?s for the VE guru's

[Begle1]

The port that lets fuel out of the plunger is covered up by a sleeve that slides. Sleeve position depends on throttle position vs. the speed of the flyweights, the AFC lever position, and the fuel screw position.

When the sleeve is in the full-fuel position, more fuel stays in the injection plunger during injection; when the plunger pushes on more fuel, it results in a higher pressure injection and a higher volume injection.

You can't add more pressure without adding more volume, or vice versa, by changing the sleeve's position. I guess that a longer stroke will increase pressure more than it will increase volume and a larger bore will increase volume more than it will increase pressure. Pressure can be limited with bigger injectors and lower pop pressures.

Here's pictures.
http://home.comcast.net/~vwgtd/vepump.htm

Here's a diagram of the control sleeve.
http://home.comcast.net/~vwgtd/ve_170.jpg

[Begle1]

Wow, nobody's completely shredded my understanding of the VE pump yet.

I must've gotten close.

[dragrdan]

Ok but all else remaining constant(Using the same pump with no adjustments), how does pop pressure affect performance and economy

[Begle1]

High pop pressures give you higher injection pressures; that means better atomization and a better spray pattern at the cost of a shorter duration and more tear on the pump.

Low pop pressures give a lower injection pressure; that means longer duration and less tear on the pump at a cost of a worse atomization and spray pattern.

Anecdotal evidence states that increasing pop pressures causes accelerated pump wear that outweighs any improvements made in atomization; anecdotal evidence also states that lowering pop pressures, in combination with bigger injector nozzles, is effective for reducing high-RPM, high-flow pump wear.

[bgilbert]

I thought that if the fuel went in at a higher pressure it would atomize better, with burns the fuel more cleanly, witch gives more power.
Sure it adds more stress on the pump, but if its power your after then a broken pump isn't a big deal.

CK, what pop pressure are you running?

[DTanklage]

Ok but all else remaining constant(Using the same pump with no adjustments), how does pop pressure affect performance and economy

read thru this kinda quick but didnt see where anyone explained to you that there is also a return in the system. dont know if you knew that or not. so, pump throws a squirt of fuel down the inj line by the injector, there is a restriction in the return that creates pressure, when pressure is at or above pop pressure fuel is being injected into the cylinder, if not it is just going back to the fuel tank. lower pop = longer duration.

[KTA]

Ok but all else remaining constant(Using the same pump with no adjustments), how does pop pressure affect performance and economy

read thru this kinda quick but didnt see where anyone explained to you that there is also a return in the system. dont know if you knew that or not. so, pump throws a squirt of fuel down the inj line by the injector, there is a restriction in the return that creates pressure, when pressure is at or above pop pressure fuel is being injected into the cylinder, if not it is just going back to the fuel tank. lower pop = longer duration.

Are you talking about the returns off the injector bodies? If so that isn't exactly how they work. Those returns are only fuel which has bypassed the needle valve. No fuel from the injection line side is allowed to pass directly to the return. If that was the case your line pressure would go to 0 after each injection event. Hopefully your delivery valves don't allow that to occur.

[dragrdan]

When is fuel allowed to the return lines?

[Begle1]

When the needle inside the injector is pushed open, most of the high-pressure fuel goes through the nozzle holes. But a small and vital quantity of fuel flows around the very small clearance around the needle. That fuel cools and lubricates the needle, then returns back to the tank.

[Ace]

..a small and vital quantity of fuel flows

(in my best Mr. Burns voice) Eeeeexcellent.

[cummins king]

I thought that if the fuel went in at a higher pressure it would atomize better, with burns the fuel more cleanly, witch gives more power.
Sure it adds more stress on the pump, but if its power your after then a broken pump isn't a big deal.

CK, what pop pressure are you running?

im running 240 bar right now. But it might change?