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Discussion Starter #1
Ok, I am probably going to get some heat for even asking this, but can anybody explain EXACTLY what will happen if you... A: Block off the small injector return line? :eek: And B: If you were to block off the return line from the VE pump? :eek: I would just like to hear it from someone who realy knows injectors, and the VE pump. I am trying to chase down some fuel problems, and also get the most out of the little pump for the track, and wont be using it for a daily driver, or running it for long periods. I think you can get what Im after...MORE FUEL! :idea: I blocked off the sewer pipe from the house one time, and I dont want something like that to happen! :nuke:
 

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Not sure but from what I understand fuel lubricates and keeps I/P cool cycling fuel thru it. Seems like it would generate alot of heat and be hard on I/P to block off overflow line. Low pressure pump supplies more fuel than engine requires. Someone back me up cause I'm not positive about this.
 

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From what I've read / seen of the VE pump, I'd be worried about the front seal on the VE getting pushed out or otherwise failing.. Failure due to lack of flow (overheat or friction) would be a secondary concern:

The "low pressure" pump INSIDE the VE is a rotary vane type that has no bypass or pressure limiter other than the fuel return port on the pump body. My thinking is that if you block that off, pressure inside the pump will skyrocket and push out the front seal (in addition to leaking out every other available orifice).

Now, adding a bit of motor oil to your fuel is OK, even good for the pump in many cases, but I don't think #2 is a good oil additive.
 

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Just had a another thought, though.. Maybe put a fuel pressure regulator on the fuel return line?? Increase the internal working pressure of the pump, but not so much as to cause failure, and you *might* improve things a bit.

I would put a seal reinforcement plate on the front and a fuel pressure gauge between the port and the regulator if attempting it. Keep an eye on that gauge.. If it ever fails to return to regulator limit when at idle, shut down IMMEDIATELY, as something probably just sprung a big leak.

As for the injector return.. I'd be REAL hesitant to plug that off. That's playing with the high pressure end of things. What that is returning is the "leak fuel" that goes around the pintle into the spring cavity in the injector holder. If you did manage to actually block it off (rubber hose ain't gonna hold the pressure I suspect that can build up), I'd wonder if you'd not hydaulic-lock the injectors. And that can't be a good thing.


Of course, your mileage may vary, not to be taken internally, may cause cancer in lab rats, this post AS IS
 

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Agreeing with what's been said, and: easy to get confused on volume/pressure relationship. In order to increase volume of fuel delivered a 'larger' injector is often used. In a highly modified engine with very large inectors more pressure is needed, but only to keep up with the volume of fuel being delivered through injector orifices and to provide proper atomization of that fuel. The atomization has effect on the flame front/propagation during power stroke, causing more but smaller fuel particles. Because there are more small particles there is more surface area of fuel to mix with oxgen and more easily ingnite into flame. That is there may be 10X's as many particles produced, each with its own surface area, instead of one big particle with one surface area, so more ignition is possible.

Just increasing pressure will increase atomization more than it increases amount of fuel delivered, as the injector stands as a restriction. In some cases a smaller injector will produce as much power as a larger injector because better atomization makes more fuel available to be burned. RPM has a lot to do with it, because the flame front can only move so fast. As we know, too much fuel causes black clouds of smoke, as unburned fuel being lost out the exhaust. The mechanic has installed parts and adjusted to get maximum fuel crammed into engine instead of addressing the issue of making use of the full potential power of the fuel.

So what I'm saying is it's a delicate balancing act of properly sized injector orifices, with proper spray pattern, with adequate pressure to take advantage of spray characteristics, and correct pump volume to feed enough fuel under those circumstances or parameters. Obviously the combustion chamber design, piston crown shape, exhaust port configuration and exhaust restrictions will all have an effect, as will cam timing, valve overlap, and valve diameter. Just addresing pressure leaves off with the rest of the formula and can inadvertently harm much more than it helps.
 

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Discussion Starter #8
Instead of destroying a good pump just copy the method employed in installing a Walbro pump described in the following link:
http://www.dieseltruckresource.com/dev/showthread.php?t=120066&highlight="walbro+install"
I have one of the Walbro pumps on the shelf that was used as a second pump for the nitrous on the buggy. It has 1/4in npt ports, and dosnt go so well with my 1/2in alum line and cant just copy his set up i.
I know that this questions wasnt normal, but Im just trying to figure out how this pump/system works and what other changes I can try. I wont be switching to a P-pump, since I can put in the 6bt for less than the cost of a new pump. I guess I should have put in a little more info into my question. I know that the pump is fuel cooled, and I am running 2 stroke oil to help out on the lube side. I wont be driving for long periods, and was interested in being able to shut off the return on the VE pump just befor staging at the tree, and would return it back after the 1/4 mile pass. I was sure that blocking off the injector return would be a bad thing, but wanted to see what would happen if you did from somone who knows injectors. I noticed that there was alot of fuel being returned to the tank, and that fuel pressure was droping to zero even with the 100gph/15 psi pump lift pump. I will be puting another one in the system either parallel, or in series. Thanks guys, I will be getting a core 6cyl pump to take apart so I can see the working of it, and what I can modify or adjust.
 

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Discussion Starter #10
I was looking at that site a while back, and you can understand quit a bit of it....although after about thirty minutes I was saying UH HU, and WE WE ;) I have a pdf of the VE breakdown, but it will be nice to take apart the 6cyl pump that I dont have to worry about puting back together for the first time.
 

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Discussion Starter #11
Agreeing with what's been said, and: easy to get confused on volume/pressure relationship. In order to increase volume of fuel delivered a 'larger' injector is often used. In a highly modified engine with very large inectors more pressure is needed, but only to keep up with the volume of fuel being delivered through injector orifices and to provide proper atomization of that fuel. The atomization has effect on the flame front/propagation during power stroke, causing more but smaller fuel particles. Because there are more small particles there is more surface area of fuel to mix with oxgen and more easily ingnite into flame. That is there may be 10X's as many particles produced, each with its own surface area, instead of one big particle with one surface area, so more ignition is possible.

Just increasing pressure will increase atomization more than it increases amount of fuel delivered, as the injector stands as a restriction. In some cases a smaller injector will produce as much power as a larger injector because better atomization makes more fuel available to be burned. RPM has a lot to do with it, because the flame front can only move so fast. As we know, too much fuel causes black clouds of smoke, as unburned fuel being lost out the exhaust. The mechanic has installed parts and adjusted to get maximum fuel crammed into engine instead of addressing the issue of making use of the full potential power of the fuel.

So what I'm saying is it's a delicate balancing act of properly sized injector orifices, with proper spray pattern, with adequate pressure to take advantage of spray characteristics, and correct pump volume to feed enough fuel under those circumstances or parameters. Obviously the combustion chamber design, piston crown shape, exhaust port configuration and exhaust restrictions will all have an effect, as will cam timing, valve overlap, and valve diameter. Just addresing pressure leaves off with the rest of the formula and can inadvertently harm much more than it helps.

Jimmie, you are going to have to use smaller words... it was like I was back in highschool....only I didnt have as many zits!:rasta: :grinpimp: It was kinda like shooting myself in the foot the way I asked the question. I know that pressure isnt everything, but I want there to be very little pressure drop from the 15 psi at idle to maxed out at the big end of the track. Right now I am dropping to almost zero, but im sure the addition of the second pump will take care of that. I have a very bad habit of not being able to leave things alone, and trying things that most wouldnt because its not normal. Getting the advice to switch to a p-pump isnt what I was asking for, I just needed the info on the workings of the pump/injectors so I could decide if there might be some tweeking that might be done thats not your normal turn this screw, and grind this pin. If I dont try something different then im just another same shaped cookie in the pan..LOL Thanks anyways guys...:beer:
 

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Sorry Toolman, I miss a lot sometimes! Actually didn't realize it was 'you' posting, didn't make the connection on what machine we're talking about. You probably have many hundreds of times the experience and knowledge I do. I was just trying to throw in some theory about balance on the fit tab A into slot B part.

Now that I know it's a competition truck for very short runs: from what I understand blocking the return line can blow the seals. But, so what? From what I read they're pretty easy to replace. I just went out and looked at my VE and the first thing I thought of, "I wonder if he's using the fuel solenoid?" I don't know the fuel circuit in a VE, but could a possible fuel restriction caused by the small opening in fuel solenoid be causing the pump to bypass fuel into the return line? Problem is I don't know where in the fuel circuit of the pump they decided to plumb the 'safety valve', as the return line. Don't know if it's plumbed only after the pump has done it's work of pumping and distribution, or if it's 'before' to protect seals throughout the pump? The second of the two seems most likely to me.

Next thought, "I wonder if he's using injectors with bushings to fit 9mm into a 7mm head or vice versa?" So could the fitting the injectors go into be causing a restriction to full fuel flow to injectors?

I agree something doesn't sound right if you're running ragged edge on injector size and still getting a whole bunch of return fuel. But one question is, what kind of GPM or whatever is actually being returned? An ounce a minute, gallon per minute or whatever? To get some kind of numbers on that would help determine just what the engine isn't using, if compared to GPM of flow into pump.

Some fuel has to return from the VE in normal operation. I would guess there's 2 circuits, one to feed injectors and another to cool and lubricate pump, but that's a guess. Thinking common line in and a bypass port somewhere to split pump functions of feeding injectors and protecting itself. The return or 'overflow' fuel from pump may have nothing whatsoever to do with the volume of fuel fed to injectors, but may be a separate circuit [likely]. I say that because the same pump feeds some pretty hot 6BT's and we know they require 33% MORE fuel!

Looking at the injector return line it seems to be about 1/2 the size of the fuel lines to injectors. That may say that there's again some serious overkill on fuel delivery to injectors and that it's the injectors themselves that are the only restriction to flow. Doesn't necessarily mean the VE pump is lacking in volume or pressure output.

One basic problem is the injectors can only flow so much fuel and still atomize it for combustion. That's where the pressure to volume ratio comes into play. Gotta have the volume to feed the injector, and the pressure to FORCE atomization of its spray. From what I've learned if there's a restriction anywhere in the fuel delivery system it's most likely in the injector's ouput or atomization. Pretty obvious bottleneck, especially when you find out that the stock fuel flow is enough to hog out the holes in the stock injectors over time!!!

Don't know if any of this helps but hopefully it will tickle your own grey matter to discover the solution?
 

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Discussion Starter #13
nothin to be sorry about....I just wish I coud put the thoughts that are in my mind onto the page as well as you ;) (insert ass kissing sound here)

The more that I think about it, I may have a problem in the pump. I am going to try next week to take the return lines off of a 6bt that was dropped off at my doorway (he wont mind) and see the amount of fuel that is getting returned. Even with the motor turned off and just the lift pump running, there is a steady stream of fuel. I just dont have anything to compair this dam thing to.... I just know what I think it should be doing, and what I want it to do. :rasta:

Weird thing is, I closed this thread eariler?
 

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The thread that wouldn't die hah! Just like a Cummins, it just keeps running no matter what....
 

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So I've been following this thread, and here's a few comments.

I've contacted an IP shop about this because someone recommended plugging the return line back into the supply line between the lift pump and the IP. Their response was as I stated above that the return flow is needed for lubrication.
I see you mention using a walbro electric lift pump. I also see you say you won't be putting in a p-pump.(like p7100 IP).

What have you tried as far as lift pumps?
When I said piston pump I was refering to the mechanical lift pump used on p7100 motors and they can be bought for around $45 off ebay.
 
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