I've been working on the tune for my car for quite some time. A slipped optispark hub, an unfinished ignition controller project, and life in general has slowed the progress immensely, but I've arrived at a point where I feel like it's 95% perfect and I finally have all the pieces to the puzzle together (development halt on the ignition controller and working + accurate wideband). Last fall I decided when I got to this point I wanted to run a tank of ethanol free gas through it to see what happened to trims and PE AFR. Here in the Midwest it's difficult to buy gasoline that doesn't contain "up to 10%" corn liquor. Since I did most of my tuning on a steady diet of 93 octane E10, I wasn't sure what to expect, but the shift was quite distinct so I thought I'd share it with anyone interested. Here's a quick comparison running the same tune for all the log data.
Here are the logs if anyone's interested. [link] Weather conditions were fairly consistent - hot and humid. The ones with "E0" in the filename were captured running on 10 gallons of roughly 90 octane pure dino juice. This is a MAF tune - since I didn't have a really accurate injector constant for the modified LS2 injectors I have, I made the assumption the factory MAF calibration is accurate and tried to determine the flow constant with trims and / or wideband data.
E10
E0
It's difficult to see from the graphs, but the PE lambda is fluctuating between 0.86-0.88 on the E10, and 0.83-0.85 on E0 (BLM locker patch in use).
Essentially this is a very verbose and graphic presentation of the simple idea that E10 is stoich at about a 3% richer mixture than pure gasoline. What I learned from this is that when tuning with E10 it's best to try and have your trims adding around 2%, whereas I was targeting trims that were removing about 2%. This doesn't seem like a lot, but with the E0 my cam surge is far more pronounced, so I think I'm going to scale my injector constant up a bit and see how it reacts.
The cam surge is about the only aspect of the tune I'm not really happy with. Once I have the injector constant so E10 produces BLMs in the neighborhood of 130-132, I'm then going to go back to fine tuning individual cylinder trims to see if there's any improvements to be made. I finally broke down and bought a high quality IR heat gun and after taking measurements on a couple different days I'm seeing #2 seems to be running hotter than the other 7 holes. I'm not sure if this means it's rich or lean, but at least I have an idea which cylinder might be the culprit in causing a slightly lean condition on the right bank.
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