Perhaps the most desirable mod for a 231 that makes it more like a 252 is an intercooler. One system— the Turboplus—has been highly recommended by M20K owners and it comes from Turboplus Aircraft Systems in Gig Harbor, Washington. Turboplus says it was the first company to bring intercooling for GA singles and twins in the early 1980s and there are thousands of Turboplus intercoolers and induction systems in use today.

The company says its M20K intercooler kit can yield a max speed of 241 MPH at 24,000 feet, and 170 knots true airspeed at 10,000 feet and 65 percent power, with the added benefit of lower cylinder head temperatures. The STC’d kit for the Mooney M20K is $5995 and the estimated installation labor is around 18 hours.

“My conclusion is that the Turboplus intercooler provides much improved intake manifold cooling and an increase of 3 inches in available manifold pressure at altitudes above the 13,500-foot critical altitude, while providing significant performance benefits across the board to the hot-running, non-intercooled engine in the 231 M20K,” reader Geoff Lee said of the system. He’s documented the installation in a well-written tech guide that’s available at themooneyflyer.com/issues/2019-MayTMF.pdf . That’s a link to The Mooney Flyer www.themooneyflyer.com , the official magazine of the Mooney community.

Last Year I bought a Turboplus intercooler kit from Jeff Shapiro for my Mooney M20K 231. First, the delivery was very fast and second he gave me a special price for me as member of MAPA. When I unpacked the kit, I was very happy about the really great quality of all the parts. Welding, tolerances and so on. I installed the kit in two days and it was a great pleasure to do. The fiberglass work at the cowling is also very easy, but needs a little bit of trim.

When I had finished all that work and the final adjustment of the TCM injection system, I went flying to see what it will improve. First was, that the intake air immediately cooled down about 30 deg. Celsius in the takeoff run. I operate my Mooney from a 750 meter asphalt strip. After takeoff, in the climb it was cooling by 45 deg. Celsius and raised to 55 deg. in higher altitudes. I think the NACA duct is at the optimum position. Much better and more efficient than by the 252 model, because it gets directly cool air from the outside and not via the cylinders inside the cowling on the right side in the engine compartment.

In cruise I have now much cooler cylinder head temperatures , mostly about 320 deg. Fahrenheit with 75-85 percent of power.  I was flying now for approx. 9 month with the intercooler and in every phase of flight it is a really great improvement in performance and in cylinder temperatures!!

So finally I think that is one of the best mods for a 231 model.

Regards,
Alex Haselmann
D-EMLL Mooney M20K, June 2019

The Turboplus Mooney M20K intercooler system

The Turboplus Custom Designed NACA Duct for your airplane provides the most efficient airflow systems to your Intercooler assembly and to the turbocharger. The direct airflow system into the intercooler are proven to be the most effective and efficient way to supply ambient air right at the intercooler installation.  NACA ducts are used worldwide in passenger jets, NASCAR, high performance automobiles and in the aerospace industry.

The Turboplus Mooney M20K, 231 intercooler system provides ram air through their custom designed NACA duct that directs ambient air through the custom designed intercooler assembly. The NACA duct creates no drag.

YOUR Mooney 231 can now achieve speeds up to 241 MPH.

Turboplus Aircraft Systems, Inc. is the only general aviation aftermarket intercooler kit manufacturer to offer a Five-Year warranty on their intercooler system.

Turboplus Aircraft Systems, Inc. will ship your order to your home, business or any FBO shop of your choosing. Don't fly to us when we can ship to you.

Mooney M20K Intercooler Kit

It is highly recommended:
To record the critical engine altitude, oil and cylinder head temperatures and fuel flows at given power settings before the intercooler installation. After installation, another “flight test” ensures that engine and aircraft performance adhere to Turboplus Aircraft Systems, Inc. high standards. Post modification flight test data provides a direct "Before and After" comparison of the dramatic improvement in aircraft performance and engine operation. For your convenience, we supply the pre-flight and post-flight performance documents.