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

[rweis]

I find that cooling the return fuel keeps the total fuel volume in check heat wise. HOWEVER, I also find that cooling the Vp44 BODY to the maximum extent possible even cools the incomming fuel. Many times the input fuel temp is higher than the Vp44 body temp and after a while 30 min - 1 hr of highway driving I see the input fuel temp drop. Some due to the VP44 body cooler, some due to the return fuel coolers.



One inportant consideration of the bildge blower is to have the frontal face DIRECTLY exposed to ram air. I am finding that ram air (above about 40 mph) has more cooling effect than just electric motor driven blower (240 cfm) air. The Vp44 body will cool down below the input fuel temp and then the input fuel temp slowly starts to drop. I think the cooler VP body is actually cooling the input fuel more than the heat generated by the VP functioning.



The fuel coolers and bilge blower vs ram air are particularly obvious when stopped at a stop light. The fuel coolers and blower delay heat buildup. However as soon as you get back underway the temps drop significantly (stopped the temps can build 15* in about 2 minutes, once back underway that 15* build will drop back down in about 30 seconds)



I am not quite ready to finish this thread as I have a few more things to try, but I can say I will run a frontal blower and fuel return coolers. One thing the frontal blower does is the after shutdown temp maintenance. Recently my blower failed to run after shutdown (wire failed). Instead of the normal 2* - 5* temp rise the temp rise was 30* on one occasion and 35* on a second occasion. The OAT was 98* and I was not to thrilled about the ~135* body temp, vs 105* body temp.



I think the VP44 blower to the VP44 BODY is MORE important than fuel coolers as stated above because with really good ram air cooling the VP44 body will help keep the fuel temp in check. More to come on that test though.



Gary is experimenting with reduced fan flow and noise. I tried that some and found even a little reduction in after engine shutdown air flow the VP44 body temps rise significantly. Yeah is is noisey, and it envokes a lot of weird looks, but the VP44 stays nice and cool.



More to come,



Bob Weis



Big fuel tank, I think you are going to see OAT+10* regardless of what you do to the fuel tank. I even tried water spraying the fuel tank (albet the OEM one ie NOT metal) to cool it down below OAT + 10*. Nope

 

[Gary - K7GLD]

WELL, took a 60 mile drive this afternoon with the new setup - no towing, but lots of steep grades to a nearby lake. Even with the blower turned down, I'm still within 1 or 2 degrees of the ambient temps formerly seen at lower vehicle speeds - as Bob points out, ram air effect essentially takes over and improves VP cooling vs the blower at freeway speeds. Shutting down the engine results in no more than a 5 degree temp rise above ambient, vs formerly sticking to ambient with the blower on full speed. I can live with a 5 degree temp rise - at least in our current Fall weather temps! :-laf



SO, what of significance is to be gained by full blower speed? Probably a greater volume of air change to the underhood that can benefit not only the VP-44, but other temp sensitive stuff as well, such as the APPS directly above the VP-44, and the ECM just beyond the VP-44 toward the firewall.



Measured voltage to the blower at the current setting is 4. 5 volts, and current draw is 1. 7 amps - at full speed the current draw is 5 amps, so the lower blower speed allows longer running for underhood cooling without excessive draw to the batteries. The noise from the blower has dropped from obnoxious levels that frequently drew concern from bystanders who thought something was wrong with the truck, to a gentle whir that sounds much like the heater fan - it can be heard, but is not at all objectionable. And that's a GOOD thing in a crowded campground or parking lot! :-laf



My Fall results in this cooler weather might not be the same come Summer, if not, I can easily adjust blower speed as needed - and I see no need of further experiments, other than perhaps trying to improve the front air inlet scoop as to be less of an eyesore - I'm considering buying another air dam for the front and cutting a neat opening in it to mount the air intake - we'll see whether that gets done or not... :-laf

 

[mhenon]

-and I see no need of further experiments, other than perhaps trying to improve the front air inlet scoop as to be less of an eyesore - I'm considering buying another air dam for the front and cutting a neat opening in it to mount the air intake - we'll see whether that gets done or not... :-laf

I'm surprised you haven't looked at those fog light ports as your forced air entry point. All the plumbing could be hidden behind the bumper.

Mike

 

[mhenon]

It just occured to me... ... bet you have fog lights in there already!

 

[Gary - K7GLD]

It just occured to me... ... bet you have fog lights in there already!

YUP!



One of the members here is swapping out his front bumper, and has opened the possibility of getting the air dam off his bumper - the trick is finding a way to get it from his hands to mine - he's heading from his place in Washington down to California in several weeks or so - but not sure of his route or a meeting point that isn't too far from here to be practical...

 

[Gary - K7GLD]

Just another bit of (hopefully!) refinement - bought some roof flashing for some work on the house - and decided to try making a shroud to improve and contain the airflow around the VP-44:



-



That section of aluminum closely fits around the 3 inch duct from the blower, and hopefully will improve cooling effect - the shroud attaches to the lower edge of the APPS shroud with Velcro.



Here's a (poor) shot of the finished installation:



-



Once again - time and miles will tell if it was worth the effort or not...



EDIT!) Pics were accidentally removed, and no longer available - but this approach didn't work well anyway...

 

[rweis]

I wrapped my VP44 in a thermal blanket material. I only treat the VP44 heat, not the engine compartment heat. I think it is correct to isolate the Vp44 mechanism as much as possible from other heat sources so you know exactely what is happeing to the VP44 with as little influence from the engine block etc as possible.



I used a thermal blanket material and had a good bit of tussle getting it between the VP44 and the block. NOT much room between the VP44 and the block for cooling air from anywhere (another design flaw in my book).



I do not know how much the APPS needs cooling. I would think not much, spill over air flow from the Vp44 blower does get up into the APPS housing (a GOOD thing I think)



Bob Weis

 

[RCMerrill]

Ha Bob have you herd anything about PF60 fuel attidive 6 months ago someone was trying it out it sounded pritty good i have not recieved any responce have you herd of PF60







Ray.

 

[Gary - K7GLD]

I do not know how much the APPS needs cooling. I would think not much, spill over air flow from the Vp44 blower does get up into the APPS housing (a GOOD thing I think)

ACTUALLY, there IS a rather decent sized opening in the lower APPS housing - you can easily slip a couple of fingers into it when the outer shroud is removed - and I mean the cast metal housing bolted to the intake manifold. It's located immediately above the VP-44, and will easily benefit from airflow in that area. Biggest problem is not getting air IN to the cavity where the APPS module is, but getting the air OUT - there are no escape openings of significance - but I can feel stray air leaking at various small gaps where the APPS/throttle linkage plate meets the APPS housing - probably enough for the small degree of cooling that MIGHT benefit the APPS... Sure can't HURT, I wouldn't think...

 

[rweis]

Well, time to put this thread to bed with final recommendations.



1. Water cooling fuel coolers is not cost effective and I think not system effective either. I tried water cooling the fuel coolers going to the VP44, after the VP44, misting the blower air to the VP44. Only marginal effective and not worth the water tank and pump and plumbing lines needed.



2. The DC concept of fuel cooling is flawed in concept. The DC concept is to use the fuel to cool the VP44. Fine as long as the fuel is cool itself. As the fuel absorbs VP44 heat the fuel has no way to expel the heat and it continually builds to just below (by about 20*) the VP44 temp itself. As the fuel level drops, there is even less fuel to "cool" with and the fuel temp begins to approximate the Vp44 temp.



3. External air cooling to the VP44 will maintain the VP44 at approximately the OAT temp plus about 10* (with the blower air input exposed to ram frontal air). Keeping the VP44 cooler also keeps the fuel cooler as the VP44 begins to act as a fuel cooler at higher rpms (ie more fuel passing through the VP44, more frontal air comming in the blower inlet (ram air effect)) and more effectively than fuel coolers. The VP44 body temperatures will be below fuel temperatures and fuel temperatures will begin to drop at sustained higher rpms.



4. After engine shutdown VP44 cooling I believe is important depending on your thoughts on how much latent heat the VP44 can safely handle (generally the PSG circuit). IF you think the PSG circuit can handle anything then you do not need to do anything for VP44 cooling either running or after engine shutdown. If you want to keep the VP44 latent heat after shutdown below OAT + 50* then some form of after engine shutdown cooling is needed. With after engine shutdown cooling VP44 latent heat can be reduced to OAT + 5* to 10*.



5. Fuel cooling is only somewhat effective, and only at higher rpm settings. Fuel cooling at idle settings is virtually nonexistent because of the low fuel usage and fuel throughput of the VP44. Vp44 body heat rise at idle (assumming fairly high tank levels (ie not low tank levels)) is fairly rapid and approaches OAT +50* within a few minutes. At lower tank levels the fuel is already hot (OAT +30*) and the VP44 is already hotter and the temp rise is even faster.



6. The upper end of MY VP44 body (which is wrapped in a thermal blanket to keep engine block heat off the VP44) after engine shutdown heat soak seems to be OAT + 50* with no air cooling and does not start to drop until about 1 hour after shutdown. Running with low tank at cruise rpm (with passive fuel coolers) fuel temp rises to same OAT +50*. Without the thermal barrier between the VP44 and the engine block I think these temps might be higher and rise to about block temp (180* minus some heat dissipation from the fender side of the VP44, 30* or so?, under hood temps are about OAT +10* (documented by Gary about a year ago))



Recommendations:

1. Thermal barrier between the VP44 and the engine block to keep the engine block temperatures off the VP44 and indirectly the fuel also. I also removed my OEM ff. If you keep yours (most do and I may put mine back) thermal insulate it from the block heat in the summer. Cooling the VP44 with OAT might be enough to cool the VP44 and any heat picked up by the OEM ff, but I am not sure.



2. OAT air flow to the VP44 to flood the VP44 environment and reduce the VP44 temperatures (and fuel temperatures) while running and especially after shutdown. I am experimenting with the amount of time the OAT blower needs to run after shutdown. I know 128 minutes works. I am trying 64 minutes now to see what the end temperature differences are. With 128 minutes the blower (DetMar shielded 240 CFM 4") lasted about 9 months before replacement (~$40 for the fan at a local boat supply store) (ie use a removable electrical connector (spade or the like) between your truck electrical system and the fan electrical system for easy change out). I tried the PWM motor speed reducer and felt the air flow was significantly lower with only minor blower speed reduction and went back to full voltage on the blower motor. With the blower running after engine shutdown you can feel underhood heat being displaced out the front grill area. Air is not forced out the front grill area without the blower running after shutdown. There does not seem to be any detrimental affect to the blower running 2 hours consumming 4 amps / hr (about a total of 115 watts (13. 5v * 128 minutes/60 min /hr * 4 amps/hr)) to the battery storage system. Voltage readings at engine shutdown 13. 9 after 2 hours of blower running 13. 1, about a 1 volt drop.



Good luck with VP44 cooling, fuel cooling. Maybe the newer PSG's can handle more heat and it may not actually be a PSG thing anyway (never actually proven). I do know that Bosch has a 160* maximum fuel input temperature which you can get pretty close to at low tank levels at higher OAT's (summer). I prefer to run my Vp44 (and fuel) below 110* (OAT 100* and keep the latent heat after shutdown below 110*) and have people remind me my truck "is running" after I shut it down and walk away . When asked what "that thing is" I tell them it is the accessory air turbine for high speed high hoesepower engines Oo. .



Bob Weis

 

[mhenon]

Bob, One off the all time great post on TDR! It would be a shame to let it die at this point without finding out if it works over time. A lot of us have made changes to our fuel system based on your findings here. It seems logical to do a follow-up on those members to see if the VP44 last significantly longer with "cool-fuel" than without. Don't know exactly how it would be tracked but a comparison after 3 to 5 years (50K to 150K miles) would tell the story:

a. 100 24v running OEM system for 100K miles... ... ... ... ... ... ... ..... = 12% VP44 failure

b. 100 24V running the Bob Weis "Cool-Fuel" system for 100K mile = 4% VP44 failure

or something along those lines.

Anyway, thanks to you and the others for the testing and data provided. My fuel system is highly modified based on this thread and I expect the VP to live a longer life than it would otherwise. Great work!

Mike

 

[Gary - K7GLD]

My own "final" (is ANYTHING we do to these trucks REALLY "final"? :-laf ) setup related to the fuel system is:



1. Both OEM and added pusher located down on the frame rail near the fuel tank.



2. OEM FF raised off intake manifold with nylon washers - it DID make a measurable difference in the FF case temps!



3. Multi-layer aluminum foil "blanket" between the engine block and inner body of the VP-44 - another significant reduction in VP-44 case temps by actual measurement.



4. 3 inch ducted airflow from front bumper area using a marine bilge blower similar to Bob's. Blower is controlled for length of run time after engine shutdown by an electronic adjustable timer - currently set for about an hour run time after engine is shut down. Blower is LOUD when operated at full voltage, so also use an added Pulse Width Modulator (PWM) to adjust for best compromise of blower noise vs airflow - for winter weather, the 1 hour time is great, and blower noise is only barely noticeable. I'm still constantly monitoring the VP-44 case temps at the PSG outer case, and also at the fuel return line right at the output banjo fitting on the VP-44. Actual blower operating voltage as currently set is only a bit over 4 volts DC, so blower lifespan SHOULD be optimal.



5. Added a PC type heatsink attached to PSG cover at top of VP-44 case where much of the outside airflow is directed - SUBSTANTIAL MEASURED heat reduction as seen right at the PSG outer case - also substantial reduction in return fuel temps - the PC heatsink WORKS!



In addition to what's covered above related to heat reduction measures, I also use Power Service fuel additives for added fuel lubricity in EVERY tank of fuel, ALL fuel is first pumped into an in-bed 50 gallon tank, then transferred as needed to the main tank, passing thru 2 inline filters in the process - after that, fuel flow goes first thru an added Frantz sub-micron fuel filter/cooler, and then thru the OEM FF and on to the VP-44.



Final result of all the above so far, is fuel flow to the VP-44 that runs between 10 to 20 PSI under all operating extremes, RV towing, etc. , and fuel that is clean, cool and as lubricating as I can reasonably provide - VP-44 measured temps to date have not exceeded 130 degrees under the worse summer extremes, including underhood heat soak.



And my VP-44 will probably die before the day is over... :-laf :-laf :-laf

 

[Sled Puller]

And my VP-44 will probably die before the day is over... :-laf :-laf :-laf

After all the problems with 98. 5 to 02 overvalved engines, is it not time to switch to a 12 valve??



I know I have changed enough VP44s and patched cracked blocks to last me a longggg time.

 

[Gary - K7GLD]

After all the problems with 98. 5 to 02 overvalved engines, is it not time to switch to a 12 valve??



I know I have changed enough VP44s and patched cracked blocks to last me a longggg time.

NAH - so far the greatest expense was replacement of my original VP-44 due to premature wear of the infamous Bosch brass advance cylinder liner (why'd they DO that anyway?) - the rest of the pump was still within spec at 45K miles, and all internals reused, including the PSG - that pump is now my spare.



The engine in my truck is so flexible and easily modded for power, and instantly adjusted for increased power output on the fly at the touch of a button - I can instantly set for either economy at one end of the scale, or tire-spinning power at the other end.



Pretty hard to get that instant flexibility in a 12 valver - but I know my logic will never sway the under-valved crew - and that's OK - different strokes and all that...

 

[rweis]

OK,



I noticed Gary has already done the 1hr blower to yield 130* max (assumming 100* OAT).



I did the 2hr blower to yield 110* max (assumming 100* OAT) for a year. I do not mind changing the blower 1 time per year, 10 minute job. I know the Vp44 is temperature safe when stuck in traffic and little fuel flow is happening, but under hood heat is still happening (another example of DC concept error of fuel flow cooling. There is no fuel flow cooling unless the rpms are at like driving speed, because there is virtually little fuel flow at low rpm's)



I'll do the 1 + 1/2 hr to see what that does.



Yep the blower is LOUD after shutdown, but it makes it easy to find the truck in a parking lot after shopping .



It would be interesting to see what the differences are after a couple of years of blower (fuel cooling) vs no blower (fuel cooling). I tend to think that as the PSG's get tougher and tougher it MAY make less and less difference technically. However I like the idea of an expensive replacement component running at very nominal 110* vs 150*, hotter, thinner lubrication, parts expansion fit tolerance, wear probability, etc.



We'll see. I'll do a January and July update and see what others are finding out to keep the discussion alive.



Bob Weis

 

[Gary - K7GLD]

BOB - I should mention that the 130 degree max temp i mentioned in my earlier post was when the weather was still hot, and the blower speed and timing interval reduced. Either increasing the blower speed or lengthening it's running time reduces temps in a linear fashion.



Like some have already suggested, I sometimes (well, ALL the time, actually!) wish the PSG's for these VP-44's were remotely mounted to a cooler location - easier to troubleshoot and replace, and undoubtedly MANY VP-44's with perfect mechanicals have been repaired due ONLY to failed electronics. Just think how much easier and less expensive it MIGHT be to simply unplug and replace a small module instead...



The similar mechanical rotary IP's used on the 1st generation trucks seemed to rarely fail - and the general similarities are far greater than their differences, other than the electronics.



But no use wishing for things we'll never get...

 

[JAG1]

I have read this long thread complete. I do believe it is the most interesting I have ever read. Many thanks to the contributors... ..... it has prompted me to join TDR, thus my first post.



Just a question; If the ff is one of the worse offenders wouldn't it stand to reason that conversly, it could be turned into a great fuel cooler? I intend to add a heatshield, (it is already isolated off the engine) and run a 3 inch blower to it as well as the VP. I'll start off with a 4 inch blower and 'y' off to two 3's, one for the vp, and the other for the ff. What do you think?



I am also thinking of cutting in a hood vent or grill above the VP or ff, but don't know how rain will affect that.



Thank you all again, Mike

 

[rweis]

Hi, let me welcome you to TDR first, and thanks on the comments about the thread.



You could look at the ff as a fuel cooler if you could really cool it well. The most intreguing idea I have hear of is using A/C lines to cool it. Cooling it with a OAT blower would help as long as you can keep the engine heat off of it.



The reason I took mine out is the 180* huge engine block right beside it (I find it takes I think about 1 1/2 hours for the engine block to cool to approximately OAT). I changed my final filter to a Canton inline 8um and mounted it on the frame to get it out of the heat. I also have a RACOR 690T filter and water seperator (10um) right out of the tank as primary filtering and water seperating. The Canton is to catch anything that might sluff off the entire fuel system before it can get to the VP44.



The blower idea works well. I use a DetMar 4" 240 CFM blower. I found the first one lasted 1. 23 years / 15,000 miles. One of the real keys to the blower after shutdown is Gary's rewiring of the 1416 timer circuit board so the timer (and therefore the blower) will still be powered when there is no 12volt power in the engine electrical system (not batteries obviously) after shutdown.



Right now I am experimenting on the length of the timer run after shutdown. It depends on where you live, ie the climate you are trying to manage. I live in Fl. I was at 1 1/2 hours after shutdown and when replaced the blower I cut it back to 1 hour. My target is no more than 105* VP44 body under any conditions.



On the fuel cooling I found that with fuel coolers (frame mount etc) you get more cooling with coolers in the return line. I talked with a Bosch rebuilder a while back and they have to cool the fuel on their test calibration stand because the Vp44 will heat the return fuel to over 200* when running full tilt. Bosch limit on fuel temp input is 160*. I found that cooling the feed line I could not get as much heat out of the fuel because there had been some heat absorption (and consequently heat build up as fuel levels reduce to the refuel level of 5 gallons) by the fuel volume in the tank. Working on the return fuel the temp difference between the OAT and the return fuel temp at cruise rpm's is much greater (bigger delta T) and therefore easier to remove.



I also found that the OLD thread about "pumps lines and whatnot" where BK found at idle the return fuel quantity is almost non existant, and at full tilt the return fuel quantity is approximately 30 gpm holds true. That actually creates a problem cooling the VP44 if stuck in traffic (ie idle) without an OAT blower to get the heat off of the VP44 when the engine is getting minimum frontal cooling because of no forward speed and because of no appreciable cooling fuel flow through the VP44.



The idea of a hood scoop / opening I think is one of the very best solutions. However it is pricey ($800 +) if you have it done, but at idle in traffic and no frontal air flow you could verticle vent the heat. Underway with ram airflow, you could direct the ram air right to the VP44 (or that side of the engine compartment and flush out the heat in short order). In the winter you could close off the hood scoop when you needed the heat. Gary put a cab switch on his blower because he lives in Washington state and does not need it (or want it) in the winter. Not my case here in florida.



WELCOME to TDR, probably one of the MOST fascinating places you can find on the internet. Remember, everyone has an opinion, and they will tell you theirs (as I do also), that you have to take it with a grain of salt and do what is right for you and your truck.



Bob Weis

 

[JAG1]

Bob, I appreciate the time/ effort to help us take the best path.



My latest thoughts are to place a heat shroud around the ff, and blow air at the VP only. Later I'll add another Racor to the frame (for summer) with ball valves, depending on season, I can switch between filters. I feel it is important to at least figure a way to vent the heat out above the VP while blowing the air. A hood scoop would be great but too expensive, so I think the cooler air forced from underneath, with some sort of vent for heat to force out, would be more of a natural system. Would also help if the blower were to quit. There are crome vent cowels available that won't leak rain down on VP electrical connections, and can be faced rearward to create a negative flow (suction) that may would help with venting but, this may not be a very attractive option, and I'm struggling this one. I think just a small grill would do but it rains alot here in west Oregon.



My existing fuel system does have the relocated factory LP with the Vulcan big line kit, and pick-up tube. I installed a water sep. Racor 90 GPH ff right out of the tank (before the LP). I now need to relocate the return line to the vent tube or filler neck, add fuel cooler to return line, heatshield the vp and return tube like you have.



For the blower intake I would like to use the bumper hole next to the factory fog but, there is a cooling line (I believe trans cooler) just above this almost perfect funnel like hole. If I could figure out a way to make a well fitted boot and adapt it to the 4'' duct, it'd be great except 3'' would be better because this cooling line is somewhat in the way. I'll have to go back and read Gary's results on his 3'' blower.



I am so glad to be on the right track..... I just knew there had to be something that could be done to help the vp. My suspicion all along before reading this thread, telling me there must be something wrong with DC's fueling. First clue was how good it was (fp guage) to get rid of banjo's



Very glad I stumbled on this thread... . more like a rope now the way it's got me hooked.



Mike

 

[rweis]

On the 3" vs 4":



I run a 4" blower then I reduce it down to 3" for the duct with a 4" to 3" pvc reducer because I could not get a 4" duct up to the VP44, not enough physical room around the intercooler ducting etc.



I mount my blower to the bottom of the bumper on the drivers side right out in the open. I tried mounting it behind the bumper but I also found that ram air effect with it mounted out in the oncomming slipstream made a significant difference above about 40 mph.



Fuel cooler to return line:



There are a couple of things here.



First you have to get rid of some or all of the stock fuel return line. I cut mine right after the T (when you look at the return line after the T there is a metal line then a double swege on that metal line where the stock nylon line mates to the metal line of the T. I cut mine on the T side of the double swege leaving about 3" of metal line from the T to the end of the cut off. I found that the short metal tube is exactely the ID of AN-6 line. I push 3" of AN-6 line up on this 3" metal tube and put 3 hose clamps on it to secure it. There is no pressure on this line since it open ends to the tank filler line.



Coolers:



I also found that frame rail coolers (typically 3" x 1" x 12" or 18" or 24") work as well if not better than anything else. I have 3 different kinds in my experiment. I tried the frame rail type, a long (18") finned cylinder transmission cooler, and a H7B transmission cooler. I find that the key is air flow across the coolers. When you are stopped at a stop light you can see the fuel temp rise a little and then fall as you get moving again.



I did not like the finned cylintrical transmission cooler because it is made out of aluminum and to make them cheaply and quickly the threads are not cut very well and often are cross threaded (I had to receive 6 to get 1 that was not cross threaded). When I went in with a tap to retap it clean the quality of the aluminum was not good and it tended to chip rather than cut smoothly. I tried 3 different vendors that looked like 3 different manufacturers and only finally got 1 marginal single unit that I was willing to keep and use.



I use Deralie frame rail coolers of various sizes (lengths) with AN-6 fittings already on the cooler, simple and secure. I tried to keep as much of the radiating heat off the coolers as possible by running the line right off the T (the hottest fuel) to the cooler furtherest back by the fuel tank, then next is the one more forward (and should have cooler fuel), then the last one is the one closest to the engine (and should have cooler fuel yet) then this one exits and goes to the fuel tank filler line.



I do not now think that the idea of the hottest cooler furtherest toward the back (rear) and successively cooler coolers more forward has any merit. I think the airflow is sufficient to get heat off the coolers if you mounted them in succession from front to rear. The plumbing would be a lot easier as well and shorter.



I do not think the H7B type cooler is any better than the simple frame rail cooler because the H7B type needs much more room to mount that takes it further out of the air slipstream. I even put a 1000 CFM fan on the H7B and I do not see any real benefit of the fan. I tried sucking air through the H7B and tried blowing air through it. Not much difference, certainly not enough difference to merit the cost and effort to put a fan on it.



I think the frame rail coolers are easier to mount, safe from road debris because they are mounted to the frame verticle wall, least expensive and most flexable to configure to mount. I just measured how much flat unobstructed frame rail I could get to, and that matched the length of a cooler and mounted that one there, then measured the next section of flat unobstructed frame rail and matched it to a cooler length and mounted that one there, next I mesured the last section of unobstructed frame rail and mounted one there. Then just plumb them together from front to rear.



Hood Vent:



I still like the hood vent / scoop / ??? When you shutdown and the blower is running for 1 ( experimenting with the length of time) hour, you can stop at the grill after shutdown and feel the air being forced out from inside of the engine compartment through the intercooler, radiator, evaporator package and the heat being carried out. If you do not have the blower running after shutdown an walk to the same spot on the grill you do not feel the air exiting out from under the hood through the intercooler, radiator, evaporator package. I have a temperature sensor on the VP body and can mesure the blower, no blower, difference in heat soaking.



With a hood vent of some sort the hot air could escape easier and actually get some convection verticle heat disipation. How to do this, I have zero clue short of a hood scoop. You can simulate this by poping the hood enough for the hot trapped air to escape and leaving it up a little after engine shutdown. I can measure the different length of time it takes for the engine to stop heatsoaking the Vp44 (ie getting the block to something approaching OAT or at least below ~ 100*) with the hood up and the hood down. With the hood up (and the verticle convection happening) you only need the blower about 1/2 hour. With the hood down you need it about 1 1/2 hour. The hood vent has merit, just have to figure the how at a reasonable cost.



I tried removing the air seal strip between the hood and the firewall for a couple of months. Did not seem to have any effect at all. Maybe too difficult a path for the air to convection heat out?



Ah, well. It is certainly interesting to measure, experiment, measure again and see what the differences are. I know we are getting pretty close. I have gone through 1 summer here in FL and have kept fuel and VP body temps below about 105* max and to about OAT + 10* running down the road.



Bob Weis