Thread: C5 gto
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Old 01-11-2011, 02:45 AM
Peter Miles Peter Miles is offline
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Location: Lake Forest Park, WA (Seattle)
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Quote:
Originally Posted by heinke View Post
The design choice I ended up with is double sheeted aluminum sandwiching insulation in between. The largest chassis tubes are 1.5 inches diameter so this gives me 1.5 inches of space for insulation. I anticipate the two hottest areas will be the firewall that’s exposed to engine headers and transmission tunnel where exhaust is routed and mufflers are located. My first line of heat protection is an all stainless steel exhaust system.


I decided to use rigid urethane foam sheet for the insulation. It’s easy to get (bought mine at Home Depot), comes in various thicknesses, is relatively inexpensive, easy to cut and install. My first concern was if high heat would somehow adversely affect this material. To test, I held an industrial heat gun at about 1 inch from the bare foam (not the foil covered) turned on high for over 10 minutes and there was no appreciable damage apparent. There was a little bit of melting but not much. My main concern was whether it would catch fire and it didn’t so I figured it was safe for this application.

If anyone knows from experience that using this type insulation has any issues, please speak up. While it sounds good to me in theory, I’ve never actually seen it used in automobiles before.
I posted a response yesterday, but it apparently did not stick. I'll try again.

Joel, I would suggest doing a little more research on insulation. Do a Google search on Aircraft Firewall Insulation. There are a number of good hits on the first page.

One that I've read a number of positive reviews of is the Koolmat.
http://www.aircraftspruce.com/catalo...es/koolmat.php
I have zero personal experience with this however.

Aircraft Spruce in general handles a number of different insulation products:
http://www.aircraftspruce.com/menus/ap/insulation.html

Here is a link to a MSDS sheet for urethane foam (flexible, not rigid):
http://www.auralex.com/testdata/test/foammsds.pdf

Some snippets from that document:
Quote:
SECTION 3 -- PHYSICAL & CHEMICAL CHARACTERISTICS
...
IGNITION POINT: 600 - 650 degrees F

AUTOIGNITION POINT: 750 - 800 degrees F
Quote:
SECTION 4 -- FIRE & EXPLOSION HAZARD DATA
OSHA CLASSIFICATION: Combustible solid
NFPA SPRINKLER CLASSIFICATION: Upholstery with plastic foams. Extra hazard.
EXTINGUISHING MEDIA: Water spray, carbon dioxide, dry powder
FIRE FIGHTING PROTECTION: Use NIOSH-approved self-contained breathing apparatus &
protective clothing including boots.
UNUSUAL FIRE HAZARDS: Once ignited, can produce rapid flame spread, intense heat,

dense smoke and toxic gases. Can turn into burning liquid which can drip and flow.
Quote:
SECTION 5 -- PHYSICAL HAZARDS
...
CONDITIONS TO AVOID: Strong acids and alkalis will deteriorate foam properties.
INCOMPATIBILITY: Unknown
HAZARDOUS DECOMPOSITION PRODUCTS: Combustion, hot wire cutting, heat sealing, hot
stamping & flame laminating operations of foam may produce carbon monoxide, oxides of

nitrogen and traces of isocyanates & hydrogen cyanide.
I glanced at several MSDS sheets for rigid urethane foam, their characteristics varied significantly across various products, so don't assume that the above would apply to the product that you are considering. I would search for an MSDS sheet for that specific product or contact the manufacturer, however.

I would be concerned about possible outgassing of cyanide, etc. at temperatures well below the combustion point.

I'm also not sure how well this holds up to extended periods of vibration, moisture intrusion, etc.
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