Forwarded: Header insulation

[dzorde at aesprodata.com.au]

     The hotter the exhaust is, the less dense the air in the exhaust 
     system, thus on the exhaust stroke the air can escape the engine 
     faster due to the lower resistivity towards the air coming out of the 
     engine.  Ideally the whole exhaust system should be red hot so that 
     air gets sucked out of the engine.  


______________________________ Reply Separator _________________________________
Subject: Re: Forwarded: Header insulation                            
Author:  diy_efi at coulomb.eng.ohio-state.edu at INTERNET
Date:    7/4/96 3:40 PM


At 09:59 AM 7/4/96 est, you wrote:
>
>I can't imagine you'll get too many mpg's out of this exercise, since 
>once the exhaust heat is out of the combustion chamber it can do no 
>further useful work, whatever its temperature (unless you have a 
>turbocharger).  It's just waste heat from the exhaust port onwards!
     
I don't think that this is really true, I recall that the density of the hot 
gasses tend to expand when exchanging heat with the header causing a kind'a 
clogging effect. Also, wrapping the exhaust with some heat preserving wrap 
will most definitely change the engines mixture to be on the lean side. I 
think that this is again related to the better efficiency in the exhaust 
system. I'll let some of the experts follow up with the scientific 
explanations...You wont get dramatic changes in MPG in any case. I have done 
this to a 372 chevy, and it allowed me to move up a couple of jet sizes, thus 
allowing more fuel to be burn and more power.
     
[chomp]
     
Sandy