What we call "dynamic" timing on our pumps is a loose term really...the basic timing is set, as most of you know, by altering the spacing between the timing marks on the pump/gear casing via pump rotation upward or downward....
The "dynamic" portion is contained in the function of the low pressure supply side pump's internal pressure and the resulting rise in the section as RPM increases; which in turn raises the pressure in the pump head...during that pressure rise the mechanical timing piston is made to move due to higher pressures internally...this is the "dynamic" timing.....if that is the most accurate term. (??)

You need to look at the function of the mechanical timing device, the interrelated pressures/rises etc, as well as the individual physical components and their "actions and related interactions"...

Keep reading and head scratching it WILL come to you.....I got faith in ya'll....

pb....

 

WARNING: GUESSING BELOW!

Timing device piston changes? Stiffer spring or shimmed spring to not allow the internal fuel pressure to act apon the timing piston keeping in it's initial state longer?

guess? another guess? still guessing?


Den

 

Quote:

Timing device piston changes? Stiffer spring or shimmed spring to not allow the internal fuel pressure to act apon the timing piston keeping in it's initial state longer?

Hmmmm.....lets see....
You are not looking to prevent movement entirely...but you ARE looking to alter it as you intimate....
Ok, pressure rise in on the supply side = pressure rise in the pump head...during this process the mechanical timing device begins to "advance" the roller ring up the cam plate "ramp".
This "onset" is determined by a number of things.....supply side/pump head side pressures, the rate/onset of the timing piston movement towards it's max travel/value and.........

Look closely at those functions/results and consider how you might change the onset, rate and, range of movement....just as a starting point....

Ok, that's all I'm gonna lay out at the moment....keep at it guys....you'll get there.

bob....

edit: OH BTW, the amount of advance provided by the KSB (which has a similar effect on the items above, but just achieved in a slightly different way) will provide roughly 5* advance over the idle value....I'm open to correction on that value if someone know's a more accurate value.
So, you have an idle timing value of, say, 15* advance and the KSB will raise that to about 20* advance.
Remember I raise this ONLY to illustrate the effects of mechanical timing piston movement.

 

WARNING: GUESSING BELOW!

Was I thinking opposite in my first post?

I guess orifice size in the "Passage in timing-device piston" would increase rate and if there is any "extra" material on the spring side outer edges, machining that skirt may give you more travel over stock.

My brain hurts..it's too early..off to the doctors

Den

 

Pastor, chastise me if I stray from the true path here. I don't want my ignorance on this subject to make this thread a source of misinformation.

Den-
You'd have to reduce the orifice size in the overflow valve, or shim the spring if there is one. That would increase internal pump pressure and make the advance kick in sooner, but unless the overflow valve was oversized to begin with it wouldn't change the max timing, just make the pump more prone to leaking.

I stumbled onto something in my Cummins book, they talk about not losing the shim under the timing piston spring when you pull the KSB off the side of the pump. Losing that shim would make the timing advance come on a little sooner, but I don't think it would have a significant effect on the total amount of advance - if they tell you not to lose it it can't be that thick of a shim.

One direct question for the Pastor since information on disassembling the VE is hard to come by: Can you remove the timing piston with the pump on the truck?

 

I don't think you could break down the pump to that degree with it still on the pump...in fact, no, the pump is called a "top loader" and to break it down you'd need to remove it....

"....You'd have to reduce the orifice size in the overflow valve, or shim the spring if there is one....."

OR, you could use a particular spool valve to raise the supply side pressure .....
Remember that the bleed orifice you mention is capable of handling a certain volume of fuel at a certain pressure (range)....if you increase pressure enough the orifice is still only able to deal with it's normal "max" fuel volume...

Additionally, you don't really want the advance sooner, but rather a bit later....we are all running these engines further into the RPM band and it is up there, that you want more advance, at least that is my opinion anyway......
I think you'd want generally more advance available and, to control the onset/finish of that increase.


bob...

 

OK, so increasing internal pump pressure is not the answer, didn't seem like a good solution to me anyway due to the danger of causing leaks.

I try to run with as little static advance as I can to keep the low RPM torque really strong, but I know I'm giving up HP on the top end by doing so.

Agreed. That's why I'm trying to drag the info out of you. Is there a secret handshake I need to know first? I've been looking at the Bosch VE .pdf several times a day for the last week trying to figure out what you're hinting at. The only thing I can come up with is modifying the timing piston, but as you say, it's buried at the bottom of the pump.

 

hey dave, where'd you get that ve .pdf?

 

It's copyrighted so I ain't sayin'.

 

member G1625S to answer your original quistion on timing, 16.5 crankshaft degres advance =192 mm lift when checked with correct timing tool at the pump.

 

Isn't that 1.92 mm?

 

wannadiesel yes you are correct 1.92mm now you see why I never posted before, NO typing skills and too old to learn but I did know what G162S wanted too know so thought I could share.so he would have a base to start from.my truck ran at 1.92mm and several other pump TWEEKS for several years.the guy that taught me about VE pumps used timing light methed but couldnot answer my quistion as too what my timing was vers early trucks that were timed at 1.40mm . said he had one truck in fleet that ran real good and when he checked it it was 16.5 crank degres so he set every one that he did the same. after my schooling I bought timing tool YA8331 and accs from my snap-on dealer and started tweeking, I started out in the 1.40mm range. few years latter I checked my own and it was 1.92mm I all most **** my pants, I set it back too 1.62mm that"s where its been sense 2001.

 

Thanks for the info, beachcraft! I may have to pay the snap-on truck a visit this week
greg

 

G1625S I have found these things timed all over the place I have kept A log over the years where they were set and where I sent them out.I have seen 2 trucks set at 1.09mm. checked one that he had bumped up 1/8'' it was 1.43mm, these were all 1991.5 and up trucks. so don`t know if those marks mean much.in my HUMBLE OPNION the early trucks seem to run a little better than 1991.5.& up.I wonder if I should have put that in print. we bumped that 1.43mm up too 1.52mm, that was when I started wondering about my own. so checked it and found it at 1.92mm setting.

 

I posted a few days ago trying to find a baseline for the relation between cranckshaft and plunger lift, and no one came up with anything, except .1mm =1* crankshaft. With no known base , I used the invoice from a shop that had set my timing from 7-13* with a light, assuming that the 7* was stock, or 1.25mm. This was on my dads 91.5. Target being 15*, so to raise to 15, I needed 8*, or .8mm. So I set the plunger to 2.0mm. Truck runs real nice, doesn't rattle loud, and seems to run real free and easy. actually got quieter. Is 2.0mm in the danger zone? beachcraft- sounds like you work in a shop. Have you confirmed the 1.92= 16.5 with a light and plunger gauge with pulse loss figured in yourself? Just want to get all this RIGHT! Thanks Jeff