trilkb

iTrader: (4)

Can our computers figure out if you were to do 87 octane and e85 (110 octane) mix in a ratio that would result in 93 octane? That would be a 1 to 3, for every 9 gallons of 87, you'd add 3 of e95.

Also, What if you were to do a 1 to 6 ratio of e85 and 93 pump, which would be 12 gal 93 and 2 of e85 which should net 96 octane?

my dodge stealth twin turbo I plan to run 50/50 but I'll have a fuel controller and larger injectors, reason being ill be running 18psi on larger turbos. Curious if my ls1 trans am could see any benefit from a smaller mix just to raise the octane and if the computer could figure it out?

truckdoug

iTrader: (25)

well the FF sensor cant sense octane. it has a high and low octane spark map for gasoline, and a table that adds/subtracts spark based on ethanol %


best practice would be to tune the high octane table on 93, the low on 87 and then the flex table on straight e85 (actual 85% ethanol) and let the knock sensors do their thing

trilkb

iTrader: (4)

I dont have a FF sensor or anything like that. Was just curious if our computer could figure it out on its own if you were to do a small mix?

AwesomeAuto

No, it has no way of determining octane.

aaronc7

You would be relying on fuel trims to add the additional fuel volume required. 1:3 is approx E30 and requires about 9% more fuel volume vs standard E10. 1:6 is approx E20 and you need about 4% more fuel volume.

IMO if you have a modernish ecu/pcm, letting the computer add 10% fueling is not a huge deal. But I wouldn't go beyond E30. Obviously in this scenario it won't add timing or boost or anything else, it would be more like just adding some extra octane for safety. You'd need a true flex fuel capable ecu/os to support that.

Sometimes I dump a few gallons of old E85 in my wifes car just to use it up, it works fine. I guess just try it some time, you should see LTFT increase after it mixes and learns the new fuel mix.

trilkb

iTrader: (4)

Well, you certainly told me what I wanted to hear lol. But yea I'd do it just for the added safety, should help knock right? Would you race on it?

aaronc7

That's exactly the scenario I would use it for. Heading to the track and just looking for a little extra knock protection and lower EGTs etc. I blew up my NA motor on road course and it appeared to fail only due to heat/cylinder temp, no indications of knock etc.

The best way to go about this would be to make a separate tune file with 10% more fuel across the board (or whatever ethanol mix you're running) and touch nothing else. But if that's not an option, positive LTFT should carry into WOT/PE and keep your AFRs correct at wide open throttle with mild ethanol mix. I would try to verify this though. If it's not adding any extra fuel, you will run lean....which at E30 may still be 'safer' than pump gas only but kind of defeats the purpose of running it for safety.

E30 without any sort of fuel trim correction will run about 1 point leaner than E10 gas.

Bottom line what you're after is possible, but I would try and verify things first. Some tuners disable LTFT completely in which case you would definitely run lean on E30 mix. I have personally done this, observed LTFT increase to around +10%, and the WOT fueling was spot on.

If you don't wanna bother with any of this stuff, a much easier option is a can or two of lucas/torco/boostane/vp octanium octane booster

gametech

iTrader: (1)

You only get the extra octane rating benefits at comparable fuel air ratios. Combining ethanol without adding fuel leans the mixture. You have opposing theories at work. better to just save it for something you have more control over.

trilkb

iTrader: (4)

Yea Ill run the 50/50 blend in my stealth turbo, I can control it easier once I have the stuff hooked up. I did just fill up my daily driver with 15 gal of 87 and 2 gal of e85 today. See how it does, if it makes no difference to me then I probably wont do it and just run 87 in that car lol. I doubt ill harm anything. Reading that "05 and newer" cars can run e10 as a substitute for 91 unleaded. Which makes me feel better, but of course my car is a 2004. Ive also read that E85 can clean your fuel system a bit too? I dunno, Lets hope I dont get stranded on the drive home!