Rotary Engine Porting
Peripheral porting is the most extreme form of rotary breathing enhancement - and it's (by far!) the loudest. Instead of conventional metal shaping with a grinder, the side ports are actually filled and completely new circular - peripheral - intake ports are fitted directly through the rotor housing and are easily identified on an engine by its tubular intake manifold.
Low rpm torque, drivability and economy are completely lost but it's just the ticket for peak power - often, over 100% improvements can be gained over standard. (Note that with really good engine management, a PP can be driven on the street quite successfully - but you'll need injector end-point setting facilities and other such management features.)
The effective torque band is also moved way up the tacho - beginning from around 5000 and building to a theoretical 10,000 rpm! (And building an engine to rev this high is another matter!) A PP won't idle much below 1800 rpm either - so by all accounts, it's a high revving and highly stressed engine that aren’t for the street.
However, in excess of 300hp can be found at the flywheel when combined with a race intake and exhaust. In order to construct a PP, the standard side ports must be filled or blocked off somewhere upstream in the intake.
Then, relatively large diameter ports are machined through the rotor housing (yes, on its periphery!) and into these are inserted aluminum sleeves that are shaped for best results with a die grinder. A sealant is then used to form a seal between the housing and the sleeve.
PRO'S: The ultimate form of rotary porting for maximum power
CON'S: Excessive noise, extensive intake modifications, very poor drivability and fuel consumption, relatively short engine life, very expensive, narrow power band