Engine:
On raw horsepower the ULS is the logical choice but this builder decided on the UL for the following reasons.
- The major difference is 140 HP peak to 120 HP peak.
- No need to remove barrels too lower the ULS compression to 8:1
- Cheaper base price AKA poverty pack.
- Fits allow HP range for the Air Master Propeller
- Slightly lower over all weight - 1 Kg - it all helps
- Fit 2.43 : 1 gearbox & slipper clutch - 914 specification
- New motor = known history but lost warranty due to modifications
- Both motors fit the factory supplied ring mount
- Light weight package of 6.5 kg [14.2 lbs]
- Separate oil supply and pump
- Will operate with loss of supercharger but at reduced HP
Super Charger
Inter-cooler
The personal prejudice of this builder means that the installation will incorporate an inter-cooler. Operation in Australia require a motor to handle temperature's from below zero to 60 C. The reasons for all the electronic's on a 914 is to ensure that the inlet temperatures remain in a safe operating zone.
Note: FlyGas have stated that the mixture will go rich in this condition to protect the engine and that they have no concerns.
Altitude compensated Lycoming engines of the early 1960's suffered piston failure's in service with the reason begin short period low level detonation over a long period. This was the result of high temperature at the turbine outlet created by the turbines [work] adiabatic temperature rise combining with high ambient operating temperatures. All kits of this type now feature some form of inter-cooling to control inlet temperatures in all modes of operation.
A quick bash of an old text book showed that a 16'' x 5'' x 2.5'' should handle 140 HP on a 15 degree C day. Caution: Sizing of inter-coolers is as much witchcraft as formula but it's enough to give the confidence to throw money at the exercise.
Solids modeling on the CAD system resulted in the design shown opposite with an 80 mm x 1.6 wall aluminium tube welded to a Bell Inter-cooler core with an estimated total weigh of 2 kg - remember the 1 kg saved on the motor - now it helps..!The design shown connects to the supercharger as per the FlyGas design, flow's back through the core to the rear tank and is then feed back to the carburetors.
Air for cooling of the charge will be supplied from the existing N.A.C.A. duct located on the top side of the cowl. Air for the turbine will be from an existing N.A.C.A. duct located on the starboard side of the cowl.
Included in the design is a larger balance tube between each manifolds to aid in alleviating the rough running created by carburetor imbalance or loss of a single carburetor. This is available from FlyGas as a separate kit and creates a Siamesed manifold with twin carby's.
At the time of posting a order for the FlyGas equipment and inter-cooler components have been placed and will be on display at the Flying Legend Stand at Nat Fly April 2015.
Propeller
This builder has decided to fit an Airmaster Propeller. The electric drive off the propeller means that the engine dose not require an hydraulic governor drive and governor saving about $3000 on these two items plus the weight - it all helps...!Airmaster uses a electronic controller that allows three modes of operation. takeoff - climb - cruse thus reducing pilot workload by removing the need to set rpm / mp combinations.
This combination creates in principle a HOTS [hands on throttle & stick] with the mixture controlled by the Bing carburetor's and the propeller requiring flight mode selection only. The supercharger is mechanically linked to the engine rpm [throttle position] and dose not require any input by the pilot.
The proof will be in the eating and that is a meal for the future and like most decision can and may be altered with council from wiser minds.
2 comments:
Gary,
It doesn't seem like you ever closed out this part of the blog, with the details of the supercharger, it's installation and the actual custom intake manifold.
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