Exhaust temps...

[Frank F Parker]

> 
> >Sounds like you need a better alloy with more nickel and vanadium?
> 	Like what? See above - I thought 321 was the "ultimate"
> stainless.
> 
> >Wow.  For a naturally aspirated engine, I've seen temps at 500-600 F
> >at idle.
> 
> 	Must have had a very rich mixture and advanced timing? Mine is
> deliberately retarded at idle so that it reduces the emissions.
> 	Anyone else have temp figures we can compare?
> 
> -Charles
> '81 745i

Charles,

I saw similar 1600 deg temps in a custom turbo Honda vtec I did BUT
I found the cause was high back pressure from restrictive exhaust and
cat. At only 5 psi of boost, I had 9 1/2 # of back pressure. When I went
to bigger dia exhaust and bigger cat, the back pressure went down to 2
1/2 psi and boost rose to 9 psi at same wastegate setting. Temps dropped
150 deg. Also if you lowered compression alot, that causes high temps.
In tests I have done on factory GM race cars with very high ( 16/1)
compression, exhaust temps are only 1200 deg cause of the better
combustion. If you are rich and have high back pressure, you will have
essentially a afterburner and the high emps you see.
Easy to check. Drill 1/8 hole in pipe, weld thin wall 2" length of ss
tube to a hose clamp with 1/8 just sticking thru and clamp around pipe.
Hook up gauge and make a 4th gear wot test. Should see less than boost
pressure for back pressure- the lower the better. Put in turbine output
pipe before cat.

Frank Parker
> 
>