Can i still run 42lb injectors w/ a stock fuel pump?

[Verlin]

I have a Novi 1000 supercharger, a Trick Flow intake and 42lb injectors w/ a 90mm mass air and 75mm throttle body waiting to go on my 93 GT. My question is Can I put just the intake, injectors, and mass air on my car for now? I have a Kirban adjustable fuel pressure regulator on. So can I use the 42lb ers and just regulate the fuel pressure or is that too much fuel and mass air? Will my stock fuel pump work for now? I have all the typical bolt ons (headers, h pipe, flows, 65mm throttle body, cold air intake, pullies, msd ignition, coil, wires, cap) Im sure I'll have to use my 65mm throttle body too instead of the 75mm???

 

[Michael Yount]

It's hard to tell what the drivability and a/f mixtures might be until you try it. Some make the larger injectors work just fine on combos that don't need them; others have problems. Someone else's experience isn't necessarily indicative of what's gonna happen when you try. If I were in your shoes, I'd simply wait and do it all at once (blower) -- easier anyway. Stock fuel pump will be fine - until you put the blower on, you're not likely to outrun the stock fuel pump with your mods. But with the blower - the pump needs upgrading. Either throttle body will work fine without the blower.

 

[Verlin]

If it takes 40 psi for the stock injectors, couldn't I just go ahead and install the 42lb ers and regulate the fuel to 40 psi? Not a big deal, i can always install my 19lb stock injectors and 76mm mass air. I just wanted to know if I would see any improvements w/ the bigger mass air and injectors!! Along w/ the intake.

 

[Michael Yount]

You'll see an improvement with the intake - the stock lower is the biggest flow restriction on the engine. But even with the intake improved, there's still not much to be gained over the stock throttle body and maf until/unless you make other changes that increase the flow potential of the engine. If you put the larger injectors in, you need to tell the ecu what you've done - either with a chip or by altering the calibration on the maf. Fuel pressure should be left at the stock setting.

 

[HISSIN50]

now Michael is way smarter than i, but ill toss out what little thoughts i have are.

the thing with the EEC-IV is that it is pretty adaptable (values can be +/-25% before tossing codes and going frankenstein). so if you run the fatter injectors now, when the puter trims the A/F ratio, you will get down to having a tiny duty cycle with fuel pressure set like you are talking about.

and if you lower the fuel pressure in an attempt to increase the duty cycle, the spray might suck.

i think Michael has posted it before, and it is something ive always agreed with - i would rather have an injector working at near-capacity duty cycle vs a huge injector taking it easy (low duty cycle).

that said, people get away with stuff all the time. two guys can run the same mods on the same motor set ups and it will work for one and not the other (intangibles and perhaps a difference in what is acceptable to each driver).

Michael, Feel free to let me know where my thinking is flawed - im not nearly as smart as you with this puter stuff.
thanks again for the suspension advice too!

 

[Michael Yount]

You're at the heart of the issue - the ecu won't simply adapt for the larger injector without a recalibrated maf, but once you're close, it's adaptive strategies try to accomodate. But there are limits - and of course it can't do anything about atomization of a small amount of fuel from a large injector vs. a smaller injector.

I suppose it seems like this to me - if you know you're gonna blow it and you'll need the larger maf/injectors -- you have nothing to lose by trying it. If it poses problems, put the stock maf and injectors back til you add your blower.

The biggest issue I see is the calibration of the maf. ProM will tell you I believe that the calibration of their maf for a boosted application with 42's vs. a naturally aspirated application with 42's are not the same. So it seems to me unless you just want to take a chance with the boosted calibration in the naturally aspirated application, just leave it as is til you blow it. There's little if any performance benefit to adding the bigger maf and injectors, and drivability may suffer.

 

[HISSIN50]

like i said, Michael, you are way smarter than I (being SD, i often forget about MAF's [LOL] and dont know all that much about themand the ins and outs of the calibration issues.).
like i said, thanks for letting me know where i was flawed.

 

[Rick 91GT]

Good info in this thread

One thing we have learned over the last few years with meters is to get the NA calibration on the MAF on a Supercharged car, the fuel curve on the boosted meters can reak havoc at times.

As for running a boosted calibration meter on a NA car, it can be done if you have a tunable ECU or piggy back system. We made it work on our 93 Cobra but had a lot of tuning and tweaking to get it to work and still had some slight issues....way to much work and that was with a 36# inj.