To kick off our engine build, we CNC-lightened the rotors of our 13B REW before shipping them off to be cryogenically frozen by CTP Cryogenics to improve strength and durability then finished off with WPC treatment to reduce friction, wear, and heat.
Since we plan on revving this engine to over 9,000rpm, lightening the heavy iron rotors of the 13B and reducing the reciprocating mass becomes exponentially more important as the rpms increase. However, it’s important to have the right balance between reduced weight and strength/durability since this is going to be a high-power and high-rpm engine build. Lightening the rotors will also make the engine rev quicker and be more responsive to heel-toe downshifts.
We started with a great foundation of a brand new 2,000-mile crate engine from Mazda. This engine was never overheated, warped, abused, detonated, or have any of the possible problems that could pop up when building an old engine.
The rotors were cleaned up and ready to be lightened.
From the factory, Mazda balances all 3 sides of each rotor by milling out these holes to different depths as needed. While this is theoretically ideal, almost no rotary engine builder does this. Decades of success from lightening rotors without trying to balance all 3 sides of the rotor has been proof that the benefits of lighter reciprocating mass outweigh the slight balance difference. Additionally, there are arguments that the weight of the oil sloshing around inside the rotor itself is greater than the weight difference of each side of the rotor, making it unnecessary to try to replicate Mazda’s balancing.
Our rotors were lightened using a 5-axis DMU 50 from the Japanese company DMG Mori.