Pierburg electric fuel pump

by Wayne Hubbs in General Tech Discussion 7 years ago

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Re: Pierburg electric fuel pump

by Spiros Economou » 7 years ago

Spiros Economou

2 25 92

The pump might be delivering around 1 bar or 14,5psi but between the pump and the carbs there is a pressure regulator installed (only in 914). This regulator monitors the airbox pressure and adjust the fuel pressure to be always higher by ~0.25 bar. So, the actual pressure that is delivered to the carbs has nothing to do with the pump. It has to be high enough for the regulator to operate correctly. Fuel pressure in a 914 is always different than the pressure we see at a conventional pressure gauge. Only if we can measure the difference between airbox pressure and the outlet pressure of the regulator, we can have a clear indication of how our fuel system is operating. In 914, Rotax wants to have always higher pressure in the carbs than the airbox pressure, in order to avoid mixture going lean. In a turbocharged engine you always want the mixture to be on the richer side and prevent damage to the engine.

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Re: Pierburg electric fuel pump

by Bill Hertzel » 7 years ago

Bill Hertzel

13 1.95k 7.97k

First I want to thank you gentleman for helping me find the proper exact pump that is on my Rotax 914, I think the main thing is pump pressure, I believe 7.5 to 8.0 psi. is about the maximum pressure Rotax recommends, my pressure runs about 5.0 to 6.0 psi. And I think that is about .5 bar.

Don't confuse Gauge Pressure with Airbox Differential pressure.
Gauge pressure will vary with throttle and altitude.
Differential pressure is constant and controlled by the Fuel.regualtor.

Maximum Fuel Pressure is ~5psi ABOVE the AIrbox Pressure.
Normal Fuel Pressure is ~3.5psi ABOVE the Airbox pressure. (Differential.)

At WOT(39" MAP) this would require ~8 psi Gauge Pressure at Sea Level and ~12 psi above 10,000 ft.
This is why the pump is capable of 15psi at 25 gal/hr and 25psi peak.

A 6psi Gauge Pressure would be typical of a cruise at ~24 inches of manifold/airbox pressure.

Bill Hertzel
Rotax 912is
North Ridgeville, OH, USA
Clicking the "Thank You" is Always Appreciated by Everyone.

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Pierburg electric fuel pump

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