Hot Rod vs. Stock VP44 - What's the difference?

[R-N-R]

I received an interesting message from a knowledgeable business that repairs pumps, which prompted me to ask about this. What is the difference between Hot Rod and Stock versions of the VP44. I am not looking for trade secrets here, but hopefully somebody will know at least in general terms where these configurations differ.

There is one thing in your E-mail that alarms me, when you said you're getting a modified pump (VP44), beware, there is no such thing, because of the software it takes to calibrate the injection pump. The program on the test bench will fail the pump. All you have to do is ask for the test data to prove this point from your vender, on the test sheet, it should read Verification Result OK, Pump Comparison OK, and Stat of Del. OK. You cannot alter the test spec. , the test bench won't let you calibrate pump.

Although I have absolutely no reservations about the product and where I ordered it from, I am simply curious. There is plenty of positive SOP feedback in the archives, but what the enhancements consist of seems to be a guarded secret



TIA,

Bill

 

[Beast2B]

Ditto, been wondering this myself. Higher precision parts, more efficiency in operations, ??

 

[Gary - K7GLD]

Good luck getting an informed reply to that question!



Even tho' several weak/failure points have been CLEARLY identified in the VP-44, and there are SEVERAL outfits "performance upgrading" them, NO ONE will step up and tell exactly WHAT is done inside the pumps to "improve" them. Upgraded preformance is OK, but without other serious REAL improvements and upgrades that ELIMINATES known weakness, the mere performance improvements ALONE is a waste of time and $$$...

 

[R-N-R]

One repair/exchange company shared that their pump has the

latest Diaphram (Steel) and Adv piston and housing in them. This seems like an upgrade to the factory stock "weakness" at least of some portion, but I do not expect these improvements will increase power to the extent that is evident by TDR feedback on modified pumps, the "Hot Rod" pump builders must be doing something to them... In absense of qualified information, would anyone care to speculate?

 

[Gary - K7GLD]

I suppose another approach as to whether the "hotrod" pumps also include reliability upgrades, would be a poll to see how many of THEM have failed - but unfortunately, the guys buying those pumps probably are not "typical" users, so data would be pretty questionable...

 

[Straight6Jeff]

Dyno comparrison between stock and Modded pump. same engine, same day.



For me I'm seriously considering the p7100 conversion if my next pump fails in another 30k

 

[mjoppie]

thats what i would look into if i had the vp44, a p-pump conversion. there hasnt been a lot of talk lately about the hotrod vp pump, kinda like it died off. im sure that theres a lot of info out there about it but getting it will probably consist of signing your first born over are we lookin for some good dyno numbers at the next get to gather????



but take into consideration that not all pump shops are that in depth with performance, i had a local shop tell me that it was impossible to get a p7100 to flow 800cc of fuel piers does it all the time. just some ideas.





matt

 

[Hohn]

From what I understand, a HR VP is just a hybrid of sorts between the -28 HO pumps and the -27 SO pumps.



The HO has smaller plungers (7mm vs 7. 5mm) but a more aggressive cam ring (higher discharge pressure, and/or faster discharge rate).



So, all they do is mate the SO plungers to the HO cam ring and top end.



It's basically just an HO pump with the fuel capacity of an SO pump.



Or so I have read...



jlh

 

[paulb]

From what I understand, a HR VP is just a hybrid of sorts between the -28 HO pumps and the -27 SO pumps.



The HO has smaller plungers (7mm vs 7. 5mm) but a more aggressive cam ring (higher discharge pressure, and/or faster discharge rate).



So, all they do is mate the SO plungers to the HO cam ring and top end.



It's basically just an HO pump with the fuel capacity of an SO pump.



Or so I have read...



jlh

That's in line with what I know as well...



Paul

 

[Gary - K7GLD]

"The HO has smaller plungers (7mm vs 7. 5mm) but a more aggressive cam ring (higher discharge pressure, and/or faster discharge rate).



So, all they do is mate the SO plungers to the HO cam ring and top end".



HMMmm - if true, and NO reliability mods are included to comphensate, the net effect is working an already highly stressed pump even HARDER than the stock ones... .



NO sale for me, thank you...

 

[tractorface]

love mine

Got mine from Piers, not sure who built it or what was done but the truck is noticeably stronger than stock. I run stock injectors and an EZ ripoff. Anyone in the area wants to drive it an make a report PM me.

 

[tractorface]

Food for thought

Assuming the HR pump is a Hy-brid which is what I believe, Is it less worked than say a stock pump with a wire tap box like the comp. ?



Not sure but seems to me the pump should be more within its limits as a Hybrid than with a wire tap. I could be wrong and I will post as soon as I know

 

[Gary - K7GLD]

"Not sure but seems to me the pump should be more within its limits as a Hybrid than with a wire tap. "



UMmmm - Pretty much Apples/oranges, since that isn't the basis under discussion - whether or not the wire piercing is more or less dangerous or stressful than placing more load on the VP-44 drive cam hasn't really been the issue...



But personally, *I* can't see why a respectable pump rebuilder would ignore some of the known mechanical weaknesses inside the VP-44, and instead focus purely on adding more stress due to more aggressive cam profile combined with higher fuel volume. It's much like increasing the compression, bore and stroke on an engine KNOWN to have a weak crankshaft - why not ALSO install a stronger crank while doing the other mods...

 

[KLockliear]

why not ALSO install a stronger crank while doing the other mods...

Tolerances.

 

[R-N-R]

Justin brings the spike and Keith provides the sledgehammer!



I found 18 dealers for VPs, only two of which advertise the Hot Rod pump. I'll bet that several more will provide a modified pump if you discuss it with them. I expect that a varying amount of effort is applied to each vendor's rebuild in general. Fortunately, there are qualified people here willing to share their recommendation, information, and expertise! Thank you all, I appreciate the info and discussion.

 

[832]

I thought piers quit selling the HR VP-44 because of failures occuring? Also somebody brought up in another thread that there is somebody that is about to release a bad *** VP sometime soon.

 

[Gary - K7GLD]

"Quote:

Originally Posted by Gary - K7GLD

why not ALSO install a stronger crank while doing the other mods...



========



Tolerances.

__________________



And WHY would merely providing BETTER and stronger materials in known weak and failure prone areas affect tolerances? I'm not (necessarily) talking about BIGGER components, just ones made of better stuff!

 

[R-N-R]

I do not know why Piers stopped selling the HR version, but it seems that this came about shortly after a discrepency with a customer concerning warranty expectations.

 

[tractorface]

From my short conversation with Piers when I bought mine, I gathered that I got one of the last ones they had in inventory and they were no longer advertising or selling them. I asked a few questions and was told that the couple problems were on trucks with stacked boxes. Sounded to me like Piers supplier was not backing up the warranty on pumps with damage from this type of abuse. If I was Piers I would have made the same choice. Why sell something someone is going to bad mouth you over even if you warn them first, not worth the headache. I assured them I was aware of the gamble and would act accordingly. With that said, I am not sure I agree with Gary at all. May regret that later but... ... ... ... . We all like to speculate on this and that but it seems the inner workings of the magic VP are only understood by a few and they are too busy repairing them to share :-laf

My personal choice is to NOT use a wire tapping box as I speculate that will let the pump exceed its duty cycle to the point of possible failure. I keep a real good flow of life giving fuel to mine and hope for the best. When you have a 53 the idea of a VP takin a dirt nap ain't so bad.

 

[Gary - K7GLD]

As I recall the Piers issue, a customer had a Piers pump fail due to the electronic circuit board that's part of the pump - that part apparently can't be ordered separately from Bosch, and if it fails, the entire pump has to be replaced. The customer was understandably upset over the failure after spending all that $$$, and Piers wasn't too keen on replacing the pump or refunding that $$$, when the circuit board wasn't part of the upgrades he provides.



After that, and realizing there ARE other failure points in a VP-44 other than the purely mechanical ones, enthusiasm for rebuild or "upgraded" pumps seems to have cooled a bit...



May be minor deviations on the above info - but that is my recollection...