Richied76 wrote:i'm sorry but are ricardo out of there minds? do they seriouslt think an engine will evacuate exhaust gas when the piston is traveling downwards? the "concept" above is not only usless as far as actually being ablt to have two sets of differeing cam's but the bloody thing will be as efficiant as painting your house with a tooth brush!
Four-cycle engines need to have the power stoke pressure down to near ambient by BDC. The exhaust valve opens during the power stroke to allow blow down that avoids energy losses that would result from residual cylinder pressure during the exhaust stroke. At high RPMs the exhaust has to open rather early to accomplish this.