Engine comparison: How can a smaller/more efficient engine excel over its "bigger sibling"?

Question

Recently, after a discussion with friends, I stumbled over the engines available for a Fiat Panda Mk4 (yes, this is a "long story short" situation and now I'm stuck in a rabbit-hole). And I noticed something strange; a couple of days later it's still nagging me:

How can a 2-cylinder, 900 ccm have more power, more torque, a higher top speed, be quicker, and at the same time have less emissions and get better mileage than its 4-cylinder, 1,200 ccm counterpart?

The data I'm getting is from the car's Wikipedia page; as far as I was able to cross check, the numbers are accurate. In particular, I'm looking at the two 2011 petrol engines (to keep things fair), "0.9 TwinAir Turbo" and "1.2 Fire 8v".

• The first is a straight-2 with 875 ccm that generates 63 kW, has 145 Nm of torque, with a top speed of 177 km/h, and does 0–100 km/h in 11,2 s. It emits 99 g of CO2/km and needs 4,2 l for 100 km.

• The other is a straight-4 with 1,242 ccm that generates 51 kW, has 102 Nm of torque, with a top speed of 164 km/h, and does 0-100 km/h in 14,2 s. It emits 120 g of CO2/km and needs 5,2 l for 100 km.

Granted, some of the values differ only marginally. Others, on the other hand, are quite egregious discrepancies. How can the smaller, more "efficient" (for a lack of a better word) option outshine the bigger, "hungrier" sibling in basically every category?

Somebody suggested "it's the turbo; it does all the difference" (and I've seen questions answered on this platform, but the differences were far less pronounced). "Turbo" might very well be the reason, but then another question arises: Why would anyone want the 4-cylinder option? Why is it even offered as an option if it has zero advantages over the smaller one? What are the advantages of this particular bigger engine?

Answer 1

How can the smaller, more "efficient" (for a lack of a better word) option outshine the bigger, "hungrier" sibling in basically every category?

In a word: Turbocharging

Same reason why Richard Holdener built a Big Bang Motor out of a 4.8L engine which put out over 1200 hp, yet stock (naturally aspirated), it put out around 300 hp. A turbocharger (or turbo for short), basically makes a small engine "think" it's bigger. For every 14.7 lbs (1 bar) of atmospheric pressure (or boost) you can stuff into an engine using a turbo, you'll increase the horsepower versus the same engine which is running naturally aspirated by 100% (considered a rule of thumb ... your mileage may vary). For instance, if naturally aspirated an engine produces 100 hp, by adding 14.7 lbs (1 bar) of boost, the engine should now be making 200 hp. If you added 29.4 lbs (2 bar), it'd be making about 300 hp. This is true all the way up the scale ... as long as the engine is made to take it.

Why would anyone want the 4-cylinder option? Why is it even offered as an option if it has zero advantages over the smaller one?

It is usually cheaper and the engine will usually last longer, all things considered. A turbo adds complexity to an engine, and with complexity comes cost.