Project FD RX7 Restomod: Part 12 – Rotor Lightening, WPC and CTP Cryo Treatment

Cryogenic History

The process of cryogenically freezing components to improve material properties and strength was used in the US and Europe in the early 1900s by companies such as Pierce Arrow automobiles.  After World War II, NASA implemented this process (and continues to use it today) to enhance and improve the reliability for everything that went into space in order to the survive the rigors of temperature changes in space. One of the best crank shaft manufacturers in the world, Bryant Racing, uses CTP Cryogenics to treat all of their world-class crank shafts, including all of the Chevrolet crank shafts racing in NASCAR.

Cryogenic Process Benefits

The cryogenic process is a complement to heat treatment, sort of a finishing touch. It equalizes the hardness of the materials by forming fine grain structures in the metal which greatly reduces the internal stresses that are inherently present from the production process of all metals, as well as the stresses caused by machining components.  This improves strength, hardness, and durability of the treated metal which greatly improves all aspects of performance of a part.

In many steel alloys one thing that heat treaters are constantly trying to achieve is a complete conversion of austenite (a smaller more brittle grain structure) to Martensite (A larger much stronger grain structure).  ‏‏Nothing has shown to convert austenite to Martensite more completely than Deep Cryogenic processing. Prestigious universities and even NASA labs have shown that to be the case.

Jack Roush cryogenically treats every component when his Roush Aviation company rebuilds Rolls Royce Merlin / Packard V-1650 Engines.

For the rotors of our 13B engine, equalizing the hardness of a reciprocating part with CTP Cryogenics will strengthen the rotor face against detonation inherently get more balance and reduce vibrational harmonics.

We also sent our e-shaft off to be cryogenically treated to improve its metallurgy.  The stock e-shaft is not heat treated by Mazda, but rather is only surface hardened.  Because of this, heat treating (or Cryo treating) metal that has not been previously heat treated, can cause dimensional changes vs Cryo treating a higher quality, heat treated metal.

It is important to measure the dimensions of the e-shaft main and rotor bearings prior to being Cryo treated to verify there are no dimensional changes after the process.  The rotor bearing journals should measure between 2.9120″ to 2.9124″ while the main bearing journals are actually ‘stepped’, with an inner (closest to the rotor journals) and outer diameter.  The larger inner journal should be 1.6915-1.6925″ while the smaller outer journal should be 1.6902-1.6907″

WPC Treatment gives metal a very distinctive matte finish.  WPC is not a coating, but rather a metal surface treatment that bombards metal with a special media at high velocities that leaves a hard, micro dimpled surface in a similar fundamental process that shot-peening does.

At MotoIQ, we use WPC Treatment a lot in our engine and transmission builds and I have personally won a lot of races in part because of WPC Treatment.  You can read more about the process here, but essentially WPC improves the surface hardness, reduces friction, and increases durability of parts.  All of this results in more horsepower, better performance and increased reliability to your investment whether it’s an engine or transmission.

For a rotary engine, heat management is one of the biggest challenges that affects reliability and power.  Reducing friction and heat with WPC Treated surfaces will make a big difference in our engines power potential and reliability. WPC has been used successfully on the rotary engines of FD RX7’s that raced in the GT300 class of Super-GT in Japan as well as rotary drag race, road race, and drift cars in the USA.