E85 fuel map for EMS-4 - Page 3 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 11-06-2013, 04:25 PM   #41
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Originally Posted by cukali View Post
To summarize, E85 does not create more power but allows a more optimal spark timing which allows for more efficient burning and more power. This of course only works in engines that cannot achieve optimal spark timing without knocking.

Now if what you said about all other things being equal such as "spark timing" and you create more power, then there is another variable that you havent found.
I'm well aware of the benefits of E85 and the tuning limitations of boosted cars on gasoline, but that wasn't what I was referring to. Empirical tests have repeatedly shown E85 to make more power than gasoline. My best example is on a 300whp turbo car using 100 octane and water injection (i.e. no timing limitation). Switching to E85 without altering the timing map at all resulted in ~325whp. I understand that changing to E85 alters flame speed and can change the point where peak pressure is seen in the engine, but I'm talking about seeing 5-8% gains in cars that are already at MBT.

If there's no obvious reason for the power gain, then it must be in the flame speed or charge density or something else.

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Originally Posted by Leafy View Post
Its entirely possible that the E makes more power because it burns slower and results in higher average cylinder pressures..
This, except I think you meant "burns faster and results in higher average cylinder pressures".
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Old 11-06-2013, 04:30 PM   #42
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Perhaps something along the lines of flame speed with an exponent of some kind.. aka slower at first but faster as more fuel gets ignited. So more of it gets used on the way down?
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Old 11-06-2013, 05:05 PM   #43
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Perhaps something along the lines of flame speed with an exponent of some kind.. aka slower at first but faster as more fuel gets ignited. So more of it gets used on the way down?
more like it is more stable so it isnt suseptible to detonation. but once its ignited has a crazy power potential.
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Old 11-07-2013, 04:44 PM   #44
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Except that E85 has significantly less energy density than straight up gasoline.
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Old 11-07-2013, 08:06 PM   #45
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more like it is more stable so it isnt suseptible to detonation. but once its ignited has a crazy power potential.
Energy potential doesn't work this way.
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Old 11-07-2013, 10:15 PM   #46
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Except that E85 has significantly less energy density than straight up gasoline.
Do the 30% increase in fuel you get fairly even numbers.. then you add some for the extra spark and efficiency gain and thats how you get the more power out of the E85.
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Old 11-07-2013, 11:03 PM   #47
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Oh yeah, I agree. Just talking numbers, 100% Gasoline is 33% more energy dense than E85.

The basic formula for power in an engine is fuel + air = power, more fuel and more air = more power. I am on the E85 is magic train, but the reasons why you can squeeze out extra power probably comes from the higher efficiency of the burn cycle since not as much energy is lost as straight up heat since ethanol burns so cool.
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