theres been a ton of debate on this. according to bosh 24 is ok, but it will change the pump calibration. the max they list is within the pump spec. I noticed when I put mine in at wot I had noticeable smoke and I never had before on the top end, and it felt stronger. the only problem I did have was holley pumps leaking at the base plate. once I bypasses the stock pump this never happened again, I think it was trying to bypass to much fuel internally

 

Really?????? That shows how much you understand.

 

just because you have 1psi doesnt mean your properly cooling and lubricating the IP Bosch says no less than 5psi for a reason

 

o1 ramber,
I'm sorry I wasn't clearer..the wires are in parallel not the fuel flow..the flow is in series.

at the moment I'm down to 21psi at idle cold. don't know about WOT but would guess that is 13or 14psi.

pressure is a dual edge..too high bad..too low bad..but its takes pressure to get flow. no pressure no flow. low pressure might mean low flow, but high pressure doesn't mean high flow either..so some where there is a balance. from I gather its from 10-20psi.. or am I way off..if I am please let me know..

-dkenny

 

If there is pressure there....that means some is returning to tank ?? Or the pump is not sucking, so from a hydraulic equation there is more there then being used. For safety...1 lb would be marginal .

 

thumber549,

well put..
I just think that 10psi WOT would provide a better margin at 1PSi.
of course too much pressure can/will cause problems..i want to avoid those as well.. so what's best..10-20psi? 5- 15psi?

at the moment i remove a couple of turns on my spring..now i have 21psi cold( B75 blend)..so this is ok for now. I might have to remove a turn or 2 more...
I'd like to see a max of 20 psi.. and a WOT of 10PSI. both with a new filter
thanks for all the comments

-dkenny

 

Yes 1 psi at wot is getting marginal. Point is the vp44 will not get hurt as long as there is always positive pressure. To many myths and mis-conceptions.

 

Where does it say that?

 

dkenny, If it makes you feel any better, I run the same setup as you. 27psi at idle going on three years without a hiccup.

 

I've ran for a year now 22-23psi at idle, runs fine, no leaks.

 

I have run mine for years at 40psi idle, nothing less than 37psi ever.

As far as minimum pressures, pressure is a measurement against restriction or resistance. So, just any positive pressure is not exactly an accurate way to look at these systems. It takes more than 1 psi to bridge the fitting in the pump, let alone provide the volume to completely fill the rotor at high rpm. Too many VPs have bee lost at 5 psi to debate this issue.

Obviously, running two low pressure pumps in series will always greatly increase pressure. I am far less worried about the max pressures you are seeing with your setup than the possibility of hard starts. This is especially the case when hot.

For pumps wired in series, I recommend the rear pump come on first to start the truck. A simple hobbs or low pressure switch can be run to the oil pressure port to trigger a relay for the second pump. This allows for about 10psi to start on and full pressure as soon as you get oil pressure.

This setup works and is very simple to wire.

The other options are listed of course, and they are what I prefer. A single pump leaves me with one less question in the event of a failure. But that's just me.

Dave

 

I've been in the 22-24 pound range at idle for 140,000 miles on the same VP44 and Airdog. And it only pulls down about 2 psi at full throttle but I have everything upgraded from a 5/8's standpipe all the way to the VP.

 

I need to get on the dyno and do some checking at various pressures I guess. I swore I read on some forums somewhere where Don M. was saying they got maximum power at 30 psi. I split the difference and went with 24 several years ago and have been there ever since. I'm wired through the ecm so the airdog pressurizes and shuts off for starting just like the factory lift pump so I have no hard start issues.

 

Here's how I see it. The chart above is MINIMUM pressures. The VP-44 bypass occurs at 14psi. To me, this means that 14psi at WOT is providing the maximum flow-through and lubrication of the pump at all times. Taking into account the pressure drop across the fuel filter I calibrate my LP to give me 14psi at WOT which equates to about 20psi at idle. As the fuel filter fills with particulates the pressure differential increases. At a minimum one would want to see some positive pressure at the VP with a comfortable cushion. Boosting the fuel pressure above 24-25 psi may work fine, but it also may cause leaks from the plastic parts of the fuel filter canister. As long as you have 14psi to the VP-44 it will be getting the maximum flow. Above that at the VP and you are bypassing and possibly overloading the pump bypass feature. Just my 18 cents worth....

 

Well.on the other side of the coin, 25 lbs is not squat in a 3/8 line or what ever your smallest port is.......not a challenge for the human finger or a check valve..(of any quality.)
There are fuel injectors that have a lot of plastic in them on them they hold 60 lbs EZ
Most idiot switches (prone to leak after awhile ) Have plastic between the 2 parts that mold them together.( oil Pressure SW for example )
If the VP cant Handel a measly 25 lbs. ...it is a PC of crap.
Well I guess we all know that anyway ?