8th Generation Honda Civic Forum - View Single Post - Will my 08 Si hondata reflash be affected with a e85 conversion kit?
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Old 04-22-2009, 09:02 AM   #13 (permalink)
ryker
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Quote:
Originally Posted by Rock81953 View Post
i installed my conversion with 100 miles on the odometer with no problems, the Si has a compression ratio of 11:1 that is really high.
the little r18 econo motor is only 0.5 less!

11:1 isn't high when compared to every other modern car. 11:1 is good for 93 octane. Running e85 at 11:1 isn't taking advantage of the 100ish octane. 12.5-13:1 would be needed to help account for the loss in energy content. Now the question is: can the heads flow that much air? increase CR increases air flow needed.

Timing isn't much of a power increase. Where most people see the power from timing is due to running incorrect timing on pump gas then changing over to "race" gas and then going back to correct timing. Sure there is a slight amount of play each way. But a hondata reflash isn't going to help much at all. Mixes as low as E70 can be labeled for sale as "E85" for better winter/cold starting performance, so you have to be careful if you're building/tuning an engine based solely on E85.


A gallon of E85 has an energy content of about 80,000 BTU, compared to gasoline's 124,800 BTU. So about 1.56 gal. of E85 takes you as far as 1 gal. of gas. remember though the increased octane rating of E85 will never make up for the reduced energy density.
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