Correct. Install the Racetronix supplied extra connector set on the MSD. Relay end is power source for MSD/BAP. Pump end is pump supply/ MSD/BAP output. Connect all grounds to chassis. Make sure the grounds are good and you lubricate them with the silicon grease supplied to prevent corrosion. If the BAP should fail simply unplug it from the Racetronix harness.

 

One thing that I noticed on the msd unit was that the amperage was low. It will work fine for a walbro, but anything bigger than that might give it a pretty good workout. Also, with the thing on max, it will put out 22 volts, but not until 30psi. I"m not sure if the response is linear, but I need a good amount of voltage at low boost(around 10psi).

At 5 psi, the thing is only putting out 15.7 volts at full power. This is a good amount of voltage, but Ideally, I'd like to see more adjustment at lower boost levels. I'm guessing that at about 10psi, it probably puts out about 16.5-17.5 volts.

The power rating in amperage on the kb units is significantly more than this unit. If you wanted to run 2 pumps off one unit, that's out of the question. With the kb unit, you just have to order the 40 amp one.

 

This is correct however you do not want to run a Walbro pump over 17 volts as it can start to cavitate.

There may be an easy way to modify the MSD unit to provide a higher gain vs. MAP while still limiting the plateau voltage.

 

Well, if you know of any ways to increase the gain on the unit, let me know.

Also, the 15.7 volt number @ 5 psi was with a 13 volt input source. If you're using a harness or decent wiring, you're probably seeing upwards of 13.5 volts. It is possible that 5psi might give you over 16 volts.

My ultimate goal is shooting for 500rwhp at 10-12psi, so I'd imagine that this should be sufficient pump at that voltage (about 17 volts) for my setup.

 

I understand everyone's answers, and thank you for the replies. However, nobody has seemed to address my point about running the nylon vacuum line from the intake to the rear of the car, as opposed to just a wire on the KB unit with the sender. By the way, I have the Walbro GSS340M and harness from Racetronix. I only expect to see 10-12 pounds of boost, not anywhere near 30lbs. If the switch turns it on around 3lbs, is it really any better to have the MSD unit slowly ramp up the voltage on it's trip to 10lbs? I understand you may not want the same amount of gain at 3lbs as you want at 30lbs.

 

Typically the KB unit causes a brief pressure spike when it turns on. This will cause the motor to blip and then recover from the over fueling. It will be very apparent on the dyno as to where it happens.

You should consider something better than nylon line for the MSD's MAP signal. Something more tolerant of heat and abrasion.

 

Another alternative is Greg Carrolls Super Pumper. It is fully adjustable throughout the boost range of your system. Gregs system uses a unique pressure control system with a feedback from a 2 bar map sensor, fuel rail pressure sensor and a tach signal. The controller sends a control signal to a power module which in turn sends a voltage signal to the fuel pump to control the fuel rail pressure. You can scale the pressure curve based on your particular boost and fuel requirements. This means it can either be a linear or a non linear pressure curve which is suitable for most all applications.

 

Regardless of which unit you choose ideally the power module would be located as close to battery as possible. That's because the module increases voltage at the expense of amperage. P=VxA (Power/watts = voltage times amperage). Let's suppose your pump draws 10 amps @ 16 volts. That'd be 160 watts. How many amps does it take to generate the 16 volts @ 10 amps? 160w = V x A. 160 = 13.6 (assumed battery voltage) x A. Solve for A. A = 11.76 @ 100% conversion efficiency. Assume 80% efficiency. A = 14.11 amps. So your B.A.P. or MSD needs 14 amps @ 13.6vdc to make 16vdc @ 10 amps. So the advantage to locating the power module close to battery is two fold. FIRST the module needs heavier wiring to it than from it. Second the pump at 20 feet away can be fed with a much smaller wire because so what if there is a .5vdc drop - you turn up the voltage or gain a little to compensate. Voltage drop thru wire is a function of current draw. Using OHM's law you'll see that your booster needs heavy gage wire to it (like 8 gage) and lighter gage from it to pump (like 14 even 16 gage is just fine). I won't bore you with the math. Do you want to run 8 gage to the back of the car or 16 gage? If you do locate power module at rear of vehicle and need its' maximum output then you need feed it with minimum 8 gage.

Next, if you choose the MSD and locate it at rear of vehicle you should use the tiny I.D. black nylon tubing. If you think running a large hose (like 3/8"id) is better think twice!!! The response time of the MSD pressure sensor fed with a large ID hose will be terrible because you have to compress all the air in the large hose before the sensor sees a pressure change. Remember there is NO flow in the sensor hose and therefore no advantage to a large ID hose but rather a time delay disadvantage. If you did locate MSD at rear of vehicle and are concerned about protecting tubing sleeve it with split-loom. Same comments apply to non-bleed type FMU's.

Summary - locate power module close to battery.
Offer - send me your MSD booster and I'll see if the "GAIN" circuit can easily be modified.
Regards to all on this thread and thanks for 'cudos' - Makes me feel loved - LOL