fuel needs

Heres my set up first of all. I have a 92 mustang GT, bone stock engine besides electric fan, headers, full 2 3/4" exhaust. and an sn92 with an anderson PP. For fuel right now i have the paxton FMU is all, and just realized i have the yellow injectors.. i didnt know the yellows were stock..

Im pulleyd at 4psi with the 4" blower pulley. I want to buy the 3.75" but Im thinking my injectors are maxed out and i need more fuel, correct? I plan on doing an intake and TB within a year ( and possibly heads in future) also. So how much am I in need of injectors? Then do i need to recalibrate the FMU for the pulley change? should I forget that an run something like 42lbr's and get rid of the FMU? or buy some kind of tuner..

Thanks for all help. I need suggestions!

The FMU responds to boost. It only needs recalibration for different size injectors. The FMU is the best bang for the buck.

You SHOULD be fine with the 19# injectors.

I am currently running a Ø3.75 pulley (blower) on my '86 and have no fuel delivery problems. I also have a 65MM throttle body and ported upper and lower intakes. The stock injectors are working fine.

Oh wow, ok so ill only need to change fmu discs if I change injectors.. I heard the stock 19s are good for about 250 hp, so Im worried about running lean. I have no wideband, and no idea what hp Im at now.. you have any estimates for your car?

I have no real HP estimates and am pretty sure I am running rich at full boost by seeing the carbon (black) exhaust at WOT. If I were a guessing guy I would guess between 300-325 HP. My guess may get shot down by later posts

I forgot to mention I am also running a HO impeller on my unit.

What makes you think your injectors are maxed out? If you aren't using one already, I would recommend you get an MSD box to keep that spark from blowing out. I am using a 6A unit.

I have been told by many people that the 19's were meant to handle around 250 hp at most. 24's Iv been told are meant to hold up to 300 hp. and I'm not sure about the others.. Do you have the stock fuel pump as well?

This car is a DD also, I want to make sure its in a safe A/F/R (I know a tune or handhelp tuner is optimal, but dont have $500 to throw at the car right now while its my DD)

Yes, stock fuel pump presently. I plan to get a larger one in the next couple of years or so.

I just looked today and found out i do have the HO impeller. That was a suprise. Im still only seeing 4psi at 5000-5500 rpms, shouldnt I be seeing at least 5? By the way what plugs are you mustang guys running? I just put new autolite 25's in gapped at .054, is this fine?

Most people run stock plugs gapped to around .035" gap. Mine are gapped to .038".

Pressure seems low. Make sure your belt is not slipping at the higher RPM's.

shiiiiet should I regap them? they are at .054 right now.. belt shows no signs of slipping. What size crank pulley is normal?

Regap, it is critical.

Ø6" is the stock crank pulley size.

http://www.superchargerhelp.com/showthread.php?t=4907

The above link in case you didn't know has a great spreadsheet for looking at various impeller speeds.

gotcha, ill regap to around .038 tomorrow, and also see what size the crank pulley is. That speed calculator would be nice if it had any pulley sizes even close to the ones used on the sn series...

Since you don't have a MSD or aftermarket ignition I recommend you keep the gap on the smaller side...say around .032"?

Let us know how it works out for you.

Of course you can download and change the fields in the spreadsheet to be specific to your application.