Charlie_B

iTrader: (1)

not disagreeing or arguing here...and Im sure you have more experience than me as well as some hard factual data (dyno plots). So what you are saying is that the increased benefit of the cooling of a rich mixture is worth it? I was basically tossing that out the window to a certain extent. And just comparing burn time/ign time. I wish I lived closer to a AWD dyno to some testing with different scenarios. I know the butt dyno just doesnt cut it. Heck, a car wash seems to gain 5 whp sometimes....

TouringBubble

iTrader: (2)

No, not the cooling. Fuel does a poor job at cooling the cylinder. The richer mix makes the fuel mixture more stable and less likely to detonate ... i believe it's mainly attributed to the slower flame front. So, with more stable fuel you can push a little closer to that 15º mark.

You trade a tad of power from the richer mix for more power from the timing advance.

Charlie_B

iTrader: (1)

hmmm...I may try to run a little richer, just to see what kind of timing I can get out of it. Im already impressed that I can run 12* up top on this 91 "E10" mix. I could barely get 8-9 out of regular shell 91.

TouringBubble

iTrader: (2)

Yeah. Shell reported that they add the Ethanol and then determine the octane of the fuel, but many people have seen increased knock resistance with E10. I'm included. However, I saw my fuel mix go rich in the summer which is the opposite of what should normally happen ... so I'm slightly confused still. Curves are right, but the mix is about .3 AFR richer than the last time I tuned.

Charlie_B

iTrader: (1)

The only stations in town that have the 10% sticker are the Gulfs. The Shells dont have the sticker, and with what Ive seen with my tune, I dont think it has any Ethanol in it. When I first tuned on 91, then switched to the mix, my afrs went up about a .5 point, which is what I would expect with the different lambda-afr conversion. Then going back to the shell 91, I saw them go back down .5 points.

I brought the AFRs back down about a .5 point last night and added a degree of timing in some places. I now running 11.5-11.1, but havent had a chance to review my logs from this morning. The first pull I saw the knock light flashing a little bit, but several 4th gear pulls after that, saw nothing.

OP: sorry for the OT. Timing/mixture relationship is just something I have been extensively trying to figure out lately.