Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Note on octane:  several years ago I was moderator of a group of scooter enthusiasts. The engines our scooters employed were ordinary OHC four stroke made in Taiwan. The manufacturer spec’d them for 95 octane. I did some research and reached out to the representatives in Taiwan about this, as many of our US owners were concerned.

Turns out, there are more than one way octane is measured.  Bog standard 87-89 octane US gasoline is exactly the same as the 95 octane Asian measurement. It’s just measured using a different scheme. 

Ordinary pump gas is all you need, and it’s likely the nominal compression of our little engines is more along the lines of 8 or 8.5 to 1.   That would be assuming a running engine with ideal dynamic ring sealing. Hand cranked testing would likely be lower. 

Note on tachometers. The inexpensive laser optical handheld tachs available for twenty bucks or less work great.