VE Pump

[dzlpwr]

Hey guys just got my account set up to finally submit some information that may be helpful. I have been a long time reader

but this is the first time I have had a chance to reply. I don't want to come on as a "know it all" but I feel that some of the recent posts have misinformed you guys and I would like to try and correct you on some specifics of the VE pump. I work in a fuel injection shop on various models of injection pumps, injectors, and turbos. One of them being the Bosch VE (Zexel) pump.

Some recent posts have been about a "modified" fuel pin. I think that you guys are wasting a lot of your time and money trying to make your own pins and what not. The stock fuel pin will allow the pump to come into full fuel at a point about half way down the pin on the shallow side. When we adjust the anaroid on the calibration stand we start at 0 boost with the pin in the stock position and tighten the spring until we have about half of the rated fuel output at full throttle. We then add 10 psi of boost and this is where we would like full fuel to come on by. Turning down the screw or grinding the pin will not allow the pump to gain more fueling. This only controls smoke at little or no boost. The only way to add more fuel is by turning the full load screw which is a very sensitive process without a calibration stand.

Another post I read was about "3K governer springs". The factory spring in your will allow your pump to rev up to around 3500 rpm before it defuels already. By adding a stiffer spring to raise your defueling point you may jeopardize your idling characteristics. Also, to clear up any questions regarding defueling, your pump does not have a defueling curve or anything like that. When your pump reaches the point in which the rpm is set to stop rising, (rev limit)the fuel flow will suddenly stop and then be adjusted to hold the rpm depending upon load on the engine. By raising your rpm you are essentially allowing the same amount of fuel (set by your full load screw) to be added until it hits a higher rpm (set by your high idle screw) and thats when the fuel flow is cut off. Just remember that adding fuel raises rpm and stopping fuel will slow rpm. The governer spring and governer weights work together to hold rpm by adding fuel when the engine slows and stopping fuel when the engine speeds up. A different governer spring will do nothing to help your defueling except allow you to delay it until a higher or lower rpm depending on the strength of the spring.

I would be happy to explain any part of these pumps or anything that has to do with fuel systems on your trucks if you have any questions. After all, I am only on here to help you guys otherwise I would have kept my $35.

 

[dpuckett]

rebuttal to AFC pin point

Dzlpwr,



I am by no means trying to refute your experience or the processes in the shop flowing pumps. I have however, noticed that I can gain 5-7 psi simply by turning the diaphragm so the pin goes from the minimum to maximum side of the pin, leaving everything else the same. I currently have my pin set to the "deeper" side, because I tow a considerable amount of weight. I would like a pin with the same depth travel on the deeper side, and yet have the low boost smoke control. I have my AFC wheel up 6-1/2 turns from the bottom, and the full power screw in 1 turn above stock. If I start in second gear, there is a considerable cloud of smoke, and it smokes up to about 10 psi boost. I realize some injectors may help, (mine are now stock with 10K on a clean and recalibrate), but I would still like to lower my bottom end smoke, yet keep my mid and upper range.



BTW, thanks for your point of view. It is good to have someone else with some real world knowledge of the workings of the VE pumps. I got to thinking about the GSK, and got to thinking about the 4 cylinder/5200rpm, vs 6 cylinder/ 3000 rpm. @5200, the 4 cylinder plunger is moving 20800 times per minute; @ 3000, the 6 cylinder is moving 18000 times. consider also the differences between the cubic millimeters per stroke of the VW and Cummins.



Now one last question- doesnt the AFC pin work in a similar way to a torque plate on a P7100? that is the impression I was under from reading the magazine issue on the evolution of the B series fuel systtem. If so, the new AFC pins a few guys are working on may not increase max fueling, but rather change the curve of boost vs fuel. As always, I stand for correction or clarification on my ramblings.



Daniel

 

[dzlpwr]

dpuckett,



I am not quite sure what you mean by the 5200 rpm spring used in the VW pumps. The pumps are relativly the same except the VW pump is missing two ports. The VW pump essentially uses the same spring as our pumps do. Interchanging these springs will not have any effect on raising rpm's significantly. Even if they made a spring that would allow you to run 5200 rpms, what would be the point in it if you only want to run lets say 3500 or so at the most. The stock spring will do that. If you wanted to run it that fast you would be better off removing governer weights .

No, the AFC pin is in no way similar to a torque plate. All the AFC does is limits the amount of fuel you can inject into the cylinder before you have enough air to burn the fuel properly. Lets say that you have 65cc per 1000 strokes available. The AFC will only let you have 32 cc at zero boost when you hit the pedal. Then as you gain boost, it will add a little more. At approx. 10 psi it will allow you to have all 65cc. By turning the pin to a deeper side you are just allowing the fuel to come on a little faster. Then you will have lets say 45 cc at zero boost and all 65cc by 7 psi boost. A torque plate controls rack position at a given rpm and not boost. Keep in mind that a P7100 pump also has an AFC. At zero boost, it doesn't matter what kind of torque plate you have it will not let you have any more fuel depending on whatever position the pin is in. As you gain rpm, the "feeler" will follow the contours of the torque plate and the deeper the cut, the further the rack will go. But, the AFC has control over fueling before the torque plate does.

It is however possible that your guide pin (the needle that follows your AFC pin) was gummed up partially and it freed itself.

 

[Old Smoky]

dzlpwr,

I think I follow you, but don't completely understand. A while back I found that turning the diaphragm so that the guide pin would ride to the deepest point on the control cone would increase boost pressure. About four months ago I ground my control cone on the upper end to allow for more guide pin travel. I found that I gained another 3psi over the previous "maximum" setting. I am seeing this as increased fueling. I have been working on several new designs that keep low boost fueling down, while allowing what I call "full guide pin travel. " If the AFC allows full fuel why is it that by turning the factory control cone, or installing a custom control cone, boost pressure rises? Isn't that more fuel being delivered to the cylinders causing more expansion spinning the turbo faster? Why is it a waste of time and money to do this if it nets more power? I have a lot of time and some money involved in this R&D, and would like to know why it is not worth continuing.



Concerning the 3000rpm govern spring - With my "defueling point" set at 2950-3000rpm with the high idle screw, I can see the boost start to slowly fall off before then, around 2500rpm or so. This is consistent with my last dyno sheet that showed my max hp at 2420rpm. It will still pull up to the governor fairly strong, but slows about 2420 rpm when the boost starts to drop. So, don't I actually start to defuel there, and not at 3000rpm? Some who have experimented with the 3000rpm governor spring have reported great results. These being better low-end response, stronger acceleration up to 3000rpm, and no negative results. This spring seems to be a performance improvement over the stock spring. I know that the P7100 is a different animal than the VE, but there are also some similarities, such as the high idle screw and governor spring. I have never heard of anyone adjusting the high idle screw on a P7100 pump, they all install different springs. Why would it be a good idea to do it on their pump, and not ours?



Like dpuckett said, "I am by no means trying to refute your experience or the processes in the shop flowing pumps," but would like to better understand what you are saying and what going on inside the VE pump. Thank you for you contribution to our site.



Mike

 

[HFletcher]

Mike, I recall that you once posted that you had put grease on the control cone so the "guide pin" would leave a "witness mark" and show how far up the cone it traveled. How far up the cone did it travel? Thanks, Henry

 

[HFletcher]

Hi dzlpwr, welcome aboard!! I too have noticed an abrupt decrease of several pounds of boost at about 2450 rpm's, despite the fact my high idle screw is lost. And I, too, was hoping that a governor spring change would remedy that. Are you certain it won't? Thanks, Henry

 

[dzlpwr]

I will continue the discussion tommarro afternoon when I get off work but I am starting to think that maybe we should throw some of these different styles of pins and governor springs in a pump on a test stand and see just what the differences really are. If any of you are interested in sending me some of these various items I would be more than happy to try them out in a true test and possibly video tape the whole procedure so that you can see for yourselves whats really happening. I am just as interested as you are about all of this and would like to use the specific items that you are talking about. Just let me know what you think and maybe we can work something out. If we did videotape, it would be a good chance for you to personally see what all is really happening when you modify these pumps.

 

[Old Smoky]

Good point Henry, I forgot to mention that. The control cone has a total travel of approximately 0. 485”. The measurements I have in front of me where the first ones taken, and may not be 100% accurate. In its stock form the control cone will not travel that far. The nylon washer on the control cone shaft can also be modified to increase boost (I don’t know what to call it if it doesn’t increase fueling). If the washer is completely removed with an unmodified control cone, the control cone shaft will travel too far down and the guide pin will be forced back in at the top of the cone. With a modified cone the washer can be removed and the guide pin will not be forced back in.



Dzlpwr,

Its not that we don’t believe you, it’s just that this new found information is a complete 180 of what was thought to be true, at least by me. We are all out to learn more, and want to be sue we have got the facts straight. Thanks man. Also, welcome aboard.



Mike

 

[BushWakr - RIP]

Dzlpwr,



First off, WELCOME !!! Always glad to have a new member to the group and the thoughts, info, and experience that comes with it. .



I am going to keep my mouth shut a bit, and try to learn something here. I also, wondered about the apparent connections between cone setting and boost discrepancy; overall guide pin travel (extension) and performance; and last but not least, the apparent relationship of defuel point to max RPM. I was thinking as mentioned that the defuel point did not move upward in conjunction with the high idle or WOT RPM when using the high idle adjustment method, but that it WOULD follow along in the correct proportions using the governor spring.

The one thing I had not worked thru is the downstream problems (if any) of replacing the spring only. Things like your start lever/start spring, etc etc. would then be responding to the different spring tension/rate.



I look forward to your thoughts on this and the other questions, it looks like we're gonna have to put our thinking caps on guys...



bob.

 

[dzlpwr]

I think I am starting to see what you guys really want to do with these governer springs and what not. At first i thought you wanted to change them out to gain more overall fueling but I have realized that you just want to hold a steady fueling all the way up to rated rpm instead of having the slow drop off. A different (stiffer) spring will allow you to do this but it WILL NOT give you more overall fuel. The reason is because a weaker spring has a longer reaction time than a stiffer one does. As far as using the springs from a VW model pump, this cannont be done. At least not on the earlier ones b/c they have a three peice governer spring. Springs from higher rpm models that were designed for use on high horsepower marine Cummins engines would probably work. Your idle characteristics may be affected though, due to the fact that fuel output may not be consistant between cylinders.

I checked the Bosch spec and product guide and found a couple different spring numbers available for our pumps with a higher rated horsepower. We also have a large variety of AFC pins in stock that have different contours on them. Within the next few days the service manager and I are going to try some of these different springs and/or pins out in a core pump on the test stand. By doing this we can find out what does work and what does not. My service manager is also going to grind a pin so that full travel can be obtained at the top portion of the cone so that we can see if full fuel comes into effect by then. It could be possible that some of you recieved the wrong AFC pins in your pumps and this is why you are seeing such increases in fueling. Most of the pumps that we deal with are pumps that are set for stock fuel delivery and we have never encountered a situation where more fuel can be obtained by modifiying the AFC pin. I hope this simple test will help clear a few things up for us now that all the guys in the shop are curious.

I will keep you posted on the outcome of these different springs and pins as soon as we try them out in the next couple days.

In response to Old Smokey, the VE pump and P7100 pumps have a completely different governor spring setup. The VE pump has one spring attached between the throttle shaft and the metering sleeve lever. If the force of the throttle lever placed on the metering sleeve via a spring exceeds the force of the governer weights in the opposite direction, more fuel is added. Fuel is decreased in the same way but vice versa. The high idle screw allows you to make adjustments so that the throttle lever can move further which places more force on the spring to raise your rpm. In a P7100 pump the governor springs are inside of the flyweights. Set screws on each one of them allows you to stiffen them in order to raise your high idle. An external adjustment is also provided but only for fine tuning on a test stand. The reason people replace the governor springs on these is b/c you have limited adjustment with the stock ones. By using a stiffer spring you give yourself more adjustment with the set screws.

 

[Old Smoky]

It’s interesting that you have never encountered a situation where more fuel can be obtained by modifying the AFC. I am curious to see how the tests turn out. If you need a modified pin let me know. I am aware of the different governor spring setups. Just trying to understand why changing the VE spring wouldn't be a good idea. Hopefully the test will answer our questions. Thanks for taking the time to answer questions and look deeper into this. This stuff sure is interesting.



Mike