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Old 12-28-2012, 12:02 AM   #21 (permalink)
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it seems pretty simple to me... heat go up.... insulate up I did a test with my insulator and noticed a significant increase in heat retention. 10c after 4 hours. with a little more insulation I bet I can double the temp.

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Old 12-28-2012, 09:34 AM   #22 (permalink)
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Quote:
Originally Posted by ctgottapee View Post
The issue is, and the reality is, that the insulating effect is darn near not scientifically measurable to any meaningful value.
The bubble foil has nearly zero insulating value on the underside of the hood when trying to keep heat in, and that is when you don't include all the other avenues of heat loss.

If you were to do accurate A-B-A testing you would see no difference.

There are other methods that do work, but they have limitations to:
-like The coolant heat retention method used by the prius; surely they would just line the hood for a $1 in bubble wrap if it actually worked.
-or frost heater type fittings plugged in to electrical source.


The engine is designed to shed heat fast; you can't alter that with a little cardboard.
I will live in my delusional, non-scientific world and say that, simply by temperature of the hood a minute after driving, tells me that it is working. Even cardboard has an R-value. If the R-value of both the cardboard and the bubble foil comes out to about 1, that's still double the resistance compared to air. With how little space you have to work, it's hard to find any material that will insulate beyond that.
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Old 12-28-2012, 10:15 AM   #23 (permalink)
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Quote:
Originally Posted by Frank Lee View Post
Yes you can.
shortest most accurate post in this thread I cant believe that hood insulation's effectiveness is being argued. it clearly has benefit, especially in conjunction with other mods like grill blocking.
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Old 12-28-2012, 12:43 PM   #24 (permalink)
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Quote:
Originally Posted by NoD~ View Post
I will live in my delusional, non-scientific world and say that, simply by temperature of the hood a minute after driving, tells me that it is working. Even cardboard has an R-value. If the R-value of both the cardboard and the bubble foil comes out to about 1, that's still double the resistance compared to air. With how little space you have to work, it's hard to find any material that will insulate beyond that.
Science will help you. [apologize for the length]

And yes you are correct in saying it can double the almost nil R value to nearly nil R value (an extra penny does not make a one penny man wealthy.) My initial and later responses is not an attack on your report, just adding prudent information.

-The R value of corrugated cardboard (shipping boxes) is slightly over R 2 per full Inch uncrushed.
-The R value of flat cardboard (paperstock) is approx R .75 per inch.
-The R value of the bubble foil stuff is slightly under R 1 uncrushed in this situation.

-The R value of open air vastly depends upon the environment, but the bubble foil R value is from the encased air in this environment.
If the insulation touches both the hood and any part of the engine bay, you lose the skin effect of the air space R value which almost negates any gains unless you have a large gap to fill with insulation.

This is only in a sealed environment with the heat going one direction (UP) through the material. Open air (DOWN/SIDES) or other conductive materials (metal, coolant/oil fluids) in other directions would significantly reduce these numbers, which are already almost nil to begin with. And the hood is still short circuited with its contact points (Latch, hinges, etc.)


The issue is not whether trying something out that costs basically nothing is worthwhile, the issue is whether we say it actually produces significant results: the answer is No, it is impossible. I'm all for experimentation and tinkering. I'd love to see you fill the engine bay nearly solid with spray foam but wouldn't advise it.
The best insulator approach is the prius method, or an approach of it.

And then we tackle the counter issues, like placing a highly flammable material in the engine bay,
Or the fact that the foil wrapped bubble in this case actually insulates the radiant heat from the sun heating the hood if you are trying to keep the engine bay warm while parked in the sun - yet again the gain is minimal.

We can discuss what would be the most optimal insulator in this environment and try to construct it and do some testing, but the same limitations unfortunately apply and the costs out weigh the benefits.
I'm experimenting with an electric water pump and while I could post and proclaim its benefits, at the end of the day, so far it is looking to be a wash when all factors are concerned, plus the cost - but I've still got some tricks yet to try.

I appreciate the sharing of personal experience and results, but we also must keep in mind that this web board is used to provide information for those seeking out FE gains. This thread was highly misleading (I doubt intentionally) and missing some relevant facts. As you said in the prior post, there really isn't much you can do in such a small space, and then you have to add in the other factors.


Hood Insulation = Not practical, nor provides any meaningful results in and of itself, but its inexpensive, can provide sound insulation, and one must be careful of additions to the engine bay environment.
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Old 12-28-2012, 12:52 PM   #25 (permalink)
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Your explanation sound well thought out, but results do not lie I would also argue the cardboard is one of the least flammable materials under the hood. pretty sure there are rubber hoses filled with gasoline. Cardboard ignition point is 800F nothing on the top of my engine bay gets that hot.
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Old 12-28-2012, 01:03 PM   #26 (permalink)
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I think something you are missing, ctgottapee, is that I never claimed great numbers. I charted A/B testing for a few days, each day after work, parked in my garage, and came back after X amount of time and charted my findings. In the end, it was only ~10*F difference after an hour or two... small gains. (I'd have to go see if I can find my experiment sheet. I did a few days of A/B testing with every 15 minutes recorded changes, but the immediate changes were so little, I started doing 30 minutes).

Given that, it proved it was doing SOMETHING. Properly sealing my hood, putting a belly pan together under the engine, etc. would definitely make larger gains there, as stopping the flow of air is going to make the greatest of differences. Not much different than a house, other than the walls are metal and the wind is almost always blowing on them! Killing the drafts would easily make the greatest of differences (though, while in motion, one would have a hard time doing so, but parked... whole different ball game)

what I'm getting at is that most people have these materials laying around (the cardboard at least). It's easy enough to cut out and simply throw under the hood. Results will definitely vary, but given the positive results here on the forums, I think we can all agree that nobody is regretting this mod, despite how mild the changes come out to be.

As for my current vehicle, I have a lot of work to do. I took the hood insulator I build for my last car and slapped it in w/o any other changes. Once I seal up the hood properly, I expect much greater results all together.
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Old 12-28-2012, 04:47 PM   #27 (permalink)
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it took pee longer to type that post than it would have taken to make a blanket and feel the heat retention.
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Old 12-28-2012, 05:35 PM   #28 (permalink)
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Quote:
Originally Posted by Frank Lee View Post
it took pee longer to type that post than it would have taken to make a blanket and feel the heat retention.
Blankets have very little R value actually.
While there may be a slight increase over not having a blanket, you are actually just blocking the heat from the sun.
In addition, wrapping yourself in a flammable material when you may near a stove or smoking is not a good idea.
100mm of fiberglass strand insulation surrounded by an impermeable vapour barrier would be a better idea!
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Old 12-28-2012, 05:43 PM   #29 (permalink)
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Quote:
Originally Posted by ctgottapee View Post
Hood Insulation = Not practical, nor provides any meaningful results in and of itself, but its inexpensive, can provide sound insulation, and one must be careful of additions to the engine bay environment.
Keep in mind that most folks on here already have their grilles blocked, which means less air going in. And less heat being blown out.

Sure, there are still a great many leaks - and you actually need them to get rid of the heat from the engine.

Simply blocking part of those leaks already seems to help warm up times ...
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Old 12-28-2012, 11:51 PM   #30 (permalink)
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R value is pretty irrelevant, glass has no R value but even single pane windows keep the cold out and the heat in.

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