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Working on a "next-level" fuel system

spdgofast

Active Member
Messages
210
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86
Location
Florida
Hey guys' I've been thinking about and researching a little info on the Boost Referenced FPRs and came across a little downfall of it's use on a diesel engine. If you have a tube going from anywhere just about on the intake system for boost pressure reference to the topside of the rubber diaphragm on the FPR and it ruptures and your lift pump is pumping a steady let' say 20psi and you are at idle or low boost it will pump diesel fuel into the intake and what happens next? Uncontrollable fuel and air into the engine which = run away! I know there probably are some sort of one way check valves that may be installed but will they work properly and is it worth the risk?
 

n8in8or

Well-Known Member
Messages
2,713
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3,140
Location
Kalamazoo, MI
Hey guys' I've been thinking about and researching a little info on the Boost Referenced FPRs and came across a little downfall of it's use on a diesel engine. If you have a tube going from anywhere just about on the intake system for boost pressure reference to the topside of the rubber diaphragm on the FPR and it ruptures and your lift pump is pumping a steady let' say 20psi and you are at idle or low boost it will pump diesel fuel into the intake and what happens next? Uncontrollable fuel and air into the engine which = run away! I know there probably are some sort of one way check valves that may be installed but will they work properly and is it worth the risk?
Good thought. It’s only worth the risk if it is proven that the extra pressure will do anything for us - that has yet to be proven on a DB2 application.
 

spdgofast

Active Member
Messages
210
Likes
86
Location
Florida
Isn't the idea behind it to only increase volume and pressure when needed under load to the IP thus reducing wear tear and added stress to the LP? Can't too much pressure @ low demand cause ill affects and or timing changes to the IP? Look at the working's of the Fass FPR, I now know why the first guy told me it will only raise the pressure. When either spring pressure or upper housing pressure is put on the topside of the diaphragm and aluminum piece, it just shuts off flow to the return line like a float needle and seat in a carburetor thus increasing volume and pressure to the IP . Unlike a FPR without a return port would just restrict flow thus increasing pressure but reducing volume, correct?
 

FellowTraveler

Well-Known Member
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1,869
Location
Nature Coast
Isn't the idea behind it to only increase volume and pressure when needed under load to the IP thus reducing wear tear and added stress to the LP? Can't too much pressure @ low demand cause ill affects and or timing changes to the IP? Look at the working's of the Fass FPR, I now know why the first guy told me it will only raise the pressure. When either spring pressure or upper housing pressure is put on the topside of the diaphragm and aluminum piece, it just shuts off flow to the return line like a float needle and seat in a carburetor thus increasing volume and pressure to the IP . Unlike a FPR without a return port would just restrict flow thus increasing pressure but reducing volume, correct?
The IP is designed w/overflow-return unlike a carburetor 'I suspect closing off the overflow/return even momentary would cause other issues.'
 

n8in8or

Well-Known Member
Messages
2,713
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3,140
Location
Kalamazoo, MI
Isn't the idea behind it to only increase volume and pressure when needed under load to the IP thus reducing wear tear and added stress to the LP? Can't too much pressure @ low demand cause ill affects and or timing changes to the IP? Look at the working's of the Fass FPR, I now know why the first guy told me it will only raise the pressure. When either spring pressure or upper housing pressure is put on the topside of the diaphragm and aluminum piece, it just shuts off flow to the return line like a float needle and seat in a carburetor thus increasing volume and pressure to the IP . Unlike a FPR without a return port would just restrict flow thus increasing pressure but reducing volume, correct?
Yes, that is how the boost referenced regulator works. What I’m saying is it is yet to be proven whether there is a benefit to manipulating the inlet pressure to a DB2 IP. The IP is calibrated to work with a certain inlet pressure. Changing that inlet pressure may not have much affect on the outlet pressure without other IP modifications.....or it might, I don’t know. Someone knows I’m sure, but it hasn’t been shared in this thread. The one thing I do know is that changing the inlet pressure will affect the injection timing of the pump. That is something that would have to be looked at very closely. So while the rising rate regulator is a neat idea and MAY have a cool use for performance, that has yet to be proven so I don’t think it should be the main focus. It would be nice to get a regulator with that boost reference port for future playing, but I don’t see that as a priority. The return style regulator itself should go a long way to stabilizing fuel pressure and that is the most important thing-at least in my eyes.
The IP is designed w/overflow-return unlike a carburetor 'I suspect closing off the overflow/return even momentary would cause other issues.'
I have tried pinching off my return hose in an effort to come up with an external timing advance mechanism and even before you fully clamp it off it kills the engine.
 

spdgofast

Active Member
Messages
210
Likes
86
Location
Florida
The IP is designed w/overflow-return unlike a carburetor 'I suspect closing off the overflow/return even momentary would cause other issues.'
We are talking about adding a dedicated return line and not touching the existing OEM return system. At least that's what I was meaning in my previous post, sorry for the confusion.
 

Will L.

Well-Known Member
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8,472
Location
Boulder City Nv
No knowledge just thinking steady pressure was best. That’s what we did back on the covered wagon days, but doesn’t mean it was best.

On the runaway from problem- HECK YEAH that is possible.
2 things here:
1. Maybe install an isolater like the one Leroy sells (or used to sell)
2. My hotrod trails I had 3 runaways. The first one was helpful on my e.t.- good run! Then it stuck a rod in the racetrack right at the traps. The next two runaways I pulled a cable and blocked airflow killing engine. Yup- only took one time and that eneded that. I would like to put a safety on the hummer, but a little pricey. I keep thinking about homemade affordable one.
 

n8in8or

Well-Known Member
Messages
2,713
Likes
3,140
Location
Kalamazoo, MI
No knowledge just thinking steady pressure was best. That’s what we did back on the covered wagon days, but doesn’t mean it was best.

On the runaway from problem- HECK YEAH that is possible.
2 things here:
1. Maybe install an isolater like the one Leroy sells (or used to sell)
2. My hotrod trails I had 3 runaways. The first one was helpful on my e.t.- good run! Then it stuck a rod in the racetrack right at the traps. The next two runaways I pulled a cable and blocked airflow killing engine. Yup- only took one time and that eneded that. I would like to put a safety on the hummer, but a little pricey. I keep thinking about homemade affordable one.
The isolator is a top-notch idea. I dig.
 

spdgofast

Active Member
Messages
210
Likes
86
Location
Florida
No knowledge just thinking steady pressure was best. That’s what we did back on the covered wagon days, but doesn’t mean it was best.

On the runaway from problem- HECK YEAH that is possible.
2 things here:
1. Maybe install an isolater like the one Leroy sells (or used to sell)
2. My hotrod trails I had 3 runaways. The first one was helpful on my e.t.- good run! Then it stuck a rod in the racetrack right at the traps. The next two runaways I pulled a cable and blocked airflow killing engine. Yup- only took one time and that eneded that. I would like to put a safety on the hummer, but a little pricey. I keep thinking about homemade affordable one.
Hey Will, do you remember what the intended use was for on the isolator the Leroy may have had?
 

Will L.

Well-Known Member
Messages
8,672
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8,472
Location
Boulder City Nv
Fuel pressure gauge. It’s so you can use a mechanical gauge, but no fuel enters the cabin.

I remember he stocked them. But talked about not carrying them long term, probably cuz not enough people understand how much money it saved long term to install a pressure gauge. Or too many folks like me that will run a diesel line into my cab and won’t panic if a gallon sprays on me- free cologne- haha.
 

spdgofast

Active Member
Messages
210
Likes
86
Location
Florida
I got a brass fitting today with a one way ball valve with a 1/8" NPT thread so it threads right into the FPR. It takes 3psi to pop the ball loose. I know because naturally the first think I did was blow into it each way and it didn't just flow free. I still don't like the idea of a $17.00 ball valve as engine insurance so to speak, I realize at least with the ball valve two items would have to fail to get fuel into the intake. If I use this FPR and run a dedicated return line I'm going to have to start a thread named the most expensive fuel system. LOL
 
Messages
5
Likes
4
Location
central PA
Hey Nate, any progress on your system? I haven't been on here in a while and I will admit struggling to comprehend everything that was talked about (my fuel system is stock and works for my needs right now, but I have talked to Conestoga about something better). Did you ask Mel if your pump was set up to handle 25psi input in low throttle/boost situations? Does it surge at idle/part throttle now? Or are you just concerned that it will happen with a higher volume lift pump? I apologize for my ignorance!
 

n8in8or

Well-Known Member
Messages
2,713
Likes
3,140
Location
Kalamazoo, MI
Hey Nate, any progress on your system? I haven't been on here in a while and I will admit struggling to comprehend everything that was talked about (my fuel system is stock and works for my needs right now, but I have talked to Conestoga about something better). Did you ask Mel if your pump was set up to handle 25psi input in low throttle/boost situations? Does it surge at idle/part throttle now? Or are you just concerned that it will happen with a higher volume lift pump? I apologize for my ignorance!
Hello. I worked with Mel’s old shop manager when setting this pump up. It is designed for a constant 25psi of inlet fuel pressure in all conditions. It has no surging at idle or part throttle. I’m not concerned about any problems with a larger volume lift pump - I’m trying to come up with a modestly proced fuel system that will provide the volume and pressure that the IP needs to put out maximum fuel - the current system can’t keep up so I’m leaving some power on the table.
 
Messages
110
Likes
99
Location
PA
Step away from the norm and try things that are more unique. The manufacturers don't always have all the answers, especially for a 20+ year old application. These can have a pre set regulator in the fuel bucket inside the tank or an external regulator with dedicated return. We run 1/2" line up to the primary spin on filter to eliminate any pressure drop that's present with smaller line. Dead quiet, simple and reliable with very little amp draw to boot.
 

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