anyone know how to restrict the fuel return to increase rail pressure?

[NJT 5573]

Is it already restricted? do I just install a smaller orfice somewhere in the return? where on my 92 would this be? how much will the pump take before it breaks the quill shaft? Im expecting about 2 mpg increase in fuel if its like a cummins. any ideas>

[pvcces]

Larry, if you're trying to use Cummins PT fuel system ideas on your Detroit, I think it's a bad idea.

The injectors in the PT system don't fill all the way if pedal is not pressed all the way to the floor. The amount they fill is dependent on pressure and time, hence the name of the system.

My understanding of the Detroit MUI setup is that the minimum pressure is supposed to fill the injector, even with no load. The injection is supposed to be controlled entirely with the rack.

If I have any of that wrong, maybe someone will have some constructive comments to offer.

With Detroit MUIs, I think that you are supposed to change the injector to change the fuel output.

For what it's worth.

Tom Caffrey
Suncatcher
Ketchikan, Alaska

[TomC]

DO NOT restrict the return line on a Detroit MUI system.  It is not like the PT system on the Cummins.  On the Detroit there is a lot of extra flow through the injectors mainly to keep them cool.  If you restrict the flow they will over heat and then will sieze up.  If you want to get more power take the 90's out and put in 100's.  I did that with the 1980 I had.  It was putting out 440hp to the ground (like 525hp from the flywheel), but with the MUI, they had to retard the timing which made it start harder, it smoked more since I didn't upgrade to the proper turbo and my mileage dropped.  Even though it was a rocket up the hills, I had the 90's reinstalled when back in town, and didn't play with the engine anymore after that.  Detroit knows what they are doing.  The 8V-92TA with 90 injectors, bypass blower is a very reliable, proven power plant that with some maintenance will give you many years of faithful service.  If you want to have a guaranteed fuel mileage increase, then take the 90 injectors out and install 80's-or just keep that lead out of your foot.  Good Luck, TomC