Solutions to VE high fuel flow rate problems

[ahale2772]

Remps, it always bleeds off pressure, its just an orifice so it constantly bleeds off, yet its so small that it allows the case to build pressure

[Remps]

So I'm guessing with a setup like kta's a full time secondary fuel system would have to be in place? Also guessing there wouldn't be any case pressure issues though with the vane pump controlling only timing? Probably somewhat higher pressures could be run compared to feeding through the shutoff? Also guessing feeding through the shutoff solenoid would be better for a part-time secondary fuel feed, and at least 250-300 psi case pressure could be maintained at wot with the pump I mentioned earlier, regardless of bleed off from the return and case pressure regulator?

[ahale2772]

my take on it is this....

the stock return/fuel bleed off orifice might need to be enlarged to keep case pressures down, because of the fact that the normal plunger feed is blocked off.

essentially the vane pump is just acting to control timing now, and that might allow timing to be variable by the amount of fuel pressure fed into the vane pump...or the size of the return bleed fuel orifice.

essentially its not a secondary fuel feed system, its the primary system with the vane pump strictly reserved for timing.

unless Brian could work out a way to make a check valve on his super special fitting so that case pressure would feed the plunger UNTILL his mechanical fuel supply pump ramps up and overcomes the case pressure, over rides the check valve and simultaneously isolates the plunger from case pressure

or I could be totally on the wrong track...

Also guessing feeding through the shutoff solenoid would be better for a part-time secondary fuel feed, and at least 250-300 psi case pressure could be maintained at wot with the pump I mentioned earlier, regardless of bleed off from the return and case pressure regulator?

and yes, I agree that would work out as a good part time "helper style" fuel system, but figuring out a way to make it follow the case pressure curve (which looks pretty linear to RPM) not affect timing would be the big issue

[KTA]

The fitting is machined so as it only has .001" of clearance around the snout and the snout is long enough to bottom out when tightened down so I would expect any leakage from the plunger supply to the case to be minimal. As I stated this setup requires a dedicated high pressure system to feed the plunger side of the pump. In actuality the stock lift pump is perfect for feeding the original VE inlet as it only controls timing and provides pump lube in this setup. The timing curve can be varied according to return orifice size and the springs on the timing piston. By isolating the two the fuel curve becomes strictly vane pump flow dependent and is not affected by other issues such as fuel delivery rates. Unless you are maxing a pump out again this is totaly not needed and excessivly complicates the system. The point is it is a solution for going all out, but not terribly practical for most.

[mike8061]

I have been piecing together a system that would take advantage of both systems possibly. A LP pistion lift pump would feed the vane pump through the inlet.

A high presure gear pump regulated to 150-200PSI would kick in at a certin amount of boost and feed in through the shutoff hole.

the idea being to keep a drivable setup with the lift/vane pump 90% of the time, saving wear on the gear pump system. when at high boost the pump should be advanced anyway so the extra fuel will just help maintain fuel pressure with extra volume. there will also be a check valve in the gear pump line to prevent back flow when not in use.

Anyone see any major flaws in this?

Im thinging of using and A/C clutch to switch the gear pump on/off. Any idea how much power it takes to run a gear pump?

[oldestof11]

Hate to be a Debbie downer but I (meaning me, myself, no other party involved) just see this as a crutch. The mentality is "Well, this is cheaper and bypasses the problem points. Why deal with the problems? Lets just bypass everything." This WON'T be legal in ANY pulling organization other than RWYB and ODL classes.

Mike8061, the problem with that setup is the backfeeding into the case with no check valve.

[mike8061]

Well I thought of that. I'm thinking i hook up a case gage and find out what case pressure is at the rpm i want to run the gear pump. Once i know that i can set the regulator on the gear pump slightly below that. Since the vane pump is still reciving fuel it should maintian its pressure if flow is low. When it is flowing to much to maitain the pressure then the gear pump will help.

I belive I read somwhere that KTA had a setup similar to this but using an Electric pump at 70 PSI

I'm basically trying the same idea just with enough pressure to keep the timing fully advanced (without any mods that would make it race only).

[Remps]

KTA, did you have to mod the timing piston springs and return orfice to make your timing curve work? Or did you leave them as is?

[KTA]

Hate to be a Debbie downer but I (meaning me, myself, no other party involved) just see this as a crutch. The mentality is "Well, this is cheaper and bypasses the problem points. Why deal with the problems? Lets just bypass everything." This WON'T be legal in ANY pulling organization other than RWYB and ODL classes.

Mike8061, the problem with that setup is the backfeeding into the case with no check valve.

It would be perfectly legal in all classes around here. There are no rules regarding what sort of fuel supply system you can have. As a matter of fact most of the tractors run a gear driven fuel supply setup already. Most p pumps are dual feed in racing applications no reason why a VE can't be as well. You can't fit a bigger vane pump in the stock housing without a ton of work so this is the most viable solution.

[ahale2772]

it would be cool to see some flow numbers KTA, just numbers, no need to share all your secrets.

[KTA]

I haven't yet been able to figure out how to run the fuel supply system on the test stand. Once I do I will be able to actually tweak the system to perform how I want. As for now it just kind of works, but isn't correct.

[ahale2772]

very cool, wouldnt it be nice to see a VE hit 700 on fuel???

[dazedandconfused]

Brian have you tried to set up a variable speed electric motor to run the supply pump? That would give you a chance to mess with pulley sizes to get the supply pump ramp to match rpm and preasure needs. It would be ideal if you could get both motors to run on the same variable switch so both ramp the exact same time like engine conditions. That would be the simplest way I can think to do it for testing. Have a fuel cell set up with low preasure pump and it's feed line with a psi gauge and the secondary the same with a dedicated line and psi gauge.

[KTA]

A constant or near constant supply pressure is fine for me. The problem is I don't have the time or money to fool with it very often. Work, farming, machining, and household repairs keeps me to busy to do R&D that doesn't pay.

[dazedandconfused]

I know what you mean on the time and money.