Heat mitigation in the cab

sloanstavern

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“A man’s got to know his limitations”

I do not have the time or budget to be a TLC purist, but I do want to protect the integrity of the vehicle as manufactured the best I can. Therefore I have chosen that while I own my ’74 FJ40 LHD ( which is till I die) I will keep it as pure as I want to and can afford and only make modifications that go on with a bolt or a brush

I have just reinstalled my roof, and by spending some time, have greatly reduced the rattles, and echoes, so the sound is very nice, now I have turned my attention to heat management. More particular how to lower the inside cab temp. Not trying to make it a Lexus just want to make the hottest time of year more comfortable.

Here are my objectives:
1. Having no A/C, 4 months out of the year I have to do something to lower in cab temp to make the FJ40 more enjoyable to drive.
2. I did not want the heat treatments to spoil other features of the rig ( functionally or visually)
3. Did not want any messy or permanent fixes that lead to problems latter ( glue, coatings, etc.)
4. Make the improvements removable for cleaning, and for the 8 months of the year when a little free heat does not hurt.

Here is the tool of choice and experiment parameters I tried to control:
Vehicle state – driven to full temp minimum 15 minutes including high speed and some start and stop
Outside temp ~ 80F during daylight hours
Vehicle started in the shade and cool
Measured while moving ( not often one sits with the engine just running which would skew the results)
Preexisting mods effecting heat – rhino lined the interior floor board up to the point the fire wall goes full vertical, including the tranny hump

Tool – Infrared laser guided thermometer bought off Amazon for ~$30 – great tool for lots of stuff. I could not think of a way to measure the “ambient “ tem of the cab accurately, and since there are regional hot spots using the pointer gave me more precise feedback

Success criteria are measured in two ways:
1. Quantitative difference in temp ( before and after readings after each mod to measure the effect
2. Qualitative improvement - how much did I notice the difference, if at all

Here is where I measured and the base lines each will have a min and a max ( all in °F):

Engine(parked at idle) Exhaust manifold 500-600 °F
Exhaust pipe 400-450°F
Block / Head at rear of engine 200-225 °F

Driver side Floor ( Flat surface) 90-105 (max near exhaust )
Transition 45°angle 105-135 ( max near exhaust)
Vertical fire wall 110-165 ( max at small point on “bump “about 6 inches in size on the engine side of the gas pedal)

Tran hump Driver Side 95-130
Passenger Side 90-110 very uniform

Passenger side Floor ( flat surface) 85-90 very uniform
Transition 45°angle 95-115 hotter near engine side
Vertical fire wall 110-135 hotter near the engine


Here is how is how I plan to tackle the challenge. Just like insulating a home, you have three paths of attack:
1. Air flow – stop or slow air migration from outside to in
2. Source of heat – eliminate or contain the source
3. Insulate the interior

Here is what I have done thus far and the results:
Existing mod – Rhino liner does help a bit. It is only on the lower floor away from the hottest points, but I can measure a ~ 5-10°F difference. Clearly it will not solve the problem but if you want to use it any way it will help for heat and I found it helps for sound deadening.

Air flow: this proved to be the most immediate qualitative improvement. I was shocked how hot much air I had blowing in. First I fixed the big leaks around T& T shift levers, any unused bolt hole got a bolt in it, any grommets that were loose got fitted with some closed cell black foam plugs.

All together cost me $5 and got great results, no change to measured temps since it did not change those dynamics


Source of heat :

Done: I built and installed a heat shield for the exhaust pipe. Using three exhaust clamps and some aluminum flashing folded over then bent to shape, it follows the contours of the pipe all the way down to the muffler (Pictures soon).

Results Top to bottom only ~ 10-15° drop, Not bad, but I do believe I notice the difference qualitatively. I may take it off and see what happens.


Next up: Manifold wrap – I bought some lava wrap and have yet to install it. Will test it on pipe and manifold. Since I live in the desert I am not overly concerned about moisture / ruts)



Insulation:

I bought this from Summit racing with the intent of lining the cab by gluing it to the firewall then back to the end of drivers compartment and covering with carpet. Then I realized it would be home for moisture, and it is not needed for 8 months over the year, and I would have a bunch of messy glue. So instead, I made a template and cut a pattern to fit the fire wall ( the 90° portion only).

Tru-Max BLIP12406 - Tru-Max Super Insulator Mats


US$29 for a 48X72” roll


I un bolted the heater box, did not have to remove. Removed the gas pedal, and unhooked the vent cable. Rather than glue it on, I just fit it tight and bolted all the accessories back in place and I did use some foil duct tape in select spots to help, and this resulted in a stationary shield that is easily removable if it gets damaged. I gave it a quick shot of flat black Krylon and it is barely noticeable

Results: Vertical FW only DS 90-120 a 25-45 improvement Very noticeable
PS 85-105 a 25-35 improvement

Next up: I will make some custom insulated carpet floor mats. Using the same heat shield glued to the carpet, I will sew together a one piece mat sandwich that follows the contour of the floor in driving compartment and is fully removable.


NOTE: The photo with temps below was while the vehicle sat, so it was higher, but it gives you aprox location of hot spots. I will get more photos and updates soon.
Infred thermo gun.jpg
Presentation1.jpg
 
Joined
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Do you still have the rear heater?

Can you see the picture?

I would think that a thermo-pad on the engine side of the firewall would be more effective than in the cabin. The heat will just travel up the firewall if you insulate the carpet. At least right behind the engine where you're measuring 179f. That's hotter than I would have expected.
 

sloanstavern

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I should have noted. this was a before picture and the heater box was out ( I do not have rear heater).
I will post current photo showing inside insulation to date.

Regarding insulation, I thought about placing it in the engine compartment, but was concerned about moisture, dirt, etc. Plus there is not much clearance in some spots, so rubbing would be an issue to.

If I did a frame off - I would strip and lizard skin the engine compartment,
 
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I wrapped my exhaust from the manifold all the way back right before it gets to the edge of the body in the rear, including the muffler. Did a lot of research and it sounds like it will not cause rust issues. The exhaust in under vehicle so it does not get rained on, so the only time it will get wet is driving and the heat will dry it out. I did really clean it up and paint it with the high temp porcelain paint before wrapping. Then I painted the wrap with it also. Read that as a good tip also. Got the wrap from Summit. I plan to also do some heat shielding on the trans hump also. My vehicle is not on the road yet, but driving it around a little and starting it up in the garage I did notice it made it a little quieter.
 
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Seems to be a lot of excessive heat but those digital units don't lie much if any. Living here in the Philippines it gets pretty hot as well but it is a balmy wet hot because the humidity rarely gets below 80% and temps ambient are as high as 104 f. But I do miss that Arizona climate. Lived in Phx and Chandler years ago and was last in Monument Valley and Grand Canyon in 2006. Thinking of insulating my firewall to keep some heat off of the wife as we don't have A/C either.
 
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I like your methodical and well-documented approach. Keep us posted as you continue.
 

sloanstavern

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Here are the details on the firewall interior insulation. 1st the sheet stock ( 48X72 “) it is a foil / myler lined on both sides with a fabric woven core ~ ½ inch thick and it is fire rated for automotive use. Cuts better with scissors vs. razor

I am counting on the insulating media to help for sound deadening as well. Then the temple of Kraft builders paper and cut out, finally the install.
insul shet.jpg
Cut out  firewall.jpg
Insul in place two.jpg
 

sloanstavern

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While it is not too noticeable, ,from the seat, you can see the shine of the foil, so I blasted it all with flat black now you really have to look for it.
Painted insulation.jpg
 
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Buy, a reflective heat shield for the engine bay firewall, or get one out of a junkyard from a car.

Use header wrap, or get your header ceramic coated as well as your down pipe.

In my stang, the header collector under my feet created a ton of heat. I bought a roll of metal building roof insulation,
I installed new carpet with sound deadening jute backing and lined the floor with FOIL BACKED RADIANT BARRIER.

I bolded this because it is important and will be the best 20 dollars you spend at lowes or home depot.
 
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sloanstavern

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Here is my new custom exhaust ( YEAH) and the home made shield.

I have about 100 miles on the shield and no rattles or problems. Still not sure of complete efficacy of it, but will keep it for a while
Sheild installed manifold.JPG
Sheild on tail pipt.jpg
 
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Aluminum shields like you installed on your exhaust are more effective when you place them farther from the exhaust pipe, and closer to the area you want to protect. When they are too close to the heat source, they just become secondary radiators.
 

DSRTRDR

I can mangle anything ...
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I have the same Summit insulation, and also on the floors

I have not found humidity to be an issue in AZ, and my truck has been rained into bad while I had only the bikini top on

exhaust is clearly one of the biggest sources of heat - and firewall holes (I get hot blow at the speedo cable hole :rolleyes:)

I agree that a rear opening of the cab can help with airflow

if you run a bikini top in the summer in Phoenix (which I typically do), the only other way to substantially cut down on heat would be to drive into a commercial refrigerator or freezer :doh:
 

sloanstavern

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The flashing stock "sandwich" I used for the sheild is rather thin, but it gave me a great templete I may get some thicker Al stock, add dimples and move further away from the pipe ( thanks Doug).

Plan is finish this project with a matrix of all the options tired, and the before and after temps as a reference.
 
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I am curious what the outside ambient was during your testing? I bought my 68 back in 1974 while living in Flagstaff. Moved the the oven in 79. Lucky by that time the 40 was not a DD anymore. Without A/C even with great insulation it's not going to be comfortable for half the year here. But here is what I have found out over the years. A hard top without the side vents in the back side windows is unbearable. I tried lifting the rear hatch on letting it rest on spare tires. Exhaust was over powering. Around 83 the vents windows were added to the hard top. For a while I ran a stock exhaust that ran below the skid pllate. It helped but was worthless offroad even on mid trails. There was also a heat shield for the muffler in the pre 75. When I ran the exhaust under the the skid plate I install one of those. It is still on. Plugging the holes in the firewall was almost a must even in mid temperatures here in the desert. The factory mats front and rear help. I install a H42 with a 76 transmission hump so the mats fits pretty well.

I will be watching this thread. I have a after market A/C I plan on using on my pickup. With the smaller cab and good insulation it might work preety well.

For the most part here is how I solved the valley heat. I've had the tow setup since the early eighties. Northern AZ is a great relief for the summer time heat. The big plus is the summer monsoon still means rain not just humidity.
The carrot 006.jpg
 
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Heat

I am in the middle of a rehab on my 69, patched all excess holes, repaired grommets, etc. Shot several coats of Lizard Skin hi-tec ceramic bead insulation on the outside, and lined firewall top to bottom and front floor with (generic) Dynamat. Then will build heat shields all the way back on exhaust. After ample research this should meet my needs.

Bob in CO
 

sloanstavern

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I am in the middle of a rehab on my 69, patched all excess holes, repaired grommets, etc. Shot several coats of Lizard Skin hi-tec ceramic bead insulation on the outside, and lined firewall top to bottom and front floor with (generic) Dynamat. Then will build heat shields all the way back on exhaust. After ample research this should meet my needs.

Bob in CO

WOW - Sounds like the right way to do it. Can't wait to hear how it performs.
 

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