no, Stuart's on the right page, the 18% is thermal efficiency or something
figuring volumetric efficiency
in relation to designing yer own engine
seems a little esoteric for our mundane 235's grin

Bill


Moved over to the Passing Lane

"When we tug a single thing in nature, we find it attached to the rest of the world" ~ John Muir
"When we tug a single thing on an old truck, we find it falls off" ~ me
Some TF series details & TF heater pics