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I don't know how much another 5 percent would have made of a differance but they suposedly run 15 percent gasoline minimum to give it some lube and keep from hurting rings...

Also remember that lead clogs up AF meters in the exhaust and other types just arn't as acurate.

The 105 octane rateing on the e-85 is kinda a As for if it was detonation I would think it could have happened during the gasoline run and not showed a problem till you switched to the E-85.misleading way of judging it's usefullness since it cools so much when it goes in the engine it kinda artificially increases it's octane even more.

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I mix Sonoco 112 with Sonoco Maximal 116 50/50 and add that 10% to 90% pure Ethonol. A/F on E85 was 9.6-1, and gas was 14.50-1.

the dyno owner operator said the A/F on his machine, should be 14.5 to one.

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With that engine, I would forget the E-85 and run Alky? They are both cheap, and Fuel consumption would be similar.

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I mix Sonoco 112 with Sonoco Maximal 116 50/50 and add that 10% to 90% pure Ethonol. A/F on E85 was 9.6-1, and gas was 14.50-1.

the dyno owner operator said the A/F on his machine, should be 14.5 to one.

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It is tough to say, but the engine builder that tore it apart thinks it was detonation, but maybe it was lean and burned them up (incorrect material for build). That does seem like a lot of CR for even a performance brewed E85, but judging by what they told you about A/F ratio, I can't even guess what the real A/F was and too lean could have detonated it. Especially on an engine dyno, some combos will make good power on the lean side, but that is pushing detonation, "lean is mean"

Is the dyno "14.5" based on an oxygen sensor or air and fuel flow measurements? He obviously doesn't care what the real A/F is and from his experience (on gas?) 14.5 was working for him. So when you ran E85 at "9.6" what does he think the actual A/F ratio was?
What I am getting at is that when people talk A/F on fuels other than gasoline (stoich 14.7), some people using oxygen sensors quote A/F on the gasoline scale rather than the actual scale of the fuel used.

E85 stoich is about 9.7 and E90 would be slightly higher
100% Ethanol 9.0
Methanol 6.4

I use an oxygen sensor, which by design indicates the ratio of A/F to stoich (called Lambda), so a stoich mixture is Lambda=1.0 and a typical power setting Lambda=0.85 (which is 0.85x14.7=12.5 actual A/F on gas). My engine is 13.5 CR and I have tried my E85 tune from 0.78 to 0.90 which is an actual A/F ratio of 7.6 to 8.7 (but on the gas scale it would read 11.5 to 13.2). So if your dyno run on E85 was an actual A/F of 9.6 that is way lean, basically stoich (ie from air and fuel flow measurements).

You obviously have had success with E85 for a couple years in your other motor with slightly less CR. Was it the E85 carb from that combo (ie known "good" E85 carb)?

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I did have one correction, with E90 the stoich A/F would be slightly lower than E85. A rough check:
Stoich Ethanol 9.0
Stoich Gasoline 14.7

E85: 0.85(9.0) + 0.15(14.7) = 7.65 + 2.21 = 9.8
E90: 0.90(9.0) + 0.10(14.7) = 8.10 + 1.47 = 9.6

Published numbers for E85 I have seen were 9.76. And I don't know if the stoich for the Maximal is different than 14.7 (maybe 14.5).

So, for max (safe) power, I would want to see richer than stoich, in the range I mentioned. And perhaps the dyno operator just has seen max power close to stoich on gas (but I would want to be richer to be safe). Use the cooling effect of the ethanol and put more fuel to it. But that may only be a secondary issue with the rings, not the prime cause.

Good luck.

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I did have one correction, with E90 the stoich A/F would be slightly lower than E85. A rough check:
Stoich Ethanol 9.0
Stoich Gasoline 14.7

E85: 0.85(9.0) + 0.15(14.7) = 7.65 + 2.21 = 9.8
E90: 0.90(9.0) + 0.10(14.7) = 8.10 + 1.47 = 9.6

Published numbers for E85 I have seen were 9.76. And I don't know if the stoich for the Maximal is different than 14.7 (maybe 14.5).

So, for max (safe) power, I would want to see richer than stoich, in the range I mentioned. And perhaps the dyno operator just has seen max power close to stoich on gas (but I would want to be richer to be safe). Use the cooling effect of the ethanol and put more fuel to it. But that may only be a secondary issue with the rings, not the prime cause.

Good luck.

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I may have too much cylinder pressure as a result of the cam having 112 lobe center. I am staying away from the ethanol on this engine, and staying with race gas to be safe. But on my next build, I think I'll try to build one specifically for the E85 and match the camshaft specs to that combo. Do you have any idea about what effect mixing leaded race gas with ethanol has? Some people on this thread say it doesn't raise the octane level like you would expect, and that would account for the detonation.

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I copied this from a thread on Innocate's forum:

“You guys need to know that the metallic additives used to raise the octane of gasoline lower the octane of the alcohols. TEL, TML, and MMT are pro-knock in behavior with methanol and ethanol and probably the other alcohols as well. I don’t know for a fact, but I strongly suspect, that MMT is significantly pro-knock in alcohols. I’ve seen and been told of engine wrecks that I know had methanol and MMT involved (and TEL in one).

In Obert’s book he shows the R/M octane numbers of methanol as 106/92 and ethanol as 107/89. The addition of 3ml TEL per gallon of ethanol lowers the 107 to 102. You decide what this means to you when you mix leaded race fuel with alcohol.

The octane behavior of alcohols, like any fuel except pure isooctane, is affected by the AFR. Leaner AFR = lower octane behavior. Good race fuels have well over 100-octane behavior at the worst possible AFR conditions for knock. The alcohols obviously have very low octane behavior at lean AFR’s”


One man's point of view on mixing leaded fuel with Ethanol. Hope this might help explain or get you pointed in the right direction.

Disclaimer: I found this on the internet, so take it with a grain of salt!!

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I am staying away from the ethanol on this engine

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I am staying away from the ethanol on this engine

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Have you tried richer mixtures in the carb on your other "E85" engine?

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