Was Water Injection , now header impact on turbos

[ECMnut at aol.com]

First, let me say that I'd like to hear D. Cooley or 
 F.Breitwieser comment on this topic.

There are often exceptions to rules and trends, but
the following is mostly my opinion, formed while
playing with turbos (as a hobby) for 20 years:

Actually, with many *mild* turbo applications, 
there IS some performance to be gained
by altering primary tube size/length, but I *think* it has
more to do with volume of the tubes..  Turbo Buick
owners who install the popular Hooker headers often
report a loss of bottom end & midrange torque
as well as slower spool-up, while sometimes adding to 
the high RPM power levels.  The effect is similar 
to going to a larger AR turbine housing.  For milder 
applications, there is a thoery, that keeping the
primary tube as short (small volume) as possible
tends to more directly expose the turbine to desirable
low rpm exhaust pulses, which aid in spool-up or
possibly allow you to use a slightly larger turbine 
housing.   There are other factors, but the factory
header/manifold is a good example of the small 
volume exhaust tract, when compared to the Hooker 
Headers.  Just to counter the above argument, 
 when you employ a REALLY high flowing  
 manifold/cam/port arrangement, the advantages
of going *BIG all around* outweigh the pulse benifits
of the small volume headers.  The size of the exhaust
tract (tube ID & length) are a critical part of the total 
"package" that many Turbo racers stress, when 
 discussing and planning modifications to their turbo
cars & trucks.
Comments? yes? no? maybe?
Mike V.  Thread bender for a day..

In a message dated 1/4/99 9:51:53 AM Eastern Standard Time, JemisonR at tce.com
writes:

> 	The turbine determines how fast the compressor spins. 
>  	Bigger turbine housings will flow more exhaust gases but will take
>  longer to change the speed of the turbo (expecially at low 
>  		low rpms)
>  	Smaller turbine housings will flow less exhaust gas but will spin up
>  much faster (no bottom end hole). 
>  	There is no advantage to be gained by trying to "tune" the exhaust
>  by either pipe length or pipe matching at collectors.
>