2004 Subaru impreza wrx E85 conversion

hunterc05 · 02-11-2025, 08:27 PM

Hello, I got into looking at doing an E85 conversion on my 04 subi. But im having a hard time trying to figure out what I would need. I see E85 conversion kits but im not sure what ALL I will need. I saw a post from awhile ago that I would only need bigger injectors and a tune but I highly doubt that. I am just curious if anyone can help me and explain and tell me what I need to do to swap my wrx to E85

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Laddder · 02-12-2025, 09:04 AM

I'd ensure that you'd upgrade your fuel pump and injectors. Even if the kit has all you need theres some things that you'd want to upgrade because it's worth it/supports it so well

Fuel lines doing okay, my 04 has fuel leaks, and tank doing okay?

Jack · 02-12-2025, 04:39 PM

To run on E85, you need a larger volume of fuel. Injectors, fuel pump, fuel line. You also need to be tuned to run it. It is possible to build your own sensor controller to sense how much E85 is in the fuel and adjust tuning to the level. But you do need to understand the whole system to do this and I don't see that you do with the questions posed.

E85 isn't magic that you pour in your tank and become one to dominate all. Even if you overnight fuel from Japan. You need an integrated system. If you don't want to do that, just buy a car with more power.

wrx43v3r · 03-29-2025, 12:57 AM

I have a 2004 WRX with E85. I had it done less than 10 years ago. The install was done by a popular/reputable tuner (the business no longer does tuning).

Tuning was achieved using CarBerry ROM - you will need a 2002 or 2003 ECU to use CarBerry ROM.

We used the Delicious Tuning flex fuel kit (it's pretty cool - they offer an app to monitor E85 levels). Like others have said, you will need to upgrade fuel delivery parts (I also went with rails).

Why don't you go to your local tuner and discuss everything you'll need (it's definitely possible to do it)?

02-11-2025, 08:27 PM	#1
hunterc05 Scooby Newbie Member#: 539372 Join Date: Oct 2024	2004 Subaru impreza wrx E85 conversion Hello, I got into looking at doing an E85 conversion on my 04 subi. But im having a hard time trying to figure out what I would need. I see E85 conversion kits but im not sure what ALL I will need. I saw a post from awhile ago that I would only need bigger injectors and a tune but I highly doubt that. I am just curious if anyone can help me and explain and tell me what I need to do to swap my wrx to E85 * Registered users of the site do not see these ads.

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02-12-2025, 09:04 AM	#2
Laddder Scooby Newbie Member#: 540251 Join Date: Feb 2025	I'd ensure that you'd upgrade your fuel pump and injectors. Even if the kit has all you need theres some things that you'd want to upgrade because it's worth it/supports it so well Fuel lines doing okay, my 04 has fuel leaks, and tank doing okay?

02-12-2025, 04:39 PM	#3
Jack Add Lightness Moderator Member#: 13699 Join Date: Dec 2001 Chapter/Region: NESIC Location: Hopkinton, MA Vehicle: 2021 Building It Better	To run on E85, you need a larger volume of fuel. Injectors, fuel pump, fuel line. You also need to be tuned to run it. It is possible to build your own sensor controller to sense how much E85 is in the fuel and adjust tuning to the level. But you do need to understand the whole system to do this and I don't see that you do with the questions posed. E85 isn't magic that you pour in your tank and become one to dominate all. Even if you overnight fuel from Japan. You need an integrated system. If you don't want to do that, just buy a car with more power.

03-29-2025, 12:57 AM	#4
wrx43v3r Scooby Newbie Member#: 331119 Join Date: Sep 2012	I have a 2004 WRX with E85. I had it done less than 10 years ago. The install was done by a popular/reputable tuner (the business no longer does tuning). Tuning was achieved using CarBerry ROM - you will need a 2002 or 2003 ECU to use CarBerry ROM. We used the Delicious Tuning flex fuel kit (it's pretty cool - they offer an app to monitor E85 levels). Like others have said, you will need to upgrade fuel delivery parts (I also went with rails). Why don't you go to your local tuner and discuss everything you'll need (it's definitely possible to do it)?