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Working on a "next-level" fuel system

n8in8or

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I am starting this thread a few weeks before I planned to, but the topic has come up in one of my other threads, so the timing made sense now so the topic could really get explored. In my other thread http://www.thetruckstop.us/forum/threads/going-mechanical-with-a-moose-omega-marine-ip.45204/ the topic came up when @spdgofast started planning for a large IP for his P400. I have been working on ideas for an improved fuel supply system ever since I got my Moose Omega Plus IP installed and the fuel supply system hasn't been able to provide a constant 25psi inlet pressure that my IP is calibrated for. My current fuel supply system consists of: a stock fuel sending unit with the sock removed into a filter mount with a Wix 33439 filter supplying fuel to a Raptor RP100 lift pump mounted to the frame. The fuel goes through 1/2" ID rubber hose to another fuel filter base under the hood with a Hastings FF1079 filter. The fuel then flows through -6 AN braided stainless steel hose to the IP inlet.

Here's a video of my fuel pressure under full throttle acceleration. Note that the beginning pressure wasn't even 25psi....it sometimes can't even keep up at stead-state cruising.


For about a year-and-a-half now I've been having conversations with @Ratman about a few different topics, but one of the main topics has been a fuel supply system. He has a lot of experience in fluid systems and has some great ideas on the topic. I would say that one of the main components we wanted to add to a fuel supply system was an external fuel regulator located close to the IP inlet. We also want to increase the size of the tube in the fuel sending unit from 3/8" to 1/2" to improve getting the fuel to the lift pump inlet.

I currently have my fuel system all torn apart while I am fixing rust in my Tahoe, so this is a good time to start doing some upgrades. That coupled with @spdgofast actively working on the fuel supply system for his P400 makes the timing for this thread appropriate now. I'm cross-linking this thread with my other thread so the thoughts that started over there can continue over here. I am running out of time to post right now, but will continue tomorrow. Looking forward to what ideas are come up with to get a next-level fuel supply system designed, installed and tested.
 

ak diesel driver

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I've noticed with my RP 150 that at times the fuel pressure flucuates. Sometimes it's right where it's supposed to be other times it'll read up to 5psi lower. Has nothing to do with load. I'm thinking the built in regulator along with it bypassing fuel are causing it. I've been thinking of doing a regulator with a return so I be paying attention to this one.
 

n8in8or

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Here are comments that were in the other thread that are relevant to this thread. If I missed any, please quote them and attach them here.

On the fuel system, I don’t remember if it was here or the hummer forum as Greenmeanie aka @greenmeanh1 here did the write up on his electronic controlled lift pump hat he can adjust fuel pressure on the fly. He mentioned noticable improvements in playing with it at different loads.

I can’t remember details now, but I burned it in my brain that that is seriously a great idea. It makes sense that varied fuel pressure is going to cause better performance at different rpm. Being able to tune the fuel supply just seemed obvious once I read it.

For a dd vehicle I can’t see it helping a ton. But on performance- heck yeah. Theoretically even an algorithm that auto adjust through power band/rpm range.

Following close as I am really thinking about outing my set up for something better.
Interesting. I don't recall seeing that thread here, but it's quite possible I missed it. Was his IP a DB or DS? I'll have to try to find that thread because I'm interested what the results were and how the varied fuel pressure affected injection timing. Perhaps higher pressure at higher RPM didn't affect timing because the timing was all in at that point, but it still gave the added benefit of cramming more fuel into the pump? Now you have me thinking. So if my pump is calibrated for 25psi inlet pressure, then to get even more flow it's going to need even MORE pressure. That's going to be a serious pump to get me that much pressure and flow.
He has a ds4. I think more electronics in his Hummer than any other non military unit around. I mentioned to him I think it is a marketable idea, not just for 6.5 world but all rigs that are trying to improve efficiency- whether power or mpg.
Yeah, the idea makes sense.

How about a boost and or rpm referenced lift pump pressure curve.

Sorta same basic idea behind the smoke puff limiter. Why stress the LP when the flow is not needed. But at higher rpm/boost max out the flow/pressure of the LP.
The idea does seem to have merit. I would have to understand the pressure/timing relationship more to implement that idea, but I REALLY like the idea of limiting fuel on the bottom end with fuel pressure to tame smoke at lower boost and rpm. I think you're onto something there. The puff limiter alone doesn't fully tame the smoke at my fueling level, especially during the warmer months, and I don't like being that guy that takes off from a stoplight puffing black smoke.
From what I remember, he just has a knob and a gauge- then played with it to see results. Any of us that played with ds4 know how valuable 9-13 range is under hard acceleration. But iirc he said traveling down the hiway at constant speed it seemed to like lower pressure- like 8ish maybe?

Making the leap to a computer controlling it, especially since all the info is there in obd2 rigs anyways, seems like a dream.
Now for obd1 / db2 rigs- maybe sensing the tps position as auto feed for increase pressure, then when cruise control is set it could back off a hair to preset level based on individual desired performance/mpg.

Idk electronics at all, so idk if it ends up being a $200 item or a $2000 item. But there are so many hot rodders out there in gas and diesel world that don't bat an eye at 2 grand even if it is only 2% gain.
I feel like since what you’re suggesting is for a DS4 application, this would be/could be accomplished with a good tune. Varying the inlet fuel pressure would just give somebody without tuning capability to modify one of the parameters in a DIY manner, but I doubt it would work as well as a good tune since you aren’t also varying timing at the same time. Probably close enough, sure, but you’re still just trying to reinvent what’s already been invented....again, as far as the DS4 goes. Now for the DB2/4, that could be an advantage, yes. Of course I could be wrong since I’ve never tuned a DS4, but it seems to me that the same thing could be accomplished through tuning software.
Sounds like a rising rate fuel pressure regulator however I suspect the fuel return would need to be enlarged too. Consider, a smaller tank (surge) placed close to the engine running an additional pump larger feed line and return line back to tank this can get pricey.
Yeah I have seen that. What’s funny is they don’t give that much info on FASS’s website so I was going to contact them to find out what the pressure range is - thank you for sharing that link. The price is right. Seems like it could be a contender.
I called Fass today about the FPR-1001 regulator but they said they couldn't give me specific flow pressures due to the fact that every setup varies which I understand. After looking at the housing I was thinking if the lower housing where all of the fittings go is one chamber it would take a pretty stout pump to hold 25-30 lbs with the return line relief don't you think?
I don't mean to hijack this thread and Nate if you'd rather I can start a thread on the subject but I figured you've been giving this some thought. Has anyone tried to install something like this Fuel Lab pickup tube to the OEM sender assembly and using the old pickup for a return? BTW I ordered a FASS pressure regulator today, I guess I'll be the guinea pig. LOL

https://www.jegs.com/i/Fuelab/083/21101/10002/-1?CAWELAID=230006180037512783&CAGPSPN=pla&CAAGID=44693592161&CATCI=aud-454389669042:pla-224363292071&catargetid=230006180039218437&cadevice=c&jegspromo=nonbrand&gclid=CjwKCAjw2rjcBRBuEiwAheKeL_rDdEugaDP6gBFETbGKBjm_FLNVOufpFUWTiFxknUbXXYyxANvfJhoCteYQAvD_BwE
I did once made a 1/2" pickup tube and used the 3/8" as the return. plugged the 5/16". If I had it to do again I would still cap the 5/16" and return in the 3/8". But instead of a pickup tube for the 1/2" I would just do a sump.
I was thinking of just leaving the IP return alone and use the old 3/8 for the regulator return. Just brain stormin.
Yes- unless your pump builder says you need to open up the return, leave it small. So in that case good plan.
Hey Dave, I'm not worried about a hijack, however I am thinking that if we have a dedicated thread for the topic we can keep the info more focused and flowing in the right direction. I have started a new thread for us to discuss fuel supply ideas and I am cross-linking it with this one. I look forward to the discussion and what everyone comes up with.

http://www.thetruckstop.us/forum/forums/6-5-performance.229/
Yes. It makes sense that the IP return stays isolated from the regulator return. If there was a lot of pressure in the return hose from the regulator, you don't want that applying back pressure to the return from the IP. One theory anyway.
Hmmmm. I would sure hope that a well designed regulator could quickly respond to fuel demands and maintain a constant pressure, but I guess time will tell.
Bingo. I've been looking at that tube as well as another one (can't remember by who at the moment) and use the stock 3/8" supply as the regulator return, too. FASS also makes a pickup tube that is both supply (5/8") and return (1/2") combined, but it's more pricey and probably overkill for this power level.
I've been looking at making a 1/2" tube for the sending unit, but it's hard to come up with a good way to make a bend in 1/2" steel tubing. For my particular truck, I don't like the idea of a sump - my fuel tank is low enough as it is and I don't want to add something hanging out of the bottom of the tank that could get hit if something goes wrong. A sump would sure make things easier though.
I think the sump for a rig that actually uses 4x4 occasionally isn't the greatest idea. Pavement queen by all means.
Yes, the sump I did was for a street only truck.
While this following article is about the Bosch P7100 on a 5.9 Cummins its food for thought on 'proper fuel line sizes.'

"Don't dispel using a surge tank to meet your fueling goals being fed by your stock fuel system reality is if its DD your not into the throttle as much as you would be for racing so a surge tank makes sense." With a surge tank closer to the IP than your main tank tinkering with line sizes is far less costly.

http://www.torkteknology.com/technical-article-2-the-diesel-fuel-system-inlet-line/
 

n8in8or

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I've noticed with my RP 150 that at times the fuel pressure flucuates. Sometimes it's right where it's supposed to be other times it'll read up to 5psi lower. Has nothing to do with load. I'm thinking the built in regulator along with it bypassing fuel are causing it. I've been thinking of doing a regulator with a return so I be paying attention to this one.
Now that you mention it, I too had some pressure fluctuation with my Raptor before I did the DB2 conversion. I imagine it's a lot harder to maintain a constant pressure with a non-return/internal style regulator because you're asking so much more to happen inside the housing. Don't get me wrong, I have nothing against the Raptor pumps - mine has been dead reliable for over 3 years, I just think the regulator is holding the pump itself back some.

For phase 1 of my fuel system improvement, I plan on using my Raptor pump. There's a couple reasons for this: I already have it, it has proven itself as a reliable pump, it's priced well for a true diesel fuel pump and theoretically it should be able to supply my IP at my current level. I did contact Air Dog and they told me that to bypass/lock-out the internal regulator, all I have to do is turn the pressure adjustment screw all the way in.

Oh, by the way, for the sake of future readers, at this moment, my current setup is making 350whp and 602wtq on a dyno. It also has gone 14.00 @ 95.85mph at 5900 pounds race weight - those dragstrip numbers verify the dyno numbers to be in the ballpark.

Anyway, back to the fuel pump. I contacted Air Dog back when I was swapping to my Moose Omega Plus and they couldn't provide me an exact pressure/flow curve for my RP100, but they did estimate that at 20psi the pump should be able to put out 75gph and at 30psi it should be able to put out 60 gph. I provided that info to the pump builder and here is what he came up with:


I just finished calibrating your Omega Moose pump. As it sits it made just over 165cc/1000 strokes max and held 122cc/1000 strokes @ 3500 rpm. I played around with feed pressures and found 25 psi to be the best compromise between max fuel and maintaining a good timing curve. I have not yet removed it from the calibration stand so if you wanted me to make any adjustments I can still do so.

I played with the numbers you received from AirDog and believe you will have sufficient fuel. They provided 75gpm @ 20psi and 60gpm @ 30psi. If we assume a linear curve we can approximate 67.5gph @ 25psi.
I converted 67.5gph to approximately 255,500cc/hr.
I subtracted the 37,500cc/hr return flow for a total of 218,000cc/hr
I divided by 60 to convert to 3,633cc/minute.
Divided by 8 cylinders nets us 454cc/minute/cyl.

454 divided by 2.5 gives us 181.5cc/1000 strokes @ 2500 rpm
454 divided by 3 gives us 151cc/1000 strokes @ 3000 rpm
454 divided by 3.5 gives us 130cc/1000 strokes @ 3500 rpm
454 divided by 4 gives us 113.5cc/1000strokes @ 4000 rpm

The above figures are of course considering that you are utilizing max fuel continuously for an hour which is of course unrealistic, but as we discussed on the phone since there is no reserve accumulator in the system I want to be sure the fuel is there on demand.


Based on the math, the RP100 should have enough capacity for this IP, but JUST enough. I'm really hoping that by adding an external, return-style regulator to the fuel system, the Raptor is able to keep up.

I recently talked to the guy that built my pump (Joel and he no longer works at Conestoga) and he thought that with the amount of pressure I am losing at higher rpm, I could be losing up to 10cc of fuel output.....10cc!! If that's true, I'm leaving a fair amount of power on the table, but that has yet to be proven. First step is to make a fuel system that can consistently provide 25psi of inlet pressure to the IP and then take the truck back to the dyno to see what difference it makes in power at the wheels (if any).

If the RP100 still can't keep up, I'm not sure what I'll try next. It's kind of tempting to try the RP150 since the RP100 has shown to be a reliable pump with pretty good output at a reasonable price, but I'm open to other ideas. @Ratman likes the idea of using a Walbro universal inline pump. What's nice about those is that Walbro actually posts the pressure/flow chart for the pumps so you can see what they actually put out. The GSL392 looks like it will have more than enough supply for this IP so it looks to be a contender. There are people that have used it successfully in diesel applications, but there are also others that have had it fail. It makes me nervous having this pump in place, that isn't a flow-on-fail design for my lift pump. The price is very reasonable though, so I have thought about running 2 of them in parallel with check valves so if one fails the backup is ready to go immediately.....and I may still try that, just not sure yet. I have also found that you can buy replacement pumps for the FASS fuel conditioners and those aren't priced too badly either. I'm pretty sure those would have more than enough capacity based on the trucks those are intended for, but there isn't a pressure/flow chart associated with them. I'll probably call FASS at some point to get a recommendation.

More later.
 

n8in8or

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Yes. It makes sense that the IP return stays isolated from the regulator return. If there was a lot of pressure in the return hose from the regulator, you don't want that applying back pressure to the return from the IP. One theory anyway.
I think it's also important to think about this the other way: we don't want the return pressure/flow from the IP affecting the abilities of the external fuel regulator to properly control the fuel pressure to the IP because it is seeing back pressure on the return port. Maybe it wouldn't be an issue, but then again, maybe it would be. So I'm planning on having 3 hoses between my fuel tank and the engine compartment: Supply from fuel tank to IP via a regulator (1/2"), Return from regulator to fuel tank (1/2") and return from IP to fuel tank (5/16").
 

Will L.

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Like Joel said "...since there is no reserve accumulator in the system..."

I was thinking about an accumulator last night, and didn't mention it because I know space is tight and don't like to pose theoretical solutions without plausible ideas, But need to throw this out there. It has been too many years past that I played with any, so I am hopeful somewhere out in the racing circuit there are good accumulators for fuel now days. Larger pumps are normally the easier answer, but just incase...
 

FellowTraveler

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Like Joel said "...since there is no reserve accumulator in the system..."

I was thinking about an accumulator last night, and didn't mention it because I know space is tight and don't like to pose theoretical solutions without plausible ideas, But need to throw this out there. It has been too many years past that I played with any, so I am hopeful somewhere out in the racing circuit there are good accumulators for fuel now days. Larger pumps are normally the easier answer, but just incase...
A one gallon or less surge tank will suffice for reserve fuel in most if not all applications and will fit into small spaces under the hood. Best part of this type of reserve is getting your fuel line diameter tweaked to your application.
 

JayTheCPA

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Toward regulated pressure, I found some possible candidates for bleed-off valves, but did not get any further than search phase. In conversations with the shop, they recommended to increase the intake line diameter a bit and leave the return line's side alone (even with the bleed-off supply plus the IP / injector spill). I also intended to add a low pressure switch (attached to a light) to alert me when the IP was starved.


But, . . . Seeing as you are in complete naked phase and doing a near full rehab . . .

Why keep the 4L80E? Even with that much power, the 4 speed really makes the motor work harder when it does not need to.

At best, reach out to Slim as I gave him some shift tables to make the 4L80E behave more like a stick-shift and not leaving power on the table by way of unnecessarily unlocked TCC or low RPM's with high power request. Never got a chance to use that logic as I had yanked the slushbox by the time the data was ported into the tune, but I heard that it was put in another truck and reported as very street-able and tow-able.
 

n8in8or

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While this following article is about the Bosch P7100 on a 5.9 Cummins its food for thought on 'proper fuel line sizes.'

"Don't dispel using a surge tank to meet your fueling goals being fed by your stock fuel system reality is if its DD your not into the throttle as much as you would be for racing so a surge tank makes sense." With a surge tank closer to the IP than your main tank tinkering with line sizes is far less costly.

http://www.torkteknology.com/technical-article-2-the-diesel-fuel-system-inlet-line/
That was a great article, thank you for sharing that! Those formulas will come in handy for sizing the suction tube.

Like Joel said "...since there is no reserve accumulator in the system..."

I was thinking about an accumulator last night, and didn't mention it because I know space is tight and don't like to pose theoretical solutions without plausible ideas, But need to throw this out there. It has been too many years past that I played with any, so I am hopeful somewhere out in the racing circuit there are good accumulators for fuel now days. Larger pumps are normally the easier answer, but just incase...
A one gallon or less surge tank will suffice for reserve fuel in most if not all applications and will fit into small spaces under the hood. Best part of this type of reserve is getting your fuel line diameter tweaked to your application.
I hadn't thought about or known that accumulators/surge tanks existed for fuel systems existed until you guys mentioned that idea. I can see that working well if a pump alone doesn't satisfy the needs. As @FellowTraveler mentioned, it could work well in a DD situation because you're not always needing 100% flow capability, and in fact need it only a small fraction of the time.

@Will L. this thread is a perfect place to post those theoretical ideas! Maybe that idea directly won't apply, but maybe it will spur another thought or idea. Please share all of them!
 

n8in8or

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I think the sump for a rig that actually uses 4x4 occasionally isn't the greatest idea. Pavement queen by all means.
Yes, the sump I did was for a street only truck.
A sump scares me on the street too. Curbs (sometimes those get hopped ;)) or branches in the road could be a concern for me. I'd like to keep everything for the fuel system above the frame rails and fuel tank skid plate.
 

n8in8or

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Toward regulated pressure, I found some possible candidates for bleed-off valves, but did not get any further than search phase. In conversations with the shop, they recommended to increase the intake line diameter a bit and leave the return line's side alone (even with the bleed-off supply plus the IP / injector spill). I also intended to add a low pressure switch (attached to a light) to alert me when the IP was starved.


But, . . . Seeing as you are in complete naked phase and doing a near full rehab . . .

Why keep the 4L80E? Even with that much power, the 4 speed really makes the motor work harder when it does not need to.

At best, reach out to Slim as I gave him some shift tables to make the 4L80E behave more like a stick-shift and not leaving power on the table by way of unnecessarily unlocked TCC or low RPM's with high power request. Never got a chance to use that logic as I had yanked the slushbox by the time the data was ported into the tune, but I heard that it was put in another truck and reported as very street-able and tow-able.
I'm not sure what you mean by "bleed-off valves", can you explain or post a link or something?

As far as the 4L80e, I actually am pretty happy with how the 4L80e matches my combo. Mine likes being loaded: when the converter locks up in 2nd gear, that's when you can feel the truck really accelerating. Also, shifting takes time - when focusing on shorter bursts of acceleration those tenths of a second add up. For a towing application, I can see the extra gears helping, but even then, the additional expense of sourcing a different transmission and then coming up with the means to control it don't interest me. It's an extreme example, but in the drag racing world, they like to use fewer gears to go quick (except in the Pro Stock class and maybe others?). Top Fuel cars slow down if they try to add gears so they just do a single gear with a slipper clutch, and the Powerglide is a very popular option for a lot of comparatively slower cars. I think for my application and my goals, the 4L80e serves me quite well, I just need to build one that is stouter with a properly matched torque converter for my application. I've done a fair amount of programming with my US Shift Quick 4 to make it work the way I want. My ultimate goal is to have a transmission that is strong enough to handle full-throttle shifts with the converter clutch 100% locked. I think that would really wake mine up, but I don't dare to do that right now with stock trans internals.
 

n8in8or

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While this following article is about the Bosch P7100 on a 5.9 Cummins its food for thought on 'proper fuel line sizes.'

"Don't dispel using a surge tank to meet your fueling goals being fed by your stock fuel system reality is if its DD your not into the throttle as much as you would be for racing so a surge tank makes sense." With a surge tank closer to the IP than your main tank tinkering with line sizes is far less costly.

http://www.torkteknology.com/technical-article-2-the-diesel-fuel-system-inlet-line/
So I applied that equation for the suction tube. I used 165 Gallons Per Hour because as I recall that's what the FASS pumps are rated at (we may not NEED pump that large, but I'd rather plan on the high side and not need it rather than plan too small and regret it later).

165 gph = 2.75 Gallons Per Minute Apply that to the equation:

(2.75 gpm x .3208)/2 cfm = .4411 sq in.......that works out to a RADIUS of .3747, so that means the ideal suction tube at those criteria would have an INSIDE DIAMETER of 3/4". Huh. Maybe that 5/8" FASS suction tube isn't so crazy after all? Now packaging a 3/4" suction tube is another matter altogether. I have thought about just having a tube that enters the tank from the front up high and is angled down towards the back of the tank and resting about 1/8" off the floor of the tank - picking up the fuel about 2/3 of the way back. I was worried about fitting that since the tank is so close to the axle, but maybe I need to look at that option harder and see if I can make it work?
 

n8in8or

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I should also see what the Raptor 100 should need for a suction line. I'll use the 100 gph figure of course, and also the desired 2 cfm based on me driving in a cold climate.

So 100 gph = 1.67 gpm

(1.67 gpm x .3208)/2 cfm = .2679 sq in.......that works out to a RADIUS of .3747, so that means the ideal suction tube at those criteria would have an INSIDE DIAMETER of .292" or a little under 5/16" ID. So the existing 3/8" tube is ok currently.....except that I know if necks down to a much smaller size at the factory o-ring seal. I don't know if it's really impeding pump performance right now, but it certainly isn't helping. That's interesting stuff.
 

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I'm not sure what you mean by "bleed-off valves", can you explain or post a link or something?
A simple device (commonly a spring loaded ball valve) where it opens and diverts fuel to the return path in order to prevent too much pressure within the line. It is similar to a check valve, except it will allow fluid to pass (one way) when the conditions are right. Purpose is to maintain up to a maximum pressure in the line and spill fluid when pressure tries to go over that point.

Here is an example:
http://www.murcal.com/Catalog/Check-Relief-Valves-for-Diesel-Fuel/PRV50-Diesel-Fuel-Pressure-Relief-Valve

Page 2 of this PDF has a schematic:
http://shopping.na3.netsuite.com/core/media/media.nl?id=23876&c=650659&h=25bb783bfa4f3e4e145f&_xt=.pdf

Apparently the DMax uses one and the LB7 version is noted as the most robust (per Kennedy Diesel).
 

FellowTraveler

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I should also see what the Raptor 100 should need for a suction line. I'll use the 100 gph figure of course, and also the desired 2 cfm based on me driving in a cold climate.

So 100 gph = 1.67 gpm

(1.67 gpm x .3208)/2 cfm = .2679 sq in.......that works out to a RADIUS of .3747, so that means the ideal suction tube at those criteria would have an INSIDE DIAMETER of .292" or a little under 5/16" ID. So the existing 3/8" tube is ok currently.....except that I know if necks down to a much smaller size at the factory o-ring seal. I don't know if it's really impeding pump performance right now, but it certainly isn't helping. That's interesting stuff.
I suspected you would like it.

If you decide to run new or larger then teflon AN hose is the way to go also consider the surge tank option that the way I'm going with my Cummins conversion eaving the dual tanks in place and plumbing a tank in the engine bay.
 

n8in8or

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A simple device (commonly a spring loaded ball valve) where it opens and diverts fuel to the return path in order to prevent too much pressure within the line. It is similar to a check valve, except it will allow fluid to pass (one way) when the conditions are right. Purpose is to maintain up to a maximum pressure in the line and spill fluid when pressure tries to go over that point.

Here is an example:
http://www.murcal.com/Catalog/Check-Relief-Valves-for-Diesel-Fuel/PRV50-Diesel-Fuel-Pressure-Relief-Valve

Page 2 of this PDF has a schematic:
http://shopping.na3.netsuite.com/core/media/media.nl?id=23876&c=650659&h=25bb783bfa4f3e4e145f&_xt=.pdf

Apparently the DMax uses one and the LB7 version is noted as the most robust (per Kennedy Diesel).
Interesting. Thanks for sharing!
 

n8in8or

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I suspected you would like it.

If you decide to run new or larger then teflon AN hose is the way to go also consider the surge tank option that the way I'm going with my Cummins conversion eaving the dual tanks in place and plumbing a tank in the engine bay.
Is the surge tank just a reservoir or is it a tank with a pressurized bladder?
 
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