"Exhaust Velocity"??? It is my understanding the velocity of the exhaust will spin the turbo propeller the same regardless if the exhaust temperature is 500 degrees or 1600 degrees. I'm questioning if the temperature of the exhaust passing through the turbo has a direct affect on intake temperature. This is based on heat traveling from the exhaust side of the turbo to the intake side. Are saying exhaust velocity is based on exhaust temperature?

 

The reason you want to keep the heat in the header is that you want the exhaust gas to expand as rapidly as possible, ie exhaust velocity (Thanks Zeus). The hotter the gas, the greater the rate of expansion, and the harder it will spin the turbine wheel. Does that explain it?

 

I was in a hurry to go to work and didn't have time to explain... I lot of "uncoated headers" (manifolds) in the race world are only uncoated on the outside... ask around. I would suspect this is to retain less heat in the tube walls...

 

PV=nRT: When gas cools it shrinks, don't really want gas volume shrinking in the post-head pre-turbo area I guess. More volume=better spool

 

On an turbo car, heat retained in any exhaust component is a good thing..on the intake side, the opposite holds true...you want to expel heat as much as possible.

Adam