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Food for though: Safety for stuck throttle

MoTeC M1 Software Tutorial

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Was noodling on this, and I am surprised there is not a safety for throttle issues as standard. I realize that the majority of the failure points are removed when you go to DBW, and really leaves only a pedal failure that could cause a stuck throttle. But I was thinking perhaps you could have a brake pressure limit well above normal (panic braking whether near-crash situations, first lap etc, or stuck throttle) that would reduce the engine limiter and drive the blade to idle or just above. Obviously you do not want the engine to shut off in the case of normal racing (near crash, first lap, etc) but when you are in panic braking like that you probably wouldn't even notice that the engine seems to be lazy, and of course it returns to normal when you go back across that limit (+threshhold).

As a professional level (and past pro) driver I don't think this would impact my driving, and could improve safety. Granted it doesn't happen often these days.

There are DBW safety systems in place on the OE and aftermarket ECUs I use.

The DBW system will go into a limp/safety mode when throttle plate isn't on target over a duration that causes the fault without having to touch the brake pedal or anything. If the pedal errors out, same thing.

All that isn't covered by those systems is the throttle plate becoming physically jammed open or pedal becoming physically jammed down, but if the throttle is physically stuck, the ECU can't close it regardless of control strategy. You can always shift to neutral or clutch in, stop the vehicle.

The M1 Throttle Safety Strategy is based off of the Bosch Throttle Safety strategy and has been validated against known best practice. There are a lot of validations and data checking being processed in the background that are deliberately not user accessible when it comes to the operation of the DBW system, that provide much more fail safe protection than is offered by a cable throttle.

Mike, in your case of a stuck throttle, If the pedal position drops and the Throttle Servo Position doesn't follow (Throttle Aim does not equal Throttle Position) the M1 will go into Aim Tracking Fault and apply the Throttle Servo Fault Engine Speed Limit. This is normally set to just above idle so that the driver has enough power available to move the vehicle to a place of safety and not over power the vehicle. This limit also comes into play when there is a Sensor Fault (Pedal or Servo) and when Power Save is active.

I agree the built-in strategies cover most things. Picture something stuck under the throttle, or something fails between the mechanical pedal and potiometer. Rare but possible. Could be it manages with brake pressure and maybe decel rate to make a decision to reduce engine power.

Hi Jordon,

Unless objects are stuck in both the pedal AND throttle in a manner that prohibits any movement of both devices, and retains their relative positions in doing so, the fail safes will pick it up. You only need a very small % difference to activate the safety strategies. I would have more trust in the behavior of a DBW than a cable throttle.

The "Panic Brake" fail safe can be a very difficult one to implement, it could be done in the same manner as Audi and other Manufacturers do, where any brake pressure shuts down the DBW system and only allows for restoration to normal operation after a period of time has elapsed with no pedal pressure on the brake or throttle. This can lead to inadvertent shutting down of the throttle system when it should not have. I get caught out by this often as I left foot brake in automatics and have to be very careful to not trigger the response.

Having it activating at a higher than normal pressure can also be difficult, on an ABS equipped vehicle, it may not be possible to reach this threshold if the ABS system activates, or the driver may just not be able to physically depress the pedal hard enough to trigger the threshold.

I've had more throttle issues on cable equipped engines than I have with DBW.

As a left foot braker, I'm adamantly against that sort of strategy. I hate it on street vehicles, and it would be even more infuriating in a racing environment.


ECU Master EMU Black has these options available


100% for sure DBW is safer than cable. Ive never had a DBW issue that caused a stuck throttle.

I also left foot brake in some cars as well. It would need to be only active in a panic. I am sure you have seen pedal pressure traces when someone is about to pound a wall head on. its like 20%-100% more than even initial braking in a high(ish) downforce braking situation.

biotest- pretty cool! I think I would want to add brake pressure as an input instead of the switch. I dont want it to activate unless brake pressure is panic level.

Rather than brake pedal switch, you could use a high pressure in-line switch on the brake line(s), Jordan. Some are adjustable, so you could tailor it to suit your system and preferences.

That is interesting regarding the ECUMaster settings, my reading of a lot of motorsport and road vehicle usage is that this functionality should not have the option for the end user to disable it, that it should always be active.

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