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AUSTRALIAN ROAD RIDER | 117

TURBOS AND SUPERCHARGERS

work and this gap in performance is o en

referred to as turbo lag.

Superchargers operate directly in

relation to engine RPM and hence need

power to make power. They can rob up

to a third of an engine’s power to do their

job, though a net power gain of 10 per

cent is typical. You really need a decent

amount of outright power to see a good

outright gain in power without the initial

power rob causing any negative eff ect.

So superchargers are typically less

economical and provide a smaller

output gain than a turbo, but have

more favourable characteristics on

a motorcycle and all of the system’s

benefi ts are available instantaneously.

Turbos are be er on economy, less

expensive to fi t and provide a bigger

outright improvement, but their power

delivery characteristics aren’t as good.

Effi ciency of both systems has

improved with the use of intercoolers

cooling the air between pump and

intake as the systems heat the air when

it is being pressurised — something

that limits the total performance

improvements of these systems.

But things have progressed from

these “typical” traits as manufacturers

seek improved economy. So evolved

are charged systems these days that

manufacturers have sought to eradicate

both of the eff ects the systems have

“typically” displayed in the past. Just have

a look at the eff orts Kawasaki has gone to

with the H2 (sidebar, above) and you’ll see

the future of the supercharger is looking

promising.

While the supercharger looks like the

way forward, turbocharging is more likely

to have a bigger future in motorcycling

for the same reason it is so popular

elsewhere in the automotive world: it

provides greater power gains, is more

effi cient and economical.

Turbos have been employed on

INSIDE THE BEAST

Producing a supercharged production

motorcycle takes more than just bolting

on a charger. The primary considerations

that need to be addressed by

supercharging are intake air heat,

engine heat and engine stress. Adding

power does cause a lot more than just

excitement!

Kawasaki, like most manufacturers,

has a number of divisions within the

company that build more than just

motorcycles. Within the Kawasaki

Heavy Industries (KHI) group there is a

gas turbine and machinery company,

aerospace company and corporate

technology division.

By calling on the different arms within

the company, Kawasaki was able to

design a supercharger that is extremely

compact and claimed to be highly

effi cient.

Run off the crankshaft via a planetary

gear train, the supercharger impeller

spins at 9.2 times the speed of the

crankshaft. So at redline of 14,000rpm,

the impeller is turning at 130,000rpm —

that’s pumping quite some air!

With that sort of air pressure and

power output — 300 horsepower in the

H2R — the engine unit for both H2s is

built stronger to be able to handle twice

the stress of a typical superbike engine.

The road-going engine differs

from the race version with different

cams, head gasket and clutch. The

combustion chamber is designed to suit

the high-pressure intake air and as a

result its design eliminates the squish

area — used to promote better air and

fuel mixing in normal engines — and

runs a 8.5:1 compression ratio — all a

supercharged engine needs. The piston

design is a fl at crown and is a design

from Kawasaki’s 18-cylinder Green Gas

Engine.

Getting the air in comes via a centrally

mounted ram air duct that is three times

the area of the supercharger intake

area. It’s squished in along a straight

path to the supercharger intake via an

aluminium intake chamber that keeps the

air cool and is totally airtight — you don’t

want air escaping in a charged system!

Fuel is added to the air mix through

stainless-steel nets to disperse the

fuel mixture in a mist. With lower lift

and overlap narrower than a typical

superbike engine, the exhaust ports are

straight to get an optimum route for air

chamber fi lling.

The extra effort involved in cooling

the engine to ensure the system is as

effi cient as possible requires an oil

jet system cooling and lubricating the

engine, supercharger and gearbox.

r What was to become of the Ninja H2 engine

shown as a prototype at the 2013 Tokyo Show

■ The simplicity of a turbo

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