ok im putting my thoughts in to this mostly cause i think it will help me learn something. my experience with the ve pump is limited. i have a back ground in diesel technology and spent a lot of hours both professionaly and as a hobby studying mechanical fuel sytems. im probably only going to muddy the waters but maybe my input will help (i doubt it)
Yes. Since we don't have a constant rail pressure on a VE it really makes it harder to judge SOI because fo the variables. Truthfully a CR is easier because you have a relatively constant pressure where a jerk pump is relying on a pressure wave generated in the pump to pop the injectors.
I am positive Cummins did all this when they engineered the engine. Good luck trying to find anything like that. Its proprietary.
In fact, just ry to get cam profiles from Cummins and see which rat hole you end up in.
In comparison to gasser engines where just about every nuance is understood and published, these diesels are almost a black box with respect to the pertinent info like we are kicking around here.
BTW, where do you work with all that instrumentations? NASA? A nuclear power plant?
ok all things being equal, i. e. fuel temp, lp pressure, and injector pop pressure. soi should be acurate, timing off the crank should be suffiecent too. now 36 teeth on the cam is 10* per tooth, the cam acts like an idler and since we are talking fuel and not air its timing is irrelivent. timing is measured in degrees of crank angle just like a gasser. optimum soi would be x* btdc calced for burn time of fuel, causing cylinder pressure to peak just after tdc, maximizing downforce on piston.
variables can be somewhat measured and calculated. a thick walled injector line and lots of the little rubber isolators to keep spikes to a minimum, fuel temp would probably not affect timing only power, lp pressure would need to be held constant with a good overflow valve. injector pop pressure can be mostly eliminated if taken to a shop and very carefully set.
once thats all done and all high pressure parts are in good condition. find the volume of the fuel line from injection pump at bdc all the way to the nozzle of the injector, you could find how much lift will have to be generated to reach the injector pop pressure. this would be the lift of the pump cummins measures for soi. set that lift at optimum timing stated above. you would have most of the variable eliminated or at least controled. it would not be perfect but i would bet that any variance would not noticeable and probably just barely measurable. to verify your calculations you could you a line transducer to determine actual soi. again not perfect but probably very close.
Ok guys, still been thinking (maybe too much)
One reason to advance timing, is because in the OEM configuration, timing was set as a mediocre comprimise with respect to NOx and PM emissions, and was not necessarily optimized for BSFC. So, by advancing timing (some amount), the BSFC of the engine can be increased, at the expense of higher NOx.
The other reason for increasing timing, is to counter combustion phasing being pushed later and later from the addition of more fuel. Thus, the more fuel you add, the more you have to advance timing. This is seen by the guys running 400, 500, 600 hp that are jumped up to two teeth, pump to the head, KSB hotwired, etc.
So, this brings me to my question. I don't want to increase fueling a lot... just to the ~300 hp level. I also don't want to run on the ragged edge of high peak cylinder pressure and high pressure rise rate such that longevity is significantly comprimised. Just by seat of the pants guess from looking at what others have done, it seems that maybe a 6 or 7° bump in timing is what I'm after. How do I get this? Jumping a tooth gives 10° advance, which is likely too much for me (since I tow very heavy at times). Is there enough play in the pump in the opposite direction, such that I could jump a tooth and then rotate the pump
away from the head by 1/8" to 3/16"? Such that I would get a 10° advance from the tooth jump and then retard 3 - 4° by rotating the pump backwards? ... thus ending up with a 6 - 7° advance over stock?
--Eric
Eric i dont think timing would affect bsfc directly. there is no doubt in my mind that with the work you are doing and the equipment you use you know better than i, however with a pump, hard line, nozzle set up in order for the engine to run there is a minimum amount of fuel needed, that volume is what builds the pressure and pops the injector at the right time, this in turn makes the engine operate correctly, if fuel pressure is low or volume is low then the timing retards and poor performance arises. what a timing advance would do is put fuel into the cylinder sooner allowing a longer burn time, which equals more complete burn, more power out of the same volume of fuel, which means less throttle for a given rpm, this backs off the fuel, and the engine uses less, increasing mileage and bsfc.
as to your second part in the p pumps the static timing is between 12. 5 and 14 depending on make and model, rule of thumb is advance to between 15 and 18, depending on normal cruise rpm, mods, and power goals. with the dynamic timing of the ve you have a real advantage take the static timing and advance it for peak cylinder pressure at idle or 1000 rpm. the dynamic timing will take over from there and keep it at peak through a longer rpm range, from reading the posts in the thread it looks like a kit can be had that increases dynamic range, that would be a good thing.
if you really want to get into it, determine your cruise rpm where you spend most of your time, see what timing is at, at that rpm(static + dynamic) then take your dynamic timing add it to any new static timing you set to bring optimum timing at that rpm. this will net you the best bsfc and mpg.
Umm, if I recall correctly, there are 72 teeth on the cam... . 360/72=5* per tooth. Since the cam turns at half the speed of the crank, that makes 2. 5* per injection cycle... ... . am I correct in my thinking? That means if you move the pump 3 teeth on the cam, you advance timing 7. 5* off the crank... ... ... . If you want less, move it 2 teeth for 5*, and you can move more with the pump adjustment... ... if you have any. On most of these first gens, there are three letter indicators on the cam for pump timing, D, E, and C. I think Cummins might have known we were coming.....
HHuntitall your right on those numbers, using the cam gear to pump relation would time your injectors to the valve train, not the piston. the cam and pump both turn at the same speed 1/2 engine rpm. when timing the pump the cam gear is just an idler and does not affect the pump timing, to use the timing marks on the cam, the engine and cam must be timed correctly and the engine at tdc 1. so every tooth jumped is 10* jumping a tooth and rotating the pump back (if possible) would be 10*-x*= static timing adv. then static adv. + dynamic adv. @ x rpm= total adv. @ x rpm.
on that pic does it give any indication as to what each letter means in realation to timing? they dont highlight those letters for nothing.
i hope this helps. im not trying to stir the waters up, these are just the things i ponder in my free time and love the oportunity to get a different view on what ive come up with. i do not take offense to being told im wrong, though i will try and argue it, to see if it will hold up. i also hope that nobody takes ofense to what ive said im not trying to say anyone is wrong, this is just my theory.
also Eric what kinda of degree do you hold to get a job like that. it sounds like something of a dream job to me, im working on a mechanical engineering degree with the hope of getting into something like what your doing. how do you get a job like that? what does it take?
My head hurts.
my head hurts now too.
Attention: TDR Forum Junkies 
But I think 5 degrees of cam equals 10 degrees of crank like the guys are saying, since the crank spins twice as fast.
I think we need more acronyms myself... 
uch: 
