Traction Control in a Diesel

[RacingManiac]

One question I've had since Sebring 12 Hours, and now again "sparked" by Wouter's Le Mans preview and the comment of R10 seems to be harder to drive than the R8, is regarding the control scheme for the traction control system. Not to the powerful monster like R10 only, but really diesel cars in general. In petrol engine, common way for traction control system is to first detect wheelspin, then physically reducing engine output through controlling the spark and causes misfire to cut power. With more modern diesel being used in high performance application, such system probably is also needed on diesel as well. Production cars usually have multiple driver aids, rangine from TCS to ESP to EBD...etc, and a lot of those are through actuation of individual brake to regain vehicle composure, but traction control's sole function is to curb wheel spin, and a brake actuated system may be undesirable. On a race car, such system cannot be used as braking system are not controlled by computer at all(no ABS circuit), and with R10 being diesel, no controlling of the sparks neither. Coupled with the monstrous torque output at low rev, the car is probably quite difficult to drive, and from some R10 driver's comment at Sebring this is definitely the case....

[henk4]

My 4-year old Citroen has ESP and I suppose every diesel car now sold has it.

[BjD]

Modern diesels are controlled by an ECU, adding traction control would be no more difficult than on a petrol.

[RacingManiac]

ESP does not equal to traction control though. ESP controls brakes, it does not cut engine power(though I suppose you can brake the powered wheel to limit power).

While diesel are controlled by ECU the controlling parameter is different. Spark timing is controlled in gas engine but not in diesel for obvious reason, and spark timing is the most direct and immediate way of curbing power. Fuel injector duration can be manupulated as well, though the effect will not be as immediate and thus not as effective especially as a mean of performance oriented traction control system on a race car. Other thing I can think of is maybe through throttle position sensor manipulation, though again that comes down to changing fuel map and probably results in the same thing...

[BjD]

The ECU in a diesel gives just as much control as the ECU does in a petrol. The petrol ECU would control both the spark timing and fuel injection duration to control speed. The diesel only has control over the fuel injection start and duration (maybe the number of pulses depending on the injection strategy) as they have no throttle valve.

I can't see why a petrol would have a superior ability to control its speed. Cutting the fuel in a diesel immediately cuts power output; theres nothing to burn. Truck (diesel) ECU's allow control precise enough that automated manual 'boxes hooked to them can synchronise gears without the clutch.

[henk4]

Well, I just checked, but even the cheapest versions of Audi and BMW diesels have ESP and traction control, so I guess they found a way to deal with it.

[RacingManiac]

How fast is fast though? In the diesel car to my knowledge(pardon my North American Ignorance), even when you shut it off it still runs until it stop by itself. Maybe the newer diesel doesn't have this issue.

[henk4]

How fast is fast though? In the diesel car to my knowledge(pardon my North American Ignorance), even when you shut it off it still runs until it stop by itself. Maybe the newer diesel doesn't have this issue.

that is really a thing of the past indeed.

[Coventrysucks]

such system probably is also needed on diesel as well.

"Quote of the Week", I think.

[henk4]

"Quote of the Week", I think.

may be diesel drivers are so good that they do not need any electronic assistance devices???

[Lagonda]

How fast is fast though?

Immediate. ESP and traction control (which is part of the ESP in most cars) work exactly the same and with the same speed in a diesel or a petrol engine. And ESP does cut power if needed.

[quattro_20v]

may be diesel drivers are so good that they do not need any electronic assistance devices???

I think they drive so slow they cant crash

[RacingManiac]

may be diesel drivers are so good that they do not need any electronic assistance devices???

R10 ran without TC at Sebring, and they were pretty quick, so I guess yeah....

The TC issue for R10 may just be an isolated issue with a car with 800+lb-ft of torque....

[Wouter Melissen]

R10 ran without TC at Sebring, and they were pretty quick, so I guess yeah....

The TC issue for R10 may just be an isolated issue with a car with 800+lb-ft of torque....

A big problem with the diesel engine is that the drivers can not HEAR the wheelspin. This has already caused a serious accident and severe delays for the Group Bio Diesel Lola LMP1 car.

It's remarkable that the ignorance surrounding diesel engines continues to result in childish remarks. It almost makes me want to Audi to win on Sunday.

[MrKipling]

Also, modern 'fly by wire' throttles make it much easier to regulate power. You don't have to faff about with ignition timing, the ECU just electronically backs off.

Audi winning would be great - it's giving motor sport back one of its most important aspects: real world relevance!