I have had engines that needed less as RPM went up so I would be careful
about making a blanket statement. All of those engines have small bores and
very well designed combustion chambers and ports so the mixture was very
well prepared and quite ready to light as well. Fuel atomization has a lot
to do with it also. Some of the very old Cosworth stuff used numbers like 60
degrees of lead but were large bore and lazy chambers by today's standards.
It is not unusual to only run 28 degrees of lead at 9000 RPM with a well
designed engine. This is also a sign that the chamber is pretty resistant to
detonation. Be wary of something that does not respond to a timing change
you have a bomb on your hands then as the cycle by cycle combustion is all
over the place or the manifold is so bad that you made some cylinders better
and some worse and a burned piston is in your future.. Nitro and atomization
are two words that really belong in the same sentence...LOL
Dave
----- Original Message -----
From: "Skip Higginbotham" <saltrat@pahrump.com>
To: "Mike Lackey" <mike_lackey@yahoo.com>; "land-speed-digest"
<land-speed@autox.team.net>
Sent: Thursday, May 01, 2008 11:39 AM
Subject: Re: [Land-speed] Torque Drop>From>JG Magoo
> Mike:
> I think if you look at it a little closer, piston speed is a function
> of RPM and the slow burning "flame front" of Nitro starts to get
> behind the piston speed as RPM increases so we must add ignition
> advance to keep the piston and the flame front in a more or less
> ideal positional relationship. So it is both the slow burn rate and
> the desire for higher RPM/power that drives the higher advance. Would
> still like to know how much advance the F-1 engines use at 20k.
> Skip
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