Modern day turbocharging has come a long way. Once the exclusive purview of performance cars, it is ironic that turbochargers have found their way into mainstream cars as the solution opted by many a manufacturer to meet increasingly stringent fuel economy and emission requirements.
Going back to basics, a turbocharger uses the engine’s exhaust gas to spool up a turbine which in turn forces subsequent a higher volume and pressure of incoming air for the next combustion cycle. The higher you rev your engine, the faster the turbo spins, the more air can be forced into the cylinder, and thus more power can be produced.
The biggest disadvantage in turbos, as explained by Jason Fenske of the Engineering Explained Youtube channel, is lag. In theory, the turbocharger runs on ‘free energy’, but the reality is that there is a wait between the moment you floor the throttle to the moment where the turbo spools up enough pressure to go ‘on boost’.
In our experience, modern cars do not have turbo lag as severe as they used to be, but they remain noticeable and get increasingly pronounced is you ramp up the boost levels.
Popular solutions to alleviate turbo lag include simply opting for a low pressure turbo, sequential turbocharging where differently-sized turbos operate at different speeds, or even variable geometry turbos. Now, Mazda comes into the equation with the first of its kind Dynamic Pressure Turbo.
In the words of Mazda’s PR speak, it is ‘the world’s first turbocharging system that can vary the degree of exhaust pulsation depending on engine speed.’ Sounds fabulous, but what does it mean in English?
Dato Sri Ben Yeoh, Managing Director of local Mazda distributors Bermaz Motor offers an elegant explanation by linking it to your garden hose. When the water pressure is low, you simply squeeze the tip of the hose to push the water out at a higher pressure.
Mazda’s Dynamic Pressure Turbo therefore has a valve ahead of the turbocharger that ‘squeezes’ the flow of air, thereby enabling even a low volume of air to hit the turbocharger at high pressure. With this solution, Mazda is able to offer a boost profile similar to variable geometry or twin sequential setups whilst only using a mechanically simpler single fixed-geometry turbo.
Dato Sri Ben reveals that from as low as 1,600rpm, the new SkyActiv-G 2.5 Turbo engine that will power the all-new Mazda CX-9 has access to 1.2 bar of boost enabling it to generate outputs of 250hp @ 5,000rpm and 420Nm @ 2,000rpm.