Good things come in small packages

by Jim KerrAuto Tech . Jun 01 2018
LC MediaThe motorcycle-sized, one-litre EcoBoost motor found in the 2018 Ford EcoSport SUV delivers excellent fuel economy and surprising performance for such a small engine.

LC Media

The motorcycle-sized, one-litre EcoBoost motor found in the 2018 Ford EcoSport SUV delivers excellent fuel economy and surprising performance for such a small engine.

I never imagined one day I’d be driving an SUV with an engine the same size as the one found in my motorcycle — and enjoying it.

But that’s exactly what happened recently when I tested out Ford’s 2018 EcoSport compact SUV, powered by a one-litre, three-cylinder engine.

To say I was surprised by the performance is an understatement.

The EcoBoost three-cylinder engine in the EcoSport SUV is coupled to a six-speed automatic transmission and front-wheel drive. If you want all-wheel drive, you will need to order the optional two-litre, four-cylinder engine, which is also coupled to a six-speed transmission, or select the SES model, which comes standard with the four-cylinder engine. So the big question is — are three cylinders enough or should you go with four?

Let’s compare specs.

The turbocharged three-cylinder puts out 123 horsepower and 125 pound-feet of torque with a 10:1 compression ratio. The normally aspirated two-litre four cylinder puts out 167 horsepower and 149 lb.-ft. of torque, with a 12:1 compression ratio. Both run on regular gasoline.

It would be easy to go with the higher power figures, but numbers don’t tell the whole story. On the road, the turbocharged one-litre starts its torque curve down at low r.p.m., so it feels much stronger accelerating than its numbers would suggest. The two-litre engine does feel a bit faster, but not by much.

Gearing will easily change the acceleration characteristics of a vehicle. The one-litre engine has a 4.58 first-gear ratio and a 3.44:1 final-drive gear ratio. The two-litre engine has a 4.85 first-gear ratio and 3.51:1 final-drive gear ratio. The lower gear ratio (higher number) provides quicker acceleration, so the two-litre engine should be quicker, and it is slightly, but the torque provided by the turbocharger on the one-litre engine gives it good acceleration even with higher gear ratios.

Four cylinders are smoother than three because the power pulses are closer together and equally spaced, but there is another factor in smoothness — balance. Balance is when weights counteract each other so vibrations are not produced. In an engine, the weights on a crankshaft are designed to balance the weight of the connecting rod and piston. Four cylinders are inherently balanced because as one piston is moving up in the cylinder another is moving down. Three-cylinder engines are not inherently balanced.

To keep the three-cylinder engine running smooth, the one-litre engine’s front pulley and flywheel are made unbalanced with weight in precise places to counteract the natural shaking forces of three-cylinder operation and direct them in specific directions. The engine mounts are then designed to absorb these vibrations. Any vibration is isolated from the passenger compartment.

Fuel economy is another consideration. On the highway, the one-litre is rated at 8.1 L/100km and the two-litre engine is 8.0 L/100km. They are almost identical.

Around town, it is a different story. The smaller engine is rated at 8.6 L/100km, and the larger engine at 10.2 L/100km. Both engines have technology which shuts off the engine to save fuel when the vehicle stops.

If you spend most of your time at slow speeds in traffic, the smaller engine is a definite winner.

On the road, the one-litre engine is quiet and smooth. Even accelerating up to highway speeds or passing slower vehicles, it never feels like it has a lack of power. The two-litre engine is also smooth, but acceleration in everyday driving doesn’t feel much more than the smaller engine. The two-litre engine does have a little more noise, most noticeably on acceleration.

So what engine to chose?

If it comes to fuel economy, the EcoBoost 1.0 is an obvious choice. If you need all-wheel drive, you are forced to go with the optional two-litre engine. The one-litre engine is lighter, and the same size as in my motorcycle — but it performs like a much bigger engine, and even for a compact SUV, offers amazing fuel economy.

james.kerr@sasktel.net