![]() But it’s always a compromise, even with nine speeds. The combinations of gears are carefully chosen so the engine can remain in its best rev range for either power, torque (turning force) or efficiency. In between the first and top gears are other gear ratios, and these days there’s usually a total of six but some newer automatics have as many as nine. You’ll know from driving that in top gear your engine only needs to do say 3000rpm for 100km/h – whereas 3000rpm in first gear would see you only at about 25km/h. Now the engine turns a large gear connected to a small gear, so for every rotation of the larger gear the smaller gear turns multiple times. And when you drive a car in first (lowest) gear, you’ll know that you can rev the engine quite high and the car doesn’t go very fast – this gearing is the reason.Īt higher speed it’s the opposite. It’s like using a low gear on your pushbike. ![]() For every revolution of the small gear, the bigger gear only turns a fraction. At low speed, the engine turns a small gear which is connected to a larger gear that turns the wheels via other transmission components. ![]() How an automatic gearbox worksĪ normal automatic gearbox uses gears to match engine speed to road speed. This article uses plain English to explain how a CVT works, why manufacturers are using them and how driving a car with one takes a little getting used to. The most obvious application for a CVT is when you’re trying to ensure maximum fuel efficiency, hence why Subaru has paired Boxer engines and all-wheel drive (all-wheel drive adds weight and can affect fuel consumption driving up the relative fuel consumption of a Subaru when compared with a non-AWD SUV in the same segment) with a CVT. Rather, the CVT allows the vehicle’s engine to run at its most efficient revolutions per minute (RPM) for a range of vehicle speeds. ![]() IN A NUTSHELL, a continuously variable transmission, or CVT, doesn’t offer fixed gear ratios like a either a manual gearbox, automatic transmission or a DSG (Direct Sequential Gearbox, a newer type of auto). ![]()
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