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2004 Forester XT 5MT
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13 Posts
Discussion Starter · #1 ·
'04 FXT
20G XT-R
Fully built
Still on a 5MT but will be STI swapping driveline this summer

Currently trying to plan out my flex fuel conversion.

Cobb makes their PnP Flex Fuel kit for the 2005-2008 with no support for the '04.
https://www.cobbtuning.com/products/fuel-system/subaru-flex-fuel-package-3-pin-fxt-2006-2008

They claim it does not work with the 04 due to limitations of the ECU. :confused:
I am currently installing an STI intake manifold, IAG TGV deletes, IAG side feed to top feed conversion rails, 8mm Phenolic Spacers, new hoses, etc.

I'm trying to navigate this carefully because my plan is to swap to a Spearco top mount, block off my MAF, tap IC for temp and MAP, add a Radium surge setup, and swap the 20G XT-R for an EFR7163 at the end of the summer.

I have seen this: https://forums.nasioc.com/forums/showthread.php?t=2810122
The only reason I dislike it is all of the additional junk in the bay.

Is there seriously some sort of ECU limitation in my '04 FXT ECU that would prevent me from using a Cobb PnP Flex Fuel kit?

I realize they state it's incompatible, but with the mods I've listed, it's not like I'm sitting here with a stock '04 FXT with functioning TGV's and stock fuel system.

If their flex fuel system is in fact limited by something with the USDM '04 Forester XT ECU, is it possible to swap to a later model Forester XT ECU? Or is it in my best interest to swap to a compatible USDM STI ECU?

Just confused and I'd much rather go with the Cobb Flex Fuel kit with their pressure sensor than a homemade ethanol content and pressure sensor setup. I just feel like it would be easier and more reliable working out of the box with my AP3.
 

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Premium Member
02 WRX
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499 Posts
You'd swap in an 04 STI ECU, and then treat the car just like a GD STI and run the applicable kit.

Contact Cobb and they might have another option for you that I won't confirm, but when I spoke to them this was definitely one of them.

Chase
Engineering
 

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Registered
2004 Forester XT 5MT
Joined
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13 Posts
Discussion Starter · #3 ·
Thanks for the reply and the info!

Also thanks for the awesome stuff you guys make. I had actually placed another order with you guys just before I asked that question.. lol.

Time to place another order as soon as I sort the intake and fuel system components out.

-Graham
 
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