How do street and exhuast ports affect emissions? Can I do both a street port and exhuast port and pass emissions?

 

keeping exhaust port open later increases the overlap time that the intake and exhaust are open at the same time, so more intake charge (unburned fuel) is free to go right out the exhaust from the intake.



opening earlier, i dont really know, might be an increase in unburned hydrocarbons again, due to the port opening sooner, in the power stroke.



in the real world it seems like if you have the rest of the emissions system working right, a small port will still pass

 

You are correct on the exhaust, earlier increase HC and results in an increase in Bsfc when opened earlier, no one probably cared about that till premium was a 1.42/litre... ...

Scoot got there peripheral port 4 rotor(12ax2) past emissions testing..Its pretty funny how they did it..

 

oh really? i was thinking about smogging mine, i was going to run it on alky-hall, cause i'm not going to put a converter in it