From: BAC0813@ritvax.isc.rit.edu@INTERNET on Wed, May 29, 1996 3:40 PM
>There's been a lot of discussion lately about larger diameter exhaust and
open
>air filters. By going to a larger diameter exhaust you decrease the
effective
>legnth of the exhaust. This raises the engine where produces peak torque,
since
>horsepower is a function of torque you do gain horsepower, but not torque.
>Effective you have lowered the torque output at lower rpm, but raised it at
higher
>rpms. ....
>Contary to the common belief much time and money is spent in design and
>development of all vehicle system to make them the highest quality.
Your statements are true from a pure engineering stand point, but with any
item that is designed and built, compromises are made. In the case of
automotive intake/exhaust, the compromises are developed around space
constrictions, noise requirements, emissions requirements, time and cost.
The power output is defined by marketing requirements. Addition engineering
resources are just not spent to optimize designs when all the requirements
have been met.
Being that automotive engines are in a relatively mild state of tune the cam
profile has a much more significant effect on the torque profile than the
exhaust. In many cases uncorking a restrictive exhaust allows the engine to
produce an increase in power across the normal operating rpm range (normally
at the expense of a noise increase), a choice that the factory can not
always make.
The best part of being an enthusiast is the desire and ability to alter the
factory compromises and the exhaust is one of the easist with the most
significant impact.
Dave Clement
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