HOHN

I have been running larger fuel delivery than stock for about 8 years (I think it was 2003 or 04 when I on the the Wildcat Diesel kit (haha-- Wildcat Diesel!).

My pump has lasted, so it would be tempting to say that this has something to do with it.

But logically, the larger lines cannot increase lift pump life based on flow or pressure changes.

The VP44 inlet acts like a variable orifice. Under almost all conditions, the VP is the greatest restriction in the system (only when are approaching zero fuel pressure at the VP inlet is it not).

All a bigger line kit does in term of restriction is shift the balance of the VP's restriction and the line's restriction. The total restriction the LP sees is the same, it's just split differently between VP and supply plumbing. Let's say you had stock banjos and read 9psig at the VP inlet, then swap in a big line kit and read 14psi at the VP. That means there is still 14psi of restriction to flow, and (if measured under the same conditions), you can infer that the factory banjos were 5psi more restrictive.

But you will not measure any more flow through the system.

When you step on it and the pump goes WOT, it becomes a much larger effective orifice that is far less restrictive. Thus, the pressure you will read will go down even as flow is increasing. The increase in flow makes the lines proportionally more restrictive (Just as voltage drop is a function of current and resistance, so is pressure drop a function of flow and restriction). But the VP is STILL proportionally more restrictive than the plumbing is.

As long as you measure positive pressure at the VP, the VP is more restrictive than your plumbing is.

Since the restriction that the LP sees doesn't change with a larger line, it cannot affect the internal regulating ball inside the LP. You'll still have the same amount of internal recirculation of the LP (or not, depending on flow demand).


There is one way I can see that a larger line might help with LP regulator life, and that is by damping more of the pulses from the VP that tend to hammer on that little ball and spring. If it stores fuel volume (like an accumulator) it damps these pulses like a resonator in an exhaust system similarly damps pulses.

Since I have a fluid-filled mechanical guage reading right off the VP, I can tell you that the pulsing at the VP inlet is considerable.

Justin

KATOOM

Wildcat Diesel..... What happened to them?

I understand what you're saying but I think you're forgetting to consider the overflow valve and how important the role that little component plays. Even though the overflow check ball valve is spring set at 14-16 psi for maximum flow, the fuel system always remains a constant flow of fuel with only the fuel pumps capacity determining how much volume passes. Without changing the subject, the OEM lift pump simply cant pump enough volume and pressure to overcome the overflow valve in addition to the overly restrictive fuel lines, so even though the fuel system is always flowing, its just not enough fuel to properly cool the VP along with supply the engine. If the VP was the only varying factor in how much fuel flows through the system then it would certainly cook itself in no time.

Good conversation too.

rickf

I am curious to know why, in 14 years, nobody has been able to come up with a way to relocate the computer for the pump. Chevy realized the problem on the 6.5 and relocated the board in less than two years. With millions of these trucks out there I just wonder............................................ ................
When did they stop using the VP44?
Rick

KATOOM

There has been a few people who've tried to relocate the FPCM. Apparently the electrical interference were too great and caused more issues. Not sure because there wasn't much talked about on this subject. The real reason relocating the FPCM hasn't been tackled is because it would involve experimenting with your working $1000+ VP. Who wants to do that? Who has the money to throw at that? You'd hope that some aftermarket re-manufactures would have figured something out by now but I guess not.

HOHN

Are you talking about the overflow internal to the VP or the bypass inside the LP?

dkenny

I would think that moving the electronic from the heat, would be possible..
not easy..
sure its electrically noisy..so..what's the CPU freq? 200-500MHZ??
so..
if you own a cell phone the CPU most likely run faster(not the transmitter to the tower), the part the runs the apps..as in a smart phone..think 3-4X the 200-500MHZ number..my Xoom tablet is 1GHZ dual core,,fyi,,and not a phone..many android phones are this or more..

noise..or poorly made electronics? or EPA and banning LEAD?
its crazy to think that electronics cannot be made to survive long term at 200F..
sorry just crazy..

guys the ECM of out truck is mount to the engine block..don't you think this is over 200F most of the time..do we have lots of trouble with the ECM??no its the computer on the VP44..why? heat..the ECM should as hot as the VP44.. it doesn't get cooling..by fuel or air..but it lives..so..

WHY DOES THE VP44 die from heat?

so why move the electronics? they can stand the heat? doesn't the block get hotter than the fuel? thats cooling the VP44?

-dkenny

rickf

The block will not get much hotter than 200-229 degrees because it is water cooled. The VP is only cooled by the fuel running through it. When I hook up my scanner I see fuel temps around 140 degrees on a 60 degree day and at idle. I need to get the wife to drive so I can watch the other parameters closely. Problem is that with wife driving I am afraid to look down!
I will get my laser thermometer and see if the CPU is close to that temp indicated. I do not know where that fuel temp is being taken.

Rick

KATOOM

The Overflow valve on the VP.

KATOOM

The reason the FPCM (VP computer) cannot tolerate high heat is because it contains lead free solder. Over time that EPA tolerant lead free garbage solder becomes compromised and deteriorated, leading to intermittent electrical connections. Eventually the connections get so bad that the system no longer works. This situation is so common it even has a name. Every time the engine is fully warmed up the VP temp will run at about 120*-160*, depending on fuel pressure and volume. The engine is of course much hotter at about 190*-200*. The only variable cooling the VP is the excess fuel running through it so when the engine is shut down, the fuel stops and the hot engine heat soaks the VP, bringing the VP temp up to the engines temp in about 15-20 minutes. So after shutting off a fully warmed engine off, you have caused the VP to experience one "Hot Cycle". The lifespan of the VP's computer is measured in those hot cycles. No one really knows how many hot cycles it takes before the FPCM is shot but its so recognized that making sure a re-manufactured VP has a NEW computer is very important. Trouble is, Bosch still uses lead free solder. Ya have to love this environmental stuff.