Motivation :

For the record, the main motivation to install the LAD Kit was that at 4000 feet and ISO +18°C the carburettors did not sufficiently compensate for the altitude density and gave a mixture that was too rich;
Maximum EGT at 680-700 °C and black spark plugs.

On the advice of AVIREX the circlips on the carburettor needles were placed in mark n°2, but this was not enough to get the correct mixture. Position 1 (needle in the most closed or lowest position) was not attempted on AVIREX recommendation.

 

Assembly:

Accessibility to the back of the 912S engine on the Skyranger is very limited, even when removing the exhaust.
The engine frame with its large U-shaped bracket, plus the large structural tubes, prevent access from above.

Removing the plastic cover of the ignition rotor is possible after a few contortions.
Unscrewing the nut (24 mm wrench) fortunately was not difficult; the nut had a trace of cream colour Loctite 577; even the location of the toothed wheel (injection target) is relatively easy.
I used a small camera mounted on the firewall to check the proper positioning of the target.

Remained to adjust and block the sensor “blindly” which is a whole other story…

I had too many doubts about the accuracy of my installation and I preferred to drop the engine. By suspending the engine with pulleys to a counterweight (just equal the weight of the engine + radiators + oil bowl assembly) the work of unbundling the engine is a game of patience but worth it. In fact, my sensor assembly had play of 1.75mm. This made it easier for me to clean behind the engine and the firewall. I took the opportunity to inspect the area at the back of the engine, especially the water pump hose. The dampeners were changed.

So, the installation of the target and sensor are perfect.

The pre-filter and the two pumps are installed under the cockpit floor on the left side; the fuel filter is installed and secured in front of the firewall on the large U-shaped profile.

The rest of the installation did not pose problems except for two details. The small angled tip (intake pressure connection) on the top of the right-side intake pipe is too high by 10 to 15 mm and interferes with placement of the top cowling. Problem solved by cutting the cowling and putting a plastic boss in the right place. The other difficulty was the lack of height for the connector for the left side throttle body sensor. The solution of placing the butterfly valve with sensor right side (with sensor underneath) would have complicated the too-low passage of the accelerator cables. We therefore bent the connector cable by attaching it (bent 180°) with a plastic collar.

 

The tests :

The engine runs very well.
Regarding balancing the butterfly valves; I had tinkered, for carburettor parallelism, with a system with a transparent 10 mm diameter pipe (2 metres long) and an 8 mm ball running between two 6 mm diameter venturi (spaced by one metre) which ensures that the pressure in both intakes is the same… or nearly so.

 

Assessment of adjustments:

Idle recorded and stable: Magneto 1: 1020 RPM; magneto 2:  1060 RPM on 1+2: 1180 RPM remarkable idle, smooth and nice purring!
The butterfly valves balancing should therefore be quite good.

Maximum power slightly improved: +80RPM full throttle at 5460 RPM with DUC propeller setting unchanged.
EGT 750°C or +50 at 70°C

The maximum EGT rose at least of + 80 or 100°C at 740°C (a HS EGT after disassembling and reassembling)

There is therefore a significant bonus on power.

 

Conclusion :

Customer very satisfied with the LAD Kit