Another MPG thread E85 vs. pump fuel (my tests this weekend)

[JayRolla]

I dont see how anyone gets this good of gas mileage on e85. I get 200 miles to a tank at most but I do like to boost a lot. People here that run e85 get about the same as me. Thats around 14mpg and I see maybe 17-18 with highway driving. Ive ran 14.7 all the way to 16.8 and gas mileage does not change enough for me to run 16 afr's at cruise.

 

[JusMX141]

My buddy recently switched to E85 from a 50/50 pump/race fuel mix in his '95 TSi AWD. The previous injectors were FIC650's, now they're RC1200's.

The car sees little to NO highway driving....all city, and racetrack. It sees HARD miles. The car averaged 20-22mpg with gasoline, and is now somewhere around 13-14mpg with E85.

When we first switched to E85 we were out doing LOTS of tuning, so we were beating on it pretty hard.....the car used 5 gallons of E85 in only 58 miles- closer to 11mpg.

 

[jrohner]

I would be scared to run that lean on pump even under low load.

I've read from more than one place that stoich (14.7:1 gas) is where it burns the hottest. I can't say if that's really true or not, nor have I seen anything yet to disprove it.

Anyone have some real FACTS about this? I don't believe EGT's alone prove anything; EGT's don't exactly mean combustion temperatures inside the combustion chamber.

 

[wishihadatalon]

Are we all taking in to account the weight of the cars? That would probably account why the mirage is getting such good gas mileage and the 1Gs are doing so much better. I would think that:

Lightest - Heaviest (not sure of the weights of a 1G AWD vs 2G GST)

1G GST
1G AWD
2G GST
2G AWD

Example: My minivan with just me in it and no back seats gets about 25-27MPG. I put in the seats, I get about 23-25. The weight of the seats is about 200lbs. With my GSX stock and just me with some junk in the trunk, I was getting about 25MPG hwy and I weighed about 210 at the time. If I did it again at my current weight (190) and didn't have the spare, junk in the trunk, etc... I'm sure I would be closer to 27MPG stock.

d

full weight 2g awd

 

[wishihadatalon]

I know lots of people do it. Lots of people also burn up valves when they had good wot afr's. I think a lot of people burn them up while cruising because thats what you do 90% of the time. Now when you run lean at wot its only for a few seconds at most. Lots of damage can be made while cruising, not just at wot. I guess I'm just scared and the difference in gas mileage is nothing.

Remember that the magical number of 14.7 or stoich is when a flame burns hottest. Running it leaner will probably just cause misfire issues and a loss in power. Given the slow piston speed and low cylinder pressure at cruise, I would say that your ignition timing would have to be pretty messed up to burn a valve while cruising or do any other internal damage.

 

[JayRolla]

Remember that the magical number of 14.7 or stoich is when a flame burns hottest. Running it leaner will probably just cause misfire issues and a loss in power. Given the slow piston speed and low cylinder pressure at cruise, I would say that your ignition timing would have to be pretty messed up to burn a valve while cruising or do any other internal damage.

So your saying I can pretty much run as lean as I want at cruise and the motor will be 100% fine, other than mis firing?

 

[wishihadatalon]

So your saying I can pretty much run as lean as I want at cruise and the motor will be 100% fine, other than mis firing?

[Diy_efi] Lean Cruise some good stuff there.

 

[selmerguy]

So your saying I can pretty much run as lean as I want at cruise and the motor will be 100% fine, other than mis firing?

Not "as lean as you want" But more lean. I like 16:1. it works great. The way I have my car tuned it will cruis like that all the time. But when I put the pedel down the tune changes automatically and I "normal" AFR's under high load.

 

[polarmoment]

i get about 18-20 city and mid to upper 20's highway on E85 in my MR2.

i run 16.5-17 AFR (gas equivalent) at cruise, and i keep it as lean as 13.5 all the way up to about 5psi, which helps spool the turbo, but also keeps the ECU from dumping fuel whenever you have to give it enough throttle to get near atmospheric manifold pressure (accel pump). i haven't had any misfires with it yet, and the plugs look great.