Engine/Transmission (1994 - 1998) Take your plate out!!!!!!!

[Jim Fulmer]

Don M

What pump numbers to what year models, meaning what pump would my truck have... ... . crap it's one of the so-so ones isn't it! That means I'm going to have to buy one of Piers's stupid pumps.



Jim

 

[Sled Puller]

Don M,

What tech book are you getting your info from, and where can I get one?



Gene

 

[Strick-9]

Don,



Keep in mind that when the truck is off, the plungers are rotated to a more heavily fueled position than when the truck is idling. When the engine starts, the flyweights come out and defuel down the the neccessary idle quantity. So just because the fill ports are down in the groove while the pump is off doesn't mean that is where they are at idle and low fueling positions.



I'm going to check now to locate my fill ports. Be back shortly.



Is anyone else willing to do this test? Pop out a delivery valve and remove your camplate. Push the rack all the way forward and find out where the fill ports are in relation to the groove in the plunger. You'll have to find a plunger in the lowest position to be able to see the fill ports.



-Chris

 

[Strick-9]

Plungers have a total range of motion of 80-95° depending on what modifications have been done to the fueling side. When the truck is off and the flyweights are held all the way down by the governor idle springs, the governor is pushing the rack to about 1/2 throttle to aid in starting.



I just went and popped out a DV to make sure I wasn't confused.

With the governor springs in the pump and the engine not running the plungers only appear to have about 45° of rotation.



When I push my rocker all the way until it touches the #0 plate, the fill ports are on the bottom of the groove retarding the timing. The fill port is actually on the bevel cut coming out of the tgroove, but the port wouldn't be completely closed until the lowest portion of the plunger cleared.



With the engine off and the governor in start position, the fill ports are on the bevel cut of the groove just going down to the lower portion of the plunger.



So during idling and low throttle, the engine operates at the higher timing setting and under max rack travel it operates at the retarded timing.



I believe this is one of the reasons for Piers using the 160 pumps for his race pumps. He doesn't have to deal with the retarding of the timing under more rack travel.



More advance with higher rpm would be better. Along comes the VP44.



There's always the chance that Don is right and I have a marine pump though. That's why it'd be nice if someone else did the test too.



-Chris

 

[jimk]

groove in plunger

Is the groove that you are referring to call a helix. I could be wrong as it has been a long time since I went to pump school.

 

[jimk]

pump camshaft

While on the subject of pumps have you ever heard of Colt Cam or I think that is the way it is, they grind cam shafts for pumps, in BC

 

[Don M]

Originally posted by Sled Puller

Don M,

What tech book are you getting your info from, and where can I get one?



Gene

I have a plunger and barrel assembly from my last pump rebuild.

No books on this one. This is why my verbiage for the protrusion is probably incorrect.





Chris,



Looking down the pump is not going to tell ya everything unless you remember the location of the helix in relation to the top of the plunger.

The lowest portion (the groove you called it) of the plunger on top is also closest to the helix. So if your spill/fill port is closed by the lower portion of the plunger it will also open the spill/fill port faster. The faster the spill/fill port is opened the less rack travel you have and the less fuel delivery in mm3 you will have.

As you rotate the plunger in the barrel the helix is lower on the side wall of the plunger and port opening is delayed more so the fuel will not spill out as fast. This gives you more fuel delivery and is also in relation to the advance in the plunger.



Going back to what I said earlier, the timing is set by the lowest point on the plunger (in the groove you called it) Try and imagine the plunger advance being in the lower rpm range and the trouble it would cause operationally.



The 913 pump is/was designed for a little more power, but keep in mind the advance was not built in for us to hot-rod. It is there to lower the EGT and thus lower the oxidized nitrogen molecules or NOX. If you were correct the NOX would go through the roof if timing was retarded as the engine speed increased.



You do not have a marine pump. The marine pump has a flat top plunger with a single retard groove cut on one side of the plunger. This way the rack can put the plunger in a cold start region of its travel to reatrd the timing for ease of starting.

Stock timing on the 300 marine engine is over 18 degrees. The groove lowers the effective spill/fill port closing about 5-10 degrees.



jimk,



no the groove on top that keeps being called a groove is actually the top of the plunger. Its not a groove at all. The plunger has protrusions on both sides of the top that I am calling a protrusion.

Its actually a rise from the top of the plunger to provide advance with more rack travel or better said slower port opening.

The helix is on the side wall of the plunger.





Chris again,



I took a flashlight and P&B assembly while watching a movie last night and used the flashlight to shine light into the side of the barrel. As I rotate the plunger toward the advance the spill port is closed faster and it opens later. You can see the light coming through the spill groove in the top of the plunger once port opening is accomplished. Looking at the top of the plunger I would say we get about 7 degrees of advance in the 913/887 plunger design in the upper rpm range/rack travel.



Another clue to help you would be the fact that on dyno runs the 913 pump will not make as much power after about 17 degrees of timing, but the smaller 160,175 and 180 HP pumps will make power with more timing than 17. This is a direct relation to the timing advance built into the plunger of the 913/887 being too much after 17 or so degres of timing.



I will take some photos of the plunger and barrel assembly I have and show you the relation of the protrusion and helix.

This will help clear stuff up.



Don~

 

[Strick-9]

Jim,



You went to pump school? You should be the one teaching us.



I'm sure you remember all this but I'll hit the highlights briefly.



Our pumps inject fuel between port closure and port opening. The helix opens the port at the end of the injection cycle. It is rotated around to dictate the quantity of fuel injected.



The top of the plunger closes the port to begin injection. This is the part we are referring to right now.



Don,



It doesn't matter where your dial indicator hits. When setting the timing, you zero the indicator and measure a change in lift. So if your indicator is down in the groove or up on the protrusion or anywhere in between, it doesn't make a hoot. As long as it doesn't move or slip during the adjustment.



You mentioned this:

This groove is in a position on the plunger as to only be effective when the plunger is twisted into the cold start area of the racks travel.

Where is the cold start area of the rack's travel? Obviously, it is more rack travel than idle and less than hitting the stop plug/AFC finger/camplate. Is there some magic plunger rotation angle that I don't know about? How could it not be used during normal operation? Is it just skipped over?



-Chris

 

[M Barnett]

That photo would be great!

Michael

 

[Strick-9]

Don,



The problem with holding the P&B in hand and trying to learn is that you don't know when to stop rotating the plunger.



If my plungers would rotate further, they would climb back up to the advanced portion of the plunger. But it doesn't make it that far. That's why you need to look inside your pump to see that actual range of motion you are using.



My timing is rather high right now. You can definately hear the knock under light to mild throttle. I did some testing with NO AFC, and the engine immediately quiets down with more throttle. Maybe that's because the timing is retarded?



If the timing advanced, the knock would get louder.



-Chris

 

[Don M]

Originally posted by Strick-9

Don,



The problem with holding the P&B in hand and trying to learn is that you don't know when to stop rotating the plunger.





If the timing advanced, the knock would get louder.



-Chris

It helps if you know where the spill/fill area is located in relation to the rotation of the plunger. I have the pictures taken and Im trying to resize them to fit in the readers rigs area of the TDR.

After you see the lateral groove in the helix in relation to the advance protrusion you will clearly see the advance of port closing with more rack travel or rotation of the plunger. You can see the normal timing setting and the abilty of the plunger to advance the timing with high rpm and longer rack.



Hang tite.



Don~

 

[Don M]

Originally posted by Strick-9

Don,



The problem with holding the P&B in hand and trying to learn is that you don't know when to stop rotating the plunger.



-Chris

There is no probelm with holding the plunger and barrel in your hand. Actually you can just have the plunger and still see the advance in relation to the helix on the side wall.

The light experiment I did gives me an idea of what is going on at what rack travel. I thought it might help explain or dismiss your theory that the timing is retarded at the upper rpm band.



Don~

 

[Don M]

Chris and others,



The picture is up and is not the greatest, but you can see the higher protrusion I was talking about on the top of the plunger in relation to the lowest portion of the helix on the side wall of the plunger. Remembering that port opening is delayed with more rack travel or plunger rotation you can see the protrusion advances the port closing with more rack or plunger rotation.

This is cool because like I said earlier you can run about 16 degrees of timing on the lower rpm bands and during cruising speeds so as to not hammer on rod bearings and the crankshaft, but still have a bit of built in advance for higher rpm work and power.

This saves the engine for everyday driving.

Oh, I said earlier that the timing may be advanced as much as 7 degrees I now think it may be less after closer observation.



Joe D has always maintained the 913 is the best factory pump we can get. The reasons are several, but here is one of the main ones.



https://www.turbodieselregister.com/user_gallery/displayimage.php?&photoid=1384&width=4





Don~



edit- Chris I just found this question and wanted to give you an answer the best I could. I suck at explaining most technical stuff, but Im good at political rants.



Chris asked "Where is the cold start area of the rack's travel? Obviously, it is more rack travel than idle and less than hitting the stop plug/AFC finger/camplate. Is there some magic plunger rotation angle that I don't know about? How could it not be used during normal operation? Is it just skipped over?



-Chris



On the marine pump the cold start region is full forward.

The rack actually moves into a region of rotation that is not used during normal operation. As the rack moves, the plunger is rotated to align the plunger retard groove with the spill/fill port.

Once the engine starts the rack is toggled back by the governor to normal running position and the groove is no longer over the spill/fill port. This gives the engine the normal timing to run with.

 

[Strick-9]

Don,



Not quite sure why you brought up the helix? Smoke and mirrors? We are discussing whether or not the pump advances or retards timing. The only important factors are the shape of the top of the plunger and the the location of the fill port.



I know how you think it works. I agree that a protrusion on the plunger would advanced the timing. What I'm asking you to do is take off your AFC housing and take out a delivery valve.



You can then see the location of the fill ports with your own eyes along with the top of the plunger. Now pull up your shutoff solenoid and slide the rack back and forth against your camplate.



You might be surprised at the location of the fill port.



Keep in mind that you can't rotate the plungers all the way back to the idle position because the governor is pushing the rack forward while at rest.



I remember going through this with Cord about a year ago. As we found more and more ways to use more of the helix, we eventually started asking ourselves, "what happens when you run out of helix?" We assured ourselves that the plungers were designed with more helix cut than could ever be used. Now look at your picture. If the fill port is sliding up and down over the deepest region of the helix, it still isn't at the top of the protrusion yet. I know you and Joe aren't running 21+ mm of rack travel, so why do you think you are getting up to that advance portion?



-Chris

 

[Strick-9]

Don,



Good explanation on the cold start feature! That's how my 913 works too.



That was my point in asking the question. As we start pushing more fuel through these pumps we are now using that region as part of our fueling curve.



Another interesting note about our pumps that is related to all of this is rocker height. Some of my bosch books show the rack to be full forward for cranking purposes. The rocker is supposed to be adjusted BELOW the AFC and camplate while cranking to allow the rack travel needed to start properly. Then when the engine starts and the rocker moves upward, it should hit both the AFC and the camplate. But that's not what you hear on the TDR is it?



On the TDR people have been told to adjust their rockers higher than that. This allows the fueling curve to come in earlier in the RPM range and the truck feels more responsive.



Thanks Don, I love getting into the details of how things work.



-Chris

 

[Joseph Donnelly]

I'm getting some of the advance with the rack travel I use. The helix uncovers the spill port and that is what dumps the fuel. When this happens depends on rack travel vs. degrees of crank rotation. The built-up areas (looking at it another way, cut down groove across the center) give the advance by moving this point at which the spill port is uncovered.

 

[Don M]

COMMENTS IN CAPS BELOW

Originally posted by Strick-9

Don,



Not quite sure why you brought up the helix? THE HELIX GIVES US AN INSIGHT INTO THE TIMING ISSUE OF PORT CLOSE AND OPEN. Smoke and mirrors? NO.



We are discussing whether or not the pump advances or retards timing. IT DOES BOTH DEPENDING ON HOW YOU LOOK AT IT.



The only important factors are the shape of the top of the plunger and the the location of the fill port. YES, BUT KNOWING THE LOCATION OF THE HELIX TELLS US WHEN THE ADVANCE OF TIMING OCCURS IN RELATION TO THE RACK TRAVEL OR PLUNGER ROTATION.



I know how you think it works. ACTUALLY I DO KNOW HOW IT WORKS AND SO DO THE REST OF US AFTER LOOKING AT THE PLUNGER THE ANSWER IS SELF EVIDENT I agree that a protrusion on the plunger would advanced the timing. What I'm asking you to do is take off your AFC housing and take out a delivery valve.



You can then see the location of the fill ports with your own eyes along with the top of the plunger. Now pull up your shutoff solenoid and slide the rack back and forth against your camplate.



You might be surprised at the location of the fill port. MAKES NO DIFFERENCE WHAT YOU SEE INDIVIDUAL PUMPS DOING, MOST ARE SET-UP DIFFERENTLY



Keep in mind that you can't rotate the plungers all the way back to the idle position because the governor is pushing the rack forward while at rest.



I remember going through this with Cord about a year ago. As we found more and more ways to use more of the helix, we eventually started asking ourselves, "what happens when you run out of helix?" WHEN YOU RUN OUT OF HELIX THE BARREL DOES NOT DUMP. REMEMBER THE ADVANCE CAN BE COMPLETLY IN EFFECT AND THE HELIX CAN STILL DUMP PRESSURE FOR PORT OPENING. THIS IS THE SECRET. CHECK THE PICTURE AGAIN OR GET A P&B IN YOUR HANDS.



We assured ourselves that the plungers were designed with more helix cut than could ever be used. NOT TRUE IN ALL CASES.



Now look at your picture. If the fill port is sliding up and down over the deepest region of the helix, it still isn't at the top of the protrusion yet. IT DOES NOT NEED TO BE AT THE VERY TOP TO BEGIN START OF DELIVERY THE PRESSURE IS ALREADY BEGINNING TO CLIMB WITH PARTIALLY CLOSED PORT



I know you and Joe aren't running 21+ mm of rack travel, so why do you think you are getting up to that advance portion? THE ADVANCE PORTION ONCE AGAIN DOES NOT NEED TO BE COMPLETLY ROTATED AROUND TO COVER THE FILL/SPILL PORT TO ADVANCE THE TIMING SOME. IT BEGINS TO ADVANCE THE TIMING WITHOUT BEING COMPLETLY OVER THE PORT.



-Chris

The caps above are to distinguish between your text and mine. Not yelling. I dont want others to think the plungers in the 913 pump retard timing like you said earlier. Mis-information is worse than no information in nearly all cases. Im trying to show the others the reasons for the advance and help explain why Joe always tells us the 913/887 is the best of the bunch in pumps for our engines.



Piers is changing the plungers and barrels out in the 160 pumps to 13mm size. This is to increase the amount of fuel that can be delivered. The 160 pump cam is reground as well to increase fill time to the barrel.



The cold start region is not the same on every pump. The grooves are not always cut in the same area on the plunger for all the differing pump models. They are all close though.



Don~



edit- in summary we have learned from the thread:



1) The cam plates need to remain in the pump (Chris Anderson will be shorting himself in power and potentially make himself a 1000 dollar plus repair bill, but that is his choice)

2) The 913 pump is the best to use for performance applications.

3) As the rack travel increases the plunger port closing is advanced to help power unlike the flat top plungers in the other pumps that are static.

4) The marine pump retards the timing with a groove cut into the top of the plunger to delay port closing and fuel delivery until the engine starts. At which time the rack is moved rearward for normal timing. Stock marine engines come with the timng at 18 plus degrees.



Chris Anderson would have us believe none of us learned anything in this thread when in fact it is him that has not learned anything by his insistance to leave the plate out.



Joe D does not hold out info. He has always maintained the 913 is the best pump. Further he has even given a demonstration of the pin and the damage that could occur for all to see if the cam plate is removed.

 

[Cummins Corvette]

This is an EXCELLENT discussion. Thanks very much to Strick-9 and Don.



I am with Strick-9 on the advance theory though. The protrusions on the side would advance the timing by CLOSING the spill/fill port sooner when the plunger is on its way up to create the injection pressure. According to the picture that Don posted (thanks much Don!!) the spill/fill port would get closed SOONER at low rack travel and in the VERY LAST LITTLE TINY BIT of rack travel. But if you rotated the plunger that far the spill port would only be partially uncovered when the helix finally uncovers it. It would look kind of like a crescent or sorts.



So according to what I picked up from the picture of the plunger, the timing should be advanced at low rack and EXTREMELY high rack, and retarded in the midrange.



Keep in mind that the port closure by the top of the plunger not only effects timing; it also affects the AMOUNT injected. As the plunger is first rotated to the point where it closes the spill/fill port in the groove, it is loosing some of the travel in which it creates the pressure necessary to inject fuel.



The amount of fuel injected (at any point in the plunger’s rotation) is determined in part by the distance from the top of the plunger (where the port is closed) to the helix (where the port is opened again). So when the plunger is rotated to match the port up with that groove it is not only retarding timing, but is also reducing the amount of fuel injected by the depth of that groove times the square area of the plunger. This is partially compensated by further delaying the opening of the port by the helix.



I know that was kind of off the subject, but I thought that it was necessary to bring up that it is not only TIMING that is affected by that groove, but also AMOUNT OF FUEL.



I agree with Strick-9. That groove would RETARD timing at high rack travel (except for that last little bit just before the plunger runs off the helix entirely).



I think that Don is right in that the groove was put there for emissions reasons. To retard the timing at higher power levels, not to advance it. This is a topic that HAS been hashed out. When the timing is advanced, the power goes up, the egt goes down, and the NOX GOES UP because the maximum combustion temps also go up.



That groove was put there to retard the timing to help emissions. The reason the 913 makes more power is because the helix is steeper, allowing for more injection duration.

 

[TxDieselKid]

Great thread guys, I am learning here, a 24v guys is learning.



Andrew

 

[Strick-9]

Don,



So you are willing to admit that even at the deepest portion of the helix, the fill port isn't advanced fully.



Unless your pump has been modified since we talked last, your barrels are in the stock location.



You know that mine have been rotated for maximum fueling. So at the same amount of linear rack travel, my pump uses more of the helix than yours. I also have 2 more mm of rack travel than your pump due to my custom stop plug. I still haven't ran out of helix yet. So your pump is not as high up on the slope of the advance protrusion as mine. Can we at least agree to that? My fill port is closer to the bottom of the helix than yours and also farther up the slope to more advance. That's simple enough right?



Why don't you figure out over how many degrees of plunger rotation the retarded timing occurs.



My guess is its about 45° of plunger rotation. Well, we have 80° of total plunger rotation.



If your theory of advanced timing under more rack travel is right, shouldn't the lower rack travel have the lowest timing and the upper 35° of plunger rotation have the advanced timing.



Why isn't that the case? You admitted yourself that those of us with extreme pumps are just reaching the slope to advance the timing. None of us are at the top again.



Even Joe chimmed in saying he's getting SOME of the advance.



Let's take Joe for example. If he slides his plate back does he get NONE of the advance.



What about stock trucks that don't have his enormous amount of fueling. Do they get none of the advance either.



So would their timing be advanced at idle and retarded as rack travel increases?



You're very correct about misinformation being worse than no information. That's why I'm willing to walk through this step by step.



I wish our pumps acted like you described. It would run better and stronger if the timing truly did advance with more rack travel, but it doesn't.



My question to you is, does a stock truck have advance? Take your plunger and picture where the fill port is under max fueling. Then visualize the camplate moving backward and limiting the amount of total rack travel and watch where the protrusions are.



-Chris