Had an interesting phone conversation with the owner of TST products today about the so vp44 fuel pump.

He was a Cummins employee and has worked on and has had access to testing the vp44 and prior fuel pumps.

He said that the high pressure side of the internal vane pump produces around 300 psi at 2200 rpm engine speed, and that the actual injection is done by a piston that creates the high pressure pulse and also directs it to the correct injector. This piston not only pushes the fuel to the injector but also rotates or spins to line up with the correct injector port in the VP44. He said that many of the pump failures are attributed to the piston ceasing from lack of adequate lubrication.

He also said that when the HP is pushed to high levels by programmers and oversize injectors (100 hp and up) or stacking programmers with the larger injectors, this piston can suffer from an inadequate fuel supply being able to fill the piston for every time it fires the injector(s). This can cause the power to come and go in quick spurts under heavy loading and higher rpms, even with the FASS or airdog pumps of 100 gpm flow. It's not about the fuel to the vp44 this he said can happen with 15+ psi at the vp44 fuel inlet.

He said that the hot-rod pumps that are built have different parts from Bosch that have a larger piston with more capacity, and that they no longer build them.

He also said that when a vp44 is rebuilt that the pump does not have to be put on a test bench and programmed, that the parts are all connected to the electronics and programmed when they get them from Bosch. They have even taken the internals from one pump and put them into another with no reprogramming as long as the electronics are not taken apart and reassembled. It's like taking non volatile memory out of a computer and putting it back into another computer of the same configuration.

So my question is how much hp have people been able to get from the stock so vp44 with injectors and stacked programmers without having apparent fuel starvation?

Thanks

Jim

Had an interesting phone conversation with the owner of TST products today about the so vp44 fuel pump.

He was a Cummins employee and has worked on and has had access to testing the vp44 and prior fuel pumps.

He said that the high pressure side of the internal vane pump produces around 300 psi at 2200 rpm engine speed, and that the actual injection is done by a piston that creates the high pressure pulse and also directs it to the correct injector. This piston not only pushes the fuel to the injector but also rotates or spins to line up with the correct injector port in the VP44. He said that many of the pump failures are attributed to the piston ceasing from lack of adequate lubrication.

He also said that when the HP is pushed to high levels by programmers and oversize injectors (100 hp and up) or stacking programmers with the larger injectors, this piston can suffer from an inadequate fuel supply being able to fill the piston for every time it fires the injector(s). This can cause the power to come and go in quick spurts under heavy loading and higher rpms, even with the FASS or airdog pumps of 100 gpm flow. It's not about the fuel to the vp44 this he said can happen with 15+ psi at the vp44 fuel inlet.

He said that the hot-rod pumps that are built have different parts from Bosch that have a larger piston with more capacity, and that they no longer build them.

He also said that when a vp44 is rebuilt that the pump does not have to be put on a test bench and programmed, that the parts are all connected to the electronics and programmed when they get them from Bosch. They have even taken the internals from one pump and put them into another with no reprogramming as long as the electronics are not taken apart and reassembled. It's like taking non volatile memory out of a computer and putting it back into another computer of the same configuration.

Interesting... I was always told that every VP44 has to be calibrated on a test bench before release for use... So what your say is if we could get our hands on a rebuild kit we could rebuild our own VP44's???

So my question is how much hp have people been able to get from the stock so vp44 with injectors and stacked programmers without having apparent fuel starvation?

Thanks

Jim

As for your question... I would say around 450-500 HP... Most people say they can't get a vP44 over 550-600 HP without serious changes somewhere or using drugs. So I would have to safely say about 450-500 HP...

Interesting... I was always told that every VP44 has to be calibrated on a test bench before release for use... So what your say is if we could get our hands on a rebuild kit we could rebuild our own VP44's???

As for your question... I would say around 450-500 HP... Most people say they can't get a vP44 over 550-600 HP without serious changes somewhere or using drugs. So I would have to safely say about 450-500 HP...

Yes, if what he told me is true, and my gut feel is that it is true, we could be rebuilding the VP44s ourselves if we could get the parts. (and had any special tools needed, as well as a road map of what bad things to look for)

Jim

I've been looking for a service manual for Bosch fuel injection pumps for a very long time now... It must be one of the toughest documents to hunt for... But as for rebuilding a VP44 that would be a awesome job to do...

the hot rod pumps are not calibrated after the internals are swapped as they would fail the test for too much fueling and the calibration would stop. So they use a pump that is ready and put some of the HO internals in it.

I can tell you there are many many many so pumps putting down well over 600 fuel only hp out there.

I can tell you there are many many many so pumps putting down well over 600 fuel only hp out there.

Yes sir !

this makes me think of blue chip's redline box...

This means we can guarantee to empty the rotor for each and every injection event, and therefore deliver all the fuel available to the injector.

i wonder how the pump feels about that

this makes me think of blue chip's redline box...

i wonder how the pump feels about that

Dry and rough... (I just had too)

The reason I started this thread is because, with what I have on my truck (see sig), it was cutting out and coming back quite violently when using any PowerMax setting over 4 with the smarty on anything above stock. So I was thinking that they didn't play well together. As a result I called TST and had the discussion (first post) and was told that it's possible the plumger was running out of fuel. I had already checked everything else out.

Well, I started on my trip to Montana with about 8K in tow. I kept the PM turned off as it seemed to cause some problems. Leaving TOK Alaska (about 350 miles into the trip) I got the bright idea to try the PM one more time as all other problems had gone away (including the stalling when shifting into drive - I now believe that was caused by winter fuel). I turned on the PM and set it on 3 then started to give it a little fuel. As soon as the box started over fueling the pump (green light on the box came on) there was a loud BANG from under the hood and the truck died. I coasted to the side of the road and tried to restart, nothing, tried again, nothing. Turned the key off for several minutes wondering what to do next. I tries another restart, it stumbled a couple of revolutions and started. It seemed to run perfectly, and has so far into the trip, and i'm in FT StJohn 1200 miles down the road from then.

The PM has I've discovered quite literally lost it's mind. the displays of EGT and boost are erratic to say the least.

At least I can somewhat monitor the boost with the SG II MAP reading.

I'll let you know what and when I can.

Jim

There is a couple of trucks in my town that are putting 550- 600 horses to the ground on fuel only.

I'm now certain that the PowerMax went out.

The display will not give accurate readings for boost and EGT. At times it will shut off altogether then come back on and work for five minutes or so then go way off again. I've checked and double checked all the connections in the harness to no avail.

Anyway I've made it to my destination in Montana, 2,400 miles of it (since the big BANG) without the PowerMax turned on and the truck is running fine. It just don't have the power I normally have with the PowerMax so I'm shifting out of OD a lot more than I usually do.

When I get back home I'm going to make some changes to the truck setup.

Before I left I put on a HX35/40 with a 14 CM2 exhaust housing. I'm finding it way to slow to spool and smokes like crazy when the engine rpm's are below 1500. so I'm going to put on the 12 CM2 housing and see how it works.

I also think that I'm going to replace the edge +80 stage II injectors with 275s to try and get back some of the lost mileage. I'm averaging about (haven't done the hand calcs yet) about 13-14 with the 8K load. That's down about 1.5 2 mpg from the trip last fall. Heck when I pulled the 17k trailer on one trip I was getting 12.5 mpg with the stock injectors and just the PowerMax when it was working, and I drove faster.

So I'm thinking that the +80 injectors and the smarty tuner and the HX35/40 are giving less mileage and less overall performance than the stock injectors with the HX35 and 14 CM2 housing and the smarty.

With the PowerMax (that works) I have the economy of the closer to stock setup but can add the power when I want it. It's more the best of both worlds for towing. Guess I'll find out for sure when I get back to Alaska and make the changes.

My setup is similar to yours. I have 90hp injectors and I have been thinking of getting 50's and a new turbo. My tcc is set at 1600 so my biggest fear is getting a slow spooling turbo. I tow heavy most of the time so I am interested in how your 12cm 35/40 works out. I think that might be the best turbo for me too.