P7100 LP pressure regulating, boost ref. or not?

Personally, I've seen way too many people say that anything over 40-45psi doesn't gain any power...so the only reason I'll boost reference my regulator, is if it drops below 40psi at WOT!

So basically, I'll run about 45psi all the time!
Chris
 
i am not using the boost ref feature so it will have high pressure when its under severe load...

using it so it will have high volume AFTER its been under severe load
 
I would set it without boost ref. Most of these regulators are designed for gasoline appications with way lower boost levels then what we are seeing. They use this so they dont lean the motor out.
 
It may be possible also to rupture the internal diaphram in the regulator due to excessive boost psi.
 
do you understand how the boost elbow works on a turbo from industrail?

can do the same thing here

so it dont see all the boost

ps - use same reg on turbo bikes - 40 psi 500 hp
 
do you understand how the boost elbow works on a turbo from industrail?
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yes, I do. Its used for delaying the boost. I understand your theory as in having more volume after a hard run. Less pressure=more volume. Running a bypass regulator and hi-flow pump is already dumping more fuel to the tank then stock by far in my eyes.
 
Mo Smoke said:
So if I remove the overflow valve and put a hollow banjo bolt it will still keep set pressure (40 psi) at the pump?
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That's not going to work.

White Knight said:
No, the AD and FASS regulate pressure in the outlet line of the pump bodies. They do nothing with the system post IP. If you were to remove the overflow valve, they would not have enough flow to create the friction needed for desired pressure.
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Although I haven't been around either system, from what research I've done the main regulator appears to be in the pump/filter assembly. They just leave the stock return line and OFV in the pump so that it will still pass some fuel through the pump and keep it cool.

I have my truck set up this exact same way and it will maintain 40psi all the time with no boost referencing, so I'm assuming that I have an adequate fuel supply for what my truck is doing right now. That may change in the future however...

DTanklage said:
most of the aftermarket regs these dayz are boost ref
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Yes, but that doesn't mean that you have to do anything with it. Mine is vented to atmosphere.

White Knight said:
But the question still remains: Should you use that feature?
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I personally don't see the point in this application.

Schevyii63 said:
I would set it without boost ref. Most of these regulators are designed for gasoline appications with way lower boost levels then what we are seeing. They use this so they dont lean the motor out.
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The reason why gasoline turbo vehicles use the boost reference port is to keep the fuel pressure at the same point regardless of boost pressure. That way the injectors or carburetor will be seeing the same amount of fuel pressure.

For instance, say you set your carb's fuel pressure at 7 psi. If you wanted to maintain that 7 psi of fuel pressure at 15 psi of boost you're going to need to see 22 psi of fuel pressure because the carb bowls see the boost pressure too.

I see no point in boost referencing a regulator in a diesel application since the IP takes care of the high pressure fuel delivery and all the low pressure system is doing is making sure there is an adequate fuel volume and pressure at the IP so it can do its job.
 
mondtster said:
.....because the carb bowls see the boost pressure too.

I see no point in boost referencing a regulator in a diesel application since the IP takes care of the high pressure fuel delivery and all the low pressure system is doing is making sure there is an adequate fuel volume and pressure at the IP so it can do its job.
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only in a blow thru system, and only if the whole carb is inclosed in a box or if there is a line ran to the float bowl vent


i just started my truck up and turned the fuel pump off for 30 seconds - it didnt idle any different with it off. i think like jay said as long as the body of the p-7100 has fuel in it you are good to go. you could pour the fuel in thru a funnel and it would run the same

but i still like the idea of slowing down the return volume while under load and then letting it increase again afterwards

don
 
DTanklage said:
only in a blow thru system, and only if the whole carb is inclosed in a box or if there is a line ran to the float bowl vent


i just started my truck up and turned the fuel pump off for 30 seconds - it didnt idle any different with it off. i think like jay said as long as the body of the p-7100 has fuel in it you are good to go. you could pour the fuel in thru a funnel and it would run the same

but i still like the idea of slowing down the return volume while under load and then letting it increase again afterwards

don
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I agree. I've run nearly zero fuel pressure when I had a fuel delivery problem (the whole reason I switched to my current setup) and quite honestly, it really didn't run much different. The only reason I threw the adequate pressure statement in there was because Smokem indicated in one thread I was asking questions in that the pressure was used to make the plungers "float" and not contact the barrels. I can tell you that when I was having fuel delivery issues that my injection pump was noisy and it went away as soon as I could maintain 40 psi of fuel pressure.

Rising fuel pressure is equally as important in an EFI setup as it is in a blowthrough carb setup to maintain your fuel pressure and have consistent fuel delivery. The only place where boost referencing fuel pressure in a gasoline turbo system wouldn't really matter is in a suckthrough carb type of system, which I have no interest in building or playing with.

Don, what are the reasons why you still are interested in slowing down the return to the tank under boost? I see nobody offering any valid points on the merits of doing things this way.

Simply put, if you can maintain your fuel pressure that you have the regulator set at under all conditions, then you have plenty of fuel volume. I would start getting concerned if you start to see it dropping, but boost referencing the fuel pressure regulator really isn't going to help correct that IMHO.
 
So your pressure drops under high fuel demand? Or are you trying to just circulate high volumes of fuel through the pump with little to no fuel pressure and want the pressure to rise with boost?

If your pressure is dropping under high fuel demand then you have a fuel delivery issue.

If the latter is the case, I really don't understand why you would want to set up your system that way, and even if you aren't achieving fuel pressure there should be plenty of volume at the pump to handle the demand anyway, provided your lift pump is up to the task.

I'm really at a loss as to what you're trying to achieve here, and it seems as though you might be overthinking something that is relatively simple.
 
I currently have an AirDog 4g165 feeding my P Pump. I replaced the OFV with an orifice that supposedly correlates to 60psi. In operation depending on fuel temp, my fuel pressure gauge is usually between 50-55 idling and normal driving. Under full load it drops to between 40-45psi. I've spoken to AirDog reps and have considered changing to a boost regulated system. In a nut shell, the boost regulated system eliminates the normal pressure regulator on the pump and uses an external bypass regulator that changes pressure with boost. They way I understand it ....Lift pump is always flowing wide open (which is easier on the pump motor). When in no boost condition the regulator restricts the bypass flow out of the P Pump to maintain initial set pressure (which I think 20-30psi is recommended). Bypass flow rate is high keeping injection pump happier due to being fed more cool fuel. When boost is added and more fuel is being fed to the injectors, the P Pump likes more pressure for filling plungers in less time etc. The boost reference progressively restricts the return flow from the P Pump to the tank forcing the fuel pressure to go up towards the max capable of the lift pump. If I understand it correctly, the theory is you can make maintain more fuel top end pressure when it is needed due to not dumping through a fixed bypass orifice.
You flow more clean cool fuel through the P pump during normal driving at lower system pressure which is easier on the lift pump motor.
I've also considered going to a mechanical lift pump. Then a pressure control and bypass system like this would be a necessity.
 
I went back to your first post and didn't see what injectors you're running or what your power goal is.
 
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