Optimum fuel pressure for VP44

[PRout]

What would your choice be if you could adjust the fuel pressure to the VP44??



Maybe 12psi? 15? What are the pros & cons for running down at 10-12 vs say 15-16, or even 20-25??



*****



Edited for Moderator: This thread was for deciding what pressure to set a FASS system for, that is why its in the Products forum, but feel free to move if appropriate. Thanks.

 

[TORQUE THIS]

IMO, 12 to 15 as long as it stayed constant under all conditions.

 

[KLockliear]

The more the merrier.

 

[Wheaties]

Actually, I think I read somewhere on the TDR, that you want to keep the fuel pressure under 25psi (I don't recall exactly) or you can generate a hard start condition, and possibly blow the seals on the VP44... does anyone recall the specifics?



Matt

 

[Hohn]

Actually, for startup, you want the pressure between 5 and 10psi. After it's running, you can run as high as 20psi, no problem.



Be advised that there aren't really any advantages to FP over 20psi, so it's kind of an unnecessary risk.



Justin

 

[jtisdale]

Is it really pressure we are after here, or rather volume?

 

[Mad Bomber]

Originally posted by KLockliear

The more the merrier.

What do you mean???

 

[ToolManTimTaylor]

Anything over 28 psi can be fatal to the internal seals of the vp44.



+ the bypass can only flow so much back to the tank.

 

[Sticks]

Originally posted by jtisdale

Is it really pressure we are after here, or rather volume?

Yes

 

[Mad Bomber]

Originally posted by KLockliear

Tim, what is that information based on? How many have you had fail over that psi to determine that as fact?

Can you anwser the question. What's too much?

 

[TORQUE THIS]

Yeah, lets hear it!!

 

[Proram]

We're Waiting!!!



Pro

 

[Gary - K7GLD]

I think a lot of us form our own "rule of thumb", based on reading a fair number of threads on the subject. *I* have never seen any documented, direct from Bosch "absolutes" concerning min/max PSI to the VP-44 - but HAVE heard/read 3 *different* values offered by 3 different roving Bosch "experts"...



For MY money, I'll settle for any reliable PSI from 10-20, as measured right at the VP-44 - "proof"? I don't have any - but since it's ME who will pay for any component failures, that's where *I* stand on the subject...

 

[jtisdale]

I couldnt agree with you more Gary

 

[ToolManTimTaylor]

Whoah easy boys.

There is a thread (A few actualy) on the VP44 and fuel pressures. TqT we just talked about this friday nite. The jist of the thread took fuel pressures / flow and broke it aaalllll down for ya. and what was discovered is that the internal bypass cracks off at 14. 7 psi. when it opens fuel is sent back thru the pump for cooling purposes and to the tank.



That's great, however the orfice that the return port uses is not very large (In fact it is quite smaller than the 3/8ths fuel line in which fuel flows back to the tank) and what was found is that fuel pressures and flow hold a very close relationship when confined in a sealed system. Once you get up to the 28-30 lbs of pressure you can only stuff so much fuel thru that bypass (Even at WOT and the most insane injectors). So that relief has to go somewhere and the next weakest link is an internal seal that resides somewhere near the rotor itself Like Wheaties said before.



I tried to find a few of the threads for you but I wasn't about to sift thru 17,000 posts.



So the more is not generally the merrier in this case.

 

[TORQUE THIS]

I think we were waiting to hear from the pro...



Dosen't seem right for a vendor to post "the more the merrier" and give no technical info to back it up.

 

[Snow man]

FWIW, i have been running a pusher pump for over 45000 miles,my fuel pressure at idle with the new factory cummins pump on the block burries my 30PSI ISSPRO guage,i used to have SPA guages,and the fuel press would read 33psi at idle. I put a mechanical guage to verify it was correct,and the mechaincal guage showed 35PSI at idle. I havent had one problem with my trucks vp44 or anything else fuel related. Ive never had hard starting either. i guess that why i never(upgraded) my fuel system yet. I can suck it down to 10-11 PSI WOT on 5x5 after about 8 seconds wide open,but by then you are haulling. my truck has 91700 miles oni t,and its got the original VP44,and its worked pretty hard.

 

[Proram]

VP Fuel press.

Dosen't seem right for a vendor to post "the more the merrier" and give no technical info to back it up.

I don't know what happened to it, but Kieth had a whole post on his experiance w/ high fp and the VP , Where did it go???!!! it was here last nite.



Scott

 

[Gary - K7GLD]

I read Kieth's reply as well - his comments related to experience running as high as 60 PSI into the VP-44 with no problems - I've read about that before. I suppose Keith removed the post for some reason of his own - it was well worded, and not the least bit offensive...

 

[KLockliear]

I removed it because upon re-read, it came off as condescending to me.



The basics were that we have installed 12v mechanical lift pumps on several trucks that we have installed cams in, and the pressure runs as high as 55-58psi to the VP44. No failures or problems reported and the drivers indicate better throttle response with the extra pressure.



4 trucks is a small cross section based against how many trucks are out there, but 4 out of 4 not having problems is a pretty good indication to me that it's not an issue.