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Old 08-03-2009, 12:03 AM   #7
Scooby Specialist
Member#: 156973
Join Date: Aug 2007
Chapter/Region: International
Location: Adelaide, Australia
2002 ADM WRX STi
STi Black/Blue


The biggest problem with any ethanol mixes (E10, E85 or anything else) is the consistency of the fuel. It changes so rapidly between tanks that A/F learning can and does jump anywhere upto +-10% (could even be higher for some cheaper mixes) and octane can drop by just as much - which inturn decreases your knock threshold and your engine starts to knock.

If possible, always use quality fuel and if you want to run an ethanol mix, either order it in barrels (which will have a printout of fuel spec and quality) or make sure that you do a lot of road tuning over several tanks of gas so your tune can take into consideration the fuel quality as well.

You may end up having to run a tune with slightly less timing and/or boost and make a little less power overall so you don't knock with a crap batch of fuel, but at least your engine won't die.

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