Patrick G just explained that idle quality and lope are a result of overlap. More overlap, choppier idle. I thought idle quality was a result of EVO. I.E. an earlier EVO would result in a choppier idle b/c the sound of combustion was reverberated past the open exhaust valve and less muffling of its sound. How does overlap effect idle quality? Explanations appreciated. Thank you.

 

Lower LSA (more overlap), nice lope at idle 'cos the car is basically trying to DIE at the lower RPM

 

The more overlap the cam has the worse the cylinder scavanging is at low RPM and the more exhaust is left in the cylinder. As Mean Green said. It's barely running and wants to die. This is why engines with real big cams have to have a higher idle.

Re'

 

That explains it...thanks