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#15
by
burn_your_money
on 06 Oct, 2011 13:58
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When I worked with Giles we tested this on a test bench. I forget the exact numbers so I am just going to make them up. We fed the pump with 6 psi at idle and the internal pump pressure was 36. We increased the lift pump pressure to 46 PSI and the internal pump pressure went up to 76 psi. The advance gauge did not move in the slightest. We tested it at 1500 RPM pump (3000 engine), feeding with 6 psi the internal pressure was 106 psi. We then fed it with 36 psi and the internal pressure was 136 and the advance did not change.
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#16
by
R.O.R-2.0
on 06 Oct, 2011 15:13
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because the advance works on the principle of pressure differentials..
the regulator keeps the internal pressure XXpsi higher than the inlet pressure..
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#17
by
Alcaid
on 06 Oct, 2011 15:21
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Thanks guys! Lift pump it is then!
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#18
by
R.O.R-2.0
on 06 Oct, 2011 15:22
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if you run your engine up to the upper RPM range much, thats where you will notice the lift pump most..
my lift pump made my car have quite a bit more up top..
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#19
by
92EcoDiesel Jetta
on 06 Oct, 2011 15:44
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What kind of lift pump do you have? What psi and gph? From what I can tell, with the small orifice in the return bolt, not much fuel is returned to the tank at idle. Do you know the return rate at 5,000 rpm? Probably not that much so the demand on your elec lift pump isn't that great and you do not have to worry about fuel starvation at high power/rpm situations. That VE vane pump is a powerful pump, much more so than your elec lift pump. I wonder if you can get the same results (better top end) by changing to bigger diameter fuel lines (from tank to IP for both supply and return).
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#20
by
Alcaid
on 06 Oct, 2011 15:52
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#21
by
R.O.R-2.0
on 06 Oct, 2011 16:11
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What kind of lift pump do you have? What psi and gph? From what I can tell, with the small orifice in the return bolt, not much fuel is returned to the tank at idle. Do you know the return rate at 5,000 rpm? Probably not that much so the demand on your elec lift pump isn't that great and you do not have to worry about fuel starvation at high power/rpm situations. That VE vane pump is a powerful pump, much more so than your elec lift pump. I wonder if you can get the same results (better top end) by changing to bigger diameter fuel lines (from tank to IP for both supply and return).
i know 1/2" is pretty standard on a hopped up cummins.. and the feed line needs upgrading worst. the return line not soo much.
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#22
by
rodpaslow
on 06 Oct, 2011 17:01
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The return line for the size of it roughly 1/8" to the ip, I'm sure it's a metric size is pretty steady at anything above idle, this adds up quickly and the return from the out of the ip is a small hole, but at pressures over 50 psi also moves a lot of fuel. If there's any restriction in return you will have problems with leaky return lines off your injectors. I had a gasser and the return line in the tank is long so it puts the return fuel under slight pressure from the weight of the fuel in the tank. I had to open the tank and cut this off so it just dumps the return fuel into the tank; otherwise I have leaky injector returns. I kept the throttle body pump that was in the tank as my (mk3) lift pump and used a cheap holley pressure regulator to regulate the fuel down to about 4 psi.
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#23
by
burn_your_money
on 06 Oct, 2011 19:48
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Whatever lift pump you go with make sure you install a gauge so you can see if it is able to supply enough fuel throughout the RPM range. The return moves quite a bit of fuel as it also is used to cool the pump.
I read a very interesting article about fuel line sizing recently with all sorts of math but I can't find it now. This one kind of covers the topic
http://sbmar.com/main/articles/understanding_fuel_line_sizes_vs._fuel_supply_restriction/
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#24
by
Alcaid
on 07 Oct, 2011 01:26
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Whatever lift pump you go with make sure you install a gauge so you can see if it is able to supply enough fuel throughout the RPM range. The return moves quite a bit of fuel as it also is used to cool the pump.
That's why I'm considering the Fuelab lift pump because that seems like one of the few options that actually has a high enough flow to not run out of steam on top.
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#25
by
R.O.R-2.0
on 07 Oct, 2011 12:36
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ill rig up a pressure/vac gauge this weekend, right before my pump.. i dont think its ever going to read vacuum, even with the crappy cheap shaker fuel pump..
you can pump a 5 gallon can of gas in about 8-10 mins with the small shaker pumps..
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#26
by
ORCoaster
on 07 Oct, 2011 13:15
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I put one of those pressure/vac gauges in before the IP and after the filter on a suggestion by Mark I think it was. I noticed that I was pulling a few lbs of vac then as it went up I would get air in the line. Once I smoothed the copper washers and fire them to a blue color they worked fine after that. I think he mentioned he used the vac reading as sort of a way to tell when the fuel filter was plugged up.
So you can and may indeed see a vac reading on that gauge once you get it in.
I have also seen some of those gauges that show actual flow. Liters/min or gallons/min, I wonder if hooking one of those to the outlet side of the IP and measuring the amount of fuel returning to the tank would be a means of gauging if you were shorting the delivery to the IP?
I also wonder if hooking one on both sides of the pump and getting a differential would allow us to determine the actual amount of fuel used. I know the ScanGauge I have gives me all kinds of numbers about that stuff but I think that comes from sensors that are part of the Electric Brain From Detroit, Japan, or other.
All we would need is a differential between in and out and miles driven to get to MPG. Time to go talk to my computer programmer son.