Injector size selection!

Sorry, just seen that the calculation is for 3bar fuel pressure......ignore me!! still, some of you may find the link interesting lol.
 

Mad

Well-Known Member
Im running 750's on my Scoob and producing 380bhp (not sure on the duty cycle but at 3bar) but I used to run 550's on my GTiR and was producing 400bhp (4 bar fuel pressure). I would say it is always better to get slightly bigger than you require but they are just fine.
 

stifler1603

New Member
[FONT=&quot]Injector Sizes and BHP limits[/FONT]
[FONT=&quot]1/6/2006[/FONT]
[FONT=&quot]Remember that the stock fuel pressur regulator will raise fuel pressure in a 1:1 ratio with the boost. For every psi of boost above ambient pressure the FPR will add 1 psi of fuel pressure.

If you are running 14psi of boost, your fuel pressure at WOT (wide open throttle) will be 43.5 + 14psi = 57.5psi. This is why you should not raise your base WOT fuel pressure above 4 bar. @ 4bar base fuel pressure and 14psi you will be running 58psi + 14psi = 72psi of fuel pressure @ WOT. This is why its important to find the right sized injector. I garuntee any stock rubber hose will be a bit stressed at this pressure and your fuel pump will be hard pressed to keep that pressure. Also your injectors may stick because the valve cant over come that high a fuel pressure.

444cc @ 3bar @ 85% @ 0.5BSFC = 287bhp
444cc @ 3bar @ 100% @ 0.5BSFC = 338bhp

555cc @ 3bar @ 85% @ 0.5BSFC = 359bhp
555cc @ 3bar @ 100% @ 0.5BSFC = 422bhp

600cc @ 3bar @ 85% @ 0.5BSFC = 388bhp
600cc @ 3bar @ 85% @ 0.5BSFC = 457bhp

700cc @ 3bar @ 85% @ 0.5BSFC = 453bhp
700cc @ 3bar @ 100% @ 0.5BSFC = 533bhp

1000cc @ 3bar @ 85% @ 0.5BSFC = 647bhp
1000cc @ 3bar @ 100% @ 0.5BSFC = 761bhp

DO NOT RAISE BASE WOT FUEL PRESSURE PAST 4BAR

444cc @ 4bar (513cc) @ 85% @ 0.5BSFC = 332bhp
444cc @ 4bar (513cc) @ 100% @ 0.5BSFC = 390bhp

555cc @ 4bar (642cc) @ 85% @ 0.5BSFC = 415bhp
555cc @ 4bar (642cc) @ 100% @ 0.5BSFC = 489bhp

600cc @ 4bar (694cc) @ 85% @ 0.5BSFC = 449bhp
600cc @ 4bar (694cc) @ 100% @ 0.5BSFC = 528bhp

700cc @ 4bar (810cc) @ 85% @ 0.5BSFC = 524bhp
700cc @ 4bar (810cc) @ 100% @ 0.5BSFC = 617bhp

1000cc @ 4bar (1157cc) @ 85% @ 0.5BSFC = 749bhp
1000cc @ 4bar (1157cc) @ 85% @ 0.5BSFC = 881bhp[/FONT][FONT=&quot][/FONT]
[FONT=&quot] [/FONT]
 

PobodY

Moderators
Staff member
hi. i am going to install a set of 550's on my pulsar. but on stock ecu? will they work fine??
No. How will it know what they are; it will keep fueling for 444cc injectors?

If you've got some way to either remap the ECU or adjust the fueling, then it can be done.
 

glen-gtir

New Member
No. How will it know what they are; it will keep fueling for 444cc injectors?

If you've got some way to either remap the ECU or adjust the fueling, then it can be done.
i have an uprated fuel pump, wider fuel pipe and a fuel pressure regulater??
 

Trondelond

Active Member
You would have to adjust the fuel pressure regulator to supply less fuel than standard then, so that the amount of fuel served by the injectors is the same as with the 444cc ones.
If you are going to increase injector size, you _have_ to tell the ECU that the injectors are bigger, or it will overfuel.
The amount of time the injectors are open will be the same, but as the 555cc injectors flow more fuel, thus leading to the overfuelling.


...and while we´re at it - I need bigger injectors. Running 600cc injectors at 4 bar, but I´d like to lower the fuel pressure to 3 bar. Anyone have real life experience here? It´s for my 3071´d Pulsar at... let´s say 1.9 bar for argument´s sake. Looks like the 700cc SARD option is discontinued, so perhaps the 800 ones?
 
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