My 3400 build!

[19Cutlass94]

yeah Ill have to see what happens when I start it up, and scan the system to see whats going on. Then once I know that, I can look at what I might need to do.

[IsaacHayes]

What will you be using to scan and read the data?

[JMo60]

you can go bigger injectors, you wont flood out at cruise. your o2 sensor will shorten your pulse width and correct fueling, as long as you dont go with way bigger injectors.. same thing with the regulator, the computer will compensate for cruising. I have an aeromotive LT-1 AFPR on my 3400.. it required a little bit or grinding on the upper intake / plenum, but it fits ok on my engine other than that. it works out real well too..

i have yet to see any better performance however with adjusting the regulator... maybe im maxing out my injectors.. i donno

[ForcedFirebird]

you can go bigger injectors, you wont flood out at cruise. your o2 sensor will shorten your pulse width and correct fueling, as long as you dont go with way bigger injectors.. same thing with the regulator, the computer will compensate for cruising. I have an aeromotive LT-1 AFPR on my 3400.. it required a little bit or grinding on the upper intake / plenum, but it fits ok on my engine other than that. it works out real well too..

i have yet to see any better performance however with adjusting the regulator... maybe im maxing out my injectors.. i donno

That wasn't the case when I went to 24# injectors. The car wouldn't idle to save a life, diveability sucked. I had to turn down the FP to get it to run, then have it raised again during boost. Better off just leaving the stock inj, and raising the FP if you aren't going to tune in the ECM.

[IsaacHayes]

Yeah BaldEagle was running the stock FPR, and just swapped to the 3400 injectors before we were able to tell him to keep the old. Well it ran crappy until he switched back and it was all good.

[19Cutlass94]

Im going to be using an OTC scan tool to read all the data... Itll read just about everything in the system.

I know for a fact that all Multec 2 injectors ( like the injectors that came with this motor ) flow tooo much and I just cannot use them at all. Really the only bigger injector I can go with that isnt crazy is the DOHC injectors. But Ill be looking into the FPR

[Superdave]

the injectors that came with the engine are 22.5# @ 55PSI, if you drop that down to 43.5 they'll be around 19#.


BTW, the AFR you are seeing on that scanner is the commanded AFR, not the actual. For this application i'd suggest a true wideband setup.. It's an easy install and it'll make tuning a breeze.

[19Cutlass94]

yeah I cant use those injectors... the stock 3100 ( L82 ) are 19# @ 43.5... if I went with DOHC injectors.. those are 21# @ 43.5.

[19Cutlass94]

Ill have to find a place for a WBO2 somwhere so I can see that.

Now question; once I know the a/f is there anyway to determine what # injectors Ill need... or can I figure that out now?! Cause Im looking through injectors here and I can get the L82 style injectors at various flow rates.

[IsaacHayes]

The problem even with AFPR or RRFPR/FMU is that the motor may need more fuel in a particular RPM and none or less in another RPM. If you are lean across everything then you could up the pressure or injector rate and be better off but not perfect. I'm just really wondering if the PCM can reduce the pulse enough at idle and cruise for larger injectors, even very slightly larger.

The WB would let you know what's going on at least so that will be interesting to see.

[ForcedFirebird]

Ill have to find a place for a WBO2 somwhere so I can see that.

Now question; once I know the a/f is there anyway to determine what # injectors Ill need... or can I figure that out now?! Cause Im looking through injectors here and I can get the L82 style injectors at various flow rates.

I have found if you go to a bolt/fastner specialty store, you can buy an 18mmx1.5 nut, cut it in half the long way, and BANG! Instant o2 sensor bung. Then you can just drill a 5/8" hole anywhere in the exhaust tract and weld the nut on. I bought 3 nuts for $3, still have enough to make 4 more bungs . Just make sure you mount your WB somewhere between 9 and 3 o'clock on the pipe to avoid moisture problems from standing water.

[19Cutlass94]

Now should I be mounting the WB before or after the cat? Ive got PLENTLY of room, but its after the cat... I think before the cat is going to be next to impossible... Although what I could do ( since the cat is just bandclamped on ) is just cut a piece of pipe with an O2 bung in it and just use that?

[IsaacHayes]

Before the cat. The cat will burn off unburnt fuel/etc and screw with the reading. You can run some WB's in place of the normal O2 as they have simulated NB output for the PCM. But don't run them ALL the time as they have limited life.

[19Cutlass94]

yeah Ill just make up a test pipe to go in place of the cat with an O2 bung so I canuse the WB

[mbear2489]

did you get that from linders by chance?