1981 Mooney M20K 231/252 Firewall Forward

The M20K 231 was the first non-pressurized Turbo Mooney.  Introduced in 1979, the 231 (numbered for it’s top speed) was hailed as the fastest single-engine production aircraft in the world.  It was an instant success and even outsold the ever so popular Mooney 201 during the first two years of production.

For the 231, the Mooney engineers capitalized on the aerodynamic airframe improvements already added to the Mooney 201 by installing an engine with a high horsepower to weight ratio – the Teledyne Continental TSIO 360 GB. This combination of engine and airframe gave Mooney drivers the optimum blend of high altitude flying coupled with incredible speed and performance synonymous with Mooney Aircraft.  The 231 included other improvements such as the NASA air scoop placed in the dorsal for improved cabin ventilation, new wing tips for better slow-speed control and enclosed navigation and strobe lights. 

In 1984, Mooney upgraded the GB  engine with the TSIO 360 LB1B which included a redesigned fuel distribution system plus nitrited cylinders, steel belted pistons, and a new rod design that resulted in more efficient power and extended service life.

In 1985, Mooney’s engineers were tasked with making as many improvements as possible to the 231 and bringing to the market a vastly improved airplane in 1986 – the M-20K 252TSE.  Among the improvements were improved engine cooling and a redesigned primary air induction system.  Just as monumental, TCM listened to customers and made big improvements to the LB engine that resulted in the MB1 version. The changes were many.  Most important were a tuned induction system for more even induction airflow to the cylinders, a larger Garret turbocharger, a manifold pressure controlling system allowing full throttle operations for takeoff, and the incorporation of an intercooler that cooled induction air temperatures by as much as 100 degrees F.  The improvements resulted in the 252 that ran cooler than the 231, required only 36 inches of manifold pressure versus 40 with the 231, and flew 10 kts faster than the 231.

In March 2000, a factory zero-time TSIO 360 “MB1” (252) engine, turbocharger, intercooler, and wastgate were installed.  In October 2016, the engine received a complete tear-down with six new TCM cylinder assemblies, a new cam, lifters, and bearings.  At the same time, the 3-blade scimitar hot prop was overhauled.  In essence, this is a 252 – firewall forward.  It’s mechanically strong and a fast airplane!.