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

[Gary - K7GLD]

Greg - looks like you were typing your post as I was sending mine!

 

[Lsfarm]

Yes I was

Gary, that is exactly what happened, when I submited my post you had beat me to it. LOL.



I do believe that the simple duct I made is helping, but an actual fuel to air cooler in the return line would be better. The duct should be sending a fair amount of ambient air that didn't go through the radiator directly to the top of the VP.



The problem for me with a fuel to air cooler is that I live on 1. 3 miles of dirt road that is often muddy, and in the winter the slop, slush, ice and SALT make a real mess of the underside of the trucks on all roads. So I'm not sure a cooler is in my future or not. If I could find a small cooler and MAKE myself install it and remove it for the seasons it may happen, but that would be just one more maintenance item to add to the existing list that is rarely done up to date... . SIGH



And being away from home and the shop 15-18 days a month certainly doesn't help.



What would be interesting would be to drive my '98 12v on a comparable trip and see just how hot the fuel and P7100 get. Not that it would change our hot-VP44-computer probem but maybe a bit of perspective on the situation. ??



Greg L

 

[rweis]

The P7100 drive would be REALLY interesting data.



Bob Weis

 

[Texas Diesel]

Observations while towing with a fuel cooler.



Load - 3 ton 5th wheel @ 70MPH

Tank - 3/4 - full

Temp - 99F

Exit fuel temp - est 140-150F ( little too hot to hold )

Fuel temp exiting cooler - Same as ambient air temp. (felt the same temp as metal bumper)



Since the LP pumps 300GPH (?) the contents of the tank are exchanged fairly quickly allowing the fuel to heat up in the tank. Since the tank is 1/4" polyurethane it will act as a good insulator keeping the fuel hot.



Supplying the VP-44 with 99F fuel is MUCH better then supplying it with 140-150F fuel.



The suggestion by lsfarm, barryG & Honn to cool the return fuel was a good idea.



Obviously the VP-44 will benefit from cooling the fuel.

 

[rweis]

More data:

The RASP is installed, VP fuel return is in the vent pipe, RASP fuel return is in a seperate fitting in the vent pipe, fuel cooler and fan are not yet installed.

Condition, tank, fuel in, electronic bay, fuel return, VP body, mileage, OAT

30-35,1/2,89,92,97,104,55941,75*

70-75,1/2,96,105,108,126,55962,75*

60,1/2,92,103,105,116,55978,75*

30,1/2,95,100,104,115,55980,75*



My general feeling: I only have a input fuel psi as the VP fuel psi went T. . 's Up (replacement on the way from Westach). Input fuel psi 15 idle to 18 at 70 mph. More fuel psi (within reason) seems to significantly cool the VP. Prior to RASP electronics bay avg was 136*, now 100*. Need to make a couple of runs during high OAT to confirm. General overall VP temps dropped 20* - 30*.



I think the next key is to be able to cool the VP fuel on its return to the tank so the tank does not get above the OAT temperature as Texas Diesel did for the same reasons. I think dumping the VP fuel into the rear of the tank is better than dumping it into the pickup cannister, the fuel cooler is the best option though.



By monitoring the fuel temps supply to the VP (gauges in about 2 weeks) it will give good insight as to what you can expect in temperatures at the VP. Use fuel temperature gauge to determine when to fill up?



Seems we are starting to get a fair handle on this. Oo.



Lots of fuel (pusher pump added to the OEM (by the tank), RASP, FASS (or equivalent)), and 1/2 tank or more or a fuel cooler seems to be most of the results. Think that about sums it up?



Bob Weis

 

[Gary - K7GLD]

JEEZE - the stuff I do in the name of science and experimentation! :-laf



OK, after reading a few comments as to running air ducting from the radiator area back to the VP-44, I decided to add that to my list of shadetree mods. At the local Ace Hardware, I found some neat aluminum ducting - 3 inch diameter was the smallest they had, so I decided to give it a try.



Here's the layout:



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Here's a closep at the VP-44:



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Airflow is primarily directed across the top of the VP and some down across the fuel lines.



Here's the buttoned up setup from the top - a bit tight now that the battery is in place, and my added Frantz fuel filter - the ducting is slightly crushed for clearance, but probably still flows more air than an UNcrushed smaller diameter duct:



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And here's the inlet - this will be secured better, and neatened up a bit shortly - and I plan to look into incorporating a small PC type muffin fan on a delay timer to continue flowing outside air to the VP-44 for a preset time after the engine is shut down...



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Now, for a few more local temp test runs to see if any effect is noted - and then the longer RV haul in a couple of weeks! Oo. Oo.

 

[rweis]

A bilge blower comes to mind, if it will fit.



The Turbo uses a revolutionary in-line design to provide quick, efficient ventilation of bilge gases. Water resistant. Turbo in-line blower offers a special sealed motor, for installations where heavy moisture may be present. Their durability is proven under rigorous moisture tests. It provides 230 cubic feet per minute air flow and draws only 3. 5 amps for longer blower and battery life. For 4" I. D. hose. Five-blade design maximizes air flow, exceeding other blowers by up to 25%. Amp draw is 20-40% less for higher efficiency, less battery drain, and cooler running motor. Compact in-line design for easy installation. Meets ABYC, USCG and ISO standards; NMMA listed. Dimensions: 5-1/8"L x 6-1/4"W x 4-3/4"D.



I use one of these in an 5er RV 4" A/C duct in the bedroom to draw the air from the downstairs.



Bob Weis

 

[Gary - K7GLD]

Afraid that blower is a bit too big - especially too deep - to mount up front of the radiator brace behind the grille = and not many options along the duct run either...



A thinner muffin fan will fit - but the smaller ones I have are too small and ineffective - I'll check around for the next size up from what I have. I don't think a great rush of airflow is needed after engine shut-down, just enough gentle outside flow to negate underhood heat buildup...

 

[Gary - K7GLD]

HOOoookay - another test run with the newly added fresh air ducting - ambient temp - 86 degrees, 20 mile test run, 2/3 tank of fuel, A/C on.



fuel canisters - 108 degrees

VP body and top - 116 degrees



Seems the added ducting has effectively countered the added underhood heat caused by running the A/C, haven't yet checked with the A/C off - but A/C on is the normal condition in the scenarios we are most concerned about anyway...



After a good 20 minute heatsoak in my 95 degree temp garage, VP body temp rose to 137 degrees - here's where the time-delayed fan feeding into the added ductwork could pay off...

 

[Texas Diesel]

The problem with what you are doing is that you are reading surface temperature which has very little correlation to internal temperature, which is where the electronics live.



Surface temperature will vary considerably but internal temperature is what kills the little hunks of refined sand.



Heat will flow or properly be "sinked" away from the hot side to the cool side. What you are doing is like takeing the temperature of the surface of the radiator and useing that as an indicator of cylinder head temperature. Which it is sort of via conducted heat (coolant flow) but will not be very accurate. You are only getting a very rough / crude estimate of VP-44 internal temp.



As I mentioned in an earlier post, the only way to cool the VP-44 is to continue fuel flow after shut down. Question is 1. how? and 2. How long? #2 can be answered by time lapse readings (every 5 minutes) untill temp stabalizes.

 

[Hohn]

Guys, we got off track on this whole thing.



Air ducting is probably a complete waste. It just too complicated to route cool air to the VP in such a way as to make it effective. To make it worthwhile, you'd need a shroud of some kind that encapsulated the VP. You'd have to get outside air to the VP in such a way as to 1) keep it cool and 2) ensure underhood air didn't get to the VP to warm it up.



Both of these are simply impractical, imo.



And even if you *could* get a thermally insulated, air shrouded setup to duct outside air to the VP, you're still trying to cool it with AIR. Air is a poor cooling medium. it can't absorb much heat before it gets hot itself and will cool no more. Air cooling really only works if you have a HUGE HUGE reservoir of cool air. Meaning it would take HUNDREDS of CFM to get enough airflow to the VP to make it effective at cooling.



This leads me to conclude that FUEL is the cooling medium of choice. Apparently, Bosch and others agree. The specific heat of fuel is MUCH higher than air. This means it takes less volume of fuel to dissipate the same amount of heat.



Also, I think we have it backwards on fuel PSI. If lower temps are your primary concern then LESS pressure is what you want. Remember, pressure is a measure of restriction, or opposition to flow. We long ago established in the legendary "pumps, lines, what not" thread that increasing fuel pressure does NOT increase the flow of fuel through the VP!!



So what happens when you increase fuel pressure? Let's actually back it up a little bit and ask another question: what are the sources of heat to the fuel?? Of course there are the VP and injector flow stream, or just engine-related heat. Then there's the ambient heat from outside air temp and radiant heat off a hot asphalt road to a black fuel tank.



But there's another source of heat. THE FUEL PUMP(S). The more load is placed on a fuel pump, the more heat it generates.



Question: under what output conditions will a fuel pump run the coolest?

Answer: ZERO pressure, like an open ended garden hose. If you run your fuel pump's output into a bucket, the pump will run cooler than if it was trying to pump through any kind of restriction. The more restriction relative to flow, the more "pressure" in the line--- and also the harder the pump must work, so it runs hotter.



So, from a pumping perspective, you want to ensure the following is happening:

1) The VP is is the only significant restriction in your fuel system loop

2) You are only trying to pump as much fuel as you need for a given engine demand. 18-20psi at idle is wasteful and hard on the pump(s). Much better, imo, to use a bypass regulator that ensures the pump never has to work against more than 12psi of resistance or so.

3) Overall fuel delivery (pump flow rate) should be matched to engine usage. No more, no less. If your pump can flow enough to maintain 5psi or so at WOT, then you have enough pump. If you have 20psi or so, you have TOO MUCH pump, especially at idle. Idle is the toughest on the LP of all possible operating conditions. This is because the opposition to flow is the highest, so it's working very hard.





So, that's my spiel on pump flow. Overpumping fuel will cause heat to be generated, and this heat ends up in the fuel.





PART 2.

~~~~~~



Cooling asssistance to the VP should be done through fuel cooling only, and this fuel should be cooled on the RETURN side. I've laid out my argument for this reasoning in an earlier post in this thread.





Finally, why not plumb the return side of the fuel system with Copper hardline? In the absence of a dedicated fuel cooler, the high thermal conductivity of copper would offer a cooling effect that's sure to help at least a little bit.



Not trying to discourage anyone or flame anyone, but I feel strongly that both the air ducting to the VP and the INCREASE in fuel pressure are at best ineffective, and at worst, a step in the wrong direction.



RWEIS-- try lowering the FP on your RASP setup to 10psi or so at idle, and tell us how that affects your readings and/or performance, if you are able and willing to do so.



Comments?



Capt H

 

[rweis]

On the blower, you could mount it anywhere as long as it got outside air, it would not have to be forward, it could be behind a headlight as long as it had access to outside air. Being 12v and low amp draw a timer that triggered with engine shutdown might be a possibility. At 3. 5 amps / hr you could run it 2 hours without much detriment to the electrical system. You could also run it when the engine is running, just more outside air on the VP.



On the internal temperature of the Vp, that is probably correct, but unless you have a way to get an internal temperature then it is the next best thing. One of the things we are taking is input fuel that goes internal. I think you have to admit that if input fuel is 30* - 40* cooler than it was before fuel system changes then that is probably a good thing.



The other thing we are finding is the whole outside body of the VP is cooler than it was by 20* - 30*. Not an internal temperature true, but could quite probably give an indicationthat the internal temperatures are cooler as well.



Using your analogy of the radiator and piston temperatures. If the radiator temperatures are less then there quite probably are lower internal temperatures and vice versa. You would have a hard time measuring piston temperatures, but use radiator temperatures and EGT's to indicate how the probable internal temperatures are going.



I think we have come up with some actual data that says feeding the upper limits of the VP input pressures (14 psi) at more volume than the VP is able to ingest (hence the bypass back to the tank in the RASP system) (and quite possibly the VP bypass being somewhat open to bypass fuel as well) that you will get more cooling internally in the VP than feeding it 10 psi with only the OEM lp.



I am not educated enough on the internal workings of the VP, but as I understand it, it has to be rotating to pump fuel and therefore use fuel to cool internally.



It should be interesting to see how to measure internal VP temperatures. Possibly a case bolt with a temperature probe mounted inside the bolt?



I'll keep working on cooling the input fuel while you figuer that one out.



Bob Weis

 

[Gary - K7GLD]

The problem with what you are doing is that you are reading surface temperature which has very little correlation to internal temperature, which is where the electronics live.



Surface temperature will vary considerably but internal temperature is what kills the little hunks of refined sand.



Heat will flow or properly be "sinked" away from the hot side to the cool side. What you are doing is like takeing the temperature of the surface of the radiator and useing that as an indicator of cylinder head temperature. Which it is sort of via conducted heat (coolant flow) but will not be very accurate. You are only getting a very rough / crude estimate of VP-44 internal temp.



As I mentioned in an earlier post, the only way to cool the VP-44 is to continue fuel flow after shut down. Question is 1. how? and 2. How long? #2 can be answered by time lapse readings (every 5 minutes) untill temp stabalizes.

You might be correct - IF - all we were relying on was a single test run, and NOT making any changes. BUT, if modifications are made that then show REDUCED external surface temps, that the INTERNAL temps must be reduced as well?



I sorta doubt you could affect one, without also affecting the OTHER! At least, if that WAS the case, we could all throw away the radiators on our trucks!



As to my duct test, a review of previous runs (which clearly shows the VALUE of accumulated data!), shows no appreciable improvement with the added ducting - at least in the relatively short-haul test I made - but I'll leave it in for a while to test under other more strenuous circumstance.



But yeah, I agree, cooling the FUEL is likely to be FAR more effective than any air cooling is likely to be - I only tried this approach because it was quick, cheap and easy - sorta like ME...

 

[rweis]

Hohn,



I think fuel is the way to cool as well. I have to get a replacement 0-30 psi sensor from Westach before I know what the input VP psi is. Susposedly the RASP bypass is set at 12 psi out of the box so the VP gets 12 psi. I do not know what happens as the RASP pumps at higher rpm until I get the replacement sensor. Actually until I get the sensor I do not know what psi is going into the VP. I do know the pre filter psi is 14 - 18 psi (if my pre ff psi sensor is accurate). I do not know what happens in the filter or after yet. Sensor for the input VP psi should be here in a week.



I also agree the return line of the VP to the tank is where the fuel cooler should be. I do have a question though. I have bypassed my VP to the tank filler line (back end of the tank). I cut the VP return hard line by the forward end of the tank and it was . 311" od. It fit inside the AN-6 easily. I think the AN-6 id is . 330". 3 small hose clamps and no leaks (line is not under pressure). Today I was up front working on re-running sensor lines so they would not have to deal with the engine compartment heat. The VP return line after the T on the rear of the engine is encased in a rubber outer tubing. If you pinch the rubber outer tubing there is a gap between it and the inner fuel tube. I pulled the outer tube back where the inner tube is mated to the hard line and the inner tube is sweged INSIDE of the hard line. The hard line is 5/16 od, the id would have to be less, the od of the VP fuel return in inside the 5/16 od so the id of the VP return line must be what? 2/16"? 3/16"? Anybody ever measure it? Can't be very large. Maybe small so the VP return fuel has time in the VP body to pickup heat? Interesting.



One of the key things is tank volume I think. I am mounting a 1000 cfm fan on the fuel cooer (H7B) and a temp sensor (30* - 150*) on the VP input fuel line. I am going to gauge when to fill the tank based on VP input fuel temps. If the fuel starts to heat up as it gets to low tank warning I will turn on the fan to try to control the VP input fuel temp to below 100*. If that does not work then based on OAT and load on the engine with the fuel cooler fan on when the fuel input temp reaches 100* I stop and refuel regardless of what the tank level is. That will be an interesting set of data. Rather than refuel based on tank level, refuel based on VP fuel input temperature



Maybe a VP fuel input temp gauge should be one of the standard gauges?



Refuel at fuel low light or VP input fuel temp of 100* whichever comes first. Then the guys that do not want to mess with the fuel coolers etc can see what their VP input fuel temp is and make their refuel decision based on tank level or VP fuel input temp. They can choose what ever VP fuel input temp they want, knowing VP fuel input temp of 160* is maximum. Would not matter what load you are towing, or what speed you are going, or what the road conditions are. Low tank warning or VP input fuel temp of 100* which ever comes first.



The VP cooling is like the 47RE cooling. We put in aux coolers (some with fans) for the transmission when we tow heavy, hot conditions, or rugged terrain. This concept we are doing here is the same. VP cooling when we are towing heavy, hot conditions, or rugged terrain.



Sure is an interesting ride!



Bob Weis

 

[Lsfarm]

Cooling and pressure heating

Hohn, while I do agree with your post, the facts are that it will be virtualy impossible to insert a temp probe into the computer to read the actual internal temperature. So what we are reading is the best that can be done. And like stated above, any reduction in external temperatures will mimic a reduction in internal tmperatures. Maybe not 1-1, but mimic it nonetheless.



Now, for the temp rise with pressure. There is very little temp rise with only a few psi rise in pressure. I don't have a graph, but the low pressure fuel pumps on aircraft fuel tanks [submerged pusher pumps] don't have any issues with temp rise of the fuel. The only place we have a temperature consideration is raising the hydralic fluid pressure to 3000psi, and this does create hundreds of degrees of heat. There are monitoring systems and coolers for the Hydralic systems.



The VP44 is creating significant output pressures [much higher than 3000psi] and associated heat. This is why the abundance of fuel circulated through the VP and back to the tank for cooling .



Reading fuel pressure is like the external temperature reading it is the easiest, not the best way to approximately measure flow. But we do know if the pressure is low, the flow is less and the VP dies, and nobody has proven that 20-30 psi damages the VP, it only causes hard starting if the pressure is applied prior to the start.



There is no doubt that putting a cooler in the fuel return line is the best way, but it is at least a 2 hour job to hack a system together and probably at least a 4-8 hour job to do a nice clean install of a well thought out system.



The very simple air duct that I used and Gary installed took like 20 minutes, including in my case looking for the old extra shop vac hose. Now air is a poor conductor of heat, but accessing unheated ambient air that hasn't gone through the A/C compressor, intercooler and 190* radiator HAS to be better than blowing allthe 190-200* air on the VP and it's external mounted computer. ANY effort to cool it has to be an improvement.



When I was on my towing trip the under-hood temperature of items like the radiator shroud, the plastic cover on the TPS, and other items under the hood were in the 170* range, while the top of the VP was around 135-140* I attribute this to the 'only' 95* outside air ducted to the top of the VP The fuel cooling of course had a significant imput at well.



The true best case will be a remote mounted computer near an A/C duct outlet in the cab, but that is a long way off. Next would be a refrigeration unit on the VP, next an Air-to-fuel cooler in the return line, then the very least is the outside air duct to the top of the VP. My system is the very least,system, but far better than nothing.



Has anyone done a Poll on WHEN during what season [hot or cold] their VP44 died??? More polls, and maye more info??



Greg L

 

[rweis]

My VP coded 0216 towing a 5er (13k) 1100 miles in July (hot, A/C on) from FL to IN by way of Chattanooga (mtns). Lp replaced (10 psi) in FL and eventually VP replaced in IN. No codes on the way back. New lp 14 psi to new VP on the way home. Same route as up and no 0216 codes. 53k

 

[Hohn]

My VP died when the warmer weather came this year. New one went in June under warranty

 

[Gary - K7GLD]

Sorta seem to me, different folks are willing and able to employ varying levels of mods or corrective fixes.



And yeah, some are recognized from the outset as likely to be more effective than others - but for some, other priorities rate a bit higher, and while a guy might not be in a position to go whole hog, he MIGHT be willing to take a smaller step if a worthwhile one is provided.



The different readings we are seeing here are based on several different fueling setups - a bigger cross-section would be better, but for now we have to go with what we got!



To me at least, this is ALL about keeping the VP electronics as cool as reasonably possible - I have no reason to suspect the internal VP mechanicals would know the difference between a 160 degree operating temperature and a 110 degree one as far as failure rate is concerned - but the internal electronics sure might!



It's quite likely some approaches will be better than others - providing more fuel with a pusher or more efficient single pump may well provide the most dramatic result - or maybe the added fuel return cooler - both together even better yet. The simple duct may prove to be somewhat effective, and the refrigeration VP top cap has yet to check into the game.



But all in all, a lot is great, but even a little bit is better than nothing - you pays yer $$$, and makes yer choice!

 

[Gary - K7GLD]

Hope I'm not speaking out of turn here - but a private message from Bob indicates he is seeing an added 20-30 degree VP-44 temp reduction due to the improved fuel flow from his newly installed RASP setup - it's very fortunate he was taking the pre-install VP temps, or that valuable info would have been lost!



Here's my reply to him:



===

That's very encouraging info on the cooling effect on the VP-44 with the rasp - I'm sure any similar fuel flow increase from other setups, like mine, deliver the same benefits. Sorta amusing that we were so focused upon the direct FUEL related benefits od added or improved fuel delivery, we were totally unaware of the heat related internal computer control issues - but had already helped THAT issue as well!

===



Sometimes those of us who like to experiment and gather data get laughed at and ridiculed for our efforts - and sometimes the stuff we do might SEEM pointless or foolish - but eventually, SOME of this stuff settles out, and forms the basis for mods that actually CAN be very beneficial - either by themselves, or incorporated with others...

 

[RClark]

With all these studies has anyone looked at the efect of a 180 thermostat vs the Dodge 190?