4-stroke carbon pipe design Q's

[John Ferrell]

As I recall, when the YS120 head was changed to big valves most flyers 
agreed there was little if any difference!
Once again it was proven that fixing what ain't broke is a waste.

I don't want to be the first with rollers in my YS.....

John Ferrell
http://DixieNC.US

----- Original Message ----- 
From: "John Pavlick" <jpavlick at idseng.com>
To: <discussion at nsrca.org>
Sent: Monday, May 23, 2005 11:25 PM
Subject: RE: 4-stroke carbon pipe design Q's


> What would be really cool to see is roller tappets. The trick with a 4
> stroke is to maximize the charge going into and out of the cylinder, while
> maintaining compression. A roller tappet / cam maximizes the area under 
> the
> curve because the tappet can lift faster and with less tendency to float
> because you can use stiffer valve springs. They also reduce friction 
> (heat).
> Roller tappets are a good thing. It would be a challenge to make a roller
> cam setup for our little motors but it would proabably make a lot of power
> and smoothen the idle a little too. Almost all modern high performance
> motors run roller cams.
>
> John Pavlick
> http://www.idseng.com
>
>
>> -----Original Message-----
>> From: discussion-request at nsrca.org
>> [mailto:discussion-request at nsrca.org]On Behalf Of Bob Richards
>> Sent: Monday, May 23, 2005 9:48 PM
>> To: discussion at nsrca.org
>> 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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