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In my first chapter I want to address APEX SEAL reliability in regards to exhaust porting. It's very crucial to the life of the apex seals. In this picture you will see the factory CHAMFER,BEVEL that is left by Mazda when the rotor housings are manufactured. This Bevel is very important to the apex seals reliability. I will explaine with pics as I go along.



below is a pic of stock port with a factory bevel

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At this point you want to measure this factory bevel that is made by Mazda. It's 2mm. This will come into play later in my thread.

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caliper pic showing the 2mm measurement

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This picture is showing the rotor housing ported and the bevel is gone. When the rotor housing is ported to allow the port to open earlier and closed later this factory bevel is ported away. When this happens a super sharp edge is left behind.

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If the exhaust is ported and this sharp edge is left behind the apex seal will crash right into the edge and create some serious damage when closing the port. Ill show were the damage will be done.

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This picture here shows the exhaust ported to improve flow and port timing. When this is done the factory bevel is removed during the porting. I have found many engines done by other people that have left this sharp edge behind creating some serious damage and premature wear on the apex seal including radius lost on the apex seal.

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When the exhaust is ported and after it's done you have to create to an exact replica the 2mm bevel that was manufactured by Mazda. Here I'll show some pics. This is done to protect the apex seal when the rotor is closing the exhaust port. The apex seal is being pushed in and out by the force of the springs and centrifugal force through rpms and that edge is a danger zone.



one more picture of sharp edge and apex seal. then the bevel replica

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This picture shows the exhaust ported improving port timing and flow returning to the factory 2mm bevel.

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When this is done correctly, you will improve port flow,port timing and apex seal reliability which is first and fore most.

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I hope you guys enjoyed and learn a bit from this chapter in exhaust porting. Next week Ill go into my second chapter. Which will be port matching to the factory diffuser and port timing showing pictures of a degree wheel in before and after top and bottom dead center.