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Discussion Starter · #1 ·
Since I bought in my '04 Sable, I noticed its A/C is inferior to my friend's Corrola, Camry in the hot summer.
R134-a pressure checked, normal. It just took ~3 min to blow out mildly cool air from the vent. And even
set @ Max. Cool, the performance of the A/C is just so so.

When I looked under the hood, I found the dryer/tube attached to the compressor, is located so closely to
the front-bank exhaust manifold. So there must be tremendous heat exchange between dryer and exhaust gas.
Thus, the refrigerant in the A/C system was heated up somewhat before it reaches the evaporator and the
overall performance of the A/C was lowered. My idea is the use the following tape to wrap the exhause maniford,

http://www.amazon.com/Thermo-11022-Graphit...f=pd_sbs_auto_6

so the heat from the exhaust gas escaping the cylinders will be constrained inside the exhaust housing.

As we know, many problems and failure are associated with heat and high temperature in the hood, such as
hose crack and liquid leaking, electrical connector malfunctioning, and etc. By this modification, the working
temperature under the hood will be reduced dramatically. The A/C performance will be restored and the
lifetime of all the plastic/rubber components will be prolonged.

But the potential disadvantage is: increasing exhaust gas T may also increase its pressure, according to pV=nRT
The pressure in the exhaust maniford is actually back-pressure, which contributes negatively to the output
of the engine. So by elevate the exhaust gas T, will the engine power be reduced? And any other
hazards to the 3-way catalyst or muffler? Inputs are welcome for this topic.
 

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There are no downsides to the heat wrap. Also me to explain. If the expanding exhaust is hotter, it also moves faster. Thing of it like a spring. Yes, there is more resistant to compressing a spring more, but it will also spring farther once released. It will also be hot when it exits the engine whether it is contained or not. If the heat is kept contained within the exhaust, there should be performance gains, since as the exhaust looses its heat, it also looses speed. This loss in speed can produce backpressure as the exhaust slows down in front of the gases that are exiting from the next cylinder.

I use a heat warp on my van to reduce the amount of heat that gets to the transmission. It works well enough that you can actually grab around the pipe without getting burned.
 

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I don't know what's wrong with your '04. My '97 was ICE cold, before the compressor was smashed. Exhaust wrap is good, but try removing the rubber piece on top of your hood, nearest the windshield. It'll create a current over your engine, starting from the pocket that the front manifold heats up.
 

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Discussion Starter · #4 ·
Thanks for the explanation.
But if the gain is so significant, why the auto-maker doesn't install the heat wrap as a default?
It is such a simple modification, and the cost may be just $30.

QUOTE (KhanTyranitar @ May 31 2010, 06:47 PM) index.php?act=findpost&pid=808177
There are no downsides to the heat wrap. Also me to explain. If the expanding exhaust is hotter, it also moves faster. Thing of it like a spring. Yes, there is more resistant to compressing a spring more, but it will also spring farther once released. It will also be hot when it exits the engine whether it is contained or not. If the heat is kept contained within the exhaust, there should be performance gains, since as the exhaust looses its heat, it also looses speed. This loss in speed can produce backpressure as the exhaust slows down in front of the gases that are exiting from the next cylinder.

I use a heat warp on my van to reduce the amount of heat that gets to the transmission. It works well enough that you can actually grab around the pipe without getting burned.[/b]
 

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Because it doesn't cost so little. Some automakers are more hung up on heat shields than others, but in the speed of an assembly line, wrapping the manifolds takes too long. This slows down the entire line, which in turn costs a heck of a lot more than $30. There are benefits, but don't expect them to be huge.
 

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no problems in my 97 vulcan, just wish it wasnt so cold when at max cause my wife thinks it has 2 settings, OFF and MAX...

when i bought the car 90% of the hoses (even the bit from airbox to throttle) were wrapped in foil... don't know why, dealer said it was already like that when he got it... they've been replaced since and i've seen no difference, also took the foil off the intake cause it looked like sh*t and was starting to fall apart
 
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