36 Pounders, FMU, Fuel Pressure Q?

[StangQuest]

How's it goin guys. Here's the deal. I have a 95 GTS with a P600B w/ 3 Core IC along with the usuall bolt ons.....heads, cam, intake.... . I'm presently running 36 pound injectors, 190 in tank and BBK 255 in line fuel pumps, NO FMU and NO CHIP. I'm looking for advise on whether or not I need the FMU. Ive got my timing at 9 degrees advance and my fuel pressure bumped way up to 50 psi....I'm scared to death of going lean and detonating since I have about 110,000 miles on the shortblock. When I first put the blower in, two weeks ago, I had my timing at 12 degrees and my fuel pressure at 40 vaccum off and experienced alot of pinging above 5000 RPM's. It was because of that that I decided to make it as safe as I could. I'm also running a 75mm Pro M calibrated to 24 pound injectors with a Pro M Opitmizer to tune the MAF output to match the 36 pounders. I'm looking for any info that will stop me from pulling my hair out because of the uncertainty of the tune. Thanks in advance.

Justin

[paluka21]

Originally posted by StangQuest
How's it goin guys. Here's the deal. I have a 95 GTS with a P600B w/ 3 Core IC along with the usuall bolt ons.....heads, cam, intake.... . I'm presently running 36 pound injectors, 190 in tank and BBK 255 in line fuel pumps, NO FMU and NO CHIP. I'm looking for advise on whether or not I need the FMU. Ive got my timing at 9 degrees advance and my fuel pressure bumped way up to 50 psi....I'm scared to death of going lean and detonating since I have about 110,000 miles on the shortblock. When I first put the blower in, two weeks ago, I had my timing at 12 degrees and my fuel pressure at 40 vaccum off and experienced alot of pinging above 5000 RPM's. It was because of that that I decided to make it as safe as I could. I'm also running a 75mm Pro M calibrated to 24 pound injectors with a Pro M Opitmizer to tune the MAF output to match the 36 pounders. I'm looking for any info that will stop me from pulling my hair out because of the uncertainty of the tune. Thanks in advance.

Justin

Justin,
On a heads/cam/intake blower car its going to be a good idea for you to use an FMU or upgrade your fuel injectors.36# injectors are just plain too small for what you have. Depending on what boost level you are at, and the heads/intake etc you are using will determine what size injectors you will need.
Off the top of my head a set of 42# injectors would probably be sufficient fuel (again depending on the above stated), or getting an FMU with a 6:1 disk should do the trick as well.
It would probably be in your best intrests to get the car on a dyno and see exactly what a/f ratio's the car is at instead of guessing, especially since you seemed to be concerned about too many miles on the motor.
Until you can get an FMU or larger injectors I would keep the timing down to where you have it, and keep the fuel pressure in the mid to upper 40's with vaccum on to play it safe until a dyno tune.
Dan

[WA2FAST]

I agree completely with Dan. Keep your timing down, fuel pressure up around 50ish and don't rag on the car till you get it on the dyno to see exactly what your A/F is and what you need to remedy it. You can run a FMU, but if you want to do it the best way, I would sell the Optimizer, the meter, and get yourself a 3.5" Univer callibrated to whatever injector that you determine neccessary (which will probibly be #42).

[StangQuest]

Thanks for the responce guys. I think I'm going to take that advice. Another question for yal, how much HP will these 36 pounders handle? I'll see no more than 10 psi and I should be at just over 400 HP to the wheels. The guy I bought the blower from had a similiar setup and put down around 390 RWHP.....although he was running 30 pounders, no FMU, base fuel pressure way way higher than mine and a poor tune.........hell, this guy was getting no more than 100 miles out of a tank of gas!!! Anywho, thanks again.

Justin

[WA2FAST]

Yea, that guys car was not set up even close to right... I'm supprised that he didn't cause damage. If he would have had a larger injector, or been running a FMU, he would have been in better shape as far as what he was laying down. Check out Pro-M's website... or here's a link to the section that has the formula for the injector sizing (actually, has TON's of usefull information on that page too). Look all of the way at the bottom for the injector info. That website is full of usefull information, hell, it was developed by Pro-M! Anyway, check it out and it should clear up a lot of confusion for you.

http://www.pro-flow.com/tech%20info/mustmath.htm