This is true only with cast iron cylinders.Jim LaGuardia wrote:Erik, The bigger the bore, the less sealing surface at the top of the cylinder to the head and forged pistons require more wall clearance as they expand more than autothermic(cast)pistons.
We run less than one thousandth of skirt clearance with the LN "Nickies" cylinders. The units I am using on the "baby" engine are set up with exactly .001
The ability to run less skirt clearance and tighter ring gaps was engineered nto the metallurgy of the cylinder's base material, a special Alcoa extrusion of solid billet aluminum.
Less skirt clearance and insanely tight ring gaps seal off cylinders, reduce compression losses and allow lighter tension rings- all these make power and efficiency.
Having to run loose skirt clearances can make for an oil contaminated chamber and that fouls spark plugs and impacts power and efficiency negatively. It screams "misconfiguration" loudly to me.
As for as an off the shelf solution to the induction arrangement, well that would more than likely impact effectiveness and that's all I care about. There are space constraint, component placement and other challenges to combat with this development and I'll say that myself and my Engineer, tom have explored most everything possible. This plenum was the only real answer.
If we can't do something the best it can be done, we have no desire to do it at all.
While I may have to run more wall clearance with forged pistons, they do perform well and do not consume excess oil. 
