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Old June 14th 08, 12:56 AM posted to rec.aviation.owning
JGalban via AviationKB.com
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Posts: 356
Default Lycoming to approve 93 octane auto gas for O-360 & IO-360

Newps wrote:

Temp has almost nothing practical to do with the octane required. What
matters is the internal cylinder pressure.


I agree that cylinder pressure is the primary factor, but intake
temperatures can push detonation margins lower. That's why intercoolers and
water injection systems were invented.

Down here closer to sea level, when the official temp is 115F in the shade,
it's not unusual to have temps greater thatn 135F, 3ft. above superheated
asphalt. I've got two vehicles (truck and motorcycle) that are supposed to
run on 87 octane that will detonate lightly in the summer unless I bump the
octane up to 89. Both run fine on 87 with ambient temps below 100.

John Galban=====N4BQ (PA28-180)

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