so I hear mention that the HO is more difficult (?) to upgrade... or maybe more expensive... can someone explain exactly what the differences are and what makes the SO a better candidate for upgrades?

 

From what I have read around the boards I have gathered this:

I think if you put a box on an HO and an SO you will end up with the same amount of power. But, the SO will gain more power to get to that HP level because the HO doesn't have to gain as much to get there. Does that make sense?

The previous may have been a total waste of bandwidth so if I am copmletely wrong then somebody please correct me.

Joey

 

I believe that the HO version has a 17:1 compression ratio, and the SO is 16.3:1. I have also heard that the SO are more easily upgradable than the HO, however I do not understand why. The only other difference that I think is the Turbo is silghtly different, and different computer programming for more power. If someone else knows more speakup so we all can learn.

 

The stock HO has smaller injectors and a higher pressure injector pump than the SO.

 

Aswell as compression differences the SO has a 7.5 mm Plunger on the vp-44 where the HO has a 7.0 mm. The HO makes 15% more power with injectors up to about the 150-175 HP mark( higher hp injectors can be run with a HRVP44) , where as the SO can run much higher HP injectors do to the bigger plunger.

 

I'm not sure I follow here... can you explain?

 

The SO vp44 is capable of more fuel flow due to its larger internal fueling capablitites. So if you had the SO you could run 155 horse injectors with no fueling problems. If you had the high output vp44 it will stumble at higher rpms because it cant deliver enough fuel. It doesnt make sence I know but the high output has increased horse power by the increased compression. It may have been done to protect the engine somehow who knows, but thats the way it is. The HRVP44 is the exception though. Shiede diesel makes those I think. Hope this helps

 

what i did was take the HO pump off my truck in favor of the SO pump for more fuel delivery. it really helped powerwise and doesn't studder/stumble at mid to WOT anymore with the injectors i have.

 

if i had my VP-44 replaced by the dealer under warranty, would they most likely have gotten an HO pump for it by ordering using the VIN? or is it possible the dealer didnt care that it was HO and just put a SO pump on the truck?

 

You would not get a SO pump or better known as a rev 027, the HO pump is a rev 028 and the FED EX pump is a rev 029. The HO ECM will not cummunicate with a SO PSG. The HRVP will communicate with either ECM. Actually it would be nice if you could just get a SO pump and bolt it up, unfortunalty you would also need to change the ECM.
As far as fueling boxes on a HO no matter who's box you put on 90 hp is all you will gain, where as an SO will utilize 140-160hp, depending on who's box you use. The compression is different between the 2, and timing is a set different between the two.

 

found this link in another thread... pretty much sums up all the answers to this thread.

http://www.dodgeram.org/tech/dsl/Facts/01ISBspecs.html

 

How? what else did you change to make it work?

 

Please inlighten me also, I have yet to be able to bolt on a ETC pump onto an ETH unless you find a ECM that will comunicate with the pump.
Only one place that I am aware of that has figured it out is Industrial Injection with the PSG they use in their HRVP, but then again that is not a SO or HO pump is it?

 

There are a few other differences between the SO, HO, and the mid range vp44
The SO and Midrange pumps share the all the same parts these days however the programing in the psg is a lot different. Not so long ago the were different psg part numbers for the different pumps.
The HO pumps share most of the same parts except with two major differences. The camring and the hydraulic heads. Timing in the pump is a little different and the plungers are smaller than the SO.
The midrange engine uses the same pump on all the different hp engines. Here the ecm and injector flow make the difference.
All rebuilt pumps get the same psg part number now days (AKA fedex psg) if it is rebuilt by a bosch pump shop. No matter who's shop it is.