Increasing Pump Inlet Pressure
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Elder User
Joined: Dec 2006
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From: On a farm.
Increasing Pump Inlet Pressure
Two Questions:
1) Has anyone here fooled with increasing the inlet pressure on their DB-2 pumps by eliminating the mechanical lift pumps and replacing it with a higher pressure/volume electric? The GM 6.2L guys have and claim small benefits. If you have, what pressure did you use and how did it work?
2) In light of the above, without pulling the lift pump, does it use a standard bolt pattern for the pump that could be covered with a standard block off plate?
1) Has anyone here fooled with increasing the inlet pressure on their DB-2 pumps by eliminating the mechanical lift pumps and replacing it with a higher pressure/volume electric? The GM 6.2L guys have and claim small benefits. If you have, what pressure did you use and how did it work?
2) In light of the above, without pulling the lift pump, does it use a standard bolt pattern for the pump that could be covered with a standard block off plate?
Lead Driver
Joined: Nov 2003
Posts: 6,900
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From: Campbell River, B.C.
Electric pumps have been used on these before. Word on the street is the holley red is the best for the job. Makes filter changes easier and cold starts less problematic for those with chronic air intrusion problems.
I have heard that a standard block off plate will work to close off the hole if you remove the OEM mechanical lift pump.
Not sure what sort of power difference there would be. I wouldn't expect a night and day improvement.
I have heard that a standard block off plate will work to close off the hole if you remove the OEM mechanical lift pump.
Not sure what sort of power difference there would be. I wouldn't expect a night and day improvement.
Post Fiend
Joined: Oct 2007
Posts: 10,501
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From: Faibanks Ak.
I don't think you will get a power increase as the fuel returns anything its not using allready. There are benifits that David 85 mentioned.
Years ago on the old 220 cummins we got power increases by putting vise grips on the return line restricting it.
Years ago on the old 220 cummins we got power increases by putting vise grips on the return line restricting it.
Lead Driver
Joined: Nov 2003
Posts: 6,900
Likes: 3
From: Campbell River, B.C.
Factory should be 5-6 psi pressure in the low side of the injector pump. Even a small drop in pressure there can certainly affect performance in a negative way. Increasing the pressure has been known to cause surging in some cases. I certainly wouldn't go any higher than 8 psi but I'm not an expert with the internal settings of the IP.
Maybe some one else will know.
Maybe some one else will know.
Postmaster
Joined: Apr 2008
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IIRC the perofmance gains seen by the Chevy guys are due to the high inlet pressure advancing the timing of fuel injection. You know how the truck pulls like a freight train just before running out of fuel? Same thing, it ain't good for the IP either. You can definitely run a large volume pump tho, factory is 30GPH but I'd really wanna have a 110GPH in mine, this way not having enough fuel (big issue with running WMO sometimes) will not be a problem.
Postmaster
Joined: Mar 2008
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From: Sweet Home, OR
Holley "Red" (PN 12-801-1) and big block Chevy block-off plate.
I agree that too high of an inlet pressure wouldn't give any more power and could cause problems.
I agree that too high of an inlet pressure wouldn't give any more power and could cause problems.
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Posting Guru
Joined: Sep 2007
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From: Las vegas
It wont increas preformance the seat-o-pants dyno has a funny way of saying its faster wen you spend oney on something. The lift pump lifts the fule to the IP where the transfer pump inside the DB2 ranps it up to IIRC 210psi if you feed 20 psi to the transfer pump it will still only create the presure it is set for now if you realy know your DB2 and have built your engine better than Dave S. built his and can use more fule than the DB2 can put out in the stock setting then you can turn the transfer up to get more fule but all the other settings i the pump will need to be changed.
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Elder User
Joined: Dec 2006
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From: On a farm.
Yep, these are pretty much the answers I've been getting from elsewhere too. I spend a "fascinating" evening reading the DB2 instruction manual. It doesn't go into this, of course, but it can be deduced from the material that as long as the pump gets the required volume, more inlet pressure is of no use.
Postmaster
Joined: Mar 2002
Posts: 3,545
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From: Coal Region
i have nothing to add but i enjoy reading ur articles, mr. allen.
on a side note, before i replaced my mech. lift pump i could feel the truck being to run sluggish. after i replaced it, it runs a lot smoother, revs quicker and feels 100% better. so i can definatly say, having low inlet pressure really affects the power outout.
on a side note, before i replaced my mech. lift pump i could feel the truck being to run sluggish. after i replaced it, it runs a lot smoother, revs quicker and feels 100% better. so i can definatly say, having low inlet pressure really affects the power outout.
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Elder User
Joined: Dec 2006
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From: On a farm.
Well if all goes right, I'll be able to try it at 7-10 psi. I've got a call in to a Stanadyne guy to see how much input pressure they can (or should) take and exactly what happens to them.
The Holley Red pump everyone talks about is a 97 GPH (@ 2 psi) pump (79 GPH @ 4 psi). Right now, my truck makes 2-2.5 psi with the engine running at idle. I get conflicting reports as to the capacity of the OE mechanical, either 23 or 30 GPH @ 3-4 psi.
The Holley Red pump everyone talks about is a 97 GPH (@ 2 psi) pump (79 GPH @ 4 psi). Right now, my truck makes 2-2.5 psi with the engine running at idle. I get conflicting reports as to the capacity of the OE mechanical, either 23 or 30 GPH @ 3-4 psi.
Lead Driver
Joined: Nov 2003
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From: Campbell River, B.C.
Should be 30 GPH and should be 5-6 PSI right at the schrader valve of the fuel filter. I used a tire gauge to check mine a few years ago, but it worked (barely).
Keep us posted because I have seen modified injector pumps where you had to adjust both "fuel screws" to properly set it up for higher performance. I've always wondered what that screw would do on an otherwise stock injector pump.
There's a guy on oilburners.net that is selling something called a "moose pump" and it has to be tuned with both fuel screws. It's supposed to put out more fuel than a DPS pump without sacrificing fuel economy at lighter power settings. Based on the testemonials of other guys on the forum, I am seriously considering going with his pump when mine finally lets go.
Keep us posted because I have seen modified injector pumps where you had to adjust both "fuel screws" to properly set it up for higher performance. I've always wondered what that screw would do on an otherwise stock injector pump.
There's a guy on oilburners.net that is selling something called a "moose pump" and it has to be tuned with both fuel screws. It's supposed to put out more fuel than a DPS pump without sacrificing fuel economy at lighter power settings. Based on the testemonials of other guys on the forum, I am seriously considering going with his pump when mine finally lets go.
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Elder User
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From: On a farm.
I got a reply from my DB-2 expert and here is what he said. His answers in italic.
1) What is the safe maximum inlet pressure (lift pump) for a DB-2?
I don't know of a max "safe" inlet pressure. In a stock system I wouldn't go above about 10. You should have at least 2 psi at WOT full load.
2) A modified engine can probably use more flow but is there any advantage to running more pressure than stock? Seems to me that the transfer pump will regulate the pressure that goes to the delivery valve, so I'd guess higher inlet pressure couldn't effect injection pressure (you tell me). From there, my understanding gets dim. Wouldn't higher pressure increase the housing pressure and, once the housing pressure regulator is maxed out, and housing pressure goes higher than designed, would that effect how the timing advance works? I think too much pressure might also cause some leaks in the low pressure part of the housing.
There is an advantage to running more pressure on a modified system. Some tractor pullers will run a "boost pump" with as much as 200 psi feeding the pump. This does not work on a stock or slightly modified system since it will cause the timing advance to advance too quickly. The higher pressure puts more fuel into the pumping chamber on this system causing it to inject more fuel. These guys usually eliminate the transfer pump completely. Some will keep the transfer pump and use it to step the pressure up. The transfer pump regulator will allow the pressure to increase since it simply returns excess fuel to transfer pump inlet. The reason that some pullers run a boost pump is that the difference between the transfer inlet and outlet pressure should never be over a 120 psi. If the transfer pump creates too high a pressure it will cause a pump seizure. But by running a boost pump they get a little higher metering pressure so they take the chance.
The housing pressure is controlled by two things. The vent wire and the housing pressure regulator valve. The housing is fed from the transfer pump pressure by a very small orifice with a wire in it, the vent wire. In addition to the vent wire there is internal pump leakage from the timing advance, plungers to rotor and rotor to head. Unless the transfer pressure were extremely high the housing regulator valve should handle the flow. You are correct that the housing pressure affects timing advance. Higher housing pressure will cause the timing to retard slightly and also slightly decrease fuel delivery. Highly modified pumps do not run a housing pressure regulator valve.
1) What is the safe maximum inlet pressure (lift pump) for a DB-2?
I don't know of a max "safe" inlet pressure. In a stock system I wouldn't go above about 10. You should have at least 2 psi at WOT full load.
2) A modified engine can probably use more flow but is there any advantage to running more pressure than stock? Seems to me that the transfer pump will regulate the pressure that goes to the delivery valve, so I'd guess higher inlet pressure couldn't effect injection pressure (you tell me). From there, my understanding gets dim. Wouldn't higher pressure increase the housing pressure and, once the housing pressure regulator is maxed out, and housing pressure goes higher than designed, would that effect how the timing advance works? I think too much pressure might also cause some leaks in the low pressure part of the housing.
There is an advantage to running more pressure on a modified system. Some tractor pullers will run a "boost pump" with as much as 200 psi feeding the pump. This does not work on a stock or slightly modified system since it will cause the timing advance to advance too quickly. The higher pressure puts more fuel into the pumping chamber on this system causing it to inject more fuel. These guys usually eliminate the transfer pump completely. Some will keep the transfer pump and use it to step the pressure up. The transfer pump regulator will allow the pressure to increase since it simply returns excess fuel to transfer pump inlet. The reason that some pullers run a boost pump is that the difference between the transfer inlet and outlet pressure should never be over a 120 psi. If the transfer pump creates too high a pressure it will cause a pump seizure. But by running a boost pump they get a little higher metering pressure so they take the chance.
The housing pressure is controlled by two things. The vent wire and the housing pressure regulator valve. The housing is fed from the transfer pump pressure by a very small orifice with a wire in it, the vent wire. In addition to the vent wire there is internal pump leakage from the timing advance, plungers to rotor and rotor to head. Unless the transfer pressure were extremely high the housing regulator valve should handle the flow. You are correct that the housing pressure affects timing advance. Higher housing pressure will cause the timing to retard slightly and also slightly decrease fuel delivery. Highly modified pumps do not run a housing pressure regulator valve.