IP pressures

[seeker1056]

what is the approximate pressure leaving the IP pump return line and what is the pressure in the injector return line?

thanx
Ken

[KTA]

Approx 0 psi. They are open returns to the tank.

[seeker1056]

Hi Brian

Help me out here please

If the second fuel pump line is being T'd into the hollow bolt on the fuel overflow, then how does a one way valve need to be involved when there is zero pressure
Wouldnt one just need the 70 psi +/- that the pump supplies

or have I misunderstood where the second feed line is attached ?

I am just starting into the fuel system, and building a new IP pump so would like to get it right the first time if possible as funds for R&D are slim right now and pulling season will soon be here

thanks
Ken

[KTA]

I will try to describe this as best as possible without pictures. In my setup there is a t fitting screwed into the pump where the standard fuel return line goes on with the special banjo bolt. This t fitting essentially adds 1.5" to the pump hosuing, then the standard return line and special T fitting is re-attached. Now the only diffrence with this setup from stock is there is now a port open to the VE case pressure chamber via the return. I placed a check valve coming off this port in reverse from a standard feeding chack valve. In this manner if there was no hose hooked to the additional port the check valve prevents fuel from getting out through the port and the pump functions as stock. The 2nd feed line is then fed into the check valve. As long as the pressure in the case is greater than the pressure in the feed line there is no fuel flow. If pressure in the case drops below line pressure then the check valve will open and allow fuel to enter the pump via the return port.

[seeker1056]

Hi Brian
Thanx for the description - I had thought i understood what you had done and I think I was spot on from your description.

Therein lies my confusion and the original question of return line pressures

If there is no pressure to speak of in the return line, ergo also in the banjo/T-fitting/return, then would the outside fuel supply from the electric lift pump not always be supplying full pressure (70 + psi) to the T-fitting/return line?

Would this not interupt or in some way change the proper operation of the fuel discharge from the plunger, sleeve assembly and or case pressure?

Or is the outside pump pressure and fuel supply just diverted through the return line until the internal IP fuel supply can use whatever fuel is supplied

I have studied the Bosch schematics for the fuel routing into and out of the rotor head assembly and the manual ( which by no means, means that I know anything at all, lol) and this passage sticks out in my mind in this regard

"Overflow restriction
The overflow restriction (Figure 6) is
screwed into the injection pump’s
governor cover and connected to the
pump’s interior. It permits a variable
amount of fuel to return to the fuel tank
through a narrow passage. For this
fuel, the restriction represents a flow
resistance that assists in maintaining
the pressure inside the injection pump.
Being as inside the pump a precisely
defined pressure is required as a function
of pump speed, the overflow restriction
and the flow-control valve are precisely
matched to each other.

I know your system works, obviously, lol, but I am just tryin to understand it, so If you wouldnt mind maybe elaborating more on how the second line supply "works", it would be hugely appreciated

who knows - someone might even improve on it a little bit once its understood better

thanx
Ken

[KTA]

The t-fitting is always at case pressure because it is between the special banjo bolt and the case. The case pressure typically operates at at least 30psi, so as long as the feed pressure is less than 30psi the check valve is shut and no fuel flows through the auxillary feed. Since I use a boost refrenced regulator this is my case. Now if you don't use it and instead have a constant 70psi fuel supply then yes it will over ride the check valve and maintain case pressure of at least 70psi. In this scenario the timing plunger and check valve are no defeated so you had just as well delete the check valve.

[fergavs]

Basically if I understand this correctly it is the banjo bolt that is actually controlling the fuel return from the pump not the port or internals. So by having the banjo bolt after the t fitting you keep the stock fuel return functioning but have access to either watch case pressure or feed fuel into the case to maintain pressure. Sound right?

KTA, wish I knew this before a certain ummm hehe "pump builder" drilled a useless hole in the side of my case that I cant use to watch case pressure. Oh well there will be more pumps built.

[seeker1056]

now I got it - thank you for your patience Brian

See I was thinkin on T-in the line before my regulator, to provide as high a pressure to the pump as possible at the case T - this based on reading how the case pressure seems to fall under extreme demand with the 14mm

So is a base 20 psi or there abouts as a secondary feed enough in your experience

I do have the regulated boost referenced regulator feeding the regular port

I havnt set up the boost reducer yet tho, so the regulator doesnt do 1:1 boost reference so it isnt hooked to boost at the moment


Do yu think one of those $10 Ebay boost regulators is sufficient for this task?

Where is the best place to read case pressure in your expert opinion

What am I lookin for for case pressure, under normal driving, and under full power at 60 psi boost

How much is too much case pressure

[KTA]

Yes the orifice in the banjo bolt is the case pressure regulator so to speak. I only run 10psi with no boost. The stock lift pump is only capable of like 7psi max, so by running 10psi I have plenty of fuel and it does not effect the internal timing controls of the pump. I think case pressures above 130psi or so are probably more harm than good. There are issues to this setup that need to be addressed for optimal performance. I have to keep some tricks for my hard earned and sometimes expensive knowldege. lol Unlike some I don't spew my theories as recomendations. I only discuss what I have tried and know to work or not work in my experience. I don't want someone mistaking theory for fact and costing themselves money on my account.

[fergavs]

The best place to watch case pressure is at the return on the pump. Just use a fitting before the banjo bolt. Same place you would feed the 2nd fuel supply. This is recomended by my very experienced local Bosch tech. It is how he watches case pressure while setting up a pump. As far as the case pressure dropping under hevey load with the 14mm you are correct. My tech said he really had problems getting the case pressure up to spec under full load.

[seeker1056]

Thanx guys
And Brian - thanx for what you have divulged- most would keep even that much a secret for all thier hard work

Cudos


As to theories - I would love to hear any you may have - I have three pumps I can play with and with my new Shied front cover - changin out pumps will be a breeze
Now all I need to do is come up with an adjustable pump gear so timing changes would be easier
Anyone know if the P-pump gear will fit the shaft of the VE
If not its off to the machine shop to make a stock gear adjustable
The fun never stops


Ken

[randyswelding]

Ok I now need to look at my lines I got off the motor,man this is some good stuff thanks guys

[Begle1]

I have a case pressure gauge made up out of a gutted shut-off solenoid that got a fitting soldered into it.

[CaptainChrysler]

Anyone know if the P-pump gear will fit the shaft of the VE

The p-pump has a considerably larger input shaft.