Injector sizing

[spetz]

I have a friend with a red top SR20DET
He is getting bigger injectors, but without chaning the fuel rail

So his only realistic choices are 740cc or 550cc
I am trying to tell him 550cc will be big enough for a good amount of power and 740cc will be hard to tune and be rough with bad idle

How much power can 550s make?
Car has 217rwkw now

[Slow96GSR]

Read here (http://www.edelbrock.com/automotive/sport_compact/index.html) in the tech section. They discuss how to size and even work the math backwards to see if you are actually getting what you have. It's easy math too.

[spetz]

Ok I am probably an idiot but that completely is wrong???

I used my car as an example
166cc injectors = 15.8 lb/hr injectors

[(15.8Lb/Hr injectors X 85% Duty Cycle) / .50 BSFC] X 6 injectors = 161hp engine hp...

Well my engine stock is 200hp??

550cc injectors on a 4 cyl gave me 362hp at the engine which seems very little?

All calculations at 85% duty cycle

[Slow96GSR]

What car do you have? 166cc seems low for a Honda, if it is. They are normally a 200cc+ injector. I came up with a duty cycle hp of 161 for your car with the specs you gave. When the dealer tells you the motor puts out 200 hp he means that at the flywheel. Edelbrocks calculations are for at the wheels power and only an average at their location, not meant for high or low altitudes or weather changes. The average 550cc will handle 400-500hp at the fly wheel. I have seen more and have seen them not handle that high.

Also why only 550's or 740's?

[spetz]

Because for other cc injectors he needs to buy another fuel rail which he doesn't want to

Engine is a 2L V6 MIVEC
And I don't know... a friend got 132kw atw from an engine like that with same injectors. That's roughly 180hp already... though he did have a aftermarket fuel pressure regulator

[Slow96GSR]

I would just find some RC injectors. They make them so you don't need an aftermarket rail. Then you can do it up right with the proper size injectors.

[dsp26]

here are some injector flow rates:
http://users.erols.com/srweiss/tableifc.htm

and here are some software/duty cycle tested values:
http://www.ozhonda.com/forum/showpost.php?p=739608&postcount=69

and your right, 550cc are adequte

[iamhappy46]

550cc@3 Bar is good for 400Hp@crankshaft. I would go for the 740cc's and a 250+Litres per hour fuel pump. Most ECU's these days can compensate for such large injectors although they do run a little richer than stock at idle.

[poid]

with any decent ECU (and tuner) the 740's would run fine, he may as well get them in case he wants to upgrade further down the track.

For what its worth my accord runs fine on 680's, no issues with the idle at all.

[iamhappy46]

Another option would be to get 550cc injectors and run 4Bar rail pressure(with metal or braided fuel lines) which would allow those injectors to flow around 650cc.

[spetz]

Ok the 740s went in after all
Car goes pretty ok and smooth (well as smooth as a SR20 can be I guess)

Made 247rwkw on a dyno dynamics dyno on 16psi

[destrukshn]

fock, what mods does he have?
247rwkw on 16psi, is good! lol,
my mates only crackin about 215-220 on 15psi,

[spetz]

Nothing spectacular actually
FMIC, BOV, GT28RS, manifold, dump pipe, exhaust, and greddy emanage blue

Oh and the injectors and FPR

Before the injectors and this tune it only did about 200ish atw or so