It got cold , your AFR went up. I noticed mine did that, and I didn't switch gas. Gotta change the air temp adjustment tables I guess. (I just retuned) I was at 11.5 and took it out when it got down to like 17deg and saw 12.5!!! Consider drastic temp change.

 

Different types and brands of fuels have different specific gravities. This WILL change your AFR! If anyone does not know what specific gravity is, google it, or wait until you reach 8th grade or so when you'll cover it in science class.

To give an example however, most pump fuels will have .75-.76 SG, while the Sunoco 117 I run has a SG of .70. Some elf fuels are over .80.

 

I know specific gravity, but how come when I used to get 100octane (from Sunoco) my AFR's did not change? I had wideband in my DSM and I got 100octane all the time because my local Sunoco had it.

 

I couldn't tell you, I don't know the properties of the two specific fuels you used. You can look it up though, sunoco has specs available. Actually, I think they have racegas or racefuel dot com. Some fuels are close enough that I don't see the AFR shift, with others, it's more obvious. In fact elf claims right up front that you will have to retune for the higher density of thier fuels, but I have never used them personally and am just relaying the info/specs available online. Just wanted to make the concept/mechanism known, since I hadn't seen it mentioned yet in this thread.

 

i got a dumb question. as always but if you got your evo with all the bolt on's and your tuned for 93 oct at about 23 psi and then get a 100oct tune map boosting 26 27 psi what kind of power gains will you net. or a guesstamit???

 

anyone?

 

Id say anywhere between 25-30whp.

 

wow. more then i thought.

now can you run 100% meth and 100oct at the same time and still see better resolts over 93oct and 100% meth?

 

My guessitmat would be 30-40, ususally smaller turbo's can make 10+whp/1psi of boost. That's provided turbo is in it's efficiency range and the tune/fuel support it. You can't just turn up the boost, go wot and expect max gain.