I am building a 1983 300SD for 1 mile LSR racing...just beginning the project...i cannot find a spec for the min and (more importantly) the max pressure at the injector pump inlet??? does anyone have any experiences they would like to share of replacement lift pump options?

In Liberty,with Velocity

Dave

Increasing the lift pump pressure won't do any good. First there is a pressure relief valve on the back of the IP in the return line banjo bolt. This will limit the pressure. Second, Diesel is incompressible so your not going to force anymore fuel into the plungers and thus injectors by increasing the lift pressure.

Even though we call them "lift" pumps they should actually be called "transfer" pumps. They work on flow not pressure.

The injection pump is really a compressor with timed release valves (the line outlets).

Transfer pumps generally deliver X amount of fuel at less than 5 psi. As was pointed out in the previous post, any excess pressure is vented into the return line.

You can increase the pressure from the pump with internal adjustment which of course means you have to change the nozzles and readjust them or you could just have the pump and nozzles caliberated to each other. For peak ultimate performance that is the way to go.

14psi is the relief valve pressure.

I thought there was some talk on superturbodiesel.com about 12V cummins guys getting some gains from adjusting the spring in the bypass valve.

This works also for the Benzes. Some old style valves can be disassembled and the spring length can be increased (30mm is a good value) to provide complete filling of the elements.
The larger elements have an increased (and funnel like) bore compared to the originals so there must be some possible gains.
Using vo or even wvo sometimes when the temperature is not reached the fuel supply is not sufficient and in this case increased pressure in the gallery of the ip helps (either from the lift pump or from the tweaked by pass valve or both).

Tom

So what kind of flow rate would one be looking for in an electric pump?

Why would you want to use an electric pump when the mechanical pump is more than adequate?

Just playing around with ideas. Do know what the spec would be?

welll... an electric pump would allow you to prime the system without ruining the starter..

A lift pump from a Dodge with a Cummins would work more than well enough.

On the VE pump TDIs people noticed more low end torque and more top and HP when using a transfer pump to help the IP.

-Jason