On 27 Sep 1998, Joe Curry wrote:
> The 10:1 compression engines normally require hi-test fuel but
> sometimes operate ok on lower octane.
Octane requirements according to CR depends on many factors, but whatever
you do, I very, very much doubt that you can use 10:1 on lower octane
fuel without serious pinging, and consequent loss of performance and risk
of piston ring damage. At least if you intend to use the engine to its
full extent, which would surely be the raison d'etre behind seeking
performance increases anyway.
IMHO, 10:1 is the highest compression ratio you can use on high
octane (98 RON) fuel, and even then you have to be pretty careful with
combustion chamber equivalence, ignition timing, deck heights etc. The
Triumph bathtub combustion chambers adds to the problem by being more
prone to detonation than do hemispheric chambers.
Do keep in mind that the highest 9.5:1 CR ratios used by Triumphs were
designed for the no longer available UK five-star, which was equivalent to
100 RON.
> The 12:1 definitely would require
> higher octane fuel or octane boosters.
You won't get away with 12:1 except perhaps on racing cam profiles, and
even then not on pump high octane gasoline. Running on aviation fuel, or
pump fuel with loads of toluene added might work.
Egil
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