Governor mod and max RPM screw interaction

[tylernt]

Few questions about this...

1. If you do the governor mod and leave your max RPM screw* the same, does your max RPM increase? Under no-load and load conditions?

2. If the governor mod does raise the max RPM, does screwing in the max RPM screw to restore the factory limit take away some, all, or none of the governor mod benefit?

3. If you open up the max RPM screw to allow more pedal travel without doing the governor mod, do you increase high RPM fuelling and HP? Like a poor man's governor mod?

* Max RPM screw = the travel stop for the throttle cable opposite the idle speed screw

[Black Smokin' Diesel]

1: yes, yes

2: no, don't think so

3: you only increase RPM, fuel is still cut off by the governor.

[scopefrfd]

"If you open up the max RPM screw to allow more pedal travel without doing the governor mod, do you increase high RPM fuelling and HP? Like a poor man's governor mod?"



I was told increasing the cable travel is one of the first mods to do.  If you increase the cable travel will will increaase fueling and hp because you will be infact pulling harder or increasing the pressure on the spring which in turn will give you more fuel.  You should also turn back the idle stop and turn up the fuel screw to compensat this way you get max travel out of the governor assembly.

[tylernt]

"I was told increasing the cable travel is one of the first mods to do.  If you increase the cable travel will will increaase fueling and hp because you will be infact pulling harder or increasing the pressure on the spring which in turn will give you more fuel.

That was my thought... how does the pump know when to cut off fuel at "high RPM"? How is "high RPM" defined? The stiffness of the governor spring, the throttle shaft position, something else...? I figured if we moved "high RPM" maybe we can also move the point at which the fuelling is reduced. But while I'm learning all I can about these pumps I am still quite ignorant.  

[Black Smokin' Diesel]

The way the governor works is that is stretches when the accelerator lever is pulled. When the lever reaches the stop screw, the governor has stretched to X lenght. If you increase RPM, the governor will keep stretching and continue to cut fuel. Of course there's a limit to the gov's stretch and the amount of movement it has within the pump itself.

So you can up the revs but fuel will still be cut at the same pace as before, thus yielding mediocre results. If the engine runs out of fuel at 4500rpm when the redline is 5300rpm, it's still gonna run out of fuel at 4500rpm even with a 6000rpm redline.

[scopefrfd]

The way the governor works is that is stretches when the accelerator lever is pulled. When the lever reaches the stop screw, the governor has stretched to X lenght. If you increase RPM, the governor will keep stretching and continue to cut fuel. Of course there's a limit to the gov's stretch and the amount of movement it has within the pump itself.

So you can up the revs but fuel will still be cut at the same pace as before, thus yielding mediocre results. If the engine runs out of fuel at 4500rpm when the redline is 5300rpm, it's still gonna run out of fuel at 4500rpm even with a 6000rpm redline.

Yes, you are partially correct...but if you increase travel you'll will be increasing tension/compression on the internal governor springs.  This extra tension will increase both rpms and fueling over previous levels until the 3 springs are full compressed.   This is what shimming the intermediate spring does..it increases the spring rate.

[Black Smokin' Diesel]

The way the governor works is that is stretches when the accelerator lever is pulled. When the lever reaches the stop screw, the governor has stretched to X lenght. If you increase RPM, the governor will keep stretching and continue to cut fuel. Of course there's a limit to the gov's stretch and the amount of movement it has within the pump itself.

So you can up the revs but fuel will still be cut at the same pace as before, thus yielding mediocre results. If the engine runs out of fuel at 4500rpm when the redline is 5300rpm, it's still gonna run out of fuel at 4500rpm even with a 6000rpm redline.

Yes, you are partially correct...but if you increase travel you'll will be increasing tension/compression on the internal governor springs.  This extra tension will increase both rpms and fueling over previous levels until the 3 springs are full compressed.   This is what shimming the intermediate spring does..it increases the spring rate.

True, it does increase the spring rate. I'm not sure if the governor has enough space inside the pump to fully compress its springs. Still, it's not nearly as efficient as the governor mod.

[jimfoo]

So after doing the gov mod and advancing the timing, I get a lot more smoke. I assume that's normal. It would barely smoke before those mods, but the fuel had been turned up a bit before I got it. It also started smoking a bit more after I had overheating problems before the rebuild. Could the heat have affected the injectors? I plan on getting them rebuilt fairly soon anyway. One other thing, since I have the 1.9, I don't remember a star wheel in the LDA. If there isn't one should I put a stronger spring in? The pin has been ground a bit, so isn't straight.

[Tintin]

I figured if we moved "high RPM" maybe we can also move the point at which the fuelling is reduced.

It's exactly what occurs,  the governor in the pump reduces the quantity of injected fuel while pushing backward the control lever to limit the RPM at a fixed point.

Impossible to take 5000rpm without proportional injected fuel, unless descending an abrupt hill in fourth gear and downshift in third  :lol:  :lol: