AVweb
Going to the Moon Was Easy Compared To 100UL
Car engines routinely have compression ratios (CR) of 10:1 or higher and run fine on mogas. In significant part, it’s because of far-better engine management systems (EMS) which are totally lacking on traditional aircraft engines. But fundamentally, it’s possible only because their small cylinder volume automatically makes pre-ignition much less of a concern. Upgrading from 1928 ignition systems to EMS is technically quite easy and relatively inexpensive, but FAA certification is a byzantine and expensive proposition. Reducing CR with shorter connecting rods is also relatively easy. Turbo engines already have mechanically-lower CR and could be “fixed” by limiting boost. Reducing the effective CR reduces power of course. Expensive true.