fuel injector flow rates

[kprofthestrs]

95 3100 injectors on a 2000 3400. 95 injectors rated at 19 lbs/hr?
the 2000 injectors are rated at 22.5 lbs/hr?

is my information correct?

if information is incorrect what are the correct numbers.

[AaronGTR]

That is correct. 2000+ 3400 injectors are 22.5lbs/hr. The '99 3400 injectors where 19lb/hr, so I imagine the 95' 3100's could be the same.

[Superdave]

um, I always thought that all the 3400 injectors were #19...

[Azrael]

Injectors from a 95 3100 are 17 lbs/hr last I heard. I can't seem to find a reliable source to back that up though.

[kprofthestrs]

so the info is close enough to correct. so that leads me to my next question the 95 injectors are high impedence? the 2000 are low impedence?
duty cycle should never be above 80%? correct

[AaronGTR]

um, I always thought that all the 3400 injectors were #19...

Nope, they changed in 2000 from 19lb bosch style to 22.5lb delco injectors.


Don't remember off the top of my head if they're high or low impedance, I know I've seen it before but can't recall. You're correct that you should keep them below 80% duty cycle since they are pintle style. If they were disc style you could take them to 90%.

[kprofthestrs]

i want to change the injectors. i am running the 95 injectors in a 2000 3400. the stock pcm won't run the multec injectors. the injectors i want to use are out of the 2000 3400 #25323971 the do appear to be disc style. i will be adding a 3500 top end to this motor in the near future, should i wait and use the 3500 injectors or is there even a difference in the flow rate. i ask because i am adding a megasquirt system to control fuel for now and after that a 35 shot nos system and want to be sure i get injectors that will be able to handle the extra flow that wil be required. and really don't want to have to redo anything if i can get what i need first time out.

[kprofthestrs]

i found a flow rating for the #25323971 and it says 200cc/min which converted is 19lbs/hr is that correct or is the info off. if there only 19 i don't think these will be enough flow for what i am planning to do.

[mfuller]

IIRC, that's what Witchhunter flowed my injectors at, but that measurement is at 43.5psi. The 3400 runs around 55psi, so actual flow rate is probably closer to 22.5#.

[kprofthestrs]

ok well then that makes sense. now if i am looking at these right the 25323971 are disc style? they have a flat type injection point.

[AaronGTR]

ok well then that makes sense. now if i am looking at these right the 25323971 are disc style? they have a flat type injection point.

No, they are not disc style. I don't have the part numbers in front of me so not sure on that, but if they came out of a '00 3400 they should be right. Might want to double check the number with the part guy at a dealership.


Delphi rates their injectors for flow in grams per second at 380Kpa pressure. If you do the math 380Kpa is 55psi. 55psi is about the peak fuel pressure at WOT, so they are rated at 22.5lb/hr under their normal max pressure load for factory tuning purposes.

[kprofthestrs]

ok there not disc style. would the 3500 injectors be a better choice?
since i am still running the 95 injectors with the pressure regulator shouldn't i eliminate the regulator when i change to a newer style injector to get the pressure there tested and rated for. i did have a adjustable regulator but i removed it after the diafram below out after 3 monthes of use. i believe it was the same style regulator that is on the 60*v6 store. have not been able to locate a rebuild kit for it either.

[SappySE107]

3500 injectors won't work with the 3400 rail as they aren't long enough. The 3500 rail is returnless.

I use new regulators with my adjustable units. I have 1 left before I have to get new ones made. Price will go up on the new units so if you don't care how it looks, id grab it.

I want to know what the max pressure you can run is. I have new 4.2 injectors that are 28# at what I assume is 55 PSI. The engine is 99 so I am putting an adjustable setup on it. Id like to get it closer to 33#, which is 65 psi.

Not trying to hijack, as I think this info would help with the topic since GM changed the pressure from 43 to 55 psi when using multec II injectors.

[kprofthestrs]

not exactly sure. i messed with it a little and with the stock regulator it runs about 34 at idle/ if i remove the vaccum line it goes up to about 43. as for under load i do believe it will raise the pressure i would have to hook a external gauge up to the rail to be sure cause my fuel gauge is mounted under the hood so i can only see what its doing sitting still and not under a load. would like to find a rebuil kit for the regulator i have. don't feel like forking out another 100 for something i allready have.

[SappySE107]

just get a new regulator and cut the top off. Then mount your adjustable setup on it and make sure its air tight.