<VV> Turbo and Dual exhausts [LONG]

[BobHelt@aol.com]

Hi Frank, Jim and all,

This is the third time that the turbo exhaust system has been referenced 
lately and so I feel it necessary to comment. Yes, the turbo system maximum boost 
is limited by design and construction so that no sophisticated and expensive 
controls are necesary for the stock system. But As Frank said, the restriction 
is mainly in the carburetor and intake system. The restriction is not in the 
exhaust system. 

In fact the mufflers used in the stock Corvair turbo system were specially 
designed to have a very low restriction. It is now ancient history, but in the 
1970s, everybody wanted to use turbo mufflers to reduce backpressure. The 
Corvair turbo muffler was the hot item for years as muffler manufacturers rushed to 
get their turbo muffler version on the market. Several of the popular car 
magazines ran articles in which they tested the different brands of turbo 
mufflers to see which ones had the best flow and least restriction. Turbo mufflers 
offered less backpressure and greater flow than most of the stock mufflers being 
used and offered as replacements at that time.

If the Corvair designers had chosen to restrict the exhaust for some reason, 
that would just have added more heat to the Corvair's already overloaded 
cooling system, which would not be a good thing. What they wanted was to get the 
exhaust out and away from the engine after it did its work in the turbo.

Regards,
Bob Helt

 
In a message dated 3/4/04 8:51:55 AM Pacific Standard Time, FrankCB writes:

<<  Personally, I've always felt that the small YH carb is far more 
restrictive to increases in boost than is the stock exhaust system downstream of the 
turbo.  Someday, when I get the EFI installed on my 180 with a different 
throttle body but with the stock exhaust system, I'll find out.  Before then, I'll 
install a vacuum gauge downstream of the YH (upstream of the compressor) to find 
out just how restrictive the stock YH is.  I remember somebody (perhaps Bob 
Helt??) quoted the figure of 7 in. Hg. vacuum downstream of the smaller YH on 
the 150 engine.  >>