Specialist Mazda Rotary Rebuilds & Services

01249 408888

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Forced Induction

Throughout the years Mazda turbocharged a large number of rotary engines from the factory, most commonly the FC and FD generation RX-7s however any rotary engine is a great candidate for turbocharging.

Turbochargers function by utilising the otherwise wasted exhaust gases to produce a compressed air "boost" back into the combustion chamber via the intake. A rotary engine has an extremely hot exhaust flow which contains a large amount of thermal and kinetic energy - perfect for driving the turbine within a turbocharger.

Mazda did a very good job specifying the turbocharger systems on their OEM RX-7 models, however there is always room for improvement as mechanical and technological advances improve the parts and sub-systems to enable better efficiency, reduce turbo 'lag' and increased horsepower.

At RotaryMotion we have extensive experience in modifying and increasing the performance and reliability of turbocharged and supercharged rotary engines. We also supply and fit turbocharged or supercharged conversion kits for the RX-8 and normally aspirated rotary models.

Superchargers

A supercharger is a belt or chain-driven compressor that creates a flow of pressurised air, fed directly into the intake. This "boosted" air fills the compression chamber with more air molecules that a normally aspirated engine whilst the combustion process remains identical to a normally aspirated engine.

Modern superchargers are generally simple devices and are capable of generating high numbers of engine horsepower. Their torque output is immense and essentially there is no throttle 'lag' or delay. Boost production is immediate and very linear from idle up to the redline. However they are generally not very efficient and require a relatively large amount of eccentric horsepower, between 15% and 50% to drive the blower sufficiently enough to create an adequate cubic feet per minute (CFM) increase. Because of this, supercharged rotary engines rarely exceed 300whp without really pushing the levels of boost

Cooling the pressurised air can also be a challenge with some systems (such as Pettit) using a liquid-to-air heat exchanger to combat this. Belt-drive superchargers can also stress and distort the front shaft extension of the eccentric shaft, more commonly on older rotary engines where their thrust bearings are smaller and cannot resist the increased loads.

Superchargers can be excellent performers but come at the cost of efficiency. Whilst If you want the most efficient form of forced induction, you should consider a turbocharger.

Turbochargers

With a normally aspirated and even supercharged engine, a significant quantity of combustion energy is wasted through the exhaust at the end of every combustion cycle. A turbocharger works by harnessing this 'waste' energy and redirecting it through a turbine to power a compressor. All the benefits of a supercharger, but without the huge eccentric shaft power drain.

Once generated, the pressurised air is then typically passed through an intercooler to reduce its temperature before being directed to the intake manifold. A wastegate is used to control the amount of boost pressure created to help prevent engine detonation.

Larger turbochargers suffer from a delay in the build up of pressurised air otherwise known as 'lag'. This delay in the spooling of boost pressure caused by wheel inertia is a common drawback of turbocharged forced induction.

Whilst simple by concept, a properly designed turbocharged engine can be very complex. Care must be taken in not only selecting the right components but also ensuring the rest of the engine is evenly matched to the turbo. By under or over specifying any of these components the result can actually be poor engine efficiency, weak power production or even detonation.

1986-1992 Second Gen RX-7 (FC3S) Upgrades

Both S4 and S5 versions can be modified for increased performance including high-flow exhaust systems, wastegate porting, boost increase, upgraded intercooler systems and more modern replacements for the OEM Hitachi turbocharger.

1993+ Third Gen RX-7 (FD3S) Upgrades

From 1990, Mazda launched the 13B-REW engine in the Eunos Cosmo before launching 3 years in the final generation RX-7. Exhaust upgrades, Intake & ECU modifications, Turbo and Intercooler upgrades and auxiliary enhancements such as aftermarket knock sensors, fuel system, electronic boost controllers.

Turbocharging a Normally Aspirated Engine

At RotaryMotion we can help you source or provide all the turbocharging components, modify the engine internals to handle the increased stresses of boost, install all the necessary wiring, intercooler systems and engine management upgrades required to run efficiently and effectively.

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  • Stockham Marsh Farm

  • Foxham

  • Wiltshire

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