Engines and Transmissions

Engines and Transmissions

The Mazda2 is available in the UK exclusively with a 1.5-litre SKYACTIV-G petrol that’s offered with a choice of three power outputs: 75ps, 90ps and 115ps.

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The Mazda2 is available in the UK exclusively with a 1.5-litre SKYACTIV-G petrol that’s offered with a choice of three power outputs: 75ps, 90ps and 115ps. The 75ps engine is matched to SE+ and SE-L+ trim, while making up the bulk of the range the 90ps version is offered in SE-L Nav+, Sport Nav+, while the 115ps engine is exclusively matched to the flagship GT Sport Nav+ trim and a SKYACTIV-MT six-speed manual gearbox.

With the 90ps engine there’s a choice of five-speed SKYACTIV-MT manual transmissions and a six-speed SKYACTIV-Drive automatic transmission. Mazda’s engineers eschewed the current trend of exploiting tried and tested technology such as forced induction and downsizing engines and opted instead for a fundamental rethink that would allow them to ‘right-size’ these innovative new engines. The result is a combination of exceptionally high levels of economy, refinement and flexibility without compromising performance.

This clean-sheet 1.5-litre all-alloy unit bucks the current trend towards downsizing with ‘rightsized’ advanced technologies including intelligent direct fuel injection, low-friction design, and a radical high compression ratio of 14:1 (12:1 for 75ps) - one of the highest ever recorded for a mass-produced petrol-powered passenger vehicle.

Although increasing the compression ratio considerably improves thermal efficiency, it also decreases the chances of knocking – unwanted premature ignition – as the temperature at top dead centre also rises.

In the SKYACTIV-G petrol engine, the top-dead-centre temperature is lowered by halving the level of residual exhaust gas from eight to four per cent, and introducing an extended and looped four-into-two-into-one exhaust system that prevents exhaust gas leaving one cylinder being forced into the combustion chamber of another.

In addition, the piston heads were fitted with cavities to prevent the initial combustion flame from hitting the piston and interfering with the flame’s growth, and low-temperature oxidation – an exothermic reaction in which the bonds within the molecules of petrol break and produce energy – was exploited to further boost torque across the rev range.

Both 90ps and 115ps variants boast an innovative four-two-one exhaust manifold, which lowers the in-cylinder compression temperature to help prevent knocking, improve the scavenging effect and with it combustion efficiency, and deliver extra torque – especially at low engine speeds.

The ‘standard power’ 75ps version of the 1.5-litre SKYACTIV-G petrol engine comes with a lower 12:1 compression ratio, variable valve timing on the intake manifold only and simpler four-into-one exhaust manifold. Despite its smaller exhaust, simpler valve timing, lighter engine cover and smaller oil pump, this version still produces more torque than Mazda’s previous-generation MZR 1.3-litre petrol engine.

All versions come with i-stop idle-stop system as standard. Developed entirely in-house and tailored specifically for its application in Mazda’s new generation of SKYACTIV-Engines, the i-stop idle-stop system uses combustion energy for restarting the engine, and only requires an electric-powered starter motor to provide a small degree of momentum during the initial restart phase.

The lightweight SKYACTIV-MT five- and six-speed manual transmission delivers the same crisp and precise wrist-flick gear changes, as those enjoyed by MX-5 drivers. The key element to achieving this quick and decisive gearshift action is a larger gear lever ratio, but this in turn effectively reduces the internal stroke.

To counter this, Mazda’s transmission engineers developed a small module spine that allows for exceptionally precise synchroniser and torque transmissions even with the desired 45mm short gear lever stroke. Shift effort gradually falls away during the gearshift action, resulting in a reassuring resistance during the initial movement of the gear lever, followed by a lighter touch to create the tangible feeling of the gears meshing cleanly in to place.

By reviewing the function of each component, common first and reverse gears were also adopted, further reducing weight, enabling the length of the secondary shaft to be reduced by a full 20 per cent and doing away with the need for the reverse idle shaft.

Combining competition-beating torque capacity with lower internal drag, the five-speed transmission weighs seven per cent less than the current Mazda2’s five-speed gearbox, while both five- and six-speed transmissions require 45 per cent less transmission oil.

The SKYACTIV-Drive six-speed lock-up automatic transmission used in the Mazda2 is a new version that’s smaller and lighter than the SKYACTIV-Drive variant used in the Mazda6 and Mazda CX-5. As in these models, the key requirements were strong fuel economy, a direct and engaging feel, smooth and quick shifts and prompt responses.

This resulted in the development of a torque converter with a lock-up clutch, which locks the torque converter’s turbine to the impeller to improve fuel economy and enhance the driver’s feeling of connectedness. It features a wider lockup range - 93 per cent as opposed to 89 per cent in the larger Mazda models – for even smoother standing starts.

Weight was saved by ditching the one-way clutch, using a smaller planetary pinion, torque converter and valve body, and employing a thinner and lighter transmission casing. As a result, it is a useful 17kg lighter than the version used in the Mazda3 and Mazda6. It also features a ‘Sport’ mode, which delivers more torque and an enhanced acceleration response at the flick of the drive selection switch located just behind the gearshift.

Maximising the lock-up range enabled by a significant reduction in noise, vibration and harshness. Lock-up performance was further enhanced by employing a multiple-disc clutch with optimised oil flow for enhanced cooling.

The SKYACTIV-Drive automatic transmission also features an advanced hydraulic mechatronic control module. By locating this control module inside the transmission, rather than outside the gearbox, the accuracy of oil pressure monitoring has been significantly improved.