[Colin P]

Okay I've narrowed it down to 2 options: 550's or 650's.

I'm not trying to chase a magic number, I just want to select the right sized injector the first time. This is for my commuter 91 GSX.

Mods: ported/clipped big 16G (actually a mini-mutt), mild crower cams, FMIC & piping, 3 inch turbo-back, Walbro 255, B&M regulator, HKS S-AFR. I dont run more than 18 psi, 14 psi daily. I've never raced the vehicle.

I'm leaning to the 550's, but it seems so many people with the same mods I have use 650's.

Please, any input is greatly appreciated. RC says to use 550's but I'm hoping somebody had some real-world experience.

Thanks

 

[16g-95GSX]

You should consider the HRC 625cc's they are 400 dollars and work well. 550's might be able to hold you over but I would just go for slightly larger just for the fact of having more potential as the 550s can only take you so far and with a FMIC and a big 16g, you are actually getting some decent air flow.

 

[Dallas J]

From what ive seen the 550s are plenty for the b16g. If you were doing something like a FP green then i would say 660.
-Dallas J

 

[jw]

It all boils down to how much HP you are looking at. There is close relationship between HP and injector size.
http://www.vfaq.com/TMO/Tuning-Tips.htm
shows you some example HP @ 80% IDC and 100% IDC. Go with what you target at.

 

[Cazzo]

With larger injectors, you may be able to run more boost on pumpgas Currently, I run 22 psi with the b16g and 100 octane mix ( probably around 95 octane at most), and I have it leaned out well around -34% on the 660's. I don't think I could use race gas (112+) with these as I would be close to -50% ( i was at -39% with straight 103 octane unleaded). 550's might be a better choice for this turbo. Just a thought. I plan to get a bigger turbo in the next year so I wanted some injectors (660's) that would be able to produce enough fuel if indeed I upgrade my turbo. I wanted to buy injectors only once since I seem to buy everything else twice.

 

[jw]

Cazzo, what is your base fuel pressure?

 

[Cazzo]

I Honostly don't know. I run rich at idle -18% on the S-AFC because fo the webcams. Since I do not have a Walmart 255 pump, and my fuel trims are normal, I'm pretty sure my Fuel pressure is 35 psi like stock. This is a guess though. If I upgrade my turbo, I will probably do the -6an fuel lines and the FPR just to be safe.

 

[jw]

2G base fuel is 43psi. I have read with Walbro pump, you will get around 50-60psi which is plenty rich. The stock FPR will be outrun depending on your base fuel pressure and the boost you are trying to run. Well, since you are not lean out at full boost, you have not outrun your FPR

 

[Cazzo]

Ahh just pulled 35psi out of my ass. 43 sounds right though. Yeah I'm sure I'm not over- running it yet because of my pump (Denso). Sorry I forgot the correct name of the Walbro? pump too.

 

[Colin P]

i have one of those dsm performance "mini-mutt" turbos, it has a garrett compresseor wheel in a td05 housing. i dont know what it flows or what it's comparable to.