Octane tech

tonybolton · Jan 4, 2016

What would be better for a hi-po motor / turbo setup....91 octane pure gas or 93 octane with +/-10% ethanol?

onepieceatatime · Jan 4, 2016

Re:

I don't know much about motors but I can tell you that 93 octane with 10% ethanol. Is just 91 octane pure gas with ethanol to boost it up to 93. Dunno if that helps.

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Trailabite · Jan 4, 2016

Octane Facts
• Knock occurs when cylinder pressures are high. It is normal for an engine to ping a little at full throttle
because cylinder pressures are very high at full throttle. Engine knock, however, should not be ignored
since it can result in serious damage to the engine.

• High octane gasoline burns slower than low octane gasoline. The slow burn prevents engine knock when
cylinder pressures are high.

• If your engine runs well and does not knock or ping on low octane gasoline, there is no advantage in
switching to higher octane gasoline.

found here: http://forum.ih8mud.com/threads/high-octane-fuel-vs-low-octane-fuel-facts-and-myths.160442/

zukimaster · Jan 4, 2016

^^^ True dat! 99% of the people have no idea about gas, I get cracked up when I hear someone say if you put racing fuel in your car, it could burn it up! The higher the octane, the slower it will burn and harder to ignite.

Zjman · Jan 4, 2016

When i used to run the mud boggs guys would kill me buying cam2 and putting it in a stock engine, they swear it runs better. Haha

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Rohlingoffroad · Jan 4, 2016

E85 is where it's at on the turbo setup mine has been great

muddinmetal · Jan 4, 2016

Rohlingoffroad said:
E85 is where it's at on the turbo setup mine has been great

If you can get good consistant quality e85

tonybolton · Jan 5, 2016

Re:

This is for a daily driver / inline 6 / twin turbo car with a computer tune.

I've ran the 100% gas that was 91 octane and now the 93 w/ethanol. The 93 felt better/smoother which I figured would the opposite.

I plan to run a meth injection setup later.

Rohlingoffroad · Jan 5, 2016

muddinmetal said:
If you can get good consistant quality e85

I buy mine from a local gas station 30 gallons at a time and check it there has only been a few times I have had to blend it to make it correct only trouble I have is this time of year when they start mixing it for winter

Technician · Jan 5, 2016

tonybolton said:
This is for a daily driver / inline 6 / twin turbo car with a computer tune.

I've ran the 100% gas that was 91 octane and now the 93 w/ethanol. The 93 felt better/smoother which I figured would the opposite.

I plan to run a meth injection setup later.

What motor you runnin Tony?

FlatlandFSJ · Jan 5, 2016

My guess is the one in that bmw he posted in the random pic thread. :driving:

SB406 · Jan 5, 2016

I think it depends what you're going for as well. Power or milage.
Ethanol (such as E85) has a higher octane rating (push more boost or compression).
But ethanol is less energy dense than gas. (takes more of it to do the same work). 1 gallon of E10 has 96.7% the energy of 1 gallon of pure gas, according to this:
http://www.afdc.energy.gov/fuels/fuel_comparison_chart.pdf
There's other stuff inlolved too like the volumetric efficiency of forced induction vs NA, but whatever. That's apples & oranges.