http://web.camaross.com/forums/showt...threadid=90648


Please see that thread, we have a pretty good debate going and i'm kinda wondering who's right. I think it'd be good information to have.


Thanks,

Mike

 

Yes, you can increase the flow capacity of injectors by increasing the pressure:

(P2/P1)^0.5

Yes, if you program the new flow rate and offsets into the PCM, the PCM will function correctly. It will still meet the "tuning" that is in the PCM. It doesn't magically deliver more fuel unless you tell the PCM to enrich the mixture.

The question in my mind is how you accurately program for a blower on a stock PCM that can only read a 1bar MAP sensor. That's where the FMU appears to make sense.

 

thanks for the reply


The '93 cars are almost impossible to tune without an FMU, since they're speed density, but other years are not too hard since you have the option of playing with the MAF tables.

The other option that i've read about for the '93s is to swap out a syclone/typhoon ecm that has the cabablility of using a 2bar sensor.

 

Mikael: I never thought of doing it the way you suggested. I don't see why it wouldn't work as well as simply using larger injectors at a lower FP.

As far as Fred's concern about tuning for boost using a 1-bar MAP sensor, I also have mixed feelings in that regard. A lot of people are doing it, but it seems pretty crude to me. That's one reason I use the Superfueler, though if I were starting over I might just go right to an aftermarket system with the capacity to directly control the 8 "main" injectors using a >1 bar MAP sensor. OTOH, that would keep me from using an MAF, which I really like. A relatively low boost setup never maxes the MAF, which is a more accurate method for measuring airflow than an MAP sensor anyway. That's one big reason why the large injector/stock FP combos work - they are running off the MAF.

Not sure the above made sense, it's been a long day. Let's just say that in additon, I never understood the anti-FMU bias. It is one easy way to (roughly) tune for boost. After all, the stock FP regulator is an FMU with a 1:1 ratio anyway.

Rich Krause

 

I dont think that you'd have problems with boost tuning on a 4.5# setup. As for the injector thing, yes, Ford SVO 30# on an LT1 car, setup for 43.5ish PSI instead of 39PSI, will be about like a 32# injector or so. This is one "cheap" way of getting more fuel capability to the car.

I wouldn't even think you'd need a pump upgrade, and I dont think you'd have to worry about fuel all that much at all, other than an injector upgrade. If you wanted to run higher fuel pressure though, a "better" pump would probably live longer. I know some people run Boost-A-Pump, which sends more voltage to the pump, but I dont know the reliability of such a thing since its overdriving the pump, I'm sure it would work in the short term though.

As for the pressure regulator being defeated by the PCM in closed loop, yes that will happen, but thats not really an issue. You will be tuning with Tunercat or LT1 Edit correct? Use this to bring your BLMs together for closed loop driving, and of course to do your tuning at WOT, both timing adjustments and fuel. The regulator just lets you up the pressure a bit if you want to get a little more out of the injectors.

I would go with a 30# or 36# injector, maybe Fred or someone else has an idea on which would be the better of the two, I would lean towards the 36# just because I'm picky, but I would say the 30# would probably work great as well.

Some people go speed density to avoid maxing the MAF, and other people play "PCM tricks" to get past it, one of those tricksters is in the 9s on a stock PCM along with a low impedance injector box, so tricks can be done even though I dont generally like them, and I'm sure most would prefer not to have to resort to them, but its a way to save money. If it works, it works.

Other cars use FMU (rising rate pressure regulator), like on the old turbo cars, because we can't really get into the computer, which is analog (old)! I dont think you need to worry, but yes they work.

With 4.5# though I feel pretty confident you wont have any real problems, best of luck.

 

Like stated above, increasing your fuel pressure will result in more fuel to the cylinder and a better injector spray pattern if the injector is functioning correctly. Too much boost could "lock" injectors, but at 3.5#'s and a 90% + duty cycle, there should be no problem. Feedback with EGT and A/F ratio should prevent any problems with running lean accidently. You should be able to effectively "push" the envelope on injectors over their rated flow without problems if you keep an eye on the above variables...