Jump to content

best start to power upgrades

Recommended Posts

evening, I've got a 2001 forester s turbo, ej205 engine and I'm wanting to make a start on some lower level power mods.

I'm going to get it remapped once funds allow but is it worth doing it as standard or better off upgrading some bits first? moneys tight so I've gotta get the biggest boost for the money and its my only car so can't afford to do everything in one go.


Plans are a decat as soon as, is a panel filter upgrade worth the money over standard air filter? what about fuel pump/ injectors? not thinking bigger turbo etc at the moment just wanting to make a start, theres that many variants of engine and models etc i can't figure out which injectors would be needed or if there even worth it at this point, any pointers would be great thanks (I've looked through the typical upgrade path threads but don't think they apply to my model)

Link to comment
Share on other sites

Given the age of the car I woud do the fuel pump any way as part of giving yourself a good steady pressure in preparation for the remap.


Yes a map over the standard will potentially give you some gains and better mpg as it is tailored to your engine filter and pipe.


Hi flow panel filter, a free flowing pipe (decat etc) and a fuel pump will show improvements with an associated map.


Not sure how restrictive or not your intake pipe is though or what injectors to recommend - one of the more knowledgeable mambers will be along shortly I am sure :)

Link to comment
Share on other sites

To add about decat down pipe, keep your old cat for "mot" unless you have a friendly mot tester. Also with the decat it could give you an overboosting issue because of the lower back pressure and free flow from the turbo. That is corrected with a remap so ideally you want to leave the decat off until a few days before map and stay off boost.

Completely agree with what Jay said. Go for a fuel pump. On it's own it doesn't increase performance but it will provide your engine with the safety of good constant fuel pressure. One of the first upgrades I did myself (classic impreza on 170k miles)

With air filters try to get one that isn't oily. A few members make it known they effect the maf over time. A free flow panel filter is a great upgrade when coupled with others. On its own you may not see much gain power wise but the throttle response will be quicker and you'll get a nice raspy tone.

Link to comment
Share on other sites

Just to make you aware, the heads on the foz are different to the wrx so you may not see as huge an increase as the impreza in bhp, real world you'll get more (no idea as to what til it's been dyno'd) I only got about 20-30bhp extra, but huge torque and mpg increase,can't remember is yours an import or uk car ?

  • Like 1
Link to comment
Share on other sites

Thanks for the replies, I'll keep the old cat like you said for mot time, it's a UK model stants, and was looking for better driveability more than dyno figures, would doing the fuel pump and air filter be worth it before remap or would it cause issues like doing a decat pre map? Is one upgraded fuel pump the same as all or does anyone know what to look for when choosing one?

And I'm better off going fuel pump and air filter then decat then remap?

Link to comment
Share on other sites

From memory yours has a tf03 trubo, a td04 would give you a lot more power for relatively cheap outlay, the fuel pump would need doing to stop the possibility of it running lean when the boost is wound up, so before the map is a must, any non oiled filter would be an advantage, cosworth are pretty good, but it needs replacing every year, if you removed the 2nd cat that would free up some horses and not effect the running too much,

Tf03 is 170bhp as stock so you may see 200 ish depending on if it can keep up,

Td04 would see you pushing up to 270 depending on heads and how well the car takes to mapping,

Best off emailing some mappers and see what the recomend

  • Like 2
Link to comment
Share on other sites

Cheers stants, it's already had the second cat removed so just the one in the downpipe remaining, is it a walbro 342 fuel pump I need? Seems to be the number that floating around various sites, is a td04 a simple unbolt old one and bolt new one on job? Or is there other things that need to be done to fit it, are injectors not worth it around this stage?

Gonna get a fuel pump done first and panel filter seen as they can be done without anything else needing being done

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Create New...