I have an adjustable fuel pressure regulator and the LT1 edit software, stock injectors and fuel pump. Do I still need to get an FMU?

 

Well i can tell you i had the 4.5 psi and im going to the 6.5 psi kit and im still going to be using the FMU and 30 lbs injectors .By the way is that rwhp with the blower or before...

 

It's before the blower. I haven't had time to get to the dyno with the blower.

 

I'd crank up the fuel pressure to about 68psi, that'll give you 30lb injectors, which should be enough. Get a pressure guage and make sure the pump is keeping up, otherwise you may need an inline.

 

The computer will relearn and defeat any mechanical fuel pressure change via injector on time and pulsewidth. You really need at least 30# injectors and some enrichment in the PE vs RPM table to go without the FMU. I would suggest 36 or 42# squirters if you're going to do it though ......that way you're prepared for the future and have a safety zone in the area of duty cycle.

 

I don't know where Mikael is getting is info but its all wrong. Jacking your pressure up will have it idling like complete crap and wasting gas.

You'll need to put on the afpr (you can set it to only 40 at idle which will keep down the smell of gas at idle) and get an inline fuel pump.

Hal

 

Thanks for the input. Please read my post again carefully.

I didn't tell him to just wildly crank it (the fuel pressure) up and think things will be fine. By running that fuel pressure instead of the LT1's stock 3 bar, his injectors will effectivly be 30lb injectors, so he needs to adjust this in LT1 edit. I recommend this since he already has what he needs to do this effectivly without spending any more money.

 

So, it looks like I can do this. Tell the pcm the injectors are larger then they are and adjust the a/f and fpr. If that doesn't work, then get a in line fuel pump.
Is this correct?

 

Mikael, I can tell you right now that car will stink of gas and ping like crazy if he tries that setup. Just setting the injector flow rate to 30 isn't the trick after adjusting the pressure up. Also, you should know that the stock pump cannot support anything over 55lbs at wot so it will be detonating like crazy.

Adding an inline pump and fmu isn't the worst thing to have to do. If you don't want to do that I KNOW you won't want to change out your blown(up) engine. Where is Dr. Mudge through all this?

Hal

 

Yeah, install the FPR, make the changes in LT1 edit, and hook up a guage to make sure you're holding the pressure. I got one from DAP for 10 bucks and just had it haning out the hood, it doesn't need to be permanent.


If it won't hold the pressure, get an inline from ebay, they will hold up to125psi for $35.


I'm not aware of the LT1 having a fuel pressure sensor that will adjust fuel flow in the ecm. By running this elevated fuel pressure his injectors will be flowing the same amount of fuel as a 30# injector, which is why he can do this.


Look at the LT1/LS1 comparison. The 28lb injectors are rated at 28lb because the car runs 4 bar(58psi) vs 3bar (43.5psi) that the LT1 engine runs. Decrease the pressure on the LS1 to 3 bar and you'll have a 24lb injector.

 

Michael, Upping the pressure will run an injector higher then its rated value but certainly not make a 24 into a 30 (been there, done that). You'll also pay heck trying to find a good inline for only $35 even on ebay. Add to that the stainless lines, connector, and relay and your well over a hundred.

Also, you don't know the injectors sizing can be changed in the pcm (no longer called ecm)? Not that I am trying to have a pissing war with you, but after all the years I have been reading and adjusting my own blower setup, I don't want to misslead or see someone give info that is odd and unrecommended. What is your background in supercharging or turbos?

Hal

 

I used this: http://www.csgnetwork.com/fiflowcalc.html

That's why i picked 68psi , i can't spout that out off the top of my head.

There's a person that sells an inline on ebay for $35, i acutually purchased one. Its sold under the name of msd and others, but its the same pump, even has the same inscriptions on it. I'll have to find his email, i have it somewhere.


I used tunercat on my '93, which allows you to tell the pcm what size injector you're running, if you put 30lb injectors in a completely stock car and change the computer, it'll run exactly the same, only with a shorter pulsewidth. I'm currently using LS1 edit which has the same feature, and i'm quite sure LT1 edit can do the same.

Running too high of a pressure can be detrimental, my stock 22lb injectors wanted to lock up on my '93 when the FMU got the pressure too high. I replaced them with 30lb svo's and the problem went away, and that was at 90psi, i doubt he'll have problems.


I acutally made a turbo kit for my '95 V6 camaro, and have now lost all the pics, which is unfortuante since i did a really good job. Then it was my '93 TA that i put a powerdyne on for a short time, until i got tired of all the electrical problems the car gave me, and didnt want to push an already tired motor. Currently i have a powerdyne head unit in pieces in my room, waiting discount auto to order one more bearing so i can get it back together and put on my '99SS. Looking for 425rwhp, but i'll be happy with anything over 400.

Take care

mike

 

My stock 97 injectors (24) handled the 85+ psi ok but came out with low 02 readings (850) at around 5#. It knocked until I dropped the wot advance 2 degrees (33 overall) and subtracted .7 per # with a btm. I later added svo 24 which allows it to go over 930 at 85+ psi (all pressures started at 38 and increased with powerdyne 10:1 fmu).

Hal

 

An AFPR will make a difference on a '93 MAp car but not on a 94+ MAf controlled vehicle.

 

In open loop it does and kind of does even in closed loop.

Its obvious it does in open loop or else why would they make a fmu?

Closed loop it will as long as the pressure was either needed to make the 02 run at their desired level, or the amount of pressure increase or decrease does not effect the desired range the pcm is looking for. I leave mine set to around 38 at idle (I;m at sea level) so that my garage doesn't reak of gas. Not sure if the smell is from the return line canister vent or if its unburnt gas coming out the tailpipes.

Hal