I remedied a few minor problems, like a flaky TPS and gutted the questionable catalytic converter, which turned out to be fine, but oh well....who needs a cat anyway? Drivability improved, and I knew I was on the right track, but still everything was not right in hairdryer M30 land.
Anyway, after consulting with Todd (many times...thanks for the patience bro), we concluded that the air/fuel ratio I was seeing under boost was too lean and likely the source of my detonation (all I was really worried about at the time). Tried adjusting the FMU and AFM and dancing a jig while summoning the dark spirits in the driveway, but nothing worked...and the old lady next door was staring at me. Nothing I did would get it to fatten up above 5k where I was having the problem.
I installed a fuel pressure gauge on the line so that I could monitor the situation while driving, and sure enough, as the RPM climbed the fuel pressure started dropping. From 60 psi or so down to about 40-45 at 5500!
Not good. I now knew that I had a fuel delivery issue of some sort. I had a new filter on it, stock BMW main pump that looked remarkably new, and the 255 lph in-tank pump from the TCD kit. Everything should be fine, but it was not...First thing I went to check was the in-tank pump, as I had a hunch that when I installed it, I may have positioned it too low, mashing the pickup filter sock against the bottom of the tank and restricted the flow. When I pulled that bad boy outta there, I was shocked to say the least. The sock was fine, but the damn pump was basically not even connected to the fuel line! There is a piece of rubber hose that connects the pump itself to the pickup assembly, and that bastard had split right down the middle and peeled away, basically allowing the fuel to just shoot out of the pump, through air space, and hopefully land somewhere near the pickup tube to maybe make its way to the engine! Doh!
AND the fuel that it actually was getting was completely aerated when the fuel dropped below half a tank! It was completely my fault, and I had just jammed it on there and clamped it too tight and I was in a hurry at the time. I should have done it right the first time, which included modifying the pump itself to make it seat well.Well, I had another rubber hose from a shot in-tank pump I had lying around, and I trimmed and installed that. Plugged the ECU back in, cranked it up, and my jaw dropped. It has NEVER idled this well since it was built! Sweeeet. Took it for a drive, and WHOA! Now this is what I'm talking about! All of the drivability problems I had are now gooooooone! Nice and smooth, and even faster! I can break the tires loose in an extra gear now! Too cool. That hose had been busted since Day 1 ( or 2 or 3 or whatever). 10,000 miles of mostly trouble-free driving like that. Amazing. Can't believe it ran as well as it did...
Sometimes its the stupid small things that throw you off.
Oh, and BTW, it ran a 14.2 @ 102mph at the track in this condition.
Can't wait to run it again, I'm sure it will be in the 13s....
Runs like a sewing machine and doesn't burn oil...gotta love junkyard parts. If it ever blows up, I can build another one for under $500. Try that with an S38!