Thanks for all the feedback!
Prior to the event, I had adjusted the sweeper arms on the AFM by pulling them up/away from the contact patch. I tried to bend the arms to get better contact, but maybe I didn’t do a good enough job. I’ll have to take a look at this again. Friend of mine has a “known good” AFM, so I can also borrow that and hook it up for the same test.
Kind of a non-critical question, but what is generally meant by “40% throttle”? Seems like it could mean 3 things – the cross sectional area of the open butterfly valve (unlikely, since it would be a pain to calculate), or it could be the degree of the butterfly being open (45 degrees being “50% throttle”), or it could mean the distance that the end of the throttle cable has traveled in relation to the full range of travel. I’m guessing it’s the last one?
My oil temp was around 150-170, which is generally where it sits, if I remember right. Under 150 would have stood out to me. This was measuring off a manifold connected to the oil pressure switch location. So I’m guessing the coolant was up to temp / normal operating temp. It definitely took more than 1 or 2 laps to turn off the light.
Water pump had about 6 or 7 hours on it – I replaced it beginning of 2014. But maybe it did suck. As part of converting to the new style cooling, I’ve also purchased a new pump.
Good to know about the thermostat, thanks… yeah, I guess that wouldn’t be the problem then.
As for the radiator, I don’t know how old, but probably pretty old. When I got back to the pit, it was spraying from the middle of the core onto the timing belt cover. The rest of the stuff had been replaced, with the exception of the expansion tank.
I replaced the transfer pump before this event. The starvation issues I got prior to this were very sudden cuts in engine power and happened any time I tried to run a second session on a tank. I had none of those experiences at the last event, and even let my fuel drop below half full for a session to test. That said, I can’t really rule it out – who knows, maybe the bogging was a different type of starvation effect. The slow creeping at 4500 up didn’t feel like starvation, though.
I had the injectors cleaned prior to the event, but I also did a head swap. Who knows, maybe I wasn’t careful and some crap happened to drop into the exposed fuel line while I was doing this and clogged up and injector. I’ve purchased a fuel pressure testing kit, so I’ll see if that looks normal. Would be nice to have the pressure/a-f to a data logger, but realistically don’t see that happening this season.
I would love to do a lot of these little tests while on a dyno. You could easily test the TPS out-of-the-butt theory by unplugging it. That would effectively tell the DME that there’s part throttle all the time. Might not idle right, but if that’s your only difference, I imagine you’d expect to see the same shaped graph after 4500 RPM, right? Same test in reverse – good TPS, unplug the AFM. If TPS at WOT goes to internal maps, then again you’d expect identical graphs from 4500 RPM and up. A test that might be fun would be to plug a trimpot to the coolant sensor wire and run a handful of different tests to see how sensitive the performance is to an incorrect reading – are we talking 1-2hp or 4-5+? Unfortunately, while the dyno runs are like $60-75 for 3 runs at the track, it’s twice that at any of the local shops here, and 4 times that to get an hour “tuning session”. Not sure I’m ready to spend $250-300 on experimentation yet.
Som