RESULTS with the NORTON ROTOR

(Translated from an article by Reiner Nikulski in ‘Wankel News’, reproduction authorized by autor, herr Reiner Nikulski)

The Norton Rotor turns in my Wankel for 12’000 km. The byke has been used mainly for middle and long town to town trips, although there was also a short ‘daily bread buying’ phase. During a trip to the Alpes mountains, the engine was put under heavy load in very steep mountain passes.

Below 2’000 rpm, under load, the engine cracks a bit, so I avoid this speed range. Instead of this, I exploit the whole range between 2’000 and 7’000 rpm. Riding this way in City Traffic, the byke allows (with only the rider) to be ride correctly in 6th gear at 2’500 rpm with no problems. To speed up or climb a sloped Street, high gear ratios can often be kept.

The only problems I had were carburettor icing below 0º C (perhaps somebody has a tip)* and overheating of the rear parts after a long standing load. (As an example more than 20 min at full throttle without intermediate gas control releases), but it’s an old problem. In these trips I let the byke go at 80-90 km/h in 6th gear. This way, temperature remains quite acceptable and very good fuel economy results.

The trick of the advanced combustion chamber.

The included sketch shows that the flame front from the sparkplug advances only in the direction of the turning (research from Daimler) Because of this, the mixture placed behind the spark hole burns only very late or even in the exhaust. In the Sachs engine the plug is placed quite ahead, hence only minor changes are needed. With the advanced (LDR) Rotor Recess, more mixture is placed near the spark hole at the ignition point. More mixture is normally burnt, and the combustion is faster.

Results

From the first rides, the byke gives a subjective feeling of being more powerful. So you can leave ahead of everybody after a traffic stop and look back. Should you need different data, I briefly measured some of it in a dyno. Here it come some: -Compared to the results of the stock engine, the power output is increased in 2-3 HP for every rpm range. –Because of the faster combustion, the ignition timing must be delayed, hence producing a reduced termal load. I moved nearly 8 mm the mark in the flywheel (around 10º), but there may be other options for timing. –The 155 high jet gives the best results. Both with the 150 and the 160 gauge jets, some power loss at high speeds is seen. So you must pay attention. Hercules is

probably against the temperature load of the 160 high jet. –It’s also quite remarkable that the directly measured results/curves are somehow shimmy, and thus, it must be entered into the measurement computer with a buffer factor. Fort he Guzzi racing engine the factor is 4, the japanese four cylinders need always 1.5 too. The Sachs engine allows it to be set at .5, provided it’s not out of tuning. The engine runs also quite regularly for a Wankel engine.

Fuel use

It’s quite reduced. Each point in the plot represents a full tank refueling. The average fuel use with the Sachs Rotor was 7.5 lit/100 km, with the Norton Rotor fuel economy is 6.3 lit /100 km. The reduced fuel needs come not from a friendly travel plan, but from a ‘narrow way’ with many local visits and speed measurements. In any case it comprised clear highway travelling.

Results

As in the installation I changed just the Rotor and I mounted again the 30’000 km old other engine parts, the improvements should be attributed only to the different Rotor / Recess. This was known in Japan since since 1973 (!) and published in Europe, the people at Sachs may well have avoided the development discontinuation.

Duration

After a short time period, (for curiosity) I dissasembled the engine and saw in the side housings an eating binge. As usual, I stablished the axial clearance of Rotor at 0.2 mm. It was too small, and my fault. The Norton Rotor needs its 0.4 mm axial clearance, that it self-administers, because the Norton Rotor is 0.2 mm narrower than the Sachs Rotor. It’s also to be advised making some measurements, as the English are quite indulgent with themselves about tolerances. As usual, there’s enough oil cooling of the Rotor, and the rear parts were quite violet-coloured. The side seals were not glued, and the other parts of the engine perfect.

All’n all a fine thing, if it were not the Price of 700 DM for the nude Rotor.

*(Translator’s Note) -The carburettor icing may be prevented by heating a bit the gasoline or oil/gas mix entering the carb by the fuel tubes, but this has the inherent dangers of vapor lock and fires.