Thread: USDM STI yellow side feed injectors - Definitive flow rate

We're talking about the side feed fuel injectors that come stock on the 2.5L '04 through '06 Subaru Impreza WRX STI sold in the US.





Ever since nissanwulf questioned the flow rate of these injectors gomba and I have been on a search to find out their real flow rate.

I did some preliminary searches that seemed to support nissanwulf's claim that they are 565cc injectors. However, this does not seem to be the case. gomba points out that initially chriscar had a set flow tested by Clark at JWT and they flowed 520cc at 3 bar.

gomba then took my suggestion and asked the very knowledgeable folks over at NASIOC what the flow rate for the injectors are. Here's that thread:
STI Yellow Side Feed Injectors -- Flow Rate?? A Mystery it seems.. - NASIOC

In that thread people mention having them flow tested anywhere from 500-520cc. Someone thinks that the reason people may flow test them at 520cc is because they are using a different fluid (water?) to test (instead of gasoline?) and they would trust the company who reported them as 500cc more.

They also say the factory ROM tune has them at 503cc.


Unless we find out that Clark at JWT tested them with something other than gasoline, we can only guess. It would seem the flow rate is somewhere around 500-520cc (I'm leaning towards 500cc) but the jury may still be out.

I can't say any evidence supports they are 565cc. There are some pink top feed STI injectors that are 565cc and maybe that has caused the confusion. Please see the NASIOC list of Subaru injector flow rates for more information:
Injector, Fuel Pump, and Fuel Rail FAQ: Read if you are thinking of upgrading! - NASIOC

Interesting. These injectors a cheap upgrade for those guys running a disco? If tuned for 4 bar they should work ok.

4 bar they are good for about 400whp at 100% flow.

@Ben: '06 also used them. '04-'06 STI.

These are are direct drop in for the SR20 fuel rail. The only downside is that you need the 'clips' which are the harnesses/plugs + wire that came off the Subarus. You just have to crimp them into the SR20 fuel rail. Supposedly there are multiple models you can get the clips from, idk the specifics.

Well what I read somewhere was that the subarus don't use them at 3 bar. there used at like 3.25bar which could bring up the different cc's for them. I'll see if I can find the thread where this was said.

nissan guy needs some help - IWSTI.com: Subaru WRX STI Forums

Post number 4

Exactly.

All of these threads say 3 bar or 43 psi

1000cc side-feed injector? - NASIOC
Modify your Fuel pressure regulator for FREE - NASIOC
Injector, Fuel Pump, and Fuel Rail FAQ: Read if you are thinking of upgrading! - NASIOC
http://www.witchhunter.com/injectorcalc1.php4

Which all come from the great NASIOC FAQ.

Says all over the place static/stock fuel pressure is 43

I'll trust, which i'm sure I could find, 100's of posts confirming 43psi as stock pressure VS 1 post from a guy saying it's 45-50.

Ok, I was just saying. That's all I've read up on about them.

It's good you remembered that post, but it's posts like that guy from IWSTI that said 3.25 which confuses everyone else. So I'm glad we are getting to the bottom of this issue.

so there 500cc? So we need to use 503 when using it for a bin? I wanna get these installed this weekend and I'm trying my best to figure these out. A guy on the non dash has a bin up for 550's and hes using his sti's in it. Can't the K value compensate for that though kinda?