changing dme weirdness

[svandamme]

scored me a spare 944S brain on ebay
just got it , and hooked it up
car started fine, idled nice, smooth

till i gave it some revs, first time at 4500 K it bucked

back to low revs, smooth again

i give it another revs, this time till 5500 k till it bucked

back to low revs again

3rd time, full revs, no bucking


it was like a full cutoff of everything , and then back on once i let go... not like bouncing of the rev limiter though ,

would this be something where the brain has to "learn" the engine ?? o2 , knocking sensors and whatnot ??

or maybe because i didn't have it fully mounted, just to the wire loom , no ground??

[fast924S]

i would check your AFM, pop the black cover off and see if the wiper arm or area is worn out

[svandamme]

nothing wrong with my afm , it never did this before i plugged in that new DME , and hasn't done it after the initial 2 times, or after putting the original one back on...

besides, the AFM isn't used at those high revs, the flapper is fully open by then, and the engine runs on a rpm/tps map then, maybe o2 as well, not sure

[svandamme]

just found the answer in the Bosch FI management book

Porsche used Motronic ML.3, which is adaptive, it learns what the driver does and adapts it's characteristics accordingly

takes 10 minutes to learn, and then stores it's operating parameters on volatile memory

book also mentions how cars can gain or loose "spirit" if they were driven i a bit lame, and then went to the track , it would take some runs to regain it's power...