Thread: E85 fuel FAQ
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Old 08-20-2005, 03:01 AM   #42
Scooby Specialist
Member#: 14141
Join Date: Jan 2002
Location: [email protected] @ 5800 ft on 13T
2002 Impreza WRX


If you're modifying your Subaru to run E85, you wouldn't buy expensive injectors. Instead, you'd install an adjustable fuel pressure regulator.
Of course it depends a bit on your priorities and local conditions. One strategy would be to use fuel pressure and possibly a small change in injectors to reach a point where your 0 fuel trim location is half way between and E85 tune and a gasoline tune, and let the ECU take you most of the way to a final tune using long term fuel trim.

The other would be to have a Utec or similar tuning solution with 2 or 3 maps. A gasoline only max economy map, and middle of the road runs reasonably well on either fuel, and a max power E85 only map.

I see lots and lots of options here depending on peoples budgets, local supply conditions and personal agendas.

I'm going to go with the duplex approach with upgraded injectors and an adjustable fuel pressure regulator that at max pressure setting will give a max power tune for E85, and at minimum pressure will give a middle of the road tune that gives good performance on high ethanol mixes and acceptable performance on gasoline only using the fuel trim authority of the reflashed ECU.

now if we can get Ecutek to come look at the code and increase the fuel trim authority of the ECU then the whole problem goes away with an injector that falls in the middle of the required flow for both gasoline and E85.

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