So no more fuel pickup?
- Thread starter Noreaster
- Start date
I thought about using a bulkhead fitting like most poly chemical tanks use, but I don't think the rubber washers would hold up very long being exposed to diesel.
Don't use rubber. Nitrile or Buna-N should last.
Like this one, http://www.jegs.com/i/JEGS/555/110562/10002/-1
How well would it hold up on a DD I wonder....
Anybody know how thick the tank is?
I didn't install the one that came with the Airdog. Debated about it then decided it wasn't worth the hassle at the time.
I have been thinking about this..... you are not loosing fuel pressure with a lift pump, so therefore if you have the same pressure to the CP3 it doesn't matter what the pickup does or doesn't do. As long as there is 15 psi going into the CP3, it doesn't matter if it goes through a 1/4 hole or a 1/2 inch hole. Maybe I'm all wet.
1/2" at 15psi flows more (double) than 1/4" at 15psi. The pressure is the same but more volume. Since the pickup is constantly under vacume the bigger it is, the less resistance. Doing mine sucked, but it was worth it i guess. I never ran the lift pump/big tunes without it so i have no comparison. Still glad i did it.
While I agree that a 1/2 line flows 4 times more than a 1/4 inch line, it doesn't matter, because if you only have a 1/4 inch hole at the CP3, then you effectively pushed a ton of fuel to a choke point.
A chain is only as strong as it's weakest link. You can only pull, or in this case, push as much as the smallest point will flow at a given pressure.
That's my take on it. It's like trying to get a chain that will break at 2000 pounds to pick up 2001 pounds. There are other limiting factors.
That's like saying the needle and seat orifice in my Holley carb is only .110. Therefore, I don't need to run anything more than (2) 1/8" fuel lines for my double pumper carb.
The key is the supply. We run bigger lines and lift pumps to make sure the CP3 is operating at 100% VE at all times under high fuel demands.
Restriction is based on pressure drop per a given length.
The pressure loss of the 1 foot section of 1/4" tube on the motor would have only 10% of the restriction compared to the section from the tank to the engine if it was 1/4" as well. This is why the fuel line is 1/2". In this case, the flow capacity is the sum total of all combined restrictions, not the biggest restriction in the system.
Also any restriction before the pump is much more critical than after. Starving a lift pump can cause cavitation, & also most pumps do not deal well with inlet restriction, since they are meant to pump, not suck. This is why a bigger fuel pickup can help.
I specialize in custom automotive fuel systems for late model fuel injected engines & deal with this type of design on a daily basis, so this is proven info. For reference, some intank performance gasoline fuel pumps that I use have a 1/4" diameter outlet with a check valve that resembles a valve core. Somehow this very restrictive opening will flow enough for 550rwhp, but the same pump needs a 3/8" line to support the same flow without excessive pressure drop.
The pressure loss of the 1 foot section of 1/4" tube on the motor would have only 10% of the restriction compared to the section from the tank to the engine if it was 1/4" as well. This is why the fuel line is 1/2". In this case, the flow capacity is the sum total of all combined restrictions, not the biggest restriction in the system.
Also any restriction before the pump is much more critical than after. Starving a lift pump can cause cavitation, & also most pumps do not deal well with inlet restriction, since they are meant to pump, not suck. This is why a bigger fuel pickup can help.
I specialize in custom automotive fuel systems for late model fuel injected engines & deal with this type of design on a daily basis, so this is proven info. For reference, some intank performance gasoline fuel pumps that I use have a 1/4" diameter outlet with a check valve that resembles a valve core. Somehow this very restrictive opening will flow enough for 550rwhp, but the same pump needs a 3/8" line to support the same flow without excessive pressure drop.
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It basically comes down to 3 things.
1) Time:
How quickly do we need to deliver the fuel to a specific location in the vehicle.
2) Pressure: How much pressure can we run in the system.
3) Orifice: What is the area of the delivery conduit and how long is the distance.
1) Time:
How quickly do we need to deliver the fuel to a specific location in the vehicle.
2) Pressure: How much pressure can we run in the system.
3) Orifice: What is the area of the delivery conduit and how long is the distance.
We have been thinking of running twin lift pumps with one close to tank and one under the cab on the frame. first pump is on constant with fuel filter before the pump and the second pump comes on at 10psi of boost(with bypass and check valve). 5/8'' fuelline and do away with factory fuel filter. Any thoughts on this? Truck is a CCLB.
IMO
Large Pickup -> High Vol, Low Press Lift Pump near tank -> Filter -> High Pressure Pump -> Big line to engine compartment -> boost compensating bypass regulator under hood -> optional OEM filter -> CP3
But what do I know.
Large Pickup -> High Vol, Low Press Lift Pump near tank -> Filter -> High Pressure Pump -> Big line to engine compartment -> boost compensating bypass regulator under hood -> optional OEM filter -> CP3
But what do I know.
We are running a pump with adjustable pressure, an aftermarket fuel filter, no OEM filter, and 15 Psi at the inlet pressure on the CP3.... how is a bigger line going to get fuel through the CP3 faster? That is still my question.
It keeps the gear pump in the CP3 from cavitating at higher RPMs by assuring there is still positive pressure feeding said pump when the fuel flow goes from mild to wild in the line.
You can get similar results in your case without going big because you don't have the OEM filter and it's pressure limit. (15 PSI?) However, at some point the flow increase from bumping the supply pressure will not be enough to feed the volume needed by the CP3.
But what do I know.
You can get similar results in your case without going big because you don't have the OEM filter and it's pressure limit. (15 PSI?) However, at some point the flow increase from bumping the supply pressure will not be enough to feed the volume needed by the CP3.
But what do I know.