This is absolutely correct. It may not break for 6 months, but either the
weld or part of the hanger will fail.  Even having the exhaust bolted to
the engine is no guarantee as sections will often have a different moment
of inertia than the engine assembly which can lead to asyncronous movement.
This in turn also causes failure. In design of a good system, attention
must be paid to proper balance and distribution of mass with respect to the
engine's
axes of movement and the exhaust's own suspension. Additionally selection
of when to put rigid welded sections vs. loose(clamped, or flex coupled)
sections is vitally important. It is very difficult to achieve this balance
of cost, longevity, performance(engine and sound dampening), and fitment.
Good luck, and the devil is in the details!

Jim

At 06:56 PM 8/8/2005, Malcolm Stebbins wrote:
>I have been told that attaching the exhaust pipes, or the muffler or the
>tail pipe to the FRAME is
>NOT a good idea, as the engine vibrates upon startup, and at idle, & while
>running, all
>DIFFERENTLY than the frame vibrates, so it is just a matter if time before
>some part of the
>exhaust system will break.  The design is to have the exhaust system
>bolted to the engine so they
>can vibrate as a unit.

________________________________________
Jim Akiba
Bostig Engineering
http://www.bostig.com/products/zetec/
978.772.3274
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