by loucrane » Thu Oct 01, 2009 1:07 am
Jim may wel be right, although several older engines used this to supplement the amount of air "inhaled" during the intake cycle.
It worked, to a degree. Today, most everybody wants to run a muffler. Mufflers and sub-piston induction don't work well together. Instead of a chance to draw clean cool air in while the bottom edge of the piston is exposed, mufflers tend to trap the hot exhaust residues, filled with burned gases, near the opening.
Engines like this often run too hot, and at less power, with a muffler. Neither one is desirable for a long-lasting, powerful engine to use.
If you don't need a muffler to fly around home, sub-p induction usually doesn't do any harm. Remember, tho, many older black-fin McCoys -iron piston in steel cylinder - do better and last longer on 25% castor oil fuels...