Considering an E85 Experiment

[Ladogaboy]

I've recently done a little more reading on E85, and I'm contemplating an experiment. I only have a few stations in my (greater) area, but it happens that one is near my regular route (it adds about 4 miles to the total trip).

Anyway, my car (even tuned) runs on the rich side (~11-12:1 AFR), but I was reading that stoich for E85 is actually 9:1. Now I know that I might be seeing a decrease in power, but would this essentially be forcing my car to run in a lean-burn mode?

I'm also thinking that, given the bad gas we have in CA, I would only see benefits from the higher octane rating. The idea that E85 is ~ $0.50/gallon cheaper and I only have to fill up once a week (i.e., I'm only going 4 extra miles out of my way every ~ 350 miles) is also appealing.

Regardless, I'm thinking that I might want to test this out... if nothing else, just to see the results. I've fallen into a pretty good routine, and though I wouldn't be able to give an accurate A-B-A testing, I could probably come up with a good estimate of how e85 affects my FE.

I'm due for a fill up tomorrow night, so unless I hear "Danger Will Robinson," I think I'll give it a try.

[Frank Lee]

You could go whole hog, or ease into it with blends.

[kurzer]

i did drive some ethanol in my mx5 (miata). the car is verry rich running in open loop. with plenty of ethanol it was at lean verry often. cold start, cold run (was noticeable affected, some kind of bad throttle respond), WOT, and high revs. as long as the o² sensor was aktive, everything was normal. with the higest level of ethanol i tryed, the open loop was lean burn always, with one exception: verry high revs, 5500 rpm and more. in this area the setting is so rich, the ethanol doesn´t catch up.

in the mx5 i can adjust the FAR with the airflow sensor. i decided to klick it to the lean side so far, that the open loop will stay in the middle of the scale, maybe a little lean. then the verry high rev setting will be rich of course. for safety on trackdays.

fiddeling with ethanol is to complicated for me, i will make a one for all setup. if i hadn´t the adjustment to make, i would search for the best percentage of ethanol.

btw, AFR is monitored by a ARF gauge and the stock o² sensor.

[roosterk0031]

I would ease into it, make a E25-30 something blend first tank, go to E35-40 next tank.

You might find a sweet spot where it actually gets better MPG with a blend.

[Ladogaboy]

Hmm... I might want to wait a week, then. That way, I know I'll have ~ 4-5 gallons of gas, and I can top it off with 8-9 gallons of E85.

[roosterk0031]

Check out the Stratus fuel log, that's what I've been doing. Just never that heavy on the E85, don't know when the E85/E70 switch over is so it might be E70 your buying.

[shovel]

FWIW, before I modified my 4.3 s10, as long as I had 1/4 tank of e10 I could top off with e85 and stay within the stock ECU's +25 fuel trim bandwidth.

On my 4.7HO jeep, fills-up from empty on E85 keep me inside +20 fuel trim on the stock ECU (trim runs at -1 to +1 when I fill from empty with E10) - but the HO engine has higher flow rate injectors.

It should be noted that the stoichiometry difference between ethanol and petrol has the natural benefit of reducing pumping losses - specifically since the fuel delivers some of the oxygen necessary for combustion, less air needs to be drawn through the engine for a given level of output. So as has been noted elsewhere, between the timing benefits of a higher octane fuel and the reduced pumping losses of a more oxygenated fuel, there have been reports of improved MPG on blends despite the lower BTU count per unit of volume.

[roosterk0031]

What did you do to convert the 4.3 to FFV, zr2 truck for sale near by w/5 speed is tempting me & what's it mpg with E85?
I need to figure out how to get those fuel trim setting out a SG2.

[shovel]

Originally Posted by roosterk0031

What did you do to convert the 4.3 to FFV, zr2 truck for sale near by w/5 speed is tempting me & what's it mpg with E85?
I need to figure out how to get those fuel trim setting out a SG2.

Not much really, at first I put a Flex Fuel "kit" on it... what this device does is adjust the length of injector pulses by + or - 15% and lets your o2 delta do the rest. Brilliantly simple and it operated beautifully on that for ~40k miles. I then started looking for more power & kinda felt like tinkering so I had the stock ECU reprogrammed by wait4me with a map I specified after studying the software they use (and a few other tweaks) and at the same time replaced the old fashioned poppet type injector setup with the 2004+ style new injectors - and due to the new ECU program I installed a higher flow aux. fuel pump inline to maintain pressure at WOT - all of which negated my need for the FuelFlex kit that had been previously installed. I have another ~30k miles on those modifications with no difficulty, and simply love the way it runs on ethanol blends.

Note that I had zero trouble with the "kit" and if I hadn't wanted to do more tinkering, I would still be using that kit today and have no doubt it would continue being trouble-free. I already sold the kit I removed to a friend, but if you buy that ZR2 & are interested I have a second GM 4.3 fullflex kit that's never been installed, would be happy to sell it for a mutually agreeable price.

As for MPG's, it should be noted that my aerodynamic profile is a little different due to the 5" of suspension lift and the live front axle hanging below the frame ( from the factory these vehicles have independent suspension in front and a smoother underbody profile) and I also undertake literally zero effort whatsoever to "hypermile" my drivign habits - on ordinary E10 pump gas I usually get about 275-320 miles before topping with 17 gallons, and though I don't frequently get to run back-to-back fills of e85 (to ensure it's really e85 not some blend in the tank).. scangauge and partial refills have indicated that I average around 16-17mpg on straight E85, and closer to 18mpg on blends I estimate live around e50

[Ladogaboy]

@ shovel: I'm hoping for some similar results. The timing is very far advanced, and the stock fuel system feeds enough to run super rich on gasoline (E10?). I think that right now, for experimentation purposes, I will also try to shoot for the ~ E50 mark.

It doesn't really matter to me whether they are currently providing E85 or E70... The ethanol count will still be increased far higher than my current fuel. I'm not quite ready to jump fully onto the 100% E85 (I'm looking for ~ 2:1 mix with gas), but even if I were, I should be fine. Given the current tune for my car (and my estimates for stoich AFR), even pure E85 should be 1.1 to 1.2 lambda during cruise and dropping to <1 lambda under boost.