Stock 3400 injector size??

[phantom505]

Actually none of you are quite right, but none quite wrong.

The 1999 injectors are Bosch OBDI style and are rated at 19# for 40 psi.
The 2000+ are OBDII style and are raged 23# for 40 psi.

I just put 42.5# injectors (44 psi) and they fit just fine and they are the Bosch style. So the 2000+ can use them, but you have to change the harness. Use MSD P/N 2400 that you can pick up from Jegs, Summit, etc

[SappySE107]

I assume you also reprogrammed the computer and are boosting the engine.

Where did you get those numbers?

[JohnyG]

Actually none of you are quite right, but none quite wrong.

The 1999 injectors are Bosch OBDI style and are rated at 19# for 40 psi.
The 2000+ are OBDII style and are raged 23# for 40 psi.

I just put 42.5# injectors (44 psi) and they fit just fine and they are the Bosch style. So the 2000+ can use them, but you have to change the harness. Use MSD P/N 2400 that you can pick up from Jegs, Summit, etc

I tested the fuelpressure for the multec1 fpr and for the multec2 fpr, multec1 was at 45psi idle while multec2 fpr was at 55psi @ idle.

-John

[SappySE107]

Well, the ratings GM uses is 43.5 PSI, ford uses 39 PSI. I have also read that 2000 saw an increase in fuel pressure for the grand am 3400, but that was in 2000 and I dont have the press release info for that anymore. Hmm, im thinking brad may have put that type info on the site though. Ill run across it when I finish the new site design/redo parts of the information for it.

[AaronGTR]

Actually none of you are quite right, but none quite wrong.

The 1999 injectors are Bosch OBDI style and are rated at 19# for 40 psi.
The 2000+ are OBDII style and are raged 23# for 40 psi.

I just put 42.5# injectors (44 psi) and they fit just fine and they are the Bosch style. So the 2000+ can use them, but you have to change the harness. Use MSD P/N 2400 that you can pick up from Jegs, Summit, etc

Actually, I'm 100% right. I researched this extensively before I bought new injectors for my car. Those numbers came directly from my contacts at GM and Delphi. I also had my injectors flow tested by RC engineering to make sure. OBD1 or 2 has nothing to do with injectors. All that matters is high or low impedance. The brand of injector changed from '99 to '00+ from bosch to delphi, but both were high impedance type with similar flow ratings. Fuel pressure remained the same. The injector pulse was changed in the fuel map in the PCM between years to acount for the difference, and of course the injector plugs were different.

PS. Fuel pressure for all 99+ GA's is 48psi at idle, and 54psi at WOT. This is in the tech manuals and confirmed by my fuel pressure gauge. I get 62psi now under boost with the CFPR.

[SappySE107]

So how about the 96-99 3400s then, are those 55 PSI systems as well or 43? You said they kept the same fuel pressure but I want to make sure thats correct.

[AaronGTR]

I don't know about those years because they didn't have the 3400 in the grand am then. I just know that's what the fuel pressure is in all 99+ n-body's with a 3400. Others years/cars I don't know. I could probably find out easy enough from my dad though.

[Cliff8928]

Actually none of you are quite right, but none quite wrong.

The 1999 injectors are Bosch OBDI style and are rated at 19# for 40 psi.
The 2000+ are OBDII style and are raged 23# for 40 psi.

I just put 42.5# injectors (44 psi) and they fit just fine and they are the Bosch style. So the 2000+ can use them, but you have to change the harness. Use MSD P/N 2400 that you can pick up from Jegs, Summit, etc

The old style injectors may look like Bosch injectors, but they are far from it.... Bosch injectors are a POS, The GM ones, AND the MSD injectors are of the Multec design.. (Multec injectors don't have a clog-prone pintle)

Cliff Scott
89 BerettaGT
89 Volvo740 <-had bosch injectors, now MSD Multecs