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

[Mundgyver]

I suppose we could always put louvers in the hood like some of the hotrod boys do. That way the hot air just escapes out with no problem and thereby eliminates the need for opening the hood. Run the fan of of a solar panel. That way when the truck is sitting out in the sun, you have a fan running to help get rid of the heat and it does not draw on the batterys.

 

[nps]

I suppose we could always put louvers in the hood like some of the hotrod boys do. That way the hot air just escapes out with no problem and thereby eliminates the need for opening the hood. Run the fan of of a solar panel. That way when the truck is sitting out in the sun, you have a fan running to help get rid of the heat and it does not draw on the batterys.

Yeah, maybe one of those sporty Hummer hood grills huh?

 

[tgee]

What about a fuel cooler that works off of the AC? Some kinda bypass of the R-134a to cool the fuel via an heat exchanger... . Just thinking out loud.



Marco

Good idea, but wouldn't that put the AC under more load, thus the engine too?

 

[rweis]

A new use for the Scotty II firewall hole?



A new use for the fender air filter hole? Draw air in when ignition is on, push air out when ignition is off? You electronic guys should be able to figuer out the power supply changeover. Even if it takes 3 - 5 amps / hour, run it for an hour after engine shutdown.



Bob Weis

 

[Texas Diesel]

At some point this needs to stop at reasonable.



134A cooling of the fuel is, well, a rather exotic idea.



I dont know where the heat comes from, carried by the fuel from the VP-44 or picked up from the head via injector return but the fuel destined for the tank is VERY warm. Est 150F, a small cooler works because of the low flow volume. At the outlet of my mini cooler, the fuel is at or near ambient



IMO, no more is needed. Having a fan on the return flow is (possibly) overkill but atleast that way you are not dumping heat back into the engine (like I am doing with the pre intercooler cooler I am using). However, it is a small amount of heat anyway. I dont favor placing the cooler between the filter and VP-44, as Honn pointed out, heat rejection is greatest where the fuel temp is the greatest. Prior to his post I was going to add the cooler between the VP and filter. By cooling the return fuel only the VP gets heated fuel if the filter thermostat is satisfied and calls for the heating element to power up.



I'm satisfied that I am at the 80/20 point and any more complication or effort with be met with diminishing returns.



However, I will pay considerable attention to those who go a different route. The results will vindicate the technique used to solve the problem.



The hood scoop idea, even though it might sound funny, would be a good way to allow engine heat to escape after shut down. So does raising the hood slightly but the neighbors have hours of fun kidding me. They would laugh at the hood scoops too :-{} They used to stop by and get out their jumper cables :-laf

 

[rweis]

On my 02, there is a rubber seal between the firewall lip and the hood when the hood is down. What's the purpose of the rubber firewall lip seal?



Does it make the fan air flow down the engine? Is it for noise abatement? To keep the snow out?



For a couple of days here in the almost 100* day time temps I think I will take the rubber seal strip off and see what happens to the under hood heat after being in the sun all day. I can always put it back on if it contributes nothing, or can put it back on in the winter if it contains heat under the hood.



Any thoughts on what the rubber strip does?



Whatever it winds up being, it has to be fairly significant amount of air flow difference to make a difference I think. The natural heat convection would create bottom to top air flow on shutdown and across the entire hood width. Even if it were only a 1/2" gap, might make a difference. The hood even slopes up toward the windshield.



Bob Weis



I checked by hand the difference of the VP fuel cooler H7B with fan cooling after driving home this afternoon (17 miles). The bottom fitting from the VP was too hot to hold firmly in my hand. The top fitting after cooling was warm but not uncomfortable to be tightly held. My guess would be 20* - 30* heat dissipation. Then the return fuel is dumped into the tank vent line. The tank is 1/2 full and the tank was about OAT of mid 90's*.



The VP electronics bay cover was very warm, but you could hold your hand on it firmly.



Temp gun should be here tommorrow per UPS tracking.

 

[Texas Diesel]

The rubber seal is there to keep rain water out from running down the hood and getting on the engine. Plus it gives us something to cuss at and keep putting back on because it slips off.

 

[rweis]

I drove to work with the rubber seal removed. NOT much air flow comes through that area with the seal removed. I do not think it is enough air flow to even be able to measure. I am going to put the seal back on. Oh, well.



Next attempt at controlling under hood temps after engine shutdown is going to be an inline marine bilge blower. I looked at computer fan blowers, but until you get into the 9" dia the cfm are fairly small. The 3" bilge blower model moves 170 cfm, 4" model moves 235 cfm.



I think I am going to mount the pickup end to the underside of the hood (or maybe somewhere on the frame of the VP?), and the motor blower end maybe behind the grill somewhere blowing outward. The motors seem to be 3. 5 amps so they can run for hours with little effect on the electrical system.



Other Ideas? How do we get large amounts of latent heat away from the engine quickly, and keep the temperatures (especially the VP) from rising when the engine is shutdown?



I did not want to put anything in front of the radiator system to suck heat out as it would be in the way under normal driving. But, there is a lot of latent heat in the radiator and intercooler. Who knows, what do you think? Someone else want to put a "sucker" fan in front of the radiator to pull heat out in that direction?



Bob Weis

 

[rweis]

nps - "I think that getting cool fuel to the VP as soon as possible after startup would be desirable, and also easier to accomplish than cooling the engine compartment. "



I think one of the primary problems is the ff and VP heat soak Marco referred to. Only cooling the engine compartment after engine shutdown around the ff and VP will accomplish that. I am puting together a marine bilge blower and timer concept that will extract the heat from the engine compartment and not allow the ff or Vp to heat soak.



On startup the VP will can get fuel at OAT temps at the very worse, and I think the tank temps will drop as the tank empties or that particular engine run gets longer in time. I think that I can take more heat out of the return fuel than the Vp and inj can put in, which will result in a cooler tank volume. I also think that I can SAFELY use the last 1/2 tank without fear of the fuel getting hotter and hotter as it does on the stock setup.



I have 1/2 tank right now and the temp gun is here. Data collection starts in the morning for several weeks. It will be extremely interesting to see if I can take MORE heat out of the fuel return than the VP / inj have put in and therefore actually cool the tank as you use fuel.



I will tow again over Labor Day and that will add more data.



So far I think there are 3 main points:



1. You have to provide more fuel than the VP can digest and get the VP bypass open to help cool the VP while running.



2. You have to cool the input fuel to the VP while running.



3. You have to not allow the VP to heat soak after engine shutdown.



I think you can help #3 with providing more cool down time before shutdown. I am trying by not shutting down before the pre turbo pyro is at 200*. I use to use 300*. Now I idle longer letting the whole system cool down more. One of the "turbo cool down timers" would be a good asset to do this. Set the timer on 5 minutes for EVERY shutdown.



Bob Weis

 

[Texas Diesel]

Bob, for curiosity why dont you shoot the Cummins ECM temps too. The ECM is on the block below and rear of the VP.

 

[rweis]

Can do!



Bob Weis

 

[nps]

I think one of the primary problems is the ff and VP heat soak Marco referred to.

Bob Weis

Bob,



Agree with the 3 points.



The way I interpreted Marco's post was that the fuel filter and VP hold a certain amount of fuel that gets heated through heat soak, and this heat is retained in the fuel system for quite a long time after restarting the engine. I suspect the reason this heat gets retained in the fuel system is because of the stock fuel return design in the fuel module, as you have speculated.



Your setup is different for 2 reasons: 1) you are cooling the hot fuel before it gets to the tank, and 2) you have modified the fuel return into the tank. I would expect you to see significantly different results from what Marco posted.



It seems a cooler between the FF and VP would take care of the hot fuel inside the FF thus getting the VP cooling fuel right after startup. That leaves only the fuel inside the VP that will be quickly recirculated soon after startup.



I'm still not convinced that underhood heat is a VP killer when its not operating - at least not the electronics part of the VP - because there doesn't seem to be alot of failure of other electronics that are also attached to the engine block. It will be interesting to see your test results including the ECM temps as Texas Diesel has suggested.

 

[CORed]

Not being critical of anyone's ideas here as I have enjoyed reading this and may attempt a fuel cooler myself soon. But I have ALWAYS had a problem cooling down to 300* pre-turbo prior to shutdown since I bought the truck. Either when everything was OEM or after adding the AFE drop-in (not that I expected much). In fact, after a reasonably easy drive prior to parking, I'd have to wait 4-5 minutes EVERYWHERE I parked before my truck cooled to 300*. I have since waited until 350* and I still wait sometimes 2-4 minutes. I know a 4" exhaust and a Scotty or AFE mega-cannon would help that tremendously, but come on... the Cummins manual says after easy driving all I should need is about 1 minute I believe. In fact, soon after startup with a cold engine, my idle is sometimes just over 200* so I'd never make it to 200*. Not sure how you can do it Bob, but awesome if you can.



One other thing I have noticed. I drive maybe 25 minutes home from work. Most of it is averaging 25 miles an hour or so. I pull into the garage and pop the hood and the VP is hot... hot enough to have to take my hand off it within a few seconds. But here's the kicker... it is still hot enough to necessitate removing my hand in 3-5 seconds after more than TWO hours. This is in a OAT garage under the house with no additional sun adding heat. There also is no air flow either. But geez... that's a long time to be that darn hot!



These are just my observations. Thanks to those doing all this experimentation. Been a good read!

 

[Texas Diesel]

Bob,



I'm still not convinced that underhood heat is a VP killer when its not operating - at least not the electronics part of the VP - because there doesn't seem to be alot of failure of other electronics that are also attached to the engine block. It will be interesting to see your test results including the ECM temps as Texas Diesel has suggested.

That's it exactly. If latent heat was THE problem the ECM package would die as well. They hardly ever fail.

 

[nps]

Bob,



Your fuel return line goes to the filler line and bypasses the fuel module - right?



Did you notice a drop in measured fuel pressure after making this change?



The reason I ask is in relation to the new intank fuel LP module. People are posting low pressure - some as low as 0 WOT. The dealers are telling them that the new pump is one of those newfangled low pressure - high volume units. Seems impossible to believe unless there was a restriction in the old fuel module return line causing the pressure to build, because everything else is pretty much the same with the in-tank LP or the old fuel module/LP.



Since your return line should be restriction free, I would expect you to see a drop in pressure. If not, then the new in-tank LP is a BIG POS.

 

[rweis]

CORed "But here's the kicker... it is still hot enough to necessitate removing my hand in 3-5 seconds after more than TWO hours" and I think this is the problem with the electronics board. I am going to put a bilge blower in that side and exhaust air for as many hours as it takes to keep the electronics bay much much cooler during the heat cycle. The electronics boards seem (seem, not scientific mind you) to fail or go noisy when they are heat cycled one too many times. I am going to TRY to reduce the heat cycle peaks as much as possible by powered exhaust of under hood heat.



When I park the pre turbo is about 300*. WITH THE A/C OFF it takes about 2 - 5 minutes to get to 200* (maybe 220*, needle point is right on the high side of the 200* line on the gauge). It is not so much to cool the turbo, but to cool the VP and engine, radiator, intercooler etc. I think if I can shut down 100* cooler the latent heat problem will be easier to work with.



On the fp. I went to RASP when I went to vent line return for the VP. I actually have 2 vent line returns. 1 for the RASP & 1 for the VP. I did not want them competing or even interacting. The fp at the VP with the RASP is ALWAYS 14+. At stop lights to insure fuel flow I will go into neutral if I think I am going to be sitting for more than 30 seconds because the engine is not lugged down and the VP will see 15 psi at least just sitting there waiting for the light. I think the intank lp is not a Oo. thing. I know what the RASP will do and why. I can not say that for the in tank pump. I read what Bosch criteria is and the in tank lp does not in my mind meet the criteria.



I also think the fuel module has something inherently flawed. One is the return fuel is dumped right where the fuel pickup is, ie heat. BUT, in DC's defense, my 02 is now designed to operate in FL with a meticulous operator, ie Stanadyne PF etc. DC has to build it to work ANYWHERE with ANYONE driving. A lot of people swap vehicles every 3 - 5 years and that time frame is probably all DC is interested in. WE however want it RIGHT! and RELIABLE!, TDR member values are greater than DC's. WE want mechanical correctness! I think the lp tank thing is a patch at best.



Now I do not get into the VP/inj return line until it turns into steel line by the transmission. Look at my previous observations, I think the VP return line to the steel line is maybe 1/8" - 3/16" id. It is not much. I did not get into it at the engine because I thought that it may take some restriction to ensure it picks up heat from the VP. The return line on the side of the VP is WAY BIGGER than the line after the T. The steel line is . 31 od, and has the VP return line crimped INSIDE of it, then there is some wall thickness to the VP line. . 31 id - ~ . 06 wall thickness ~ . 25 id - . 06 wall thickness ~ . 20 id for the VP return line as it goes into steel line on the frame.



On the ECM pkg heat. It might have been designed to be bolted to the engine and designed to take the kind of latent heat. As I recall it has a lot of square surface area to sluff off heat. The VP electronics bay is way smaller in square surface area. THe ECM is also verticle so heat sluff should be fairly good. VP electronics bay is on top and not near as conducive to sluff heat. Just my thoughts. However I will take ECM temperatures as well.



I really think we are understanding the problem better.



Bob Weis

 

[nps]

Maybe DC was attempting to get heated fuel for cold climate operations when they designed the fuel return line/fuel module. Everyone thinks about cold #2 as a problem, but not much thought about hot #2 until it starts causing problems.



My mind is made up - I assign POS status to the in-tank LP. And to think I was one of the persons trying to defend it and give it a fair shot when it was first announced.

 

[rweis]

First day measurements

To work 0730 17 miles

At work

OAT 81

Tank 1/3

ff 95

electronics 105

return fuel 104

filler vent return 92

tank 88



From work prior to engine start 1800

OAT 93

Tank 1/3

ECM 98

ff 98

electronics 97

return fuel 100

filler vent line 99

tank 98



Arrive home 17 miles

OAT 91

Tank 1/3

ECM 131

ff 107

electronics 116

return fuel 114

filler vent line 102

tank 99



10 minute idle at home

OAT 91

tank 1/3

ECM 125

ff 112

electronics 120

return fuel 114

filler vent line 102

tank 99



after 30 minutes shutdown

OAT 90

tank 1/3

ECM 146

ff 122

electronics 137

return fuel 98

filler vent line 98

tank 100



after 60 minutes shutdown

OAT 90

tank 1/3

ECM 123

ff 127

electronics 138

return fuel 97

filler vent line 98

tank 99



Notice how the ECM peaked and started to cool (big square inches of flat verticle surface?), the ff was still climbing slightly, the electronics had stopped climbing, the rest of the return system was stable at ~ 99. It will take a little time for the bilge blower system to be assembled and mounted.



I will do this again tommorrow and see what it yields.



Bob Weis

 

[nps]

Interesting Bob. Were you running the A/C?



A couple of other initial observations:



1. Looks like your 10 minute idle only helped the ECM. Everything else either cooked or stayed the same. I would speculate this is due to the lack of airflow as a result of driving.



2. The ECM is sustaining higher peak temps while operating and during the cooldown cycle. The same attributes that allow it to shed heat also contribute to its absorbtion of heat.



3. The return fuel temp looks to be close to the VP temp while running. I assume this is pre-cooler? Suggests the fuel is an effective coolant.

 

[rweis]

Agree with your #1

Agree with your #2 and probably designed to do that.

Yes the "return fuel" is the VP input to the fuel cooler. Much more accurate and repeatable to measure than trying to measure the banjo bolt.



Bob Weis