4-stroke carbon pipe design Q's

[Lance Van Nostrand]

I want to thank everyone that replied with information.  I have a much 
better idea of what to try to make something that will give best 
performance.  I had already figured that we would want to avoid matching the 
reflected wave and instead would want a pipe that was "long" so it would 
help scavange.  Now I can see several benefits of this:
1. helps draw in new charge during overlap
2. reduces blowback diring overlap.
A simple diffuser may reduce noise but will not address these advantages. 
I've heard that maybe a few hundred rpms are all that can really be gained 
so accuracy will be important.

I'm not sure if the overlap timing of 4 strokes differs much and how 
sensitive I should be to that.  I have a YS120. Would it have the same 
overlap as a DZ?  If no one can tell me the exhaust timing of a DZ, I'll 
have to get that info on my own before diving into the design too much. 
This will be interesting.
Thanks again.
--Lance

----- Original Message ----- 
From: "Bob Richards" <bob at toprudder.com>
To: <discussion at nsrca.org>
Sent: Monday, May 23, 2005 8:47 PM
Subject: Re: 4-stroke carbon pipe design Q's


> Bill,
>
> Ok, if I understand you correctly, the low pressure
> helps suck in the new fuel/air mixture during the
> valve overlap.
>
> Come to think of it, isn't this similar to the way a
> pulse jet works?
>
> I guess any kind of backpressure would defeat or
> minimize the process, which I think is the case with
> our setups.
>
> Bob R.
>
> --- Bill Glaze <billglaze at triad.rr.com> wrote:
>> 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
>>
>
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