thats the difference in the "programing"

[apk919]

Originally Posted by fitfan

traction control is not created equal... in a lot of ways -


your BMW has "stability" control, which is different than just "traction" control...


that data recieved, the action of the system based on data, and the systems that are manipulated.

for example, one manufacture my control each corner of braking, and each drive wheel independantly, and my set those limits very conservation or liberal. another may not employ differentail torq control (lotus does not i believe - only throttle control based on fw speed vs rw speed - hence only "traction" not stability)

the BMW will split torq delivery (i am pretty sure, or uses brake to limit wheel torq) and will brake each corner -also the BMW is very intrusive (conservative) ... brilliant in the snow! anyoing with good grip. BMW system analysis steering yaw vs vehical yaw vessus 4 corner wheel speed.

similar to porsche, but posrche is MUCH better (for agressive driving) BMW is not a stability system for performance driving - it is stability control for foul weather driving. - thats the difference in the "programing"

+1

There are so many acronyms... so many rationales, techniques, etc for "traction control".

Some manufacturers emphasize safety, some performance, some inclement weather capability, some off-road capability. No two approaches are equal...

[PECivil]

very interesting.

So what, exactly does the ELise TC do mechanically to control the car?

I am bummed I thought I was improving but turning off the TC the truth comes out.

So now I wonder if my driving would improve more if I just turn it off and drive that way, maybe being slower now but faster later,

or if I should keep it on and turn it off at some future point, or never turn it off.

thing is I know the best autocrossers dont have any TC type controls on so at some point I will need to turn it off if I am to keep improving but when?

its hard to make yourself slower on purpose....

[apk919]

Originally Posted by PECivil

very interesting.

So what, exactly does the ELise TC do mechanically to control the car?

I am bummed I thought I was improving but turning off the TC the truth comes out.

So now I wonder if my driving would improve more if I just turn it off and drive that way, maybe being slower now but faster later,

or if I should keep it on and turn it off at some future point, or never turn it off.

thing is I know the best autocrossers dont have any TC type controls on so at some point I will need to turn it off if I am to keep improving but when?

its hard to make yourself slower on purpose....

From the Lotus Manual:

Lotus Traction Control
Lotus Traction Control (LTC) is a software programme within the engine electronic control unit (ECU)
which uses inputs from the wheel speed sensors to determine the degree of wheelspin occurring, and when
necessary, modulate fuel injector delivery to control engine power output until grip is restored. If an LSD is
fitted, the LTC also operates to stabilise high speed vehicle behaviour under high cornering loads or extreme
manoeuvres.
An LTC tell tale is provided in the
instrument panel, and if this lamp, together
with the tell tale light in the LTC button (see
below) is seen to flicker, this is an indication
that traction control has been triggered and
electronic intervention is taking place; the
tractive limit has been reached and driving
style should be modified accordingly. If the
lamp is continuously lit, this is an indication
that the LTC has been manually switched off
(see below).

[kwancho]

To be honest, unless you're FI'd, the TC on the Elise probably isn't doing much. +1 to what everyone else said. TC can operate on a number of different functions, and analyze a number of different parameters, and have different limits. The Lotus TC cuts fuel to individual cylinders when it detects slip, meaning it is one of the quickest reacting, most direct, and least heavy-handed methods of TC.

[lotusland]

Originally Posted by kwancho

To be honest, unless you're FI'd, the TC on the Elise probably isn't doing much. +1 to what everyone else said. TC can operate on a number of different functions, and analyze a number of different parameters, and have different limits. The Lotus TC cuts fuel to individual cylinders when it detects slip, meaning it is one of the quickest reacting, most direct, and least heavy-handed methods of TC.

So can this cause the same problems as lifting? Seems like shutting down anything when at the limit of adhesion may make things worse.

[apk919]

Originally Posted by lotusland

So can this cause the same problems as lifting? Seems like shutting down anything when at the limit of adhesion may make things worse.

It's actually very subtle... it doesn't completely shut down all the injectors... it seems to shut down just enough firing cycles to reduce power slightly, not completely. So it's not like a complete "lift"...

[TedDBere]

Originally Posted by PECivil

So now I wonder if my driving would improve more if I just turn it off and drive that way, maybe being slower now but faster later,

or if I should keep it on and turn it off at some future point, or never turn it off.

....

IMHO you should leave it on while you're on the street and turn it off at an Autox.

The issue with learning to Autox with it on is that you'll learn to lean on the system to get your car to it's limits. Until eventually you'll go over it's limits anyway, but you've now learned to drive your car with TC, which is slower than with it off. To go faster you'll have to turn it off and relearn the new limits of the car with TC off.

If you turn it off you'll learn the limits of the car without any computer assistance and will be able go faster sooner.

Have fun!

[ads_green]

The lotus system in some cars (like the 211) is variable so you can tune the degree of slip (from 12% to 0%). Lotus recommend using it at about 7-8% slip as this gives a fair amont of driver scope but still a small bit of correction by the ecu.

[kwancho]

Does it really go to 0%? That's odd. I like that they actually give you a %slip (which is essentially a comparison of how fast your wheel is spinning to how fast you are going: [wheel speed - actual speed] / [actual speed]), but you can't actually accelerate with 0% slip.

[PedalFaster]

Originally Posted by kwancho

To be honest, unless you're FI'd, the TC on the Elise probably isn't doing much.

I strongly disagree -- I've inadvertently left it on a few times and noticed immediately. If you leave traction control on and it "isn't doing much", you're not applying enough throttle at apex and corner exit.

Having said that, I find the Elise's traction control the best / least intrusive of any car I've driven. While it definitely slows you down in the dry, my codriver and I think it may be better for us to leave it on in the wet, as we both have insensitive throttle feet.

[IBCJ]

To be fair, the TC/VSC/VDC on the M cars (namely the E46 M3) is not tuned the same as the stability control on the rest of the BMW's. I'm not sure if fitfan was referencing the M cars or not when speaking of the BMW's, but I have found the VDC on the E46 M3 to be far less invasive than on other non-M3 E46's. I actually think they dialed it in nicely. Throwing the car into a corner in the wet with VDC on is pretty impressive - it brakes individual corners and straightens the car out impressively fast (and in a way that no human could do - unless you mastered four brake pedals). With that said, the fastest (and most fun) way around is certainly with it off.

Unfortunately, on the E46 M3 it is binary - either on or off. I really like what BMW did on the E60 M5, which gives you three different levels of VDC - useful for the street IMHO. However you will most likely want to drive with it off all the time, which is how I drive my M3 on and off track/course.

And AFAIK, apk was spot on - the Elise will only reduce power output in a slip condition. However, I thought it did so by retarding the timing - not modulating fuel delivery. It may do both, but it from above, it looks like it only limits fuel delivery. If so, that strikes me as running the motor towards the lean side - but what the hell do I know. I trust the guys at Hethel (along with the Toyota / Yamaha guys) a hell of a lot more than my backyard analysis...

[sandsmuseum]

I have an Exige S 240 with limited slip and traction control, I can set the slip angle. I drive with the traction control on and slip angle set at 7%. This means the car will allow me to achieve approximately a slip angle on the tires of 7% before reducing power. I can also turn the traction control off by setting the slip angle above 9%.

The GGLC recently had an autocross, my first in six months. Because I have forgotten how to setup my car prior to a run, my first two runs were in the low 50 seconds. The car felt neutral and I did not feel the loss in acceleration. Remember the S 240 can get significant wheel spin on corner exit, even with the limited slip.

However I felt there was something missing and suddenly remembered the wonderful feeling the Exige has on corner exit when it actually pushes into the corner. (The properties of the torque sensing differential are to cause understeer on corner entry and oversteer on exit.)

I turned the traction control off and immediately gained a bit more than a second. I suspect I might gain two seconds in a 60 second course. However I now needed to be much more careful with the throttle, particularly in the areas where the course was dirty.

One of my students was driving a normally aspirated Elise with traction control. I got the impression the differences with it on and off were less dramatic.

Michael

[kwancho]

Michael, which one was yours? Was that the grey wingless one? Confused the hell out of me when I first saw it.