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Fuels, Compression, Detonation

To: land-speed@autox.team.net
Subject: Fuels, Compression, Detonation
From: ardunbill@webtv.net
Date: Sun, 8 Apr 2001 10:25:46 -0400 (EDT)
Hi Folks, just a couple more tidbits to throw into the recent discussion
on Nitro, EGT, etc.

NHRA has reduced the percentage of Nitro of Top Fuel and FC this year
from unlimited, to 90% to reduce engine explosions.  One driver
commented on TV, "Now I don't hear all that loud rattling (of
detonation) the whole run like we used to."  Can you imagine the
violence of the detonation that he could hear in his helmet, with ear
plugs,  with all the pandemonium of the exhaust, blower, wind, and
everything else on a Top Fuel run.  No wonder they scattered so many
engines!  The poor old thing had sledge-hammers beating on the pistons.

Other thing is I recall from the '50s and '60s when the 45 inch
Harley-Davidson KR flathead twin was dominant on dirt tracks and Daytona
in AMA Class C racing, authoritative articles in the press stated that
the best tuners and the factory could find a reliable 60 HP from the
engine.  The lore was that to get the best gas-flow on the sidevalve the
compression was only about 5-3/4 or so.  AND, the factory recommendation
was to use only REGULAR (not premium) pump gas which gave best power
with the low compression they used for best volumetric efficiency
(cylinder-filling).

Cheers Bill

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