First what would I have to change around I wanna run the L92 but somebody said you have to have heads with diff valve seats, I thought it was just the rubber components you had to worry about? And anybody know the octane rating of E85 and the air fuel ratio change from regular gasoline?

 

E85 is around 110 octane if I remember correctly, and you use roughly 30% more fuel. If you search there is quite a bit of info on E85 and E85 conversions.

 

I ran E-85 on an 02 H/C/I LS1 without any mods to the fuel system other then bigger injectors. No problems.

 

So can an engine that runs on E85 at say 12.5:1 cr.....run the tank dry and fill it up with 110 octane and just drive normally. Then the next fill up use E85 again?

 

No...

E85 is typically 105 octane and has less energy(BTUs) than gasoline. Thats why you have to add ~30+% more fuel with E85, to get enough energy out of the combustion.

Stoich on gas is 14.7:1, and typically makes power between 12.5 - 13.2:1
Stoich on E85 is 9.76:1, and typically makes power between 6.9 - 8.4:1

So if you just change from gas to E85 and back, on a non E85 sensing fuel system, youll have all kinds of issues because it will not try to add the extra ~30% of fuel.

 

GM has been offering Flex Fuel - Ethanol mixes since the LS1 days.

The 09 L92's in some trucks come E85 ready, 5.3L's have been running it for some time. In Brazil all cars must run E25 minimum.

The fuel system does need to be ethanol ready, as ethanol is a lot more conductive, and attacks seals/hoses that are not ethanol ready (over time) and will absorb moisture more readily that gasoline.

So GM engines have been ethanol ready for some time. They did run a hard sensor to measure ethanol content or "composition", and switched to a Virtual Sensing system a couple years ago. Rumors abound that they are going back to hard sensor.

When running in closed loop (which is most times except for the first seconds after start up, and in power enrich mode), the O2 sensors adjust for ethanol as they are targetting the right mix regardless of fuel (within limits).

In open loop, a different matter.

Start up is more difficult, especially in cold weather, and power enrichment requires re-calibration (as SweetS10V8 notes) too.

In my experience, if you are running regular gas, engine is fully warm and running closed loop, pull into a gas station and fill up with E85, then just drive off and as the "fuel composition" changes as the fuel line runs out the previous gasoline, the O2's adjust adding the extra fuel to achieve the stoichiometric (chemically correct) mix.

Then back home or to the shop to adjust power enrich, and maybe the cold start mixture as well.

 

So no way to have the best of both no matter how its set up?

 

I hope they do, the virtual sensor doesn't work for **** in my 07 Sierra. Its consistently about 20% off.

 

How does that show up?

 

Dashhawk will show it. Fuel % is a PID.

 

Sorry man, guessed you were looking at the SAE.E85R PID in some way, but how does it show the 20% off during normal use?

Hard starting? Hesitation? Other?

And does it typically show high or low against the calculated mix in the tank? Or do you run pure E85 all the time?

 

It shows you the total % of alcohol. It would take 3-4 tanks to get even to accurate, and even then it was never 100% accurate.

Lets say I was running E85 for a while. PID shows around 80%, which is accurate enough. Then, I run that tank near empty, and put in 20+ gallons of E10. One would think the PID would go to around 10-20% alcohol at most, but no, it will go down to only 50 or so. When the ECM thinks you have 50% alcohol in the tank, but really are mostly gasoline, it runs PIG rich, and gets shitty mileage. I would have to run that tank down to near nothing, and then put in full Gas again. Then it would drop to maybe 30-40. Then one more tank, to get it to the expect 20% range.

I guess what I am saying is it takes 3-4 "learning cycles" for it to get even in the ballpark. In fact, once when I went from E85 to gas, it tossed lean codes it was so messed up. Id prefer a real time physical sensor then this virtual crap that doesn't work right.

 

Ok I got it now. No wonder there are rumours of going back to the hard sensor. 3-4 tanks of gas is way too much to wait to get it right.

 

I converted my bolt-on LT1 to E85 for about 7 months. I adjusted the fuel injector constant to 28% smaller injector size (to trick the PCM into adding fuel), had to use bigger injectors which I was still maxxing out 30# SVO's at 4400 RPM. Once I got the LM1 wideband I was able to get the tune pretty dead on, but then the oil pump pickup came loose, and lost pressure, so I put the car away until I can afford to rebuild it as a dedicated E85 385 around 12.5CR. My experience from it was, yes the mileage went down, but E85 can tolerate a slightly leaner than stoich cruising mixture and at the time gas was over $4/gallon, so it was still cheaper per mile for E85 for me at the time.

 

Good stuff. What sort of mpg did you get with E85 vs gasoline, with the slightly more lean E85 cruise?

 

Can you mix E85 with 93 gasoline. If I have 5gal of 93, could I add 2gal of E85?

 

I agree with SweetS10V8 you must have a fuel compostion sensor and vehicles that are flex fuel usually have higher ouput fuel pumps...

 

this might help, pretty in depth:

https://ls1tech.com/forums/fueling-i...r-ls1-e85.html

 

E85 octane rating is about 110 and you'll use more fuel in comparison to gasoline. It is really resistant to detonation and allows you to use high compression.

It will eat through rubber, you'll need to upgrade anything rubber to stainless steel and update the valve seats. Also, special injectors that are resistant to E85's corrosive nature are also required.

 

I wonder, has anyone with an adjustable pressure regulator, running E-85, tried to see how far off fueling was by switching back to gas AND LOWERING their fuel pressure 30%? I'm curious to see if you could do this in a pinch if you drove somewhere E-85 wasnt available and had to use gas in an emergency.