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Oct 23, 2004
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Just as a point of interest on this quench business, and maybe some related issues, way back in the dark ages (the '50s actually) the British were out to beat the world in Formula One racing, having been sidelined by the Italians and Germans previously.  They put together a company called BRM (for British Racing Motors) and designed and built an engine to the then formula of 1 1/2 liters blown or 4 1/2 liters atmospheric - they decided on the 91 cubic inch engine, and built one with 16 cylinders - you'll remember our Offy 91 inchers in Midgets were 4 cylinders, and they were considered small, so the 16s cylinders were really small.  The cars never performed to expectations, I don't remember if they ever won a race, even when driven by Moss, Hawthorne and people like them.  Anyway, after they retired the cars Shell Oil bought one or two and ran a series of test to try to find out why they could not get decent power.  The first thing they found was that ignition timing was hardly a factor - they could run the timing backwards or forwards 10-12 degrees from normal with no appreciable change in power - they engine ran on some exotic fuel, and they could vary the octane and btu rating all over the map and the same - very little change in power production. To make a long story short, the conclusion was that because of the completely hemispherical chamber and flat piston, there was very little turbulence and the burn rate was so low that even with the tiny combustion chambers they were not getting complete combustion and ergo nothing like the power they expected.  They also went into possible fixes and one was using a "Ricardo" chamber which I understand was a high turbulence design with plenty of squish - and in the report they mentioned work they had done with a test engine set up to vary the squish distance and if I remember correctly they concluded that very tight squish (below .015) created high pumping losses whereas over .060 was ineffective. 

As I remember the gist of the report was that for maximum power the hemispherical chamber was the way to go, but that turbulence had to be maintained by either piston shape or intake tract design, but that for efficiency the squish chamber was to be preferred.

This should probably be in the "off topic" section, but  :bs:    Best regards,  Bob