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Old 11-22-2011, 03:41 PM   #1
wrxkyle
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Default Sidefeed to top feed conversion faq

Disclaimer, i am not a mechanic or a lawyer, as with all mods you run risks of voiding warranties, causing damage to the vehicle and others. lets face it, if you're in the power levels where you're considering this mod you already should know that. i assume no liability for anything.

Big top feed injectors are often better and smoother-running in large sizes, like those used with the E85 crowd. They are also safer to the engine in events of O-ring leaks (sidefeeds can both leak out the side/top of the rail starving the engine and creating a fire hazard, or leak through the bottom of the rail flooding the engine.[note, topfeeds can also leak through their orings but it seems much less common, though without the GBOD's they also could pose a certain fire hazard in a bad crash.])

I haven't been able to find a definitive guide for what's needed to do a full sti side feed to top feed conversion so I decided to make this thread. What I know so far is that
YOU WILL NEED:

TOP FEED FUEL RAILS
You will need top feed fuel rails, either stock or aftermarket. (note there are conversion rails made by ultimate racing as well as t1 race development that use the stock manifold and side feed tgv's, while using top feed injectors)
You can get stock rails from complete car part-outs, junk yards, or the private for sale classified's section.

you may want to consider doing a parallel fuel mod while you're in there with the mani off and swapping rails anyway. here's the link to that, though keep in mind this is a link for a sidefeed setup, not topfeed, so adapt the setup to work with your top feed rails, it's the same principle though. you will need a fuel rail adapter [weapon R and eBay have them] to use your sti fpr, though if you use the stock topfeed rails in stock series plumbing then you can just use the wrx fuel pressure regulator, (assuming it runs the same psi as the sti one, which i don't know if it does)

TOP FEED INJECTORS
When getting into bigger injectors in the 1000cc+ range top feeds are almost always better than side feeds and miss-fire less. They are also cheaper and there are a lot more options out there.
many retailers sell bosch and denso(and other) top feed injectors in sizes up to 2200ccm+. five-0 motorsports and injector dynamics are two that come to mind, but there are plenty of others.

TOP FEED TGV HOUSINGS
You can either buy top feed tgv's and sell or store your side feeds or kill two birds with one stone and order tgv deletes from a vendor specifying that you will be sending in your side feeds but need top feeds in return. There seems to be enough spare sets out there that many vendors will offer this service at no additional charge. (you will need some sort of tuning to turn off the tgv's cel, or only partially delete them,leaving the rods in place, see the tgv delete FAQ (link) for more info)
engagedperformance and grimmspeed are the two that come to mind, but there are others, most of these companys will port match the intake manifolds to the tgv's for an extra price.

don't forget new gaskets for the tgv to manifold and tgv to head. also you might consider installing phenolic spacers while you're in there as another optional upgrade.

Mike[/quote]


MANIFOLD?
as long as you get the right tgv housings then you won't need a different manifold. thanks GrimmSpeed for the information below.
Quote:
Originally Posted by GrimmSpeed View Post
02-07 wrx top feeds will bolt up to 04-06 sti intake manifolds. 07+ sti and 08+wrx/lgt/obxt/fxt use the new style top feed tgv that requires an intake manifold with a different bolt pattern so they are not interchangeable with earlier models.

Mike

HONORABLE MENTION-
APS also makes a topfeed tgv delete that utilizes 8 injectors rather than the usual 4. as i understand it those are best suited for HP drag cars, and obviously require a standalone and some balls to use and tune. I don't know much about them
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Last edited by wrxkyle; 01-19-2012 at 12:52 AM. Reason: adding info and polishing
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Old 11-22-2011, 05:40 PM   #2
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02-07 wrx top feeds will bolt up to 04-06 sti intake manifolds. 07+ sti and 08+wrx/lgt/obxt/fxt use the new style top feed tgv that requires an intake manifold with a different bolt pattern so they are not interchangeable with earlier models.

Mike
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Old 11-22-2011, 09:58 PM   #3
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I suggest replacing all the hardlines inbetween the two sides with soft fuel injector lines. To help with ease of installation and removal. I also have yet to find a blockoff plate for the stock fpr on the topfeed rails.
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Old 11-24-2011, 12:11 AM   #4
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The Honda fpr adapter works for the fuel rail block off to use an adjustable or relocated fpr. weapon r makes one and there are eBay ones as well. More info on that in the parallel fuel thread? I'll add this good info in the first post when I'm not on my phone, thanks grim speed huge help there.
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Old 12-10-2011, 07:54 PM   #5
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I will be converting my 05 STI to top feed within the next few weeks, so I will be able to chime in with some pics and experience from the conversion. My plans are to use WRX TGVs (deleted), ID1000 injectors, and stock WRX fuel rails.
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Old 12-11-2011, 09:13 PM   #6
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so 02 wrx topfeeds will not fit an 06 intake manifold?
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Old 12-16-2011, 09:32 PM   #7
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Quote:
Originally Posted by 2.5gtbx_44 View Post
so 02 wrx topfeeds will not fit an 06 intake manifold?
they will fit 04-06 intake manifolds as Mike said
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Old 12-17-2011, 12:10 AM   #8
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I meant an 06 legacy. Sorry forgot I was on nasioc and not lgt.com. More than just leggies. Lol.
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Old 01-19-2012, 12:50 AM   #9
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i don't have any info on the leggy's or foresters, but if people can test it out and chime in i'd be happy to include it in here.
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Old 01-19-2012, 01:21 AM   #10
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updated with some good info, thanks to those that contributed.
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Old 03-08-2012, 11:10 AM   #11
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I recently did the conversion and documented it pretty well:

http://www.iwsti.com/forums/how-inst...onversion.html
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Old 04-27-2012, 01:52 PM   #12
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ok im confused... i think im misreading. i have an 07 sti and it has the wrong year intake manifold apparently. do you have one available for 07 sti? or was 07 sti+ diff manifold?
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Old 04-28-2012, 03:04 PM   #13
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Quote:
Originally Posted by TRaley88 View Post
ok im confused... i think im misreading. i have an 07 sti and it has the wrong year intake manifold apparently. do you have one available for 07 sti? or was 07 sti+ diff manifold?
You have top feed injectors. Disregard this thread.
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Old 05-06-2012, 02:46 PM   #14
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Yes you have topfeed injectors already, this thread is for converting from sidefeed to topfeed, you're lucky enough to already have top feed injectors and only need a replacement set of injectors.
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Old 05-30-2012, 05:57 PM   #15
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I also wonder if it'll work for the 05-07 legacy gt as well and if there is any kind of converting or short cuts since our intake manifold is plastic and doesnt seem to have much room for the fuel rail?
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Old 05-30-2012, 06:07 PM   #16
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Quote:
Originally Posted by Ongbak View Post
I also wonder if it'll work for the 05-07 legacy gt as well and if there is any kind of converting or short cuts since our intake manifold is plastic and doesnt seem to have much room for the fuel rail?
I thought you guys were top feed already?
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Old 05-31-2012, 09:10 AM   #17
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I've done a simple Topfeed conversion on my 06 STi. Modded 850CC WRX injectors, TXS WRX Topfeed SS fuelrails, P&P and deleted WRX TGV housing (Thanks to Grimmspeed for helping me source those). The WRX injectors will fit the STi connector if you shave off the dummy proof guide on each injector. Will require tuning of course. I've had the like this for 3 years with ZERO problems.
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Old 11-04-2013, 09:37 PM   #18
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Why is everyone on here trying to go the cheap way instead of just bucking up for a true top feed conversion. Why don't you look at Agency Powers Top Feed conversion or Injector Dynamics? They send new 300 PSi line and an adjustable fuel pressure regulator. God forbid we do this the right way. I will post the real way to set this up as i am in the middle of it right now waiting for line and fuel pressure reg. And guess what i did TGV delete myself and saved $200 and the top feed injectors will fit in the side feed holes. Just have to get rid of the entire stock fuel line. Been working on subaru's and yes i have done the cheap ones but when you want to step up to meth injection it's a whole nother hassle.
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Old 11-05-2013, 07:55 AM   #19
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Maybe because this thread is older than your join date.
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Old 11-08-2013, 10:57 AM   #20
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^^^ **the crowd goes WILD**
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Old 11-08-2013, 11:04 AM   #21
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Quote:
Originally Posted by theotherguy View Post
Maybe because this thread is older than your join date.
Not sure what your point is. I already had the ID top feed conversion kit installed on my '05 for nearly a year before this thread was posted, they're not new, and they had been around plenty long enough for the OP to know about them before making this thread.
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Old 11-08-2013, 08:08 PM   #22
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I guess my point is that there is no reason to dig up an old thread to criticize people for going the "cheap way", "god forbid we do this the right way", etc.

Is there a right way? Should I have bought new rails and id injectors instead of using the wrx tgv's, turboXS rails and top feed injectors that I already had on my 20g'd sohc/ej257 with an NA '06 big plenum short runner manifold? God forbid...

I am cheap.
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Old 11-09-2013, 12:51 AM   #23
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I'm confused a bit, what's recommended as of Nov 2013 for stock 2005 STI wanting to go to ID725 injectors on a DD 300-350 whp motor? I've got deleted top feed TGV's on the shelf paid $200 never used on my previous WRX.
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Old 06-10-2014, 12:40 AM   #24
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Currently trying to undertake this conversion on my V4 WRX,

I have a set of top feed rails (aftermarket) and some spacers that go into the manifold

I have two main problems ~ hoping for the solution

1) fuel rail has 14mm hole for injector, injector O ring is 11mm - what can I do here ? I've seen aeromotive adapters ? Are these what I'm looking for ??

2) the Subaru blues have a lower manifold cushion that seems a bit loose in the manifold - what is the stock size and is there a larger size normally used ??
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Old 06-10-2014, 12:59 AM   #25
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