Longest day of the year – it’s all downhill from here!
Went to a local Saturday morning car get together, sort of a mini Cars and Coffee. Same thing though, anything and everything shows up, from new Ferraris to an authentic Ford Model T. I talked to the owner and learned that not only are the brakes cable-actuated (stretching as they’re applied), they’re also only on the rear axle. It reminded me of a story my mom told us how when she was a kid, her family moved from the midwest to the west coast, passing through Colorado. She said that to this day she still remembers them nearly going off a steep cliff and her seeing a river down in a canyon way too close. I think they were in a Model T and it wouldn’t take much to overheat the brakes – the drums looked like they were about 6″ diameter.
Also at the car meet was a BMW M6 with the total “hella flush stance” (Google that to see what it takes to be one of the cool kids). He had about 1.2 millimeters of clearance between the tires and fenders, never mind 8 degrees of camber – no, that’s not a typo or exaggeration. He got a lot of admiring glances and comments from those his age, one guy saying, “That’s the most awesome car here.” I suppose.
Took the car out 5:30 am Sunday morning, expecting to find a deserted freeway for doing an engine pull to set the knock sensor noise floor. There were more cars than expected, so I had to slow down until those behind almost caught up, giving enough room ahead so that I could complete “the mission.” For this sort of thing, the rules are: no passenger, no passing, and no swerving across lanes. The idea is that from way behind it makes it tough to say how fast a car up ahead is traveling, or that’s the theory. Anyhow, I got a surprise, just not what you’re thinking. I got up to 7000 rpm and felt the engine go a bit weak. That’s always a bad sensation, so I called it a day and headed home. The logs were downloaded and the answer was – unclear. The problem is in two parts:
First, not expecting to have this problem, only engine speed, MAP, lambda, and the four knock sensor variables were logged, and sure enough, at around 7000 rpm, MAP dropped from ~200 kpa to ~150 kpa. That’s odd because I had removed all boost control, so the turbo was running solely off its ~200 kpa wastegate springs.
Second, for some reason, the ECU datalogger app didn’t display lambda, even though it was on the list. So not only don’t I know what the fuel mixture was at the time of the problem (identifying whether it was cutting fuel), but I also didn’t log spark timing. It has to be one or both of these, since engine rpm didn’t drop (as would be expected if an rpm limit was hit). Another variable that should be in the logs is air temperature coming out of the turbo. If that got too high, the engine protects itself. So first I have to figure out why lambda didn’t get logged, then log the other variables to figure this out.
Now that I think about it, it’s possible this rpm problem has been around for a while. I remember at the last track day event feeling something similar, but a lot has changed since then. Different ECU, no water/methanol, possible knocking, it’s too many variables. It’s mostly my own fault, I keep changing things and introducing new variables. That said, things will settle down now that the engine’s is fully “done”, it’s now just a matter of squeezing out the last few bugs in the system.