Originally posted by JGK
Berrigan,
I had the same questions last winter and posted it on the TDR. Got several answers, and by “pasting” them together mentally, and doing some outside research, I came up with the following understanding. I’m not a mechanic so this is just my take on it based on what I’ve read and done on my truck.
The governor stabilizes the quantity of fuel output by the pump at a given throttle setting. Without it, it would be very difficult to keep a constant RPM at a given throttle setting. The engine may even race away without it. It also adjusts the fuel being delivered at a given throttle setting as the load on the engine changes. So as you start up a hill at a specific throttle setting, and the load on the engine increases, thus slowing the engine, the governor will increase fuel to compensate as best it can. Of course at some point, you have to add more throttle for even more fuel. The governor isn’t perfect. Different governor springs causes it to behave differently. The 2 kits you can get (3K and 4K) just restrict it from defueling at higher revs, thus letting the engine rev higher. Throttle response is much better with these kits, by the way.
The AFC controls fueling in the low rev range before there is much turbo boost. It holds back on fueling until the boost comes up enough to supply the air needed for efficient burning. By backing off the star wheel or sliding the housing forward and thus reducing the AFC’s restriction on low-end fueling, you get more fuel at low boost. Hence, more low-end smoke. But low-end response is better. So adjusting the wheel and moving the housing is the way to balance smoke with response. At about 8 or 10 lbs of boost the “finger” in the AFC is out of the way and no longer has any effect on fueling. It’s all up the plate now.
The plate controls the fueling once the AFC moves out of the way. The profile of the plate controls fueling over the range of RPMs, and, with the governor, will add or reduce fuel at a given RPM based on engine load. As bighammer said, moving the plate forward moves the whole profile while grinding a section just affects fueling in the associated range. I think the pump is very sensitive to small changes in the profile. That is why it is suggested the plate be moved only a few hundredths of an inch at a time. A lot of research went into the plate’s profile for optimum performance. Still, many do a little customization and get good results. Some folks are running with no plate, or a “0” plate, which is essentially just a flat surface. Notice how most plates slant back in the upper part to reduce fueling it higher revs. Without that, you get extreme EGTs at higher revs, which can only be controlled with your foot.
Next is the rocker arm. This is the arm or “finger” that follows the contours of the plate. Piers suggests adjusting where the arm initially contacts the plate when the plate is changed. Doing this adjustment makes the engine respond much better. The arm often hits the plate too low, usually under its “nose” and it takes more throttle and higher revs for the arm to get up over the end of the “nose” and into the power range of the plate. By adjusting the arm to hit just above the tip of the “nose”, the engine performance is much better. You’re right at the point of the power curve of the plate as soon as the AFC gets out of the way.
Finally, I guess, is delivery valves. These I know little about, other than they control the amount of fuel pushed out by the plungers. Bigger valves allow more fuel to go to the injectors. They seem to be more of an issue with the earlier, smaller horse power pumps when bigger injectors are put in. I don’t think they are as important with the 215 hp pump until you get really huge injectors.
Oh, yeah, speaking of injectors, I guess that’s really the final, major component. Big injectors mean greater fuel delivery. However, how far the injector sticks into the cylinder, the number of spray holes, and their angle of spray relative to the axis of the injector are important. That’s why only certain ones are recommended for our application, such as the 370 Diamond Bs available from various sources. Custom made injectors from the performance shops, like the extrude honed ones and so forth, have been designed to work with the Ram CTD.
Sorry for the length of the post, but I wanted to return the favor for those that answered my questions in the past. All you experts please correct me where I’ve gone astray.
-Jay
Attention: TDR Forum Junkies 
and mine will as soon as i fixed my front gear cover damn dowel pin 
