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GameboyRMH
GameboyRMH MegaDork
4/10/19 10:29 a.m.

Finally had some time to put together video with data from the track day directly after February's autocross. The track day was pleasantly uneventful in terms of breaking things. I was still tuning the Kumho CO3's pressures and I think I had them a bit lower than ideal during the track day, but I still set a new personal record in the 1:22s:

 

I've also figured out that excessive fuel was contributing to the high-RPM weakness, but now that I'm using those higher revs more I'm having temperature problems - the high-temp rev limiter I set up kicked in just around the end of this video. After examining the data, although the higher revs alone produce a lot more heat for some reason (possible water pump cavitation?), rolling back onto the throttle seems to produce a big temperature spike. For a while now I've been running a new accel enrich setting from the electrician that seems to work well, but some richening up might fix that.

GameboyRMH
GameboyRMH MegaDork
4/24/19 8:39 p.m.

Next event was the autocross in late March. One of the C03s sprouted a sidewall bulge, and a friend was selling some 205/50/15 Maxxis RC1s for cheap, so I switched to those and kept the C03s as spares. I'd also found out that part of my custom crank sensor bracket had started to crack from the vibrations, so that would need fixing soon.

On my first run I messed up the "Z-bend" and had to reverse. It was clear that the RC1s had much less grip than the C03s, even less than I'd expect from an EPS tire. My second run was much better. My 3rd run was even quicker, but I clipped 1 cone, nearly erasing the gains, and at the end the engine seemed to lose ignition (didn't get any working data logs unfortunately):
 

 

I thought it must be the crank sensor bracket, but the sensor still seemed to be in the right position, and I was getting no hint of any crank signal, I ended up having to tow the car back to the electrician. Turned out to be an under-dash short in the crank sensor wiring. I had a chat with the electrician about the tire situation, and he said RC1s need a good bit of heat in them to generate any grip, so I should see what these are good for at the next event, a track day.

GameboyRMH
GameboyRMH MegaDork
5/11/19 4:19 p.m.

Next, April's track day. Only setup change from the previous event was a different, all-TPSdot-based accel enrich setup, and a hint more air in the tires. After the first lap the tires had way more grip, about as much as the C03s. Unfortunately I didn't get to test them a whole lot because the high-pressure PS line blew up and put a quick end to the day, as indicated by a James Bond smokescreen in the rearview near the end of this video:

 

The good news is that I improved my personal best time on the first flying lap:

 

I think the tire pressures were still a little on the low side, so there's still room for more grip. Also after reviewing the data logs, I found that temperature spikes were related to passing through an unusually lean area on the map around 4~6krpm at low/mid load - it was set that way based on tuning with the wideband sensor, but I'm going to richen it up and see if it helps. Unfortunately I won't be able to test any of that for a while, because this car's going to be put away for a few months...maybe even a year or more. Next job to do on it will be some rust repair, mainly to the roof.

GameboyRMH
GameboyRMH MegaDork
8/22/19 10:59 a.m.

Next event and last autocross for me for the year was a couple weekends ago. I had the PS line remade by a local hydraulics shop so hopefully it'll last another 2~3 decades. My first run was pretty good apart from an engine stall as I entered the downhill section which cost me a second or two. I knocked off about 2 seconds on the second run with no engine stall. On the 3rd run despite my best efforts I only managed to knock off 3/4 of a second, so I knew it would be hard to go any faster:

So on my 4th run, I tried to optimize the tire pressures a little more and did some tire warmup before the run. It was looking promising, but then I spun out on the 2nd slalom section on the top straight. The previous tire pressure settings were probably better. My 3rd run was still good enough for 3rd in class, so not bad, only 2 caged and stripped race cars on better tires ahead of me.

GameboyRMH
GameboyRMH MegaDork
9/3/19 7:46 p.m.

Wasn't sure I was going to post this one. Did another track day a couple weeks ago, and on my first session - the only totally dry session - I improved my personal record slightly, but my lines and braking points weren't great. There's still room to improve it by a bigger margin. Didn't break anything at the track day, so that was nice. I also think I made some engine tuning improvements based on the data logs to try next time.

 

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