conversion question +

[Frank F Parker]

>      rise in EGT during a 1/4 mile pass, with EGT typically rising to 
>      1550-1700F by the end. Can anyone comment on the big picture here, 
>      energy, phyics or otherwisewise, as to what is going on with turbo 
>      engines and EGT at wot? I realize that the exh manifold up to the 
>      turbine is at much higher pressure than for n.a., the turbine is 
>      extracting energy from the exh flow, etc. but is this EGT rise 
>      "necessary" for the turbo to keep up at wot/high compressor pressure 
>      ratios/high flows, ie is the high EGT sort of indicative of the 
>      potential energy "well" existing in the manifold, necessary for the 
>      turbo to draw from to "keep up" with it's chores on the comprssor 
>      side? Wow, I'm clear as mud here, right? :-)
>      
>      Todd       tking at scic.intel.com 
> 
Todd,

Corky Bell's new book published by Robert Bently called "Maximum Boost"
is all about turbos and their theory, installation and tuning. It is
excellent. From there you will learn that normal turbine back pressure
is 2-3 times manifold pressure but the lower the better to a certain
point as pressure is necessary to extract the energy as you suggested.

I found in my own turbo car that had a pretty restrictive cat and exhaust,
that I had very high temps (1650 deg F) until I lowered the pressure
after the turbo. I measured it by silver soldering a thin (.035) wall 1/8
in tube into a hose clamp, drilling the outlet pipe and clamping tube
to pipe and running hose up to a pressure gauge. I had 2 times turbine
outlet ( not inlet) pressure but after bigger cat and pipes lowered
the pressure to about a psi and lowered egt by 200 deg.

Frank Parker
fparker at umich.edu