Engine/Transmission (1998.5 - 2002) Modifying fuel system so temperature input to VP44, 80* - 100*, your inputs.

[Texas Diesel]

Quote:



Who cares what the box does? The ECM will still cut of three cylinders and deliver minimum fuel while coasting in order to keep the VP lubed. Doesn't matter what "the box" does.





That is what the DC suit doing the class told my friend, that some aftermarket performance enhancing fueling boxes, cut the fuel to zero IMMEDIATELY on overrun or coasting. This is what is causing some of the VP failures, lack of lube.



You obviously know more than I do but I am just relating a conversation we had.

 

[nps]

Sounds like the DC suit was trying to justify to the class the policy of warranty voiding for fuel enhancements so the class wouldn't have sympathy toward owners and overlook fueling boxes when doing warranty work.

 

[Texas Diesel]

I thought the same thing, and asked the tech that was there the same thing. He felt that DC was honest and not trying to avoid class action law suit.





Your guess is as good as mine. Dont know. :{ Could be some of both.

 

[rweis]

Just a little more FYI:



Went to DC to get the fan and fan clutch taken off so the crankshaft seal could be changed by someone else. OAT 60*.



The fuel temp input to the VP went from OAT + 10* -> OAT + 15* (One of my coolers is mounted on the back of a front hitch and must get some benefit from the fan blowby.



The EBC temps went from OAT + 15* -> OAT + 25* or generally the same as towing temps. Eventhough the blower was still the same as before, the slightly higher engine temps (by about 10* - 15*) reflected in more heat picked up by the VP from the engine.



Everything else was pretty normal. I tried very hard to not have any sit idle at stop lights time and was pretty successful. So all the drive time (20 minutes) had ram air coming in the radiator at 30 mph to 51 mph.



Interesting how removing the fan effected the VP temps.



Bob Weis

 

[rweis]

More testing, changes, etc:



Since a couple of weeks ago I took off the fuel cooler up front behind the front receiver hitch (it was sloshing really badly), added a (home made) fuel cooler in front of the A/C core, and moved the inline fuel filter to where the old fuel cooler was (the frame mount was too hard to change the inline filter, too burried under lines etc).



Net result:



At slow speeds (1400 rpm, 51 mph) I got rid of 5* in the VP EBC. VP EBC went from OAT +15* to OAT + 10*, the fuel temp went from OAT +10* to OAT + 8* (more fuel cooler up front). The EBC delta above the fuel temp went from +5* to +2*.



At highway speed (1800 rpm, 65 mph) I got rid of 10* in the VP EBC. VP EBC went from OAT +25* to OAT +15*, the fuel temp went from OAT +15* to OAT +10* (more fuel cooler up front and more ram air). The EBC delta above the fuel temp went from +10* to +5*.



Observations:



The tube cooler (home made, fits infront of the A/C core, 6 horizontal tubes, full width of the A/C core) is only effective at speeds of 45 mph or greater. Seems the ram air at in town speeds is insufficient to have any effect.



Next testing:



My next and probably final test will be to reduce the VP input fuel psi from 17# to 14#. The old thread of "pumps, lines, and whatnot" Bill K indicated as he raised VP input psi the temp of the tank return fuel went up. I am going to try to precisely match the input psi at normal cruise speeds (55+ mph) to the Bosch specs of 14 psi and see what effect that has on the VP EBC temp.



Results:



I am generally pleased with the fuel cooler design and installation. All it is, is 1/2" hard copper "type M" (thick wall) tubing soldered together with appropriate 90*'s and T's. The 6 horizontal tubes are spaced veritcally 4" apart. The side to side is 23" so a "d" clamp (with rubber insert) can be screwed into the A/C core mounting bracket with the existing screws in the existing places go around the 1/2" tubing and be protected by the rubber insert. I also used the air dam 6 x 1. 00 torx screws as the "d" mount at the bottom on each side. Simple and effective secure mounting without adding any mounting brackets. I have a pic in the digital camera and will get it posted in a day or so.



I now have the VP EBC down to OAT +10* to +15*. The VP EBC temp follows exactely with fuel temp +2* at 1400 rpm, and fuel temp + 5* at 1800 rpm. It is so obvious now that the VP temp is based on rpm pure and simple. Of course fuel input temp plays a role, but with same fuel input temp, vary the rpm's and you will vary the EBC temp directly.



The last test (is there EVER a LAST?) will be to match the VP input pressure precisely so as to not generate any heat from that mismatch.



A really LAST test will be to cool the tank return fuel with some sort of a passive cooler.



I want to see how the psi matching does with the VP EBC temps first though. I also want to drive the fuel cooler up front configuration through a couple of tanks to verify that low tank levels do not change its effectiveness.



For you northern guys, I also made a simple front cooler bypass, so when you do not want to cool the fuel, just bypass the cooler. Easy 1 minute, 2 coupling changes and "no fuel cooling". You could use a winter front as well to do the same job. I think if you used a winter front you might actually capture the heat off the engine to warm the fuel. You would have to test that on your own.



I'll do another post after a couple of tanks of fuel to see what the long term effects are. However I think this is getting real close to keeping the VP44 nice and cool. (In the Bosch book in the other thread some of the tolerances of the VP44 are . 1 um. That's really small!, I would think cool fuel will lubricate better than hot fuel, not to mention to keep the EBC in a better temp range)



Bob Weis

 

[rweis]

Pic of copper fuel cooler. 6 rows, spaced 4" apart. U shaped inlet because of being able to easily get to fitting.

 

[rweis]

Copper fuel cooler installed.

 

[Texas Diesel]

Bob, that looks GREAT!!!! Good job.



If you ever want to sell one, I'll buy it!!!!!

 

[Mundgyver]

What is your temp drop across that just out of curosity.

 

[ceastmen]

I have followed this post and whole heartedly agree that fuel temp is important to the well being of the VP44. Recently my son had a lift pump failure in his 2001. 5, I modified his fuel module for 1/2" line to his new lift pump. While we had the fuel module apart he noticed that the returned fuel from the VP44 is dumped right above the fuel pick up in the module. So the returned heated fuel would be picked up first. We routed the return line to dump outside the module to keep from picking up heated fuel returned from the VP44. The module is one of, if not the biggest problem the fuel system has, it pulls fuel through a . 240 diameter and dumps heated fuel on top of the pick up.

My son is a mechanical engineer and bluntly stated that whoever designed this fuel system couldn't have been an engineer! Feeding a powerful diesel engine through a . 240 diameter and dumping hot fuel on top of the pick up is an after thought at best.

Chuck E.

 

[rweis]

One of my future plans is the fuel canister. CStewart has a GREAT CNC fittings for the fuel canister ($68 for 2 fittings includes USPS). See his thread on his fuel canister rebuild.



My fuel return goes to the fuel filler vent line. Idea was to put the hottest fuel the furtherest from the pickup and to mix it as thouroughly as possible with as much cooler fuel as possible. One member did the same thing to keep his fuel mixed because he adds used oil to his fuel.



I will measure the temp drop. I do not think is is a LOT, just some more (maybe a few degrees). It is just copper tube and joints and solder and flux. The key is to measure where you are going to MOUNT it, then make it to fit. The little d clamps worked out well. 2 each side and 2 on the bottom at the air dam (using the OEM air dam screws (6 x 1. 00 nyloc nuts)).



Texas Diesel - When you move to Tampa, we'll get together and make one up. Key after assembly (and all the little solder droppings you know are inside) put a really good filter between it and the VP44, and run it that way for a very long time (filter $$ vs VP44 $$$$), like forever.



Tis fun, I think we are getting this thing figuered out.



Like "Ceastmen" eluded to, I do not think much of the engineering of the fuel system either.



Bob Weis

 

[rweis]

Front copper cooler -



Only effective above 45 mph. Temperature drop about 3. 5* between input fitting and output fitting. May not be of significant value. Since I already have it built I am going to leave it on for a while.



Oh well, some things work well, some things do not work well.



Bob Weis



Oh BTW I did adjust my RASP spring on the bypass valve back to the tank. 1/2 of one turn of spring (cut off) = ~ 1 1/3# less fuel pressure. I took off 1 + 1/2 turns and reduced fuel pressure 4#. I had to use a dremel to get the cut off cleanly. Really good spring steel. I did not have any shims or anything like that in the bypass valve to make any adjustments with.



Now I have just about exactely 14 psi going into the VP44. Matching the pressure from 17# to 14# did not seem to make any difference in the VP EBC running temperature.



Oh well, some things work well, some things do not work well.

 

[Texas Diesel]

That Diesel Engine Fuel Management book is fantastic. Good Find.



Wish I lived close enough so that we could discuss the VP over a beer or 6.



I would like to discuss the function of the accumulator (fig3, pg 221, right above "3" in the block diagram) and the throttle bore (fig 3, pg 215, item 5).

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Did you do any measurements before and after you relocated the fuel reutrn in the tank? Just curious how much hot fuel is just being returned because the return is so close the the suction.



Can you post a pic of how you tapped into the filler vent? I want to do same.



Have you given any consideration to up sizing the line from the back of the engine to the point it enters the tank? Larger return lines might yield greater total flow.

 

[rweis]

I would like to discuss the function of the accumulator (fig3, pg 221, right above "3" in the block diagram) and the throttle bore (fig 3, pg 215, item 5).



I do not know about the accumulator. However it seems to be a spring loaded device (spring to the right). My GUESS is to smooth out the vane-pump pulses hence the spring. Maybe also to "store" the vane pump output when the solenoid is not fully closed or fully open, ie in transit.



One of my questions is the diagram of the fuel feed from the vane-pump . Is the fuel trace up to the Overflow valve ALWAYS connected at the perpendicular connection, OR is the fuel trace to the accumulator one trace and the trace from the solenoid to the Overflow valve a different trace?



What psi is the overflow valve set at? Must be the HIGH end of the vane pump bar (25) or it would dump fuel pressure overboard back to the tank constantly in volume. My GUESS is the overflow valve is set SLIGHTLY above 25 bar (26 bar?) so it will dump the collpse fuel from the solenoid which is at HIGH psi (1200 bar = 17404 psi). Which means that the fuel going back to the tank is a small orifice in the Overflow valve opening up to a MUCH MUCH larger fuel return line (relatively) or the fuel return line would be at 17404 psi. The Overflow item #5 is for facilitating automatic venting of the pump. (Overflow valve #3 paragraph)



The fuel return line is sweged INSIDE a 3/8 OD line. Bill K measured 30 gph at high rpm. NOT a lot of fuel gets dumped back to the tank. I do know the fuel temp back at the tank is about 15* higher than goes into the VP44.



Did you do any measurements before and after you relocated the fuel reutrn in the tank? Just curious how much hot fuel is just being returned because the return is so close the the suction.



I think the total temperature of the fuel is made up of several things.



1. My tank is generally 10* above OAT.

2. The lp compression to get psi is about 2* - 3*

3. The OEM ff adds something about 10* - 15*

4. The VP adds 15* probably from high psi compression then dumping that into a open ended line.



OEM:

OAT + (1) 10* + (2) 2* + (3) 10* + (4) 15* = OAT + 37* and NO fuel cooler dumped right in at the pickup.

Mine:

OAT + (1) 10* + (2) 2* + (4) 15* = OAT + 27* - 10* (H7B cooler) - 3* (Copper cooler) = OAT + 14* and dumped into the tank filler line.



I actually measure OAT + 10* consistantly over a long distance so I think I have the tank getting constantly hotter and hotter taken care of.



Right now I return the fuel return to the tank filler line. I cut the fuel return line at the frame bythe tank and put the line inside AN-6 line and 3 hose clamps on the AN-6 line to secure it and ran that to the filler T.



Next attempt is to cool the return fuel passively. I had a post to find out what the fitting size was on the T at the engine, but no one knew. I am going to figuer that out (and figuer out the pressure exiting the Overflow valve) and then get the return fuel into a cooler of some type probably on the frame. Probably 2 or 3 runs of soft copper (so it can go around and over frame brackets). Some sort of a manifold to spread to the 2 or 3 lines so the fuel slows down for longer contact cooling.



FUN huh?



Bob Weis



Do you have a webcam? I discuss thees things with a couple of others with the webcam so we can show pictures and diagrams back and forth.

 

[Texas Diesel]

Yes, I have a webcam and would like to join in on the discussions.



Thanks for the answers, I'm off to bed with the book to read some more. I'll reply more tomorrow.



I think I want to relocate the fuel return on the tank like you did.

George.

 

[ceastmen]

I saw this in my newest Summit catalog. It claimed as much as an 80 deg. drop in temperature. At what speed or what fluid I don't know? Sounds to good to be true!

Chuck E.



FLX-4130 $39. 95



Brand: Flex-a-lite

Product Line: Flex-a-lite Compact Fluid Coolers

Cooler Construction: Tube and fin

Overall Length (in): 12

Overall Width (in): 3/4

Overall Height (in): 3 1/2

Cooler Material: Copper/Aluminum

Cooler Finish: Natural

Mounting Kit Included: No

Inlet Quantity: Single

Inlet Attachment: Male threads

Inlet Size: -6 AN

Outlet Quantity: Single

Outlet Attachment: Male threads

Outlet Size: -6 AN

Fittings Included: Yes

Quantity: Sold individually.



Fluid Cooler, Fuel, Tube and Fin, Natural, Copper/Aluminum, 2 1/2 in. x 12 in. x 3/4 in. , Each



Lower the temperatures of a variety of fluids with Flex-a-Lite compact fluid coolers. Their tube-and-fin design gives them excellent cooling characteristics without costing a fortune. These compact coolers will fit in most tight places and can be used to cool fuel, engine oil, differential lube, or power steering fluid. Their high-flow design makes them ideal for use with high-volume fuel pumps. Mounting hardware is included.

 

[rweis]

Actually that is cheaper than the copper tube cooler. Just have to find a place



I wonder has anyone has put any sort of a thermal barrier between the VP44 and the block? Styrofoam? Multiple layers of tinfoil? Sheet aluminum panel? Thin plywood would probably even work. What do you think?



Bob Weis

 

[Texas Diesel]

It would have to be thin, perhaps gasket material. I will try this later this Spring, the VP in this truck has a nasty habit of "bucking" while coasting down hills. Has been that way since I bought it. I plan to replace the VP before our July vacation to the Keys.



I will have a sheet of gasket material on hand and see if I can trim a piece to fit. Perhaps I can swing by your place Bob and get some temp readings of the timing case and the VP flange. To see if there is a thermal difference.



???

 

[rweis]

Sure, I carry it in the truck with me all the time. I'll ride on the engine like Slim Pickens and take readings :-laf



I may play around with something in the next couple of days. I need to crawl up and over to see what is really back there. Can you get your hand between the VP and the block on the back side?



Bob Weis

 

[R-N-R]

How about 1/2" thick industrial chemical/weld proof floor mat? It is pricy at about $20 for a 1'x3' section, but it will compress a small amount and should provide some some insulation. There are also less expensive versions of the mat.