Fuel governor shimming thread

[4Ruster]

Hey all. I've been recently looking into modifying the stock governors for our rotary injection pumps. It used to be popular with the 1.6TD Volkswagen guys, however the same tricks can easily be transfered over to our pumps.

There are two styles of governors.

The pull type all speed governor uses a pull type spring and is common on Cummins as well, the only way to modify those are to use a stronger spring. I will not get into that as I want to mainly focus on the next style

The cage style governor uses 2 compression springs and acts both as a throttle smoother, and the speed governor.

Here is what mine looks like.

Now to get into the modifications
From what I've read,

From left to right, we have the idle/start spring, the intermediate spring, and the main spring.

> The idle spring we will not focus on, it's purpose is to maintain a smooth and steady idle speed.

> The intermediate spring acts as a sort of damper, it's smooths out the throttle response, I've read when people shim this spring, it drastically reduces drivability.

> The main spring is what controls when the fuel starts pulling back on us. If you want to raise that RPM, you stiffen the spring by adding a shim.

I will add a warning, shimming the main spring will mess with the no load speed governor, so be aware.

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I installed a single washer on the main spring here,

I will update you all on how that goes.

Please feel free to jump in and share your knowledge on this, the more information, the better.

 

[ATL Cruiser]

Really dumb question here, and forgive me, because I am not a diesel fuel pump expert AT ALL. But what is the end goal in shimming the governor vs simply adjusting the fuel screw?

I ask, because I am nowhere near full adjustment on my fuel screw. I am not even close to maxxed out and could make this thing blow black smoke easily. What gain would adjusting the governor give me?

Again, apologies for the dumb question.

 

[4Ruster]

Really dumb question here, and forgive me, because I am not a diesel fuel pump expert AT ALL. But what is the end goal in shimming the governor vs simply adjusting the fuel screw?

I ask, because I am nowhere near full adjustment on my fuel screw. I am not even close to maxxed out and could make this thing blow black smoke easily. What gain would adjusting the governor give me?

Again, apologies for the dumb question.

The goal is to get more usable power before the governor starts pulling fuel back. You can blow as much smoke as you want down low but you have about 20% of the fuel at 3700RPM than you will at 2000RPM.

 

[ATL Cruiser]

The goal is to get more usable power before the governor starts pulling fuel back. You can blow as much smoke as you want down low but you have about 20% of the fuel at 3700RPM than you will at 2000RPM.

Got it. Thank you for that explanation.