[Herr-Kuhn]

For those of you who are running high flow fuel pumps in your boosted 928s...you might want to read over this thread.

I run the Bosch 044 pump on the twin turbo car. I looked into going further with an Aeromotive A1000 pump, but truth be told it simply doesn't flow that much more than the 044 does to justify the modification. Remember, on boost these systems will run 65 psig on the rails and the flow lines for the 044 and A1000 cross at about 70 psig, where the 044 actually outflows the A1000. At 35psig, the A1000 will easily outgun the Bosch, but this system doesn't operate there, it operates around 65. At the higher pressures the 044 is only down like 8% below the A1000.

So, long story short I think the 044 is the pump for the car.

I had this unit installed with a power relay dropping right off the battery for max voltage to the pump. This is VERY important as any DC motor's speed is proportional to its voltage and the pumps flow is a function of its speed. I was getting good voltage to the pump, but I wanted more safety on the fuel system.

I noticed that my car didn't run nearly as well on less than 1/4 of a tank of gas as it did when full, especially at the higher boost pressures. I'd be very surprised if others have not had this same experience. This leads me to believe that the factory pickup is just far too restrictive and small for the car. This week, I am fitting an AN -10 line system from the tank to the pump. The fuel pickup will be custom made to allow for lower restriction and will adapt to an AN-10 fitting. Having a small line feeding the pump is no longer an option for me. Remember, the strainer and the line were designed to feed 350 HP or so, not 600-700 HP.

In addition to this modification I have added an electronic device to the system to step up the voltage to the pump as a function of boost pressure. Now, I'll be the first to tell you that I'm not a big fan of bolt on electronic boxes, but this thing just makes sense. The first impression is "just put on a bigger pump". Well, when you do that on a return-line system you are now pumping anything you don't burn back to the tank...bigger pump, more fuel in and out of the engine bay and more heat into the fuel. Cruise on a long trip and the fuel is now quite hot. This is why Aeromotive doesn't recommend their big-gun pumps for street use. The control unit simply steps up the voltage as a function of manifold pressure. It's rather clever..."only on demand" is its motto. The fuel pump control unit is now mounted in the back of the car (behind the tool box). I have to monitor its running temperature but thus far it looks reasonable. You can step to 22 volts, but I'll likely just go to 16-18 volts only.

I will have some pictures later to show all of this stuff. If the pickup system for the fuel pump works as well as I think it will, then I will be offering these for sale to those who are interested. The filter media I have selected is far less restrictive as compared to the plastic strainer unit. Cavitation is a big no-no and tears the pumps up fast. The next time you hear a fuel pump that sounds strained...consider that it may be sucking through a drinking straw to get its fuel.

And always remember...it is easier to pump than to suck!