For forced induction rotary motors that include turbocharging, the rule of thumb is not to port the exhaust ports "upwards"; porting upwards increases timing overlap between exhaust and intake.  You can take out material on the sides and downward from the original, stock exhaust port.  Be warned about going too low on the exhaust port - this also kills torque, and I don't recommend going too much down for a street/mild powered engine running under 300bhp.  Keep in mind to radius all corners of the exhaust port like the original ports to keep transitions of the apex seal moving over the exhaust port smooth.

The stock stainless steel exhaust sleeve usually prevents any extreme exhaust porting; you need to transition the exhaust port walls into the sleeves to keep exhaust flow smooth.  Very few shops offer thinner exhaust sleeves for radical exhaust ports.  Overly large exhaust ports are not always a good thing for turbo motors, as the larger passages decrease exhaust gas velocity.  Higher exhaust gas velocities are wanted to push the turbocharger more efficiently.

FC3S Pro:  Exhaust Porting
	Stage I exhaust port This exhaust port is for use on an engine making about 300hp.
	Another pic of Stage I exhaust port This is a better pic than the above without the glare, as it shows the radiused edges very clearly.
	Stage II exhaust port compared to stock exhaust port This exhaust port is for use on an engine making about 400hp. This exhaust port can flow up to 600hp.
	Another pic of Stage II exhaust port compared to stock exhaust port

Questions?  Comments?  Send mail to:  reted@fc3spro.com

04/29/2004