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      09-02-2012, 02:23 PM   #54
BMRLVR
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Drives: 2011 E90 M3,1994 Euro E36 M3/4
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Quote:
Originally Posted by Mike Benvo View Post
DME doesn't have free reign to pull any amount of timing that it wants. It's restricted in the amount of retard by the code, although this can be modified in the calibration. If one cylinder had consistent knock, the car would certainly throw a fault. If there was bad knock detected it would throw the car into limp mode after a certain amount of occurences. To my knowledge, The supercharged cars have misfire detection turned off or they would be throwing multiple fault codes.

OP: Glad you got it sorted out!
I am not sure why you would think that the supercharged cars would have the knock detection turned off. A proper software file for a supercharger that is tuned properly can run with knock detection on no problem. No company worth their salt would even think of turning knock detection off on an engine that is running higher levels of power than stock.

I am willing to bet that one or more of the injectors that the OP had was not flowing the proper volume of fuel compared to the rest. This can be caused by multiple things like, the injector was defective when built, a piece of debris was restricting either the nozzle or solenoid, or the fuel rail was not kept clean on install of the new injectors when the SC was installed which allowed the debris into the system.

I am sure upon multiple occurrences of severe knock from one cylinder that the DME "might" set a code for knock sensor circuit voltage/performance high voltage. With all 8 of the S65's cylinders being monitored for knock I am not even sure that the knock sensor circuit is even monitored the same way as a conventional knock circuit (with 5V reference voltage), BMW technical info would be required to determine that. The fact that the DME didn't have any codes stored and the fact that the issue has resolved itself by installing new injectors and a software flash would lead me to believe that the injectors are the issue. ESS is a very reputable company and I am sure that the software on the DME was fine but they just wanted to double check there was indeed no issue. Their VT1-535 software is a common thing for them and it is not like it is a custom designed file for every car.

So I am going to challenge you to give me some more info on the actual knock control parameters that the MSS60 has. I assume that the amount of timing pulled was well within parameters of the engine and that is what indeed happened. Since the S65 can make up to 40+ HP from adding higher octane fuel alone I am sure it is able to pull a significant enough amount of timing to be able feel it as the video showed. I am also sure you may be correct that the DME can control the knock individually between the cylinders as you said in a previous reply, but that is only possible up to a point, Maybe 6-8 degrees max, after that it is going to cause an extremely rough running engine and actually place unwanted stress on the crank and rods from that cylinder firing out of phase with the rest of them. I personally think the the knock control system actually monitors all cylinders but it adjusts the timing across the board, this would make more sense to me. The ability to individually control the timing in the individual cylinders would be of no huge benefit to the running/performance of the engine. Monitoring every cylinder individually via resistance however would have huge benefits to be more accurate in detecting knock compared to an acoustical knock sensor as well as being quicker in reacting to timing requirements.

To the OP, Congrats on getting the car straightened out and props to ESS for providing top notch support!
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