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Hot Air 07/07/2004 (Reply) PDF Print E-mail
Hi Rephots

Early in the 20th century, as piston engines came  under the scrutiny of academics, it was noticed that if an engine was revved at an rpm where the firing frequency coincided with the natural frequency of the exhaust system, a resonance was set up in the pipe.  Soon this phenomenon was exploited to increase the performance of an engine and thus exhaust-tuning began.

However, exhaust tuning has been applied only to racing applications and high performance super cars:  until recently, that is.  The introduction of catalytic converters which can be inherently restrictive to flow, causing unwanted back-pressure, has forced a re-think on the design of conventional exhaust systems, even on a family car such as yours, with the result that the new generation cars are fitted with exhausts that are pretty much state of the art regarding power delivery, noise reduction and general vibration and droning problems.
I am not aware of an existing branch manifold for the Peugeot 307, but one can be made virtually over a 24 hour period.  However this would be purely fabrication, not development, which can take up to three weeks or so, depending on baseline development figures and noise output.

The sequence would be:  first the silencer system would be developed (without the cat) employing different diameter pipes with varying combination of silencer boxes to obtain not only the best power and torque but also the best sound.  Once the free-flow silencer system has achieved an acceptable power increase, then, (secondly) the design of the branch manifold is tackled (see HOT-AIR issue 13 & 14).

To install a bigger bore free-flow silencer system after the cat would probably not be a good idea, because the limiting factor in flow is the CAT itself which, theoretically allows maximum exhaust flow relative to the flow ability of the stock silencer system, not a big bore through-flow system.

A catalytic converter is a means of removing many of the substances that are harmful to man and environment, which are emitted because of an engine’s incapability to completely burn its air/fuel mixture.  The exhaust emissions include water, carbon dioxide, carbon monoxide, unburned hydrocarbons and oxides of nitrogen.  The new generation of catalytic converters purifies 95% of the exhaust gases, modifying the exhaust gas emission to a cleaner gas consisting of carbon dioxide, water (in the form of vapor) and nitrogen.  “Catalytic converters” is a wide-ranging subject, which will be covered specifically later.

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