4-stroke carbon pipe design Q's

[Bill Glaze]

Bob:
One small correction: the outgoing exhaust pulse, which is under 
pressure, creates a small vacuum behind itself as it escapes; this 
creates a low pressure area that helps draw the new charge into the 
combustion chamber.  I've used a "tuned" exhaust on engines as large as 
540 cu. in. The tuning takes a little time on the race course, but it's 
really worth it.  It doesn't work quite the same with a blown 
(supercharged) engine, because the blower pressure masks the small (by 
comparison) vacuum behind the outgoing exhaust.
Bill Glaze


Bob Richards wrote:

>I had an AAP exhaust system about 13 years ago that
>was tuneable to some extent. Playing with the length
>of the system I was able to hit a sweet spot and gain
>about 200 rpms, but was still a slight loss in rpm
>over open exhaust. Of course, this was until the inner
>lining of the header failed and exhaust started coming
>through the outside braid.
>
>The tuning dynamics are completely different from
>two-strokes. On two-strokes, you are dealing with a
>(forgive me if I mess up the terminology) reflected
>wave that stuffs some of the excess unburned fuel/air
>back into the exhaust port before it closes, but after
>the bypass port closes, effectively supercharging the
>engine. On a four stroke, you are using the inertia of
>the previous exhaust pulse to help extract the next
>exhaust pulse. Baffles and backpressure tend to defeat
>this.
>
>That is the limit of my knowledge on the subject,
>perhaps someone else can elaborate (or correct me!).  
>
>Bob R.
> 
>
>--- patterndude at comcast.net wrote:
>  
>
>>I've gotten a lot of recomendations to add a carbon
>>lightweight 4-stroke pipe to our lineup so I'm
>>starting to look at a 4 stroke pipe design.  I have
>>some questions:
>>1. What are the proper pipe inlet diameters that you
>>desire on pipes
>>2. Worst reasonable case: how close is the pipe to
>>the exhaust port
>>3. What max temperature at the inlet do you suspect
>>(I'll be doing detailed research on this but want
>>your opinion).
>>4. Is it possible to tune a 4 stroke at all, or is
>>the muffling the only goal?  If tuning is possible,
>>how does this work?
>>--Lance
>>
>>--
>>District 6 AVP 
>>www.aeroslave.com
>>    
>>
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