Turbo engines and motorcycles
1983, HONDA CX650 Turbo
Turbo's reason for being
The turbo, in fact, a turbocharger, also known as a turbocharger, is a mechanism coupled to internal combustion engines and which is connected to the exhaust manifold, taking advantage of the energy of the exhaust gases generated in the engine, to turn a turbine. connected through a common shaft to a rotor which has the function of pumping air to the cylinders. This rotor is a centrifugal compressor, responsible for capturing atmospheric air and compressing it at the inlet of the engine's intake or intake manifold through high pressure hoses or pipes. With the increase in air density resulting from the compression, more fuel can be added to this mixture which is routed to the combustion chamber, the increase in the burned air/fuel mixture corresponds to an increase in efficiency. Thus, if a turbo-charged was working with a pressure of approximately 1 kg/cm², the engine would be admitting 2 atmospheres, that is, twice as much air occupying the same physical space without changing the dimensions of the cylinder. In this way, twice as much fuel should be mixed in this air (so that the mixture remains stoichiometric), which would be routed into the combustion chamber. In this case, it would be possible to almost double the power of an engine. In practice, it would not be possible to double the power because the compression process also causes an increase in air temperature, which causes the opposite effect: density reduction. To compensate for this effect, a heat exchanger called an intercooler is usually used between the compressor and the intake. Despite the obvious advantages from the point of view of specific performance, Turbo systems were rarely used on motorcycles due to the response time that implied an "on-off" behavior of the engine (very sudden power variations) that made driving difficult. With the technology available today (variable geometry systems) this effect would be mitigated (as in the automotive industry) but it is considered too expensive and cumbersome for use in motorcycles. Even so, occasionally it has been used in some small series productions, such as the KAWASAKI Ninja H2 (2015) and the PEUGEOT Jetforce Compressor (2003, a 125cc scooter that intended to circumvent the legal power limitation for this cylinder), or very small series such as the ICON Sheene (2013) or the VYRUS 987 C3 4V Supercharged (2009). In the 1930s, its use in road competition was common, however, from 1946 onwards, the FIM banned the use of this technology.
In series production, the beginning of the 80s was in fact the golden age of this technology in motorcycling.
HONDA CX500 Turbo (1982)
It produced 82 hp, which may not seem like much when compared to the version that followed it (CX650 Turbo, 673cc) which produced 100 hp, but the CX500 gave a greater feeling of increased power, produced a more intense variation in power and that was how this model was thought. It is interesting to know that this MOTO GUZZI style V-twin was designed from the start to be turbocharged, although the Turbo versions only lasted a couple of years, while naturally aspirated versions were produced between 1978 and 1983. Rationally, the later version (650 Turbo) is a better bike, but the CX500 Turbo, with the more intense power variation, matches the original idea. It was only produced in 1982.
HONDA CX650 Turbo (1983)
Now yes, a true production bike and probably the best developed of all the Japanese Turbos of the 80's. Only produced in 1983, the 673cc CX650 Turbo solved most of the CX500's big problem: sudden power variation. However, when solving this problem, it removed character from the model (decreased the turbo boost and increased the compression rate, which resulted in: less Turbo than in the previous version. If you intend to have a Turbo motorcycle, you will probably value this information…
KAWASAKI Z1R-TC (1978)
While waiting for the GPZ750 Turbo, it was dreaming about its predecessor, the Z1R-TC. Sold in the USA through the official KAWASAKI network in 1978, despite being an independent preparation - it consisted only of mounting a Turbo kit on the standard Z1R, without any other changes to the original model - it was approved by the brand. In any case, whoever purchased it had to sign a document saying that they waived the guarantee conditions and the right to any other type of claim!!! The power was increased by 40 hp (to 130 hp) which in fact was excessive for the original cyclist, those who had never heard of "turbo lag" (sudden power variation), quickly discovered what it was. By today's standards, the Z1R-TC is a horrible handling bike, yet it's still worthy of desire!
KAWASAKI GPZ750 Turbo (1984)
As can easily be seen, KAWASAKI has a tendency to push the limits when it comes to designing sports bikes. Of all the Turbo bikes from the 80s, the GPZ750 Turbo is certainly the best. Launched in 1984, when the other Japanese brands had already put the idea aside, it was a good sports bike, with 112 hp and good performance. Even so, it still had significant "turbo lag" (sudden power variation), especially when users increased the turbo pressure in search of extra power. There are still some in circulation conditions and for sale at low prices.
SUZUKI XN85 (1983)
The XN85 is not the best known among the Japanese Turbos of the 80's, however it is a very nice bike with a design that evokes the Katana and a sensible application of the turbo system. The engine has a capacity of 673cc, the designation '85' is justified by the power claimed by the manufacturer: 86 hp. It has a reputation for being quite easy to use when compared to its competitors (Turbo).
YAMAHA XJ650 Turbo (1982)
YAMAHA entered the Turbo war relatively early, in 1982. Having thrown in the towel at the end of 1983 when production of the XJ650 Turbo was discontinued. It can't be called a success, but the Turbo wasn't the real problem. It increased the power of the air-cooled engine up to a respectable 90 hp, which, at the time, was exceptional for an engine of this capacity, in fact the problem was the cyclist that with a "touring" engineering could not support the sporty use that the engine woke up!
It is interesting to mention that Turbo motorcycles were part of a "black list" of North American insurance companies that made it difficult or impossible to obtain insurance for driving! In competition (speed and hunting records) Turbo engines were allowed (after which they were prohibited at speed) in the pre-World War II era, good examples are: BMW WR 750, BMW Type 255 or GILERA Rondine.