4-stroke carbon pipe design Q's

[Bob Richards]

John,

Blow, suck -- it is a matter of perspective. Depends
on which end of the straw you are standing! :-)

Remember one of the first rules of flying model
airplanes -- There is no such thing as gravity, the
earth sucks!

Bob R.

--- John Pavlick <jpavlick at idseng.com> wrote:
> Bob,
>  If you want to be scientific, remember, in science
> nothing "sucks". It
> "blows"! The atmospheric pressure pushes (blows) the
> charge in. Since the
> pressure differential is greater during overlap you
> get a scavenging effect.
> What Bill's talking about is "the fifth cycle".
> Every good tuner knows about
> this. Since overlap is good you might think that
> more is better. Not really.
> The downside to too much overlap is less torque at
> lower RPMs. Also, with a
> lot of overlap, you may see fuel coming out of the
> carb. at idle with a
> restrictive exhaust. There are a lot of tradeoffs
> but a well tuned system
> makes more power in a given RPM range than a simple
> muffler.
>  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

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