>
> On Feb 29, 2008, at 10:09 PM, Herbert Graf wrote:
>
>
> On Sat, 2008-03-01 at 14:58 +1300, Apptech wrote:
>>>> You could use heated air from the manifold when the
>>>> engine is running to
>>>> the save energy otherwise used to heat the air while the
>>>> engine is running.
>>
>>> Unfortunately when it's cold it can take a surprising
>>> amount of time for
>>> an idling engine to get anywhere near warm enough to put a
>>> dent on
>>> defrosting a windsheild. Trust me, I know, it was -25C
>>> (about -13F) last
>>> night here...
>>
>>> From startup, how long can you hold your hand on the top of
>> the exhaust pipe where it leaves the manifold? (We'll let
>> you not place it there until the pipe rises above 0 C to
>> save you some skin, but count those seconds into the period.
>> Hand off (new meaning to the term) occurs around 55C - 60C
>> unless you have asbestos hands.
>
> Right, but what do you do when the temp of that pipe reaches 300 or  
> 400C
> or even higher? (I'm unsure of the exact temp, I do know that the O2
> sensors need to be at about 800C to operate, and I also know from
> experience that the pipes are hot enough to light transmission  
> fluid on
> fire instantly).
>
> Frankly there are many MUCH easier ways to get heat then trying to  
> build
> something that can operate safely through such a wide variation of
> temperature, which is why it is almost never done.
>
> TTYL
Not to mention the difficulty of attaching an add-on unit to said pipes.

I guess you could blow air through a pipe attached to the exhaust and  
monitor the output temp and mix in ambient air to keep the temp at  
the right level.
cc


-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist