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RE: voodoo

To: "'Editors, Molecular Vision'" <jboatri@emory.edu>, "spridgets@autox.team.net" <spridgets@Autox.Team.Net>
Subject: RE: voodoo
From: Chris Kotting <ckotting@iwaynet.net>
Date: Thu, 25 Jun 1998 12:21:13 -0400
Reply-to: Chris Kotting <ckotting@iwaynet.net>
Sender: owner-spridgets@Autox.Team.Net
Actually, the major factor in having the "bang" happen closer to the 
"spark" isn't the exhaust valve opening.  It's that the "bang" has to 
happen when the piston is just about at TDC (actually a tiny bit after). 
 Much later than that and you lose power (you don't get the maximum "push" 
out of the "bang", making more of the "bang" result in waste heat), much 
before that and you get knocking and engine damage (the "bang" tries to 
turn things the other way).  (The reason that you need to advance the 
ignition timing at higher RPMs is that the time lag between "spark" and 
"bang" is relatively constant, but the faster the engine turns, the more 
degrees of rotation happen in that time interval.)

It seems to me that if you can minimize that time lag, you stand a better 
chance of being able to make the "bang" happen consistently at the optimal 
moment.  Can anybody confirm/correct this supposition?

Chris Kotting
ckotting@iwaynet.net

On Thursday, June 25, 1998 12:50 PM, Editors, Molecular Vision 
[SMTP:jboatri@emory.edu] wrote:
> True and I agree with you and Les: throwing in a hodgepodge of smoke and
> mirrors may do a lot more harm than good. OTOH, like Chris Kotting, if I
> can avoid gapping points by using a Hall cell, I'll use it if I can 
afford
> it. Having sold a couple of parts lately, I could afford it. A higher
> voltage coil allows one to increase spark plug gap, but as Chris points
> out, the coil and other downstream components (be they Hall cells or
> points) must operate at higher temps and so could fail, or rather, have a
> lower mean time between failures. The issue of whether increased spark 
plug
> gap does _anything_ beneficial or harmful appears to be the largest point
> of discussion.
>
> >From a practical standpoint, if 0.025 plug gap ignites a real-world 
range
> of mixtures that vary with winter/summer grade fuel or other fuel quality
> issues, density altitude variations, and acceleration demands, then there
> is little reason to go to a larger gap. But two questions remain: (1) 
does
> a 0.025 gap always ignite real-world ranges of mixtures? and (2) can
> further performance (whether economy or power) be realized with an
> increased gap leading to a shorter lag time between spark and bang (to
> quote Chris). Would this allow for more of the mixture to be burned 
before
> the exhaust port is opened? Is a faster burn better inherently, or must
> many other variables (mixture quality, cylinder and piston design, 
timing,
> etc) be matched?
>
> Finally, let's face it, the 500 lb gorilla here is that those gold Sport
> coils look really cool...:)
>
> At 9:00 AM -0500 6/25/98, Shawn J. Tobin wrote:
>
>
> > I used to think that throwing a kluge of performance parts together 
would
> > result in a really wicked ride.  This kind of thinking was due to a 
vivid
> > imagination and the naive assumption that advertising claims were
> > guaranteed to be true because the government kept them to their word.
> >
> ...
>
>
>
> Jeffrey H. Boatright, PhD
> Senior Editor, Molecular Vision
> http://www.molvis.org/molvis
> Mailto:jboatri@emory.edu
> 404-778-4113
>
> 

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