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

[Gary - K7GLD]

Thanks for the clarification on the top cover Jason - at this point, at least for me, it wouldn't be difficult to remove the metal cover and pack the underside with heat conductive putty - I'm running a replacement VP-44 anyway, and with the tapped wire, the warranty is dead, so no problems there. If I decide to go that way, what brand/type of putty would you recommend? I could also easily do some before/after temp runs with and without the putty to see what the difference the temps in the computer module really are, and if the putty really makes any significant difference over what I already have installed.

Wow I just now read this, that could be a great idea, why didnt I think of that. I don't think you will be able to collect enough energy with a solar panel to run it without it looking really gaudy and adding to the cost, however it may be possible to convert some of the heat to energy to supplement the battery so while its hot under the hood (heat soak) you would have plenty of power and when things cool down you dont need the cooling anyway.

I have a 4. 5 amp 12 volt solar panel that I use boondocking with our RV - it is about the same general size as the lid on my bed mounted tool/fuel box. But the reading I have done on the Peltier units led me to believe one in the 16 amp current draw range would be needed to be effective - pretty well outside the range of my single panel - and probably impractical to install 3 more ($300 apiece GE units) panels to obtain the full current needed - and only in direct sunlite at that...

 

[McDowra]

It operates over a large range of voltage and amperage, so I attached a chart



Gary It looks like 1 of those solar panels would work well, for this peltier. $300 is a tough pill to swallow even if you do just need 1 though

 

[Gary - K7GLD]

It operates over a large range of voltage and amperage, so I attached a chart



Gary It looks like 1 of those solar panels would work well, for this peltier. $300 is a tough pill to swallow even if you do just need 1 though

Well, if a Peltier in the 4 amp range would be sufficient, I wouldn't worry too much about battery current draw - my marine blower pulls about 5 amps, and runs for 80 minutes after the engine is switched off - no battery problems so far.



An added observation on the percentage of cooling transferred between the metal top cover of the VP-44 down to the actual electronics board and it's individual components - in addition to the air gap between the 2, there is also a protective membrane that covers and shields the topside of that electronics board.



I haven't seen exactly what lies immediately under that membrane, but suspect there is still another air gap that would tend to insulate and isolate the actual electronics components even with heat conductive putty between the metal top cover and that membrane.



Here's a pic of the cover underside, lying alongside the electronics module for those not having seen what's under there:



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The point being, without actually removing that membrane, how effective would the putty be in efficiently transferring heat away from the module? We can measure the membrane temp, just as we can the metal top cover - but the unknown is, what is that doing to actually cool the module itself?



My own goal and theory is, cool that top cover and the major metal VP-44 area surrounding the module, and there WILL be significant heat reduction from both conducted and radiated temperature differentials, just as commonly happens to items inside a refrigerator or deep freeze.



My own current main temperature probe is attached closely to the bakelite electronics module itself (with another probe monitoring the temperature of the fuel returned from the VP-44 back to the fuel tank) - and hopefully is displaying module temperatures fairly close to what the electronics board itself is exposed to:



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I'm not sure that even measuring the module top membrane will be any more accrate than what I'm already doing - or that it would satisfy those critics who have held to the opinion that pretty much ANY efforts to blow cool air over the VP-44 will be wasted effort - nor am I willing to butcher that membrane and exposing the individual electronics components, simply to prove what *I* believe and accept to be true based upon temp readings I see daily...

 

[McDowra]

Interesting point, the way we measured the temperature of the components or tried to is we have a probe thats apporox . 02 inches in diameter and we drilled a small hole through the membrane so the probe is suspended in the membrane, so it is still possible that it is still insulated by air under that.



Even if battery draw is not a problem we still need a way with our solution to draw air over the heat sink because after extended periods of idleing or after shutdown the heatsink is not sufficient and becomes heat soaked which creates a larger problem.



I don't know the solution, but the inablilty to absolutly prove how effective what we were doing was, and the inability to prove that external heat to the electronics was the actual cause of the electronic vp44 premature failures and not just a scapegoat for a bad design, is the primary reason I got burned out on this project.



Gary - The putty we used was a brand called Thermagon its a division of Laird Technologies. It was their T-putty 502 Series. It worked really well for both heat transfer and as a gap filler.



They have a website Thermagon.com and phone 888-246-9050

 

[rweis]

What I have done is loosly wrap the VP44 in a thermal blanket to only have to deal with the heat from the VP44 and not the adjacent engine block and engine compartment.



Then I flood the entire wraped containment area with OAT from a 4" bilge blower ~ 230 cfm. The entire rear end of the VP44 area by the injector lines is open so the air flow can easily exit there.



One theory I am working is the VP44 is a large aluminum heat sink and I am trying to cool or at least limit temperature rises on the entire VP44. This concept seems valid as when I get a LOT of ram air (60 mph) even the input fuel is being cooled even after absorbing the VP44 work effort to pump the fuel and return to the tank. That is why I am going to mist the VP44 directly. At low speeds (below 40 mph) I do not think I am getting mist from the bilge blower as the mist is too heavy to effectively get up the 3" duct to the VP44.



I measure the VP44 body temperature with a simple thermal contact thermometer. I measure the fuel temp input with a in fluid temp probe.



We have to be careful not to micromanage the problem. Yes we have a heat problem, but if you knock it down to the 2 digit range then I think the answer is close at hand. The thermal barrier and the blower seems to do that.



If the actual internal temperature is say 20* higher than the case then you are still at the 120* range and probably still ok. If you are at the 150* range then that is probably not good enough. I would offer that "measuring it with a micrometer, marking it with a grease pencil, and cutting it with an axe" needs to be kept in mind. That is why the bilge blower ($30) and common boat store inventory.



IF the whole VP44 body is 150* and you try to cool the EBC to xx* the heat is still going to migrate from the whole body to the EBC. That is why I took the approach of cooling the body of the VP44 so the EBC area never gets any hotter than the case mass temperature to maybe + 10* - 20* more.



However, whatever, each of us decided is right for them is good, at least there are some options,



Bob Weis

 

[Gary - K7GLD]

Thanks for the followup info Jason - and I see your point on the longer term underhood heat soak problem at the VP-44 if using only the Peltier device.



Also thanks for the info on the putty - I suspect there would be significant added heat transfer between the internal electronics and the top cover even with whatever remaining dead air space exists between the electronics and the covering membrane - I'll pick up some of that putty and install it at some future point.



Even as it now exists, the functioning temperature differential displayed at my current temp sensor location is dramatic in operation - and it is clearly located in a spot where I am not merely reading the effect of the cooling airflow upon the top cover alone - it IS migrating by conduction down to the lower portion of the electronics module - including the electronics themselves.



Thanks again for your data and expressed overall comments - I feel they go a long way to support and validate the similar efforts Bob, I and a few others have experienced.



Does all that guarantee a long and failure free VP-44?



Sure wish I knew! :-laf

 

[Mundgyver]

Now one more idea for FOOD for THOUGHT A few years ago I came in contact with some younger GEEKY types (Computer Kids) that were trying to soup up the venrable 486 Intel Chip to run faster. The theory was if you could keep it cooler, it would run faster to a point.



What these kids did was to stack Peliers on top of each other on top of the 486 processor. Temp differential per peltier was in the 15* range that they were getting. So by stacking 2 of them they could drop the temp by 30* in theory.



The one problem they did not count on was moisture. Once they started stacking them, they started condensing water out of the air when they got excessive (3 to 4 peltiers stacked).



So like over fueling :-laf stacking peltiers will gain some to a point. The big question is how much.



I did not know that you could use engine heat to drive one of these devices though, if I understand what has been written above already. Interesting thought, self sufficient when the engin is hot, but as it cools down, the sytem would just shut itself down. Interesting. Guess I will have to dig out some of my old books and do some application studies.

 

[Gary - K7GLD]

A followup on the "ram air" aspect in regards to ducted air to the VP-44.



As a test, using the baseline temps I was seeing using the enlarged under-bumper mounted air intake to my Marine bilge ventilation blower as displayed in an earlier post in this thread, I removed that lower portion of the ductwork, including the enlarged "ram air" intake - this placed the active intake right up at the blower - but still pretty well out in open airflow away from radiator and engine heat - but NO significant direct airflow was now applied to the blower, only what transient air was available near the front fenderwell area.



I was amazed at the result!



A full *20 degree MINIMUM increase* in the resulting temperature as recorded at the VP-44! :--)













Where I previously was seeing a nominal 10 degree temp rise above ambient at the VP, I was now seeing a 30 degree temp rise. Nor was I seeing the relatively instant VP cooldown after engine shutdown as before, or substantial cooling at slower in-town traffic speeds.



Needless to say, the ram air intake setup was quickly restored - it's uglier, and noisier than without it, but the benefits cannot be ignored! Oo.

 

[rweis]

I TOTALLY agree with Gary. The ram air effect is significant. At first I had the input to the blower behind the bumper. Then I moved the blower to hang under the bumper in direct ram air flow. I got primarily the same results. Way more cooling effect, and I think above 40 mph the ram effect actually overtakes the fan blower effect. I also agree with the after shutdown conclusions of maintaining the VP44 temps after shutdown rather than the VP44 temp increasing when the engine compartment starts to heat soak.



I have been running without the water mist for a while to make sure I understand what effect that has.



I have not gotten around to rerouting some fo the fuel cooling so all the cooling is on the return line instead of some on the input and some on the output fuel lines.



I am still finding that with longer drives at above 40 mph the VP44 ram air cooling keeps the VP44 cool and the VP44 becomes a fuel cooler.



I have one more VP44 cooling scheme yet to go before I will make final recommendations.



Oh, towed heavy last weekend and intentionally ran the tank down to the low fuel light. The DC concept of the tank being a heat sink is utterly bs. The fuller the tank is, the slower the heat rise, but heat rise none the less. As the fuel is used the faster the heat rise becomes until the ram air blower on the VP44 keeps the VP44 cool enough for it (the VP44) to become a fuel cooler. All that and I have removed the OEM ff and have 4 different fuel coolers on the return line (about 60k # of cooling) and that is not enough for the fuel to be cooler than the VP44 case by about 15* (VP44 case OAT +15, fuel OAT +30, rpm = 2400 (out of O/D) for 3 hours, 13k 5er towed, OAT = 95*).



Gary's idea of cooling the VP44 is exactely right on. His conclusion of the necessity of ram air is also correct. I added a 6" to 4" sheet metal duct reducer to the input of the 4" blower (doubles the cross sectional area) and the cooling increased by about 50%. The ram air effect was really noticiable then.



When I finish the next iteration of test I will report back further. My conclusions for the general Vp44 population so far is a blower with a ram air input as a minimum first step in keeping the VP44 in a reasonable operating temperature range (clean fuel etc etc etc must be done as well).



Bob Weis

 

[mhenon]

I'm glad to see this thread still alive and well. Great job guy's.

Was just wondering your thought's on OAT and the need to cool the fuel. At what temp is cooling actually needed, >80F, >90F or what?

The reason I ask is I took a trip today with morning temps at 40F. After an hour and a half I pulled over and reached in to feel the VP. It was warm but I could hold on to it for awhile.

Now ,my fuel system is modified and there is no OEM LP or OEM filter mounted to the engine so I'm running cooler than most, but do you think there is a point (OAT) where cooling is not really necessary?

Thanks again for all the hard work and info. This was, and still is, a great thread on keeping the VP happy.

Mike

 

[Gary - K7GLD]

Mike, if I lived where Bob does - or in other similarly hot climates, I'd probably want to include some form of fuel cooling into my setup. But here in Eastern Oregon area, as well as most places I commonly drive the truck, or RV to, what I now have installed keeps measured VP-44 case temps below 120 degrees under the worse heat scenarios we experience in this area - and I, as well as the VP, can live with that upper temperature extreme.



In fact, I'll undoubtedly be forced to deal with the opposite extreme - cold weather temps, since cold down into the low teens are not uncommon here.



I'm hoping that merely removing power from the blower will allow sufficiently safe ambient temps for the electronics in the VP - since solid state devices are sensitive and susceptible to low temp problems too - as well as sudden wide swings in ambient temperature.



A fairly rapid swing from 15 to 80 degrees just MIGHT be as damaging as one from 90 to 150 degrees as far as internal expansion/contraction stresses inside one of the LSI devices inside the VP-44 control board are concerned.

 

[mhenon]

That's about what I thought. Almost sounds as though we need a summer configuration (coolers, blowers, etc. ) and a winter configuration that allows for more heat under the hood.

Mike

 

[rweis]

That thought had crossed my mind about a summer and a winter model.



I cut the fuel return line going back to the tank right after the "T" on the engine. Right now it runs through fuel coolers, but a simple ball valve to run it direct to the tank (bypassing the fuel coolers) would be simple.



On the blower, in the early days we had a circuit board to vary the speed to the blower which you could turn the blower output air flow to whatever flow you wanted, or turn the blower off (if you have a temp gauge on the VP44).



Those two things could easily adjust to keep the fuel to whatever temperature you want.



Working backwards, one of the most significant heat sources to the fuel system was the OEM ff. Remount it for the winter and I have no doubt you would have as much fuel heat as you could stand (it even has a fuel heater in it). Might suggest a ball valve here as well.



I can see where a location problem could occur. What I think happened was DC was so focused on winter fuel gelling, they decided the risk of overheating the VP44 was an acceptable risk vs fuel gelling which would give "their" trucks a poor media image for winter driving. I think they figuered the risk wrong, but it is only their responsibility until the warrantee runs out and even then only about every 50k miles (2 replacements average, some guys more).



The Vp44 CAN PROBABLY function with fuel temps in the 120* just fine, but where is the "range" where it can not function? I would feel safe with fuel at 120*, but not at 150*. BTW when pulling O/D out @ 2400 rpms, 13k 5er, somewhat hills, fuel tank temps have peaked at 125* with all the cooling etc I run. Because of the blower, the VP44 body was 110*, OAT was 95*. I think the VP44 was actually cooling the fuel. I am changing my differential to 4. 10 so I can run in O/D on, which will lower rpms about 400 which will also lower VP44 temps 4* and fuel temps ???



Good discussion though, how do you build a truck that is "all weather" and I do have a better appreciation for that that I had when I first purchased it.



There is a new thread about flexlite building an electric fan system for 99 - 02 Dodge diesels (in final test phases now, ready for 1/07 sales distribution). You could have more control over cooling air flow and might contribute to a solution to this VP44 cooling issue. It would be simple to build an "air scoop" in the engine compartment for the VP44, run the flexlite fan "on" during the summer months to flush the engine compartment heat and keep a good flow across the VP44. Possible end solution?



Any idea of the 03 Visatronic fan clutch will fit an 02? There is a thread about being able to control that fan clutch with a cab mounted switch. I would think it would, same basic engine and probably threaded mount for the fan clutch.



More manual systems control and let the driver decide what should be on or off which is basically what we are doing.



Bob Weis

 

[Gary - K7GLD]

In our local climate, at least, we will usually only see summer temps above 100 degrees for perhaps a week - more normally summer temps run just under the 100 degree mark. Even at the 105 degree or so range, with the added nominal 10 degree temp rise at the VP-44 with my specific setup, I'm pretty comfortable with what I've done so far - and fact is, when temps get that high, we rarely do any RV traveling anyway, since most places we would RV are as hot as here, so no incentive to go camping. The shorter, local trips we do take usually are no load, trips to the local stores, so little excessive VP heating involved.



Colder temps are a bit more frequent, and last longer - but As Bob points out, if no fuel cooling device is in use, the fuel heater inside the stock FF will probably handle it's chore just fine - the relocated LP and pusher both down on the frame should provide enough pumping capability and fuel heating of their own to insure fuel flow between the tank and rest of the downstream system in our particular cold season.



I suspect simply removing power to the cooling blower will adequately comphensate for the colder winter ambient temps - and we also rarely use the truck/RV in the winter as well, for the same reasons as in hot weather. I never have used or installed the blower speed limiter Bob mentioned in his post, since he earlier reported that by the time fan speed and noise is significantly reduced, cooling is also reduced to the point of uslessness.



Generally speaking, I feel a system such as I am using will do the job just fine in temps between the mid teen winter and nominal 100 degree summer temps we commonly experience - but that's just my opinion...

 

[Gary - K7GLD]

A small update - probably mostly of interest to Bob...



I have now installed the same PWM (Pulse-Width Modulator) blower speed control board as Bob tried earlier with poor results on his installation. The PWM is a device that allows electronic speed control of DC motors and other DC devices instead of a larger rheostat - plus the PWM's are lots easier on the device controlled because the adjustable pulsed power actually allows cooler running of the device being controlled.



ANYWAY, I have initially set my own PWM at a FAR more comfortable blower speed and DB level - turns out to be a measured 4. 5 volts to the blower motor. Still good air flow, and best of all, around town and underhood temps at engine shutdown are still maintaining stability even at the reduced blower speed - definitely a win-win situation! Oo.



I'll do some more test runs, and get back with more info and pics of my electronics for those still following this Loooooong thread...

 

[Gary - K7GLD]

For Bob and others following along here - here's some shots of the added adjustable blower timer and PWM speed controller.



First, the individual boards - each mounted to it's own separate Radio Shack mini-enclosure - the timer board on the right - PWM on the left:



-



Here's everything all buttoned up - the boxes attach to the stock fuse/relay box cover for the truck with velcro strips so they can be easily moved for access to the fuse box below:



-



Triggering and power for the timer board comes from the Radio Shack relay seen mounted to the firewall at the rear - other power comes directly from the battery visible, thru the fuse also visible. The relay was one already installed as part of my added pusher pump mod - it had some extra unused contacts that worked perfectly for the needs of this timer/PWM installation.

 

[pgleavitt]

What effect do you think a replacement,60 gallon fuel tank would have? I have one and fuel up when it's at the half way mark. Which means I usually have 30 gallons to cool the V. P. It's also of steel construction and I usually fill at CFN or truck stops for savings and better quality fuel due to higher volumes pumped

 

[Gary - K7GLD]

Bob's had more experience and testing on the "fuel-cooling" side of the equation, and as I recall, didn't see much benefit after a half hour or so driving. By that time, warmer fuel being returned from the VP-44 has pretty well heat-soaked what remains in the tank. After that, even adding more cooler fuel to the tank doesn't seem to be able to overcome fuel heat that's already there.



In my case, I have a 50 gallon bed-mounted tank, and even after running the main tank down to 1/4, and then transferring new colder fuel from the bed tank has NO perceptible effect on VP-44 temps.

 

[pgleavitt]

Interesting. I run specialized heavy equipment and whenever we had a hydraulic temp. issue we increased the capacity and solved the problem. I would think that with double the volunm it would take the fuel longer to heat up as well as with the increased surface area of the larger tank it would dissipate heat better. So what you are suggesting is that fuel temp has little to do with the temp. of the VP?

 

[Gary - K7GLD]

Interesting. I run specialized heavy equipment and whenever we had a hydraulic temp. issue we increased the capacity and solved the problem. I would think that with double the volunm it would take the fuel longer to heat up as well as with the increased surface area of the larger tank it would dissipate heat better. So what you are suggesting is that fuel temp has little to do with the temp. of the VP?

I dunno about the heat-generating tendencies of a typical hydraulic setup - or how shielded from the elements the fluid holding tanks are - but I typically see a 30 degree fuel temp rise above ambient on my fuel return line from the VP-44 back to the tank. Previous flow tests have consistently displayed a 35 GPH flow back to the tank - and I have no idea what the coefficient of heat exchange might be from our truck fuel tanks vs the hydraulic setups you refer to...