I am new to this, so bear with me. I have a 1990 Gt that is stock. From the factory, it puts out 225hp. Everything that I have read states that the fuel system is good to 325hp before having to get bigger pump, injectors, etc. I am not looking for killer power, just a nice usable 300ish. This should be about 6psi of boost. The MAF is supposed to be good to 325hp as well. If I plan on staying in the 300hp range and 6psi, what is the issue with doing a draw through MAF with a good size wastegate to prevent over boost. It would seem that if I stay in the range of the MAF, it would read the appropriate amount of air coming into the engine, and compensate for the boost. I would plan on running an MSD with boost retard to back timing off for boost. My car is an automatic, and with the low boost level, I don't think a BOV would be needed. What am I missing in this equation. I know vortech runs a rising rate FMU for their similar setup. Is this necessary, and I would think it would make the car run incredibly rich. Trying to get a handle on all the pieces to the puzzle.

 

Sorry to shoot holes in your theory. You should upgrade your fuel system if you plan on adding forced induction. You will melt your engine if not. Walbro 255lph pump, 42lb high impedance injectors, and a PMAS blowthru MAF would cover you to around 500hp. If you use this setup a fmu is not needed. You will need a BOV or you can damage a turbo .

 

If you look at an injector calculator, the stock 19 lb/hr injectors are barely adequate to support the rated 225hp at .5 bsfc. At a more boost friendly bsfc of .6 they're only good for 205 hp @ a 80% duty cycle, so that should tell the story. Upgrade the pump, and the injectors (if not running an fmu). Typically boost levels under 10 psi can get away without a bov is the general rule of thumb.

 

with a rising rate regulator... sure... you can hit 120 psi of rail pressure and make it work... I doubt the stock 88 lph pump flows much at 120 psi though...

upgrade the pump and injectors

 

Why would you go to the trouble and expense of turbocharging your 5.0 and only seek 300hp? Changing the injectors and the pump are two of the easiest tasks you face if you truly intend on seeing any boost in a Mustang.