Re: [DML] New Exhaust headers

[Paul Gress <pgress@xxxxxxxxxxxxx>]

Martin Gutkowski wrote:
> I have to say that while the quality of workmanship looks to be top 
> notch, what you'll get is the sound of two 3 cylinder engines. You won't 
> get that lovely throb of a V6, and especially not the unique sound our 
> odd-fires make. For this, the twin outlets must be combined. It's also 
> not true that making the exhaust as free-flowing as possible will aid 
> performance, but will in fact hinder it after a point. Take it to the 
> extreme, and see if you can get your engine to idle with no manifolds at 
> all.
>
>   
This has to do with "exhaust scavenging".  With headers in place, when 
the exhaust valve opens a pulse of exhaust pressure is released.  This 
pulse starts traveling down the header tube then the exhaust valve 
closes.  This causes a negative pressure between the exhaust pulse and 
the closed valve.  This causes the exhaust pulse to reverse direction 
and start heading back to the exhaust valve.  When this pressure pulse 
returns back to the exhaust valve, it will bounce of the closed valve 
and start heading outwards again (away from the exhaust valve), at this 
time it would be optimal to open the exhaust valve at the completion of 
the next exhaust stroke cycle, as it will create a negative pressure 
again and aid in the exhaust scavenging.

This is what "tuned headers" are suppose to do.  This is why tube 
diameter is critical at an RPM.  The tube diameter is usually tuned to 
operate at the maximum horsepower or torque rpm.  The smaller the tube, 
the longer the pulse reflection in time or distance.

So without any exhaust manifold or headers, there would be no exhaust 
scavenging and the engine would run less efficient.

Paul


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