Tooth jump = bump?

[Mhannink]

by the way if this keeps going im probably gonna have to dig out all my lecture books on fuel systems and fuels, i remember covering this stuff in great detail on cat engines.

 

[Mhannink]

something i just thought about. the line pressure is a linear equation. also the fuel pump plungers, lines, and nozzels are all full of fuel. now all pressures being equal the equation i think would be similar to hydraulic's when figuring out mechanical advantage. the ratio of the surface area of the plunger to the surface area of the nozzel seat would be the multiplier. with that ratio i think you can find at exactly what distance of travel (mm of lift) soi would take place. using that you could determine exact timing using the method cummins dictates. now factor in that lp pressure in the plunger is lower than the line pressure to the nozzel (at least in the p pump it is) that would increase travel length before soi pressure is reached.



the other thing to factor in too is duration and volume, total time from soi to end of injection (eoi) this would be a factor to consider when setting timing and looking at the burn time. a longer duration at a lower pressure using the same volume of fuel at a fine enough atomization would increase effeciency. the nozzel design would have to be revamped though, smaller holes would increase atomization and slow injection, soi would be the same but the duration and peak injection pressure would increase. spraying fuel longer keeping the burn going. granted too long and its wasting fuel, but maintaining cylinder pressure for as long as possible with the same amount of fuel, and completely burning it would be ideal.

 

[HHhuntitall]

That's a lot to think about, and well stated..... my limited understanding will have to ponder on it for a while... .



As for the Cummins Cam marks, I have no idea what they stand for. I know you can advance or retard the pump via these marks... . I've been going to go into the pump shop at Southern Plains Forth Worth and ask, but they're always busy and I'm usually in a hurry to get parts and get something fixed. But I've often thought about it, and knowing Cummins, I'd wager is has to with engine application, with D being used in front of an automatic, where rpms are higher, and E being for use in a marine engine, where advanced timing and heat are not as big a factor as in a highway vehicle, and more torque at lower rpms is desired. D might also be for use in something similar to a Formula motor, where rpms are governed lower and overall horsepower is restricted... . but that's just a thought, and thinking gets me in trouble... ...



In your injector line equation, is compression factored? How much hydraulic compression would diesel have under a few hundred psi pressure? Would it change with sulfur or fuel additives? And what about injector wear? I understood them to change pop pressures in temperature, time and spring fatigue?



And then we get into camshaft design, where the intake valve is opening sooner, allowing better mixing of fuel/air. Here, I would surmise, a better atomization of fuel would result in better fuel mixture, and better burn, with slightly less fuel. More effecient, which I like ... ...



And now I'm just plain interested and want to learn something, screw the headache!! Oo. This is an area of limited understanding for me, as I said, so please speak up... .

 

[cerberusiam]

something i just thought about. the line pressure is a linear equation. also the fuel pump plungers, lines, and nozzels are all full of fuel. now all pressures being equal the equation i think would be similar to hydraulic's when figuring out mechanical advantage. the ratio of the surface area of the plunger to the surface area of the nozzel seat would be the multiplier. with that ratio i think you can find at exactly what distance of travel (mm of lift) soi would take place.

You can to a point and thats how the initial pump settings were developed. Again, back to the variables of which fill time, rpm, fuel temp, and case pressure are biggies.



The easist way to find the ~SOI is the timing tool that clamps to the line and sense the pressure wave. Its close but there is still pieces down stream from that to consider.



Injector spring tension, injector body seal, pintle fitting, delivery valve sealing, etc, etc, all contribute. Even on a well tuned setup 1-3 degrees variation across all 6 cylinders is not that unusual. Worse when something is amiss.



It is a mechanical system influenced by mechanical limitations therefore not an exact science every single time. Getting it close all the time is about as good as one can do. Getting it close part of the time is what most pump rebuiders and shops do.

As for the Cummins Cam marks, I have no idea what they stand for.

They are for different CPL's that use different timing requirements.

 

[Mhannink]

That's a lot to think about, and well stated..... my limited understanding will have to ponder on it for a while... .



As for the Cummins Cam marks, I have no idea what they stand for. I know you can advance or retard the pump via these marks... . I've been going to go into the pump shop at Southern Plains Forth Worth and ask, but they're always busy and I'm usually in a hurry to get parts and get something fixed. But I've often thought about it, and knowing Cummins, I'd wager is has to with engine application, with D being used in front of an automatic, where rpms are higher, and E being for use in a marine engine, where advanced timing and heat are not as big a factor as in a highway vehicle, and more torque at lower rpms is desired. D might also be for use in something similar to a Formula motor, where rpms are governed lower and overall horsepower is restricted... . but that's just a thought, and thinking gets me in trouble... ...



In your injector line equation, is compression factored? How much hydraulic compression would diesel have under a few hundred psi pressure? Would it change with sulfur or fuel additives? And what about injector wear? I understood them to change pop pressures in temperature, time and spring fatigue?



And then we get into camshaft design, where the intake valve is opening sooner, allowing better mixing of fuel/air. Here, I would surmise, a better atomization of fuel would result in better fuel mixture, and better burn, with slightly less fuel. More effecient, which I like ... ...



And now I'm just plain interested and want to learn something, screw the headache!! Oo. This is an area of limited understanding for me, as I said, so please speak up... .

compression ratio would factor in yes, how exactly it fits in i dont know if i can describe. im assuming you understand the basics of hydraulics in that fluid are not compressable. it is a direct transfer of force. as for changes in fluid, any fluid would act exactly the same. its one thing all fluids have in common.

as for injector wear and fatigue yes that would affect timing. solutions to it are rebuild injectors and make sure pop pressure is as close to the same as possible to minimize variance. also you can adjust timeing based on current pop pressure, still requires r&r and testing. any variation between injectors though cant be taken out in the pump and or timing, they would have to be rebuilt and reset. as for tempurature affecting the pop pressure i think it would have to be extermes that do that the springs are constant tempurature wont affect them greatly, at least thats my guess i could be wrong.

You can to a point and thats how the initial pump settings were developed. Again, back to the variables of which fill time, rpm, fuel temp, and case pressure are biggies.



The easist way to find the ~SOI is the timing tool that clamps to the line and sense the pressure wave. Its close but there is still pieces down stream from that to consider.



Injector spring tension, injector body seal, pintle fitting, delivery valve sealing, etc, etc, all contribute. Even on a well tuned setup 1-3 degrees variation across all 6 cylinders is not that unusual. Worse when something is amiss.



It is a mechanical system influenced by mechanical limitations therefore not an exact science every single time. Getting it close all the time is about as good as one can do. Getting it close part of the time is what most pump rebuiders and shops do.







They are for different CPL's that use different timing requirements.

would the fill time not be linear according to engine speed? if pressure and speed are constant then fill time should be. im positive there is a way to measure or calculate it. the fill time is a duty cycle percentage of time open to percentage of time closed. volume, time the plunger is open, and fuel pressure would dictate fill time. plunger open time would change according to rpm which is the variable. its still measureable and a factor to more accuratly adjust timing.



fuel temp will not affect soi timing but duration which is less important. it is also a calculateable variable. the hotter the fuel the more expanded it is the equals less parafin wax (power) in the same volume of fuel. volume is fixed, a gallon is a gallon, the density and resulting measureable weight (lbs) would change according to temp. no matter the fuel temp soi would be constant. what the temp would affect is throttle position for a given load/rpm. thinner fuel being less powerful = more fuel needed at given a given time. it relates to timing in duration. our focus here is more soi then duration. reason being soi is the crucial factor in timing. duration is variable controled more or less automatically.



what are refering to when you mention case pressure?



i am coming at this from an engineering standpoint, in that a lot of variables affected by wear and age are eliminated. what eric is asking about is possible, but your right that it wouldnt be as persice as theoritically possible. however if we were to r@r the injectors and either reset them or at least measure the pop pressures you could time accurately off of the average. some would be early some late. depending on the range of variance, it would be close enough. also yes the most accurate way to measure the soi is with a piezio electric pressure transducer clamped to the line. placement of the sensor would affect your measured reading too. in fact it would probably be best to read as close to the pump head as possible and as close to the injector as possible. im sure there would a be a slight difference that could be factored in when trying to time it that closely. injector wear and spring tension would affect it some, but these injectors are supposed to stay consistent to each other for long periods of time. cat suggested replacement of their 3406b nozzels after x amount of hours, miles, or fuel burned for this very reason.



nothing is consistent every time, not just mechanical sytems. the theory is an exact science, and even in application the ability to factor in all of these vairables is an exact science, its just impossible to counter for every change, especially since most of the changes that affect any variable are so slight or so fast that they can't be measured.

 

[Mhannink]

Hey!



I've been reading everything I can trying to get up to speed on these 1st gens.



Quick question... to increase timing, it seems some people jump a tooth on the pump gear, some people bump timing ~1/8" by rotating the pump, and some use the M&H dynamic timing spacer... and some people do any combination of the three.



Does jumping a tooth and rotating the pump do the same thing? If so, what does 1 tooth worth of timing equal? By this I mean, does 1 tooth equal 1/8" bump of pump rotation?



Thanks, Eric

ok so now that we have gone far beyond in the theory for what is really needed for the subject, i wanted to go back and actually answer the question. to jump a tooth would advance the timing 10 degrees, if your timing is 12. 5 from the factory its probably too much unless your a puller turning high rpm. static timing would be 22. 5 thats a lot. also yes rotaing the pump is the same as jumping a tooth just not as much. lets say you can advance the timing 5 degrees with pump rotation. thats just an example, i dont know how much rotation can gain. the first thing to consider is where the engine spends most of its time. 2000 rpm? 1800? 1500? decide where your cruising speed is and timing the engine for that. to find the needed optimum timing take your rpm and find the dynamic timing, add your static timing in and that is your actual timing. at that rpm find out how fast the cylinder will travel from the soi (the timing) to tdc. adjust your timing so that soi plus burn time will create peak cylinder pressure 1* after tdc. to do this, i think you need to work backwards, peak cylinder pressure minus burn time minus distance and rate of travel, the result is where soi needs to begin. after that just adjust the pump that many degrees, if you need seven degrees then jump a tooth and back the pump off 3. its hardly scientific, but to get more presicion you would need to incorperate injection pump lift, that takes into everything we have talked about.



rule of thumb and the theory i used for my p pump was just advance it half a tooth on the crank thats about 5 degrees on the eyeball, lock it down and run it. i dont know about the ve pumps but the p pump guys range from 15 to 18. depending on model static timing is 12. 5 to 13. 5 maybe 14. im running closer to 18. thats 13 factory plus 5. i like it where its at and am not going to worry about it till i have lots of disposable cash to really spend some money and play with it to an extreme.

 

[cerberusiam]

would the fill time not be linear according to engine speed?



fuel temp will not affect soi timing but duration which is less important. it is also a calculateable variable.



what are refering to when you mention case pressure?

On paper fill time would be linear, in reality it is not. The more engine rpm the less time the port is open so the actual volume filled decreases. As you turn the pump up the differential between actual and theoretical get farther apart.



Fuel temp does have an effect on SOI given all other parameters stay the same. Heavier fuel is harder to push and takes more time to move if nothing else is changed then SOI moves.



This is why the VE has dynamic to compensate for all the variables, fuel temp, intake air temp, etc. Thats a lot different than the P pump that has no dynamic timing advance.



This is where case pressure comes into play. The vane pump is generating the pressure to drive the dynamic timing curves plus influencing how the fill rates adhere to design parameters. If that varies for whatever reason your timing is bouncing.



Like you pointed out, advancing the timing puts more power into the engine and creates more efficiency. The down side its it robs boost becuase of the lack expansion in the exhaust. On a large turbine turbo this can be significant and contributes to lost efficiency at a certain point because the trubo cannot supply the air.



At a specific rpm where the IP is capable of deliverying the fuel and the turbo is capable of providing the air, timing should be able to be claculated for optimal use. Need to figure out what the dynamic timing curve of a VE is, how to measure it, then how to influence it and there is another tool to play with. An initial set of timing is one thing, the actual timing curve in crank degrees is another whole animal.



That is another difference from the p-pump, the VE uses less initial timing because it has a dynamic curve. A lot of times 15 degrees or the represenative pump position thereof, is too much. Other times its not enough, depending on pump, injectors and build.



Outside of the specific CPL's, there is not a lot of solid data on just what happens to timing, duration, etc, and what is the best setting. Trial and error then test.

 

[HHhuntitall]

Trail and error I can relate to.....



So you're saying Bosch has no specs on what the VE timing curve is, or supposed to be? I wonder if they have a comparison for running on a flow bench? Or do they just specify pressures at idle and rpms?

 

[cerberusiam]

So you're saying Bosch has no specs on what the VE timing curve is, or supposed to be? I wonder if they have a comparison for running on a flow bench? Or do they just specify pressures at idle and rpms?

Not saying they don't have them, saying they verge on impossible to find or get.



Just getting a pump shop to do anything other than run the basic tests at an idle is problematic. They are telling me there really is no spec for, say, 2000 rpms and good way to measure pressure and timing. The official party line is set to specs and it should work.



We know about what the total is for dynamic timing, 21 degrees (I think that is crank degreess but again... . ) but no real good idea what the rom curve is or pressure curve applied to it. The timing is dynamic based on case pressure which is tied to rpm but what is the link?



I don't have a map that says at 2000 rpm case pressure is 210 psi and\or timing advance is 13 degrees at 210 psi. Even this, where does the dynamic come into play. 1100 rpms? 1500 rpms? What is the pressure for the curve? 180 psi thru 260 psi?



Timing curves, pressure curves, fill rates, cam profile, etc, simply is tough to find from Cummins. Sooo, we guess and hope. :-laf

 

[Mhannink]

Im on my mobile right now so typing a long thought out response is tough. Just wanted to say I pulled my old school books out and glanced through them, they are cat specific but probably 90% of the info is still relevent. Ill get more into it later but I came across a note I had forgotten about and that's port effect. It adds . 2 degrees of timing for every 100 rpm that's from 0 rpm up. That's another factor but its a fixed linear one.

 

[Mhannink]

On paper fill time would be linear, in reality it is not. The more engine rpm the less time the port is open so the actual volume filled decreases. As you turn the pump up the differential between actual and theoretical get farther apart.



Fuel temp does have an effect on SOI given all other parameters stay the same. Heavier fuel is harder to push and takes more time to move if nothing else is changed then SOI moves.



This is why the VE has dynamic to compensate for all the variables, fuel temp, intake air temp, etc. Thats a lot different than the P pump that has no dynamic timing advance.



This is where case pressure comes into play. The vane pump is generating the pressure to drive the dynamic timing curves plus influencing how the fill rates adhere to design parameters. If that varies for whatever reason your timing is bouncing.



Like you pointed out, advancing the timing puts more power into the engine and creates more efficiency. The down side its it robs boost becuase of the lack expansion in the exhaust. On a large turbine turbo this can be significant and contributes to lost efficiency at a certain point because the trubo cannot supply the air.



At a specific rpm where the IP is capable of deliverying the fuel and the turbo is capable of providing the air, timing should be able to be claculated for optimal use. Need to figure out what the dynamic timing curve of a VE is, how to measure it, then how to influence it and there is another tool to play with. An initial set of timing is one thing, the actual timing curve in crank degrees is another whole animal.



That is another difference from the p-pump, the VE uses less initial timing because it has a dynamic curve. A lot of times 15 degrees or the represenative pump position thereof, is too much. Other times its not enough, depending on pump, injectors and build.



Outside of the specific CPL's, there is not a lot of solid data on just what happens to timing, duration, etc, and what is the best setting. Trial and error then test.

ok this might be kind of choppy but i wanna take each of your paragraphs one at a time.



i understand fill time will change with rpm, as the engine speeds up

the amount of time the fill port is open decreases. would that not be inversly proprtionate to rpm and therefore linear? also increased fuel of the pump meaning more fuel injected every event would change fill time. that makes sense, wouldn't timing for a specific rpm eliminate that? even the new electronics cant run at optimum throughout the entire engine rpm. if they could the torque curves would be flat.



i still disagree with fuel temp affects timing, even engine oil if compared at the same temp would build pressure at the same rate. im pretty sure any fluid would since they are not compressable the viscosity or density would not affect the pressure build rate. to come back to a more relisitic thought, these engines are built to be tested in a cell where all outside variables are corrected. humidity, ambient temp, fuel temp, all the conditions for testing to sae standards, they have to test every engine to make sure it meets advertised horsepower +- 3%. i think the standard is 70*f for fuel temp. now the viscosity of the fuel doesnt significantly change from cloud point through about 200 degrees. i dont think fuel temps are gonna be higher than that in normal operations. if they were you would really notice a power problem. im not convinced yet that temp would affect soi. your explanation makes me think of being between a rock and a hard place. the engine is running and has a 2:1 gear reduction to the pump, there is even more mechanical advantage provided by the diamiter of the gear compared to the plungers. the pump and engine would never notice the extra density, if it did the engine would slow and timing would stay the same anyways since the engine is not advancing as fast. what your describing sounds like parts are about to be broken. something has to give in that situation the pump wont and the fuel wont so things are gonna happen on time.



dynamic timing is not used to absorbe all the variables. it cant, dynamic timing is determined off of rpm. its purpose is exactly the same as why spark ignition is dynamicaly advanced. the fuel needs x amount of time at y engine speed to burn properly and create power. gas engines suffer much more from lack of advance then diesels do, thats why not all diesels have dynamic timing. the new scroll fuel system from cat is virtually identical to the p7100, just a supped up version of it. cat designed a timingadvance unit for its 3406b models. i know there where 2 types one was spring/hydraulic the other was hydraulic/ hydraulic. the timing advance unit allows for a wider power band, more horsepower, it also helped meet the 1986 noise emmissions as well.



case pressure. is it building that pressure in the pump body? equal pressure all over? i can see a timing advance working of fuel pressure but it doesnt seem very effective where and how much pressure is it building. if pressure is building from the vane pump around the fill port as rpm increases, timing advances, and pressure increases wouldnt fill times stay very close to steady? less open time but more force pushing it in at a higher velocity.



on the turbo issue you mentioned, addmittedly this is a gray area for me (still some black majic in the turbo) my understanding is similar to what you describe, only i thought it was more the change in temp across the housing, inlet --- outlet that drove the turbo. i do know that in the high hp pullers they like to lengthen the duration injecting some fuel too late for power but it burns in the manifold and generates more heat driveing the turbo. its the same principle either way i think. in this application though i dont think its a concern, especially since eric is talking 300 horse thats easy to size a turbo for with the advanced timing. like i said it a gray area and probaly something to be concerned about when designing an entire engine or even just trying to heavily modify an existing one to meet many different goals at the same time, I. E. big power and good fuel mileage.



on the last part comparing a ve to a p pump, i would agree with you but it looks like from what eric said earlier static timing is 12. 5 degrees the early p pumps used that setting as well. ve's just have dynamic which is probably why they tend to get better fuel mileage.



as for measuring dynamic timing and all of that, i actually have the info in my books for cats engines, obviously cats tools and what not, but the same could probably be set up and calibrated for any engine, this would allow you to measure it very acurately. then chart it, figure out your other math and you'll have it.

Not saying they don't have them, saying they verge on impossible to find or get.



Just getting a pump shop to do anything other than run the basic tests at an idle is problematic. They are telling me there really is no spec for, say, 2000 rpms and good way to measure pressure and timing. The official party line is set to specs and it should work.



We know about what the total is for dynamic timing, 21 degrees (I think that is crank degreess but again... . ) but no real good idea what the rom curve is or pressure curve applied to it. The timing is dynamic based on case pressure which is tied to rpm but what is the link?



I don't have a map that says at 2000 rpm case pressure is 210 psi and\or timing advance is 13 degrees at 210 psi. Even this, where does the dynamic come into play. 1100 rpms? 1500 rpms? What is the pressure for the curve? 180 psi thru 260 psi?



Timing curves, pressure curves, fill rates, cam profile, etc, simply is tough to find from Cummins. Sooo, we guess and hope. :-laf

i agree 21 degrees is in relation to the crank, but i think that is total degrees static+dynamic+port effect. all of my books and lectures talked about timing in degrees of crank rotation, all the literature ive ever read goes with that too. is it possible to measure case pressure? im sure timing is directly proportional to case pressure. not 1 psi = 1 degree but if we can get maximum case pressure and maximum degrees of advance possible you can get the needed ratio. then measure case pressure and it would tell you where the advance is at. if you have all that info you will know when start of advance happens and where end of advance happens. you could then map it, time it, measure it veryaccurately.



if 21 degrees is total advance and 12. 5 is static that is 8. 5 degrees dynamic timing. port effect is . 1* per 100 rpm starting at 0. so port effect for 3000rpm is 3* subrtact that from dynamic the pump can advance 5. 5 degrees of crank angle or half a tooth. this sounds about right to me. the p pumps like to run about 15* static, most any of our engines like it around 2000 rpm. so a p pump is running 16-17 degrees at 2k rpm. a ve is running at 2k 12. 5 static + 2 pe + 3. 5 to 4 degrees for dynamic thats about 18 18. 5* id be willing to bet if we figured the rest out, or if someone managed to get the info from bosch or cummins, thats where these engines run. 18 is a lot of timing, but the first gens are known for good fuel mileage, think timing could be doing it.

 

[Mhannink]

And then we get into camshaft design, where the intake valve is opening sooner, allowing better mixing of fuel/air. Here, I would surmise, a better atomization of fuel would result in better fuel mixture, and better burn, with slightly less fuel. More effecient, which I like ... ...



And now I'm just plain interested and want to learn something, screw the headache!! Oo. This is an area of limited understanding for me, as I said, so please speak up... .

we can if you want to. ever hear of degreeing a camshaft. its common on gasser race engines.



cam design is even more screwy then turbo designs. scavanging effect, cross over, total lift, rate of lift, duration, rate of closer, lobe seperation, split duration. thats just to name things i can remember. factors taken in are head design, size of valve, shape and quantity of valves, valve angle, seat angle, flow angles around valve stem and valve face, shrouding, piston design, again thats just off the top of my head.



the degreeing part is actually pretty easy from what i remember. once you have the right combonation of stuff you set up a degree wheel on the crank and i dont remember how but degreeing the cam sets it to it most optimum angle with a minimal amount of variables. they only use this if say you bolt on edelbrock heads, arias pistons, comp cam, trick flow manifold. all different manufactures, then degreeing the cam can make a big difference. if you where to have a cam cutom ground for your specific engine then there is probably no need, might even go backwards with it.



your exactly right on the results though. the cam is the brain of the engine. its funny to think about, if you reversed the cam lobes the air flow through the engine would reverse. the cam dictates function of the engine and controls so many things, money spent on a very good cam will go a lot farther then just about any other mod would. thats on a gasser anyways, i noticed when i installed a cam in my diesel there was not much difference in the operation, it did do exactly what i wanted it to and have never looked back, i also suggest to anyone wanting a more effiecent and powerful engine, but the cam by itself did not do anything real big.

 

[HHhuntitall]

we can if you want to. ever hear of degreeing a camshaft. its common on gasser race engines.

I might have heard of it before... .



And the cam upgrade comes as part of the injection and air upgrades. It's not really noticable on a stock diesel, just as it wouldn't be on a stock gasser. But where we're at in this conversation, I think we're way over stock... :-laf The diesel injection is something I've been learning about. I grew up with A, B, and RB maxi-wedge Chryslers, this degree wheel is my old man's. It's got 1979 copyright on it, so it's almost as old as me. I've never used it on a diesel. Cummins has TDC made into the camshaft, and it's gear to gear, so it's hard to get closer than pinned. Now, in experimentation, we may disregard it, but it's always where we start, the baseline, so to speak. A lot of what I've learned is on the Bosch P7100; it's the workhorse I started with. Pretty basic pump with a lot of possibilities. The VE seems much more complicated... . a marvel of engineering, really. Scematics don't really do it justice, as it's beauty is in rotation... . I think it's current specs are outdated, though. If it could be made to make more pressure at top end, I think it would be even better..... just a thought. I don't really know enough about it to really say that, to be honest. I was just thinking a higher pressure, such as the P7100 or CR would give better atomization and more fuel delivery... . and factor in it's ability for timing curve, and you get an exciting possibility... ..... but then, wasn't the VE designed for smaller CI engines to begin with?

 

[cerberusiam]

i can see a timing advance working of fuel pressure but it doesnt seem very effective where and how much pressure is it building. if pressure is building from the vane pump around the fill port as rpm increases, timing advances, and pressure increases wouldnt fill times stay very close to steady? less open time but more force pushing it in at a higher velocity.

Effective or not, thats the way the VE works with timing. There is no mechanical linkage to control timing advance, its all pressure. It gets worse internally. The dynamic timing is ported so only part of the vane pump pressure is used to advance the timing. The pressure rise with rpm is used to apply that timing thru orfices. The KSB has the ability to advance timing at a cold idle to somewhere around 12 degrees, in addition to initial.



I have this problem multiple times where the PR valve that regulates the case pressure, and ultimately timing, fails intermittently. Hit a certain rpm and the truck noses over with lots of white smoke and misfires. Also used a pump from a different CPL that ended up with the same issues at about 2600 rpms. The whole design of the pump internally defines the rpm and timing range it is capable of running in.



I am pretty sure the 21 degrees is in addition to initial timing so total, depending on where initial is set, comes up to 30-36 degrees at rated rpm. Thats not bad for the intended range of these engines, but, when you push the fuel your chopping efficieny on the top end because it simply cannot advance far enough for a complete burn.



The fill time on the rotor of the pump simply falls off after 2600 rpms becuase the size of the orfice and the density of the fuel. It simply is not large enough and open long enough to fill completely at higher rpms. Case pressure, denisty, and temp of the fuel is all going to play into fill time. How much each contributes is really and unknown.



The cam in a forced induction engine is just not as critical as it is a normally aspirated motor. The low end is where it is more noticeable with an increase in TQ. There is some differnece in the mid and upper end but once boost is up the differnetiations are much lower. An LSA that would cause a major lope and impact to the low end of a gasser doesn't have the same impact in a diesel. I am sure that has a lot to do with the length and intensity of diesel combustion.

 

[cerberusiam]

The VE seems much more complicated... . a marvel of engineering, really. Scematics don't really do it justice, as it's beauty is in rotation... . I think it's current specs are outdated, though.

Yep, thats the gist of it. There are some ways to circumvent the limitations but limitations always come into play.



It is kinda like Blue Chips plan for circulating fuel in a VP to keep the electronics from degrading so fast. Its a great idea and looks promising but the cost and work to accomplish it is the bottom line.



My son has come up with a couple design changes around the cam plate and the fill time of the piston to get around the limitations. The problem is lots of machine work and some fairly complicated porting in the pump case and head itself.



The only way to know if it will work is take the chance of trashing a pump.

 

[HHhuntitall]

Ever considered upscaling everything?

 

[cerberusiam]

Ever considered upscaling everything?

Always! :-laf



That is really open ended so not sure what you mean. Our target was a way to make 750 HP effectively without destroying the pump on every run.

 

[Mhannink]

so ya'll know i havent forgotten this thread, ive pulled out my old school books and as many specs as i can find, im going to do some calculations and crunch numbers as well as graph as much of this as i can to help us visualize whats going on. the process is sort of long and i dont have an infinite amount of time to work on it. ill report back with what i have for your evaluations.

 

[HHhuntitall]

so ya'll know i havent forgotten this thread, ive pulled out my old school books and as many specs as i can find, im going to do some calculations and crunch numbers as well as graph as much of this as i can to help us visualize whats going on. the process is sort of long and i dont have an infinite amount of time to work on it. ill report back with what i have for your evaluations.

Uhhhhhh, how can I put this..... Please?

 

[James1]

Don't intend to hijack, but the very first post in this thread posed a question and referenced the M&H spacer. M&H claims its spacer is superior to a 1/8" bump of the pump because the spacer results in a "dynamic" timing advance whereas twisting the pump results in a "static" timing advance.



1. Would someone please chime in regarding the validity of this claim?

2. Is the spacer really superior (to twisting the pump)?

3. Does the M&H spacer result in too much advance for a bone stock truck?



TIA.