> There are several things that come into play during deceleration with an
> exhaust header, especially monza systems.
>
> Firstly, since the entire system optimizes for free flow, the exhaust will
> flow freely in both directions. With a standard system the exhaust will be
> restricted further in reverse flow, lessening the sound pressure waves
> during decel - not happening in the monza.
>
> Second, since the monza does not have a pressure break collector, the sound
> pressure wave is not broken at the end of the header (which is why they
> sound so throaty and more noise under the hood (bonnet). A standard and many
> other headers do have this larger collecter which will reverse the sound
> wave within the header. At decel, the sound wave is louder because of the
> lean (slow burning) mixture burning in the header. Since the standard
> manifold is cast iron, the burn will happen quickly and quietly within the
> manifold because of the retained heat.
>
> To reduce the backfire noise, you will have to use a deceleration valve
> which will allow the throttle to remain partly open during deceleration.
> (The ZS150 standard has this valve, and it works well, even on monza
> systems - Webers don't)
>
> In order to reduce the engine noise, you will have to experiment. I used a
> 3" collector attached to the bottom of the header to remove the sound wave
> from my system. (Monza 4-2-1 w/2" output pipe) It also reduced the underhood
> noise significantly. It also allowed me to eliminate the resonator in the
> centre of the system leaving only the tail tips. I also tried unsuccessfully
> using the header wraps, but all they did was make the exhaust pipes hotter.
>
> Good luck with your car!
>
> Wayne Burton
> 1963 Triumph Spitfire4
> 1966 Triumph 2000
> 1954 Austin A40 Somerset
Wayne,
Thanks for the input. You have put a lot of my concerns to rest, for the moment.
But being a neophyte as far as exhaust systems go, exactly what is a
'collector', what does it look like and where does it go/attach? If I go to a
muffler shop and tell them I want one, they won't look at me funny, will they?
Or get the guy out back to come around with his baseball bat....hehehe. Or will
they probably know of what I am talking about (as opposed to me)
Thanks
--
Bob Norway
Rockledge, Florida
Home Page http://www.geocities.com/CapitolHill/Lobby/5953/mypage.html
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