timing knock?

why dont they make something like the variable cam timing (like honda's vtec), but for the pump gear?
 
Mack Trucks as I understand it uses a version of the p-pump with a mechanical advance mechanism on some of their engines but I've found out very little about it. It is called VMAC.

This thread is discussion about timing on a VMAC engine, and look at the pics toward the bottom. http://www.bigmacktrucks.com/index.php?showtopic=6341

There are some pictures of Mack engine pumps, but I don't know if the advance mechanism is built in or not

http://www.goldfarb-associates.com/specials/weeklyspecial092407.pdf
http://lacrossediesel.com/injection_pumps.html
 
It's too bad the little ol' VE pump on the 1st Gens didn't pump out more fuel and were more robust, 'cause they have built-in timing advance. I found a tech paper discussing the VE's timing advance and looks like it varies up to 25 degrees (probably for a 4-cylinder Volkswagen application). That would mean if timing is set to 10 degrees it would advance it clear up to 35 degrees when it hit the governor. Imagine having that kind of range!! http://www.dieselbookmarks.com/bombers/VEPump.pdf
 
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