rob vanharten

I understand that a fuel injected 509 mpi motor with a procharger starts with let's say a 40 pound base line fuel pressure. And ends up making around a 20 pound rise by the time full boost is achieved. But why does that happen when we are using a 1:1 boost reference regulater? If the boat makes 5 pounds of boost at wot, then should it not be making about 45 pounds of fuel pressure. One pound of fuel pressure for every pound of boost. I want to add my smaller pulley which should make 7/8 pounds of boost up from 5, and want to make sure I have enough fuel. Running the a1000 pump with areomotive boost reference regulater. Fuel rail is fed from both ends and has a custom return from the regulater to the fuel fill neck. All larger fuel lines to match. I am assuming stock injectors....... Am I safe to toss the smaller pulley on. And if so, should I bump up the base fuel pressure to put more pressure on the injectors at wot? What's everyone think? By the way m3 charger With the 504 cooler.

FIXX

iTrader: (2)

where is your regulator? b4 or after the injectors..

Mbam

The regulator that comes with a Procharger kit is not linear. It has "gain". Bumping the fuel pressure as the boost goes up is a crude but workable way to use the stock injectors and ECU. Tuning can be tricky.

The ideal way is to reprogram the ECU and change injectors as needed.

MILD THUNDER

iTrader: (3)

Agree. This is a normal and acceptable practice in a blow thru carb setup. Not so much to provide more fuel, but to keep the added psi from the blower not to overcome the floats in the carbs and close them off, starving the engine for fuel. Since the bowls are no longer seeing normal atmospheric pressure resistance. If you raise the psi at the carb 7psi, you need 7psi more fuel pressure so the floats behave normally. Thats really where the 1:1 idea comes from. If you think about it, adding 3 lbs of boost on your setup might produce an additional 100HP(guessing). 3psi more fuel psi on a port injected setup, isnt gonna support the extra 100HP alone.

With injection, Id want the proper LB injectors with a good tune. A 02 sensor would probably be a worthy investment.

rob vanharten

The regulater is before the injectors. This is not the regulater that comes with the procharger setup. The boat has a complete big line,big pump, good regulater setup. Not the half ass stuff procharger supplies. I have had a hard time finding different injectors for this motor. What should I be searching for? Can the mefi3 just be sent out and tuned to my boost and fuel requirements, or does that all have to happen on a dyno or in the boat with tuners? Sorry I am new to all this Efi stuff. Just trying to learn.......

rob vanharten

Maybe the regulater is the procharger one. Did they use a aeromotive boost reference unit? Is that why you see a 20 pound gain from off boost to full boost. Prochargers way of dealing with stock tune and stock injectors? Again sorry for the ignorance, just don't want to blow anything up, but do it the correct way!

Griswald

the correct way is to ditch that boost-referenced regulator and get the thing tuned. What ecu are you running?

rob vanharten

It's a 99, so that should be the mefi3 if I am not mistaken.

rob vanharten

Okay, I brought this boat home last Saturday after purchasing it. I had a chance to go over it some more this am, and can speak with some more accuracy. The boat does have the procharger regulater on it. It also has what appears to be a custom pickup from the tank (bigger) and it get returned to the tank as well. It's all big lines not sure on exact size, I am going to try to figure that out. They are earls fittings. I am going to attach some pics of this as well. The computer is definitely the mefi3. Also found a small procharger module that taps into a temp sensor and the factory harness as well. It called a ect signal conditioner. Would I unhook this module if I had ecu tuned for bigger injectors and the 7/8 pounds of boost? Which regulater should I be running on this setup with the tuned ecu and bigger injectors? Are is the rest of my fuel system up the task? My 5 pound pulley measures 4.25, and the other pulley that came Withe the boat measures 3.75. Will that smaller pulley put be into the 7/8 pound range? Photos coming!

rob vanharten

Here's a few more