A guy I met at a show today was running a Procharger set-up on his LT4 CE. My q is should he have modified the fuel system, like larger injectors and more pressure?

 

From what I understand he needs to do more than that, like lower his compression. With the high compression the LT4's have every SC tuner I've talked to has advised against installing one unless I lower the compression, or risk blowing the head gaskets on a regular basis.

Sam

 

:yesnod:

I wouldn't dare run a SC without forged pistons!!

 

You can but it will reduce the life of your engine. 6lbs of boost is better for a LT1/4 but anytime you put more stress on an compenent it'll reduce its life. As for upgrading the fuel system, it's always advised but not necessary. Upgrading the fuel sys. will yield more power and make detenation(Will kill a car) less likely. One more thing I would change would be the rev limit of my car. Vette's have a fuel shutoff at 5800 for the LT1(not sure for the LT4) and that would almost promise detenation. I would find something like MSD's soft touch rev limiter that uses the firing order of the engine to prevent over reving, and doesn't touch your fuel. I hope others with more experience chime in here soon.

 

The LT4 should already be running 28# injectors which are probably sufficient for the power he is getting out of it.

 

I'm running the 3.125 pulley on a vortech V1 S trim. 6-8 pounds of boost depending whether you shift at 5500 or 6000. I agree you need to upgrade the fuel system and watch the timing big time... I'm also using the stock 10.4 compression ratio

To keep the detonation under control, I went to a step colder plug went to carroll supercharng for a means of bumping up my fuel pressure... ( I didnt care for the FMU ) I'm running 75 pounds at full boost with 30 pound injectors. I use the LT1 editor to trim off the advance as well as a MSD AL 6 BTM.

If I go full 100 percent throttle on a hot day I still see about 4-6 degrees of knock retard and I see the intake temp got from about 113 degree to about 206 degrees. I have added 3 30# aux injectors also from Carroll supercharging... this seems to tone down the detonation, by somewhat chilling the air with ambient temperature fuel, however I'm still not comfortable with some of my data. (I'm looking for less than 1 degrree spark retard at 100%)

I have just ordered an ATI 2 coreintercooler that should take the intake temps down to about 40 degrees above ambient, which should allow me to return to stcok timing. There is said to be about 1.5 pounds of boost loss in the intercooler, which means you could possibly push it back up too 10 pounds of boost, how ever... I think 480 horse and the whine of a supercharger for the street is enough to intimidate any rice burner. The above thread didnt mention whether the LT4 was running an intercooler. Even if he is , he still needs to look at his fuel management. Most kits include a 10:1 FMU which basically gives about 8- 10 pound of fuel pressure per pound of boost, which would net somewhere around 90 pounds of fuel pressure. with 28 pound injectors as said above that would be enough to run in the neighborhood of 12 -12.5 :1 AFR

So all of this to say, don't believe Vortech or the others claims that you can just bolt on a supercharger andd run with it... you are looking to pick pistions out of the oil pan if you don't use your right foot wisely.... As it was mentioned above unless you know whats going on in the engine , stay at 6 pounds but that still does not negate the fact that you can run not leaning out at the high end (fuel management) or running too much spark advance .

If you have any questions i'll be happy to answer them, I've been working with my blown vette since last Thanksgiving , and have run over 200 tests..

Hope this helps,
mo


[Modified by Mo_Bandy, 1:26 AM 6/11/2002]