Fuel Injection gear pump

[Jerry G.]

Does anyone have a set up pump curves for the high pressure pump. i.e. discharge pressure vs RPM or RPM vs flow rate. Jerry

[Jim L.]

Re: Fuel Injection gear pump

Jerry, there won't be a curve for discharge pressure vs RPM for a positive displacement pump. The pressure rises to whatever is needed to overcome the downstream flow resistance (neglecting pump slip, of course).

Jim

[Jerry G.]

Re: Fuel Injection gear pump

I agree, i'm more interested in power(torque) on the cable vs RPM vs differential pressure vs RPM of pump. From classic gear pump data it appears the torque goes up dramatically with differential pressure. This make sense since slippage around the gears is minimal.

[Clem Z.]

Re: Fuel Injection gear pump

I agree, i'm more interested in power(torque) on the cable vs RPM vs differential pressure vs RPM of pump. From classic gear pump data it appears the torque goes up dramatically with differential pressure. This make sense since slippage around the gears is minimal.

you can tell this when you use a drill motor to drive a oil pump primer on a engine. as the pressure come up the drill motor starts to bog down in rpms

[Jerry G.]

Re: Fuel Injection gear pump

Yep, from typical data on gear pumps this increase is steep. Anybody have a test fixture to try this out. I'm interested in RPM to the drive cable between 3000 and 3800 RPM.

[Clem Z.]

Re: Fuel Injection gear pump

you could build a setup using a electric motor to drive the FI pump and read the amps the motor pulls as the pressure comes up. you could do some track tests with your car and say limit the engine RPM to say 6000 RPMs to see if the cables hold up. if they do then you know the higher RPMs are building up too much pressure for the cable.

[Duke W.]

Re: Fuel Injection gear pump

The pump is designed to deliver more fuel volume than the engine needs at all engine speeds, so testing for pressure without the spill valve functioning could produce pressure in excess of what is seen in service. My recollection from past reading is that peak fuel pressure at WOT max revs is about 200 psi for a production engine. For a racing engine with massaged heads, a big cam, and an optimally designed racing exhaust system it is probably somewhat higher.

Duke

[George J.]

Re: Fuel Injection gear pump

In the SAE Paper that Dolza, et al presented in Jan. of '57 they state that the pump provides about 200% of the fuel required at any engine rpm. I wonder if there would be some way for you to slow the pump to, say 3/4 speed and it would still provide enough fuel, while not producing the stress to failure of the cable.

George

[Jerry G.]

Re: Fuel Injection gear pump

Thats a good idea. Anybody know of a small gear reducer. I can have cable made any length. I think redesigning the gear drive on the distributor would be prohibitive.

[Clem Z.]

Re: Fuel Injection gear pump

Thats a good idea. Anybody know of a small gear reducer. I can have cable made any length. I think redesigning the gear drive on the distributor would be prohibitive.

speedometer re builders make a small gear reduction units that fit on the trans and the cable attached to but do they have the strength to drive the pump i dont know.

[Clem Z.]

Re: Fuel Injection gear pump

once you know the pitch diameter of the dist FI gear drive you should be able to change the gear ratio in the dist with different gears.

[Dick W.]

Re: Fuel Injection gear pump

Thats a good idea. Anybody know of a small gear reducer. I can have cable made any length. I think redesigning the gear drive on the distributor would be prohibitive.

Find an older HD truck dealership. They may still have an SS White kit that had all the pieces you need to build a speedo reducer. If you do not find one locally Google SS White speedometer and you will find many sources.

I am not sure that the bushings and gears could stand the heat built up by the speed you are talking about. If you could pressure lube it, I am sure that would increase the reliability.

[Clem Z.]

Re: Fuel Injection gear pump

The pump is designed to deliver more fuel volume than the engine needs at all engine speeds, so testing for pressure without the spill valve functioning could produce pressure in excess of what is seen in service. My recollection from past reading is that peak fuel pressure at WOT max revs is about 200 psi for a production engine. For a racing engine with massaged heads, a big cam, and an optimally designed racing exhaust system it is probably somewhat higher.

Duke

i would think the fuel flow would have more to do with the air flow limit of the unit. a 780 CFM holley uses the same size jets on a 302 Z-28 engine as it does on a 427 425 HP engine as the carb size limits the air flow.