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Ethrottle shutting down BMW S54


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I have this working inconsistently.  I spent 7+ hours on the dyno with this car with no faults, but it seems when the car goes out for a race it fails.  


Total resistance of the circuit of 2.5 ohms (I have 2 wire wound resistors that add 1 ohm), and only 2 throttle return springs still attached (S54 has some heavy duty spring action).  My setup is as following and the throttle responds pretty good to this.  

Frequency 500hz

PIDs - 

Prop gain 6.50

Intergral 0.148

Derivative 30.0

Max clamp 90% +/-


I run the system in 'Setup mode' because some slop in the linkage causes TPS tracking errors (Main TPS is on throttle shaft, Sub TPS is on throttle motor).  When it failed before, sometimes i would get an aux9/10 supply error so it is hardwired now with no relay even.  I might be able to bring the max clamp down, but I don't see what for.  

Anybody see anything odd with the software that would cause my life to suck?  I really need to get this to work on these cars, as it is one of the selling points for us.  


-Nick from ACE

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Hi Nick,

Still having issues with the engine we worked though earlier? The software looks good, the problem here is the engines mechanical setup is on the limit of the ECUs driving capability. Can you run the system with only one return spring to reduce the mechanical load on the throttle motor?

The only other solution I can think of is running two of the new external e-throttle modules in parallel - this will need testing from our end first.


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thanks for the response.  Ya intermittently it shuts off.  Usually on the last lap of the race too... quite embarrassing.  

I made some changes to the software yesterday.  I dropped the MAX clamps down to 65% and it still works perfectly.. So why overload it.  

Also, fixed a couple other voltage supply issues (general ones).  We are doing a test day tomorrow at NHMS and hopefully it will be ok.  I will log the runs and if something happens, I should have more info.  

I can't remove any more return springs without it becoming unsafe to drive.  The total spring tension is about equal to a 'regular' VDO electronic throttle now.   I don't think that is the issue though.  

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3 hour enduro... Fault free operation.  It was cool outside and raining (ambient was like 65 degrees).  I feel much more confident in that it's fixed.


I have a 2hz log file of over an hour if you want to take a look at it.


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