forced induction Archives

How does a Turbo Work?

The Yamaha NMAX “Turbo” was recently launched in Indonesia, and the name “Turbo” drew plenty of enquiries which pointed to some confusion. So, let us take a look at how turbo works.

Anyhow, the NMAX “Turbo” does not use a real turbocharger. Instead, it is a mode to switch the CVT into delivering instant torque for speeding up and overtaking.

There are several reasons why a turbocharger is not popular among motorcycles, although there was an era of turbocharged motorcycles.

What is a turbo?

An internal combustion engine requires air in order to work. Air is drawn in, mixed with fuel and combusted. This combustion changes the chemical energy in fuel to thermal energy (heat), which in turn pushes the piston down to rotate the crankshaft (kinetic energy).

However, each piston can pull in so much air. Not enough air means you cannot mix in too much fuel, otherwise the unburned fuel is wasted. So, since there is not enough air and fuel, the engine produces limited torque and power.

The turbo changes this by stuffing in more air, to be mixed with more fuel, so the engine can produce more power.

How does it work?

The basic premise is the turbocharger utilises exhaust gas to compress intake air, rather than letting it go to waste.

To be a little more specific, a compressor in the turbocharger pressurises the intake air before it enters the inlet manifold. In the case of a turbocharger, the compressor is powered by the kinetic energy of the engine’s exhaust gases, which is extracted by the turbocharger’s turbine.

The main components of the turbocharger are:

Turbine – usually a radial turbine design.
Compressor – usually a centrifugal compressor.
Centre housing hub rotating assembly.

Turbine

The turbine section (also called the “hot side” or “exhaust side” of the turbo) is where the rotational force is produced, in order to power the compressor (via a rotating shaft through the centre of a turbo). After the exhaust has spun the turbine it continues into the exhaust and out of the vehicle.

The turbine uses a series of blades to convert kinetic energy from the flow of exhaust gases to mechanical energy of a rotating shaft (which is used to power the compressor section). The turbine housings direct the gas flow through the turbine section, and the turbine itself can spin at speeds of up to 250,000 rpm.

Compressor

The compressor draws in outside air through the engine’s intake system, pressurises it, then feeds it into the combustion chambers (via the inlet manifold). The compressor section of the turbocharger consists of an impeller, a diffuser, and a volute housing.

Centre hub rotating assembly

The centre hub rotating assembly (CHRA) houses the shaft that connects the turbine to the compressor. A lighter shaft can help reduce turbo lag. The CHRA also contains a bearing to allow this shaft to rotate at high speeds with minimal friction.

Some CHRAs are water-cooled and have pipes for the engine’s coolant to flow through. One reason for water cooling is to protect the turbocharger’s lubricating oil from overheating.

The cons of a turbocharger

Every engineering solution creates another problem, so it is all a compromise. The same goes for the turbocharger, hence its limited use.

Turbo lag

Turbo lag refers to the delay that occurs between pressing the throttle and the turbocharger spooling up to provide boost pressure. This delay is due to the increasing exhaust gas flow (after the throttle is suddenly opened) taking time to spin up the turbine to speeds where boost is produced (due to the turbine’s inertia). The effect of turbo lag is reduced throttle response, in the form of a delay in the power delivery.

Then, when the boost pressure is sufficient, the engine’s torque suddenly increases and the vehicle takes off, sometimes surprising the operator.

There are ways around this lag, of course, but it requires a lot of tech (read: expensive).

Heat

Needless to say the system generates lots of heat, necessitating the use of oils that could stand up to the torture. Hence, only synthetic engine oils are recommended.

Forced-Induction Production Motorcycles

Forced-induction – also known as “boosted” – motorcycles are not new.
Japanese manufacturers toyed with the turbocharging concept especially in the early 1980’s.
The Kawasaki Ninja H2, Ninja H2R and Ninja H2X are currently the only bikes that are boosted.

The Kawasaki Ninja H2 and H2R made huge waves that crashed onto the shores of the motorcycle industry when they were introduced; but they weren’t the first forced-induction (by way of supercharger or turbocharger) production motorcycles by a long shot.

The Big Four Japanese manufacturers had flirted with the concept during the “turbo era” of the mid-80’s. You see, after Porsche launched their 911 (930) Turbo in 1975, “turbo” was not only prevalent in the motor industry but went on to invade almost every part of culture (just like how the word “millennium” did towards the end of the 90’s). Suddenly, almost every car had a turbo sticker on it. And remember “TURBO BOOST” in Knight Rider? Judas Priest even had a hit song named Turbo Lover (click here for our list of top 10 riding songs).

1975 Porsche 911 Turbo – Courtesy of 911-guide.com

Motorcycle manufacturers were also caught in the trend, apart from seeking more specific power output, of course. A forced-induction engine inducts more air, hence more fuel could be added to it, producing more power per given engine displacement.

Honda CX500 Turbo engine – Courtesy of www.tamiya.com

Here are seven forced-induction production motorcycles including the latest Kawasaki Ninja H2SX.

Kawasaki Z1R-TC (1978)

Guess you could call this the granddaddy of the H2. But while the Z1R-TC wasn’t produced by the Kawasaki factory itself, it was a factory approved special model sold exclusively through dealers in the USA. The bike was the Z1R with a “Turbo-Pak” bolted directly to it without any change to chassis and brakes. Horsepower was kicked up to 130 bhp from 90 bhp. Riders found it a handful to ride but oh, it’s so pretty.

Kawasaki Z1R-TC -Courtesy of jannys-xxx.blogspot.my

Honda CX500 Turbo (1982)

The Honda CX500 Turbo (also known as the CX500T and CX500TC) was built on the CX500 Standard (pejoratively called “The Plastic Maggot”) that started production from 1978. The CX500 Standard was already different by Honda’s standards as it had a transversely (across the frame) mounted 80^o V-Twin with pushrod actuated overhead valves (OHV). The Turbo version broke many technological grounds apart from turbocharging, including the distinction as the first production motorcycle to feature programmed fuel injection. The turbocharger was dialed up to deliver a peak boost of 19 psi, doubling the engine’s horsepower to 83 bhp and took the bike to 193.6 km/h (121 mph). Unfortunately, high boost pressure means too much turbo lag and production was ended in 1982 itself.

Honda CX500 Turbo – Courtesy of silodrome.com

Yamaha XJ650 Seca Turbo (1982)

It was as if all four Japanese manufacturers sat down together and decided to build forced-induction bikes, because Yamaha too, introduced one in 1982. Of the four, the XJ650 Seca Turbo looked more futuristic (in a 1980’s way, of course). Yamaha’s engineers had simpler ideas from the others when it came to build a turbocharged bike. The engine breathed through four carburetors and routed the right muffler’s exhaust gas to power the turbo’s turbine. The engine’s compression ratio was also the highest amongst its contemporaries to battle turbo lag. However, the bike was reputed to not handle well and was phased out soon.

Yamaha XJ650 Seca Turbo – Courtesy of nippon-classic.de

Honda CX650 Turbo (1983)

Honda isn’t a company that gives up quickly. Honda had mostly fixed the turbo lag issue of the CX500 with the 673cc CX650 Turbo the very next year, by upping the compression ratio and decreasing the boost pressure (it still made 100 bhp). The CX650 Turbo was arguably the best developed turbocharged motorcycle but it couldn’t find many customers due to its high price. It was also dropped within the same year it debuted, together with the CX-series. However, only 1,777 units were made, making it one of the rarest Hondas.

Honda CX650 Turbo – Courtesy of www.classicsuperbikes.co.uk

Suzuki XN85 (1983)

The Suzuki XN85 was probably the prettiest of the 80’s turbo bikes, by adopting the groundbreaking Katana’s design. The 673cc inline-Four engine made 85 bhp (hence the “85” in its name) and pulled hard above 5000 RPM but it couldn’t match the overall performance of the larger sportbikes of the period. Although it handled well due to the 16-inch front tyre (the first production bike to use it), it was bugged by reliability issues and replaced by the cheaper and faster GS750ES the next year.

Kawasaki GPz750 Turbo (1984)

Just as the rest were giving up on turbo, in came Kawasaki with the best turbo bike of the lot. Kawasaki hadn’t just bolted a turbocharger onto the GPz 750 engine, they gave the bike all sorts of top notch components: electronic fuel injection, lower compression pistons, stronger gearbox, modified oil pan with an extra oil pump, boost indicator, stiffer Unitrak monoshock linkage, and a “turbo” spoiler. It made 112 bhp and was claimed as the “World’s Fastest Production Motorcycle” at the time. Indeed, it smashed through the quarter-mile (400 metres) in 11.2 seconds at 201 km/h, before going on to hit a top speed of 238 km/h.

Kawasaki GPz750 Turbo – Courtesy of www.motorcyclespecs.co.za

Kawasaki Ninja H2R and Ninja H2 (2015 and 2016)

Kawasaki claimed that they had wanted to shake up a “sleeping” motorcycle industry by introducing the Ninja H2R and Ninja H2. Instead of sticking with laggy turbos, they learned from the past and went the supercharger route. The track-only H2R made 250 bhp, while the road-legal H2 pumped out 200 bhp. While the latter number may not be the highest among 1000cc sportbikes, one has to remember about the stupendous acceleration of the bike. Sure, they’re expensive and complex but they definitely buried the hyperbike bragging rights, when pro racer Kenan Sofluoglu hit 400 km/h on a stock H2R filled with race gas.

Kawasaki Ninja H2SX (2018)

Of course, Ninja H2 couldn’t go touring. Kawasaki said okay, we’ll build you a sport-tourer based on the H2, called the Ninja H2 SX. To fit its role as a tourer and more practical everyday machine (huh?) Kawasaki retuned the engine to provide more midrange torque (as if it wasn’t enough already), gave it a bigger and more protective bodywork, upright seating position and luggage. Want aggressive touring? This is it.

Honda to introduce supercharged motorcycles?

A series of leaked patent images seem to suggest that Honda is set to follow Kawasaki into the realm of supercharged motorcycle engines.

It seems as if some top motorcycle manufacturers are reaching the ceiling of what is technologically possible with modern day motorcycle engines.

Not too long ago, Kawasaki reintroduced the supercharger with the H2 and H2R. However, the step towards forced induction wasn’t entirely new. Back in the early 80s, the Japanese motorcycle big four all had a supercharged model for offer – Honda had the CX500 and 650 Turbo, Yamaha had the XJ 650 Turbo while Suzuki had the XN 85 Turbo and Kawasaki had the Z750 Turbo.

Anyway, the point is – supercharging isn’t entirely new for motorcycles. In fact it has been around since the 1930s, it seemingly took a break from the mainstream and now it is making a come back. Again.

New to the modern supercharging bandwagon is Honda Motorcycles, though yet unconfirmed but a leaked patent image seems to suggest that Honda will soon follow Kawasaki down the forced induction road.

The leaked image (shown above and below) doesn’t show much expect that the engine looks like a single-cylinder unit with the supercharged mounted on the left.

The patent image also doesn’t do much to suggest which Honda motorcycle will get the supercharging treatment, but word on the internet suggests that the NC750 (pictured above) could have been designed to eventually receive a supercharger.

Kawasaki has always maintained that it’s H2 and H2R won’t be the only machines to get a supercharger. So could we be at the brink of another big-four forced induction era? We certainly hope so.

Turbocharged Suzuki GSX-R coming?

Leaked patent sketches indicate possibility of a turbocharged Suzuki GSX-R being developed.

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Suzuki shows off turbocharged engine

Having shown us the Recursion concept during the 2013 Tokyo Motor Show, Suzuki’s intent at bringing forced induction into bikes is very clear indeed. Fuelling the flame further are rumours of said concept being finalised for production in the last few months, followed by the fact that the mighty S-brand’s move towards trademarking the ‘Recursion’ name and filing patents for designs surrounding the bike’s unique powerplant.

Well, at the on-going 2015 Tokyo Motor Show, it appears that Suzuki are indeed one step closer towards making the Recursion a production reality. At the heart of Suzuki’s stand was this, a compact and turbocharged two-cylinder engine called the EX7, presumably made for Recursion.

Other than the fact that it has twin camshafts (DOHC) and four valves, Suzuki did not say much about this turbocharged and intercooled parallel twin. It is presumed that the mill displaces about 588cc, which was the quoted engine size of the Recursion concept. The concept also envisioned the mill to generate just over 100hp and at least 101Nm of torque too – not bad for its size.

There is still no sight of the Recursion concept’s production version during the 2015 Tokyo Motor Show, which likely suggest that we will only see it next year or early in 2017. However, we are led to believe that Suzuki could surprise all with a reveal in this year’s edition of EICMA that will take place in just several weeks time in Milan, Italy.

Sources: Asphaltandrubber and Visordown

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