E34 M5 ECU - does it compensate for different octane fuels ?

AseanAero · 19th August 2012, 11:51

As the E34 M5 doesn't have a knock sensor does it make adjustments for various octane grade fuels or does it have a basic programming for the lowest grade fuel in the export market it was sent to ?

My M5 is a 9.2-1 low compression engine with CAT delete at the factory (basically a gulf version engine) but still rated at 232kW (310hp). I run the car on 92 octane RON (about 96 AKI in the USA) and 95 octane RON (about 99 AKI in the USA) when I can get it. I have access to 100LL avgas (I usually keep a 200 litre drum handy) and I'm thinking of blending it with normal pump gas and running straight 100LL when I want to go for a hard run.

Does the M5 adjust engine settings for the higher octane fuels automatically or is running 100LL or a blend a waste of money ?

I realise I can re-chip for higher grade fuels , the question is does the standard chip assume a base octane no matter what and then by using a higher octane we are adding a safety margin with no performance benefit ?

uk_bm · 19th August 2012, 14:04

It can't adjust without knock detection. Calibration will be for the 'worst' rated fuel... As you concluded yourself.

You may consider that more premium fuels have better additives, and if you have carbon build up the octane requirement of your engine could be a little higher.