injector flow

[IanSzgatti]

i just picked up some 3400 intakes and got the fuel rail and injectors with them thinking that they'd be 21 lbs injectors.

i checked the numbers and found they are 18lbs. Now... I thought that my 1997 3100 came with 19 lbs injectors and the 3400 and 3100 large port had the 21 lbs injectors...
(i should mention my 3.4 intakes and injectors are out of a 97 venture van)

at work im doing the lower gaskets on a 98 olds sillouhette van with the 3400... so i looked at those injectors and sure enough... 18 lbs injectors... wtf is going on... i need some educating

[geldartb]

the 21 lb ones came on the 00+ 3x00's they would be the thin pencil types. but these run at 55 psi.

the pre 00 were the fatties and should be 19lbs and run at 42 psi.

[IanSzgatti]

shat. ahh well... i guess i'd be ok with the ones i got eh?

[geldartb]

if your engine is stock then you will be fine with them.
later on if you want you can always swap over to them newer style ones. all you need to do is splice on the different connectors and either get an adjustable FPR or a stock one from the 00+ cars.

[johnnymossville]

If you used the newer FPR that is 55 psi with the 18 lb. injectors you should end up with almost 20.25 lb. injectors. Depending on your engine mods you might be ok with that.

[IanSzgatti]

if your engine is stock then you will be fine with them.

im gonna take a crack at porting the cylinder heads once i have them out.. exhaust manifolds...ported 3400 intakes, high flowing cat and exhaust, (the monte carlo seems to have a giant downpipe to work with) CAI, and one of the 62 mm TBs off this site if anyone will ever get back to me about shipping...

so no cam... just a lot more flow. I think it might need some adjustments after that... not sure, but it's little more than i did with my last 3100, and on that motor i saw some noticable high end power with just porting the small port intakes and adding a 56mm TB (exhaust all done too)...
only thing that makes me nervous is porting my own heads...

anyways... good idea Johnnymossville! but something seems too good to be true about that... i dunno

[WrathOfSocrus]

I know this has been posted somewhere before but . .

http://www.witchhunter.com/injectorcalc1.php4

That site has a lot of good info and the calculator for injectors. The two ways to change the output of an injector is to change the duration it is open (by tuning the computer) or by raising the pressure.

Obviously tuning alone wont increase the MAXIMUM output of an injector. Raising the pressure or getting bigger injectors would be the only way to do that.

[johnnymossville]

^ X2

[AaronGTR]

Actually '99 and earlier 3400's came with injectors rated at 19lb/hr @45psi. 2000 and later had 22.5 lb/hr injectors @55psi... as rated by delphi and confirmed by rc engineering when I sent them in for testing.

[IanSzgatti]

Actually '99 and earlier 3400's came with injectors rated at 19lb/hr @45psi. 2000 and later had 22.5 lb/hr injectors @55psi... as rated by delphi and confirmed by rc engineering when I sent them in for testing.

ok thats what i thought... but the site i looked up the numbers off the injectors listed them at 18.. whatever the case, it seems like installing an update FPR would boost thier output a little.... begging the question... why would someone switch injectors if it were as easy as replacing a FPR??? something seems odd

[WrathOfSocrus]

You can only increase the pressure so much before the injector's reliability becomes questionable. Also it seems that if you were tuning with the larger injector the duty cycle would be reduced further increasing injector life.

However the change in pressure between those two FPR's certainly shouldn't cause any reliability issue. Its really boils down to delivering the amount of fuel needed to meet your horsepower goals. I too may have an engine that would probably work well with that injector FPR setup. Then again a brand new rail with injectors for a 3.4 DOHC might be better suited for my 3500 build. Obviously I'm looking for alot more horsepower there!