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Old 01-08-2018, 11:01 PM   #1
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Doghouse insulation - tell me why this won't work

After searching threads on this subject, the consensus seems to be that Dynamat or similar won't hang upside-down very well, or at all.

Could I remove the old foam/fiber/batting, layer Dynamat to the same thickness, then secure it with hurricane straps bent to match the inner curve and bolted into place? I'm not worried about the bolt nuts being visible in the cab, as I'll have cabinetry hiding the doghouse.

Would there be a problem with a bolt head possibly resting against the turbo pipe, or against the rear of the engine? And would the Dynamat need a covering of header tape or similar?

(bike added for scale)

Thanks for any advice or suggestions.


Don
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Old 01-09-2018, 12:13 AM   #2
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I don't remember anybody being real happy with insulating the inside of the doghouse, either for sound proofing or heat issues.

The folks that seem happy built a cover for over the doghouse. You can have cup holders this way.
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Old 01-09-2018, 09:05 AM   #3
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I dynamatted the doghouse on my DT360. and the flat plate on my T-444E. and the result is i have just as much heat as I had nefore and not much less noise..

on the DT I had issues with the dynamat coming down from the heat...

im with robin I thinking making a doghouse cover if you still have clearance for your feet is the way to go... you can insulate it for heat and noise..
Dynamatting the inside of the footwells on the bus makes a little noise improvement but zero heat improvement..

-Christopher
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Old 01-09-2018, 11:33 AM   #4
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About the only positive feedback I have heard on Dynamat was from hot rodders who used it on previously bare sheetmetal. They claimed some noise reduction (when every square inch was covered $$$). Never heard of anyone satisfied with its' heat reduction.

Sound reduction requires mass. As in a pound or more per sq. ft. Sheet lead is toxic but still the best there is.

Heat reduction requires thermal reflectivity...absorbtion...and/or a thermal break. Think Shuttle Tiles and the way they are installed.
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Old 01-09-2018, 08:21 PM   #5
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Thanks for the input guys. Will demolish this drawing board, and go back to my old one.


Don
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Old 01-10-2018, 07:29 AM   #6
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About the only positive feedback I have heard on Dynamat was from hot rodders who used it on previously bare sheetmetal. They claimed some noise reduction (when every square inch was covered $$$). Never heard of anyone satisfied with its' heat reduction.

Sound reduction requires mass. As in a pound or more per sq. ft. Sheet lead is toxic but still the best there is.

Heat reduction requires thermal reflectivity...absorbtion...and/or a thermal break. Think Shuttle Tiles and the way they are installed.
if I took the carpet out of a car for a Build I dynamatted the whole floor and footwells.. it made a surprising difference in the amount of road noise.. I always installed or updated the A/C so i didnt care about the heat
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Old 01-10-2018, 09:31 AM   #7
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Are you using regular sound deadening dynamat? Might have better luck with the under hood dynamat stuff for insulating doghouse. Regular dynamat will hang upside down, I was a 12v installer at car toys for decade, and have done more roofs than I can count, and with good prep never had an issue with it staying on metal surfaces (regular dynamat)
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Old 01-10-2018, 10:24 AM   #8
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Are you using regular sound deadening dynamat? Might have better luck with the under hood dynamat stuff for insulating doghouse. Regular dynamat will hang upside down, I was a 12v installer at car toys for decade, and have done more roofs than I can count, and with good prep never had an issue with it staying on metal surfaces (regular dynamat)
i think the issue is that the doghouses are plastic.. at least mine is..
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Old 01-10-2018, 11:09 AM   #9
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Gotcha...that makes more sense.
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Old 01-10-2018, 01:44 PM   #10
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Would using foil backed under hood felt work?
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Old 01-10-2018, 06:35 PM   #11
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The foil over felt helps some, more with heat than noise. But make sure whatever metal the felt backs up to is well protected. The felt holds moisture like...well, felt.
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Old 01-10-2018, 07:09 PM   #12
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For this discussion maybe we need to start discussing.
how much heat an engine puts off.
For the ones with the turbo close to that cover that heat is a lot more.
I don't know mine but know I have to address the issue but am planning on doing it on the inside of my straight forward metal cover with the same access still available.
But I have access to hight temp ceramic fibre,fire blanket scraps from my work when building duct off of kitchen exhaust hoods. It is foil wrapped and encapsulated at each cut with the proper tape.
Isn't cheap stuff. But I get leftovers.
But I think an engine temp. Discussion and turbo temp discussion should be involved in deciding an insulation to be under hood and next to engine.
We can assume that it is taken into account when figuring it out but some material has a specific distance away from certain high range temps in an under hood application.
Not saying the stuff won't work but if the stuff falls down on the engine or even higher temp turbo? Will it light up?
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Old 01-10-2018, 07:28 PM   #13
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Heat proximity is indeed a big deal. An air gap, especially if it is moving air, will make a huge difference in the heat transmitted to the doghouse. My turbo and downpipe are inches away from a steel doghouse which has the potential for cooking a side of beef. One way to reduce the heat transfer is to shield or isolate the heat source.



On my shorty I had the downpipe ceramic coated inside & out...then wrapped it with the volcanic tape...then put radiant heat shields over the whole thing (with an air gap between the shield and pipe). On the turbo, I used a full wrap blanket. As much to help performance as reduce radiated heat (a turbo will spool faster if you can keep the heat in).

Once the doghouse is installed, I will coat it in ceramic paint on both sides...add some radiant foil type shielding on the motor side...and then build an "outer" wooden doghouse inside over the metal with another air gap and noise and heat insulation in between.

That's about all I could come up with on my build.
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Old 01-10-2018, 07:44 PM   #14
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I knew you would be the first?
Some builds are special and I wish I had my own special one.
As you know most are trying to build basics and I think if they know the temps under the hood/doghouse and what's close to it then might look at different insulation Underside the doghouse from the factory verses inside addition that is better protected from the weather.
High radiant temps from the engine and accessories is what needs to be considered before deciding what to type to use.
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Old 01-10-2018, 07:45 PM   #15
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My cover is plastic also, and was a very tight fit coming off, which makes me think it's resting against something when installed.

What are your collective thoughts about something like this lining the interior of the doghouse, and held in place with the hurricane straps I mentioned earlier? I also like Hybuzz's idea of a hood scoop to direct cool air over the engine then down to the ground....seems like that would help underhood temps considerably.


Don

https://www.amazon.com/Ceramic-Insul...QE8VMKH43633XV
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Old 01-10-2018, 07:54 PM   #16
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Directing airflow over the hotspots will definitely make a difference. I am looking at a dedicated electric fan to do just that myself.
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