ECMlink Let's discuss Ethanol mixing

[thakingcb7]

So recently I have finally installed my FP manifold and Green turbo. I've really hammered down on my research and tuning and have realized that I've been over looking the most important thing... fuel. I've been playing around with ethanol mixtures so I can run more timing and thus... make more power but I never took into account that I needed to change my stoichiometric settings. I've been hanging around a 35% ethanol range so by my best estimate I should be tuning for a (roughly) 12.6(?) afr at cruise but I'm not sure where I need to be when WOT. Anybody have input? I don't have e85 within 2 hours from home... just "flex fuel" which they advertise as e51-e83.

 

[GST with PSI]

How are you testing the ethanol content of your fuel mixtures?

 

[thakingcb7]

I'm testing the content of the ethanol at the pump and then using the online calculator to figure out the final mixture. Our pumps are all 10% ethanol so using the calculator saves me alot of headache.

 

[91talonts1]

The numbers on the pumps are not accurate measurements, just maximum content. It means it contains up to 10%, 30%, 80% whatever the number is. I've pumped e85 that was as low as 62% ethanol. You need a real tester to be accurate.
As for your AFR are you talking about a gas scale or ethanol scale? Because they're completely different. Using a gas scale with ethanol you should still shoot for 14.7 at cruise, and 12.0-12.5 at wot.

 

[thakingcb7]

That's what I ment by testing it at the pump. Once a week I squirt some into a jug and test it so I can figure out how many gallons of ethanol to mix with the 93 with 10%

 

[91talonts1]

Oh okay gotcha. Are you still using the gas scale? If so stoich is the same. The wideband is reading air not fuel, so it doesn't care what kind of fuel your using. If you were running pure ethanol at stoich (9.0:1) it would still register as roughly 14.7:1 on a gas scale.

 

[thakingcb7]

I haven't changed anything. I just randomly pumped a couple gallons of what tested out to be 75% ethanol in and added like 4 gallons of 93 one day and have been doing it twice a week since.

 

[91talonts1]

Then yes stoich on your wideband is the same. A wideband setup for a gas scale will report 1.0 lambda as 14.7 no matter what the actual AFR is. It's easier in my opinion to just use the gas scale than worry about the conversions.

 

[thakingcb7]

So even when doing pulls... I still shoot for like 11.1ish?

 

[91talonts1]

Well no but that's not got anything to do with the gas/ethanol scale. That's just because you can run ethanol leaner than gas without worrying about detonation. For example using the gas scale I'm tapering to 12.5:1 at wot.
I didn't read that you were at 35% before, I'm not sure exactly how lean you can run it at that percentage. There's been much debate as to when the ethanol content is high enough to benefit from it. And that at a certain percentage you either get all of the benefits or none. You might want to read more in to that. I can't comment much on that as I've never ran anything less than e70 when doing any wot work.

 

[thakingcb7]

I've seen benefits at my current mix. I used to get low amounts of knock at random points during pulls and it stopped that. I've also been bumping timing up a fair amount compared to with just 93.

 

[92AWDHX40]

Great job 91 I'm switching to a flex fuel set up as we speak.

 

[91talonts1]

I've seen benefits at my current mix. I used to get low amounts of knock at random points during pulls and it stopped that. I've also been bumping timing up a fair amount compared to with just 93.

Then there you go sounds like it's working well. I just meant someone else could help you better with advice on a safe target afr and how far you can push timing. Ethanol itself has a high threshold for knock that can give you little warning before things go south.
Another common issue to keep in mind with increased ethanol content is rich knock. I get lots of little annoying blips of knock that show up if the mixture goes even just the slightest bit too rich.

 

[thakingcb7]

I think that's what happens in my logs because I get little 0.4 degree of retard blips right around 4k when the turbo really starts spooling and I'm just a tad rich.

 

[GST with PSI]

Everything @91talonts1 said is right on. Awesome posts here.

There's been much debate as to when the ethanol content is high enough to benefit from it.

^Fact.

Regarding grade, there's almost no difference performance wise between E50 and E85, especially on a sub 500hp car where you're not running on the ragged edge. I'm making this claim based both on my personal experiences with various grades of E85 (or less) and also research I've read/studied. The batch I dyno'd on was actually around E70, and I made no changes to my tune. Unless your winter blend falls below E50, there's no real reason to be concerned, IMO. The black goo is what you have to watch out for.

Good read on E85 RON:
https://www.researchgate.net/public..._Compression_Ratio_of_Ethanol_Gasoline_Blends

The wideband is reading air not fuel, so it doesn't care what kind of fuel your using. If you were running pure ethanol at stoich (9.0:1) it would still register as roughly 14.7:1 on a gas scale.

Then yes stoich on your wideband is the same. A wideband setup for a gas scale will report 1.0 lambda as 14.7 no matter what the actual AFR is. It's easier in my opinion to just use the gas scale than worry about the conversions.

^Facts

For example using the gas scale I'm tapering to 12.5:1 at wot.

I shoot for 12.0:1 target AFR on my E85 tunes. This would apply to anything grade E50 and up, as because of what is outlined in my post above. As ethanol content drops below E50, I'd richen up my target AFRs for a bit of a cushion.

Ethanol itself has a high threshold for knock that can give you little warning before things go south.

^Exactly. By the time you see knock on E85, it's typically too late. This is exactly why you should shoot for a richer target AFR as the ethanol content in your fuel starts to drop.

This is probably obvious, but one thing to keep in mind is as you dump different fuel grades on top on each other in the fuel tank, the ethanol content of the 2 (or even 3 or 4) mixes will vary the ethanol content of the entire mix. I try and ensure the ethanol content stays above 50%, so I don't have to vary my tune. If you're constantly mixing your own grades, or pumping from stations with lots of variation, the flex fuel sensor can be pretty handy.

I'd say just be really cautious as ethanol starts to drop below E85. There are too many factors to make assumptions on how a certain grade will perform, even if it is still above E50. If you're consistently testing your fuel grade, and monitoring your tune, you should be fine.

 

[bling5tatus]

The problem with wandering e content is that your timing will never be "ideal". I run 11.3 AFR on my car and this is after "experimenting" with all the other mixtures possible. I think running it leaner than that is just burning hotter and making less power (don't fool yourself into thinking you're somehow saving gas by running leaner in boost). The only real way to know this for yourself is to put your car on a dyno and tune it differently for the AFRs in question and see the power differences.

 

[94awdcoupe]

I run about 35%. My a/f on gas scale is 11.8-12 on the dyno wideband. I run a secondary injection system of my own design. you can read up on it here:
http://www.evolutionm.net/forums/wa...-easy-tune-ethanol-injection-best-way-go.html