Background:
Like most Mooney pilots, I fly a Mooney for speed and efficiency. As an engineer and hot-rodder, I also can’t leave well enough alone. So, in an effort to climb to the altitudes where the air is thin, the drag is low, and the tailwinds can be the breath of the gods under your wings; I’ve added a Rajay manual-wastegate turbonormalizer to my 65 E model Mooney.
The system was scrounged up from a 67 E model that had been wrecked in a body of water somewhere in Georgia. It took over a year of scrounging to find one of these systems. The plane had already been parted out and I had to buy the parts from both an engine boneyard and an airframe boneyard.
Before the addition of the turbonormalizer, a number of performance modifications were already installed on my E-model including:
- Upper Cowl Closure
- Open Style Upper Cowl
- Oil Filter Relocation
- Flap and Aileron Gap Seals
- Elevator Fairings
- Tail Root Fairings
Installation:
Significant work was done prior to this initial picture including:
- Removal of the original exhaust system
- Removal of the ram air cable
- Installation of turbo scavenge pump between vacuum pump and engine case
Shown above is the first test fit of the turbocharger and exhaust system. Without the ducting, there appears to be plenty of clearance within the cowl. The end plates of the heater baffle are can be seen on the exhaust crossover tube. The design is fairly neat and the engineering is acceptable. The long, unequal length, multiple intersection header tubes waste the exhaust pulse energy that could be used to drive the turbocharger and increase the critical altitude of the system… but this will turn out not to be an issue with performance.
The turbo can be seen in this view of the initial fitting of the system. The cut off angle of the exhaust is intended to direct noise away from the cabin while ensuring the exhaust is always exiting into negative ram pressure, even during climb.
The stainless steel springs in the view above would increase the convection area inside the heater muff. Of course, they weren’t left in the heater muff. These exhaust crossover tubes provide quite a heat transfer area.
The turbo oil discharge/scavange line can be seen in the view below. There should be an anti-drainback flapper valve between the turbo and the return line to prevent the oil from draining from the scavange line back into the turbocharger and past the seals. The valve was added later.
Quite a bit of time was spent sealing up every little hole and gap in the cooling system to make sure that none of the thin high-altitude air is wasted. Here, a repair can be seen which filled in the gap in the top of the cooling baffles above cylinder number 4, allowing the installation of a one piece baffle seal across the entire back of the cowl and eliminating the tendency for the seal to flip back.
Just a bit of the oil scavenge pump can be seen under the engine mount tube by the vacuum pump.
Some added baffles on the front cylinders are part of the kit. The updated baffle seals can be seen. On the naturally aspirated engine, air is mixed with the injectors for fuel atomization. With the turbo installation, lines are installed to duct high pressure air from the turbo outlet airbox to the injectors for this atomization function. Turbo gami-injectors provide the ports for this air.
The heater muff is shown installed above. The inlet ducts air from the original air port on the cowling. Shown below is the insulation blanket that was installed and sealed on the heater muff to keep the heat in the heater system. The inlet to the injector had to be fabricated and is shown installed. The air flows from the turbo outlet, through a flapper box mounted to the filter airbox on the lower cowl, and into the injector body. An intake air temperature probe was later installed in this injector inlet tube.
A bottom view of the heater muff is shown below.
The bottom view of the turbo can be seen above. The original kit did not include a turbo blanket but a blanket was added to reduce temperatures and radiative heating in the cowl. The heater muff outlet tubing routing can be seen here. Sceet (two walled scat tubing) was used in the heater system for extra insulation of the warm air as it travels through the cowl and the heater duct was insulated wherever possible. The turbo oil scavange line is also wrapped with insulation blanket to protect it from the exhaust. The bottom of the wastegate can also be seen. From all appearances, the turbo exhaust system with the wastegate open is less restrictive than the stock muffler, yet it seems quieter than the stock exhaust. This may be due to the angled cut on the exhaust pipe.
Silicone was used to seal the small gaps in the cooling doghouse. Here it can be seen above on the repair above the oil cooler and around the valve cover.
The heater baffle was sealed as completely possible with high temperature silicone. The heater muff inlet can be seen installed in the view above.
In the picture above, the turbocharger mount is the steel tube that runs from the upper engine mount bolt to the turbocharger saddle, the silver piece across the top of the turbo. The silver color is high temperature header paint used on all of the turbo parts.
In the picture above, the scavenge pump can be seen under the vacuum pump. The top of the turbo mount tube can be seen on the engine mount. The oil pressure switch can also be seen in the turbo oil supply line in conjunction with a one way oil anti drain valve to prevent the turbo from filling with oil from the pressure side on shut down. The oil pressure switch adds a warning light on the dash, which is particularly nice since the airplane doesn’t normally have an oil pressure warning light and I don’t stare at my oil pressure guage when I fly.
The inside of the lower cowl is shown above. The outlet from the air filter box is the turbo inlet air source and the flapper valve can be seen mounted to the back of the cowl. Getting the turbo flapper valve to seal properly took quite a bit of fiddling and a nice soft foam seal normally used with air filters. A side view of the lower cowl is shown below.
The picture above shows the lower cowl installed. The packaging is a bit tight. The ducting required a bit of “tweeking” for a good fit.
The above picture shows the port side with the lower cowl installed. With the lower cowl in place, the flapper door outlet can be seen connected to the injector inlet via hump hose”. The soft black hose runs to the upper deck injector pressure line.
Seen above with all of the components installed, the engine compartment is pretty packed. Note the repair on the side of the cowl flap to ensure negative pressure at the outlet of the flap during climb. Heat reflective fiberglass insulation wrap was added to the turbo inlet pipe to shield it from the exhaust header.
The proud owner is shown above happily buttoning up the cowling. A blockoff plate is used where the ram air inlet used to be.
The view above shows the plane at its home field. The repair on the side of the port cowl flaps ensures that there is negative pressure behind the flaps when they are fully open. There is additional vent installed in the side of the bottom cowl to allow extra cooling air out at all times. There is a vent installed on the starboard side as well. These vents were installed as far forward as permissible to be as close to the low pressure area behind the front cowl radius. The louvers were installed pointing out so that they generate a small vacuum to further aid cooling.
Flight Testing
On initial impression, the IO-360 starts more quickly than ever before, possibly due to the GAMI balanced injectors. Despite the warnings to the contrary, the plane seems no louder than before, perhaps quieter. This may have to do with the angle of cut on the overboard pipe. With the turbo engaged the plane is noticeably quieter than before the installation. The heater performance seems to be improved as well. At FL 230, while wearing a sweatshirt, full heat is actually too hot for the pilot and, when the wastegate is closed fully, the plane becomes noticeably quieter.
Performance:
As of this date, I have run three tests; a timed climb to 18000 ft. before installation of the turbocharger, a second timed climb test after the installation of the turbocharger, and a less precise climb test to FL 230. All test were run at max performance. For the naturally aspirated climb, pre-turbo install, the test was run with a solo pilot, full fuel, and about 50 lbs. baggage. For the turbo run to 18000 ft. the test conditions were full fuel, pilot and flight engineer (thanks to John Cook for patiently collecting the climb data). The test to FL 230 was again solo pilot, full fuel, and 50 lbs. baggage. Atmospheric conditions were 62 F for the naturally aspirated climb and 10 degrees F cooler for the turbo climb, and barometric pressure was approximately standard and equal between the test dates.
The chart below shows a comparison of a time to climb test run before and after the install.
The performance data above shows the difference in manifold pressure beginning at 3000 ft. The jagged manifold pressure data is the result of a limit of 28.5 inches for 3 minutes, followed by 27 inches continuous power, and some noise in the data from my manipulation of the manual wastegate. With the turbo, the RPM was limited to 2500 after 3 minutes. The naturally aspirated climb was at 2700 rpm and the ram air open above 2000 ft. Also, the stock plane was leaned to 100 ROP once power fell below 75% while the turbo remained full rich for the whole climb.
The difference in climb performance really begins to show up at 12000 ft. The turbo made it to 18000 in 23 minutes vs. 32 minutes for the naturally aspirated plane. Later tests showed an indicated rate of climb over 1000 fpm to 18000 and 800 FPM at FL230. Interestingly, the fuel to altitude was almost the same in both cases, just like in high-school physics. Those who have an E model owner’s manual will note that the test climb performance matches book just about exactly if weight is estimated at about 2175 for full fuel plus 200 lb pilot.
I also plotted the CHT, EGT, Oil, and IAT temperatures for both systems as a function of time.
For the naturally aspirated run, there is a jump in EGT when the engine was leaned in the climb as power fell below 75%. For the turbo run, you can see the jump in temperature when the turbo was engaged. As can be seen, the turbo EGTs did not get any higher than the naturally aspirated EGTs when leaned.
The CHT peaked earlier on the naturally aspirated run but under both runs peaked at an equal value of just over 400F. The oil temps for the naturally aspirated run peaked at 230 F while the turbo run peaked at 210 F.
Intake air temperature was not recorded for the naturally aspirated run. For the turbo run, the peak IAT at 18,000 ft was 180 F.
Cruise data was collected in combination with a climb test to FL 230. Temperature at field elevation was 50F, BP was 29.80. Climb to FL 230 was made at 26 inches and 2600 RPM, 5 degrees pitch up from cruise attitude, full rich mixture. The critical altitude (where the wastegate was fully closed) was between 19000 and 20000. Climb rate was still indicating 800 FPM at 120 mias at FL 230. At the critical altitude, CHTs just topped 400F and began to drop at higher altitudes.
Naturally aspirated cruise performance was tested prior to turbo installation on numerous occasions by 4 way GPS method at 152-154 KTAS at 75% (2500 RPM, wide open throttle, ram air open) at 7500 ft.
Naturally aspirated cruise performance shows no measurable difference after the installation of the turbocharger system. However, engaging the turbocharger and operating lean of peak at 7500 feet and adding back manifold pressure to maintain estimated percent power on the JPI 800 engine monitor provides cruise performance at 7500 ft, 75% power and 50 degrees F lean of peak of 155 KTAS on 8.5 gph, which translates to a 20% increase in range. Cruise performance at FL180 and 75% was measured by 4 way GPS at 170 KTAS and 100 ROP. Testing at FL230 showed an indicated airspeed equal to that at FL180 between 9.0 gph and 11 gph, equating to a TAS of about 180 KTAS. Interestingly, with the wastegate completely closed, adjustment of mixture did not seem to be a penalty in airspeed within the ability to measure at FL 230 until boost pressure began to fall well lean of peak.
Conclusion:
The ability to cruise at FL 230 and above at 180 knots on less than 10 GPH, climb over 1000 fpm to FL 180 with reasonable CHTs while getting there, and take advantage of outstanding tailwinds are all fabulous benefits. However, there was significant time and energy in owner assisted installation plus out of pocket expenses of $12,000 for the turbo system components, rebuilding, and installation.
The final result is an amazing operational envelope. The ability of a turbocharged short bodied Mooney to carry five hours of fuel plus a payload of 693 pounds, operate at the above mentioned airspeeds and economy, and easily operate out of strips of less than 2000 ft makes it a fairly unique aircraft.
The more I have flown the plane with and without the turbo engaged, the happier I have been with the modification. Without the turbo engaged, the plane is the same old E-Model Mooney with a better heater, better cooling, and minus 28 pounds of useful load. But, if you want to catch a whopping tailwind or pop quickly out of icing, the power is just a control twist away.
The manual wastegate does require some fiddling on climb to maintain max performance but it is also kind of fun to fly a vintage hot-rod airplane and keep fiddling with all of the knobs.
