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The Science Behind Power To Weight Ratio

Sometimes buying a new car or any car for that matter can be confusing as well as tiring. There are many aspects when we look for a car to suit our needs. That said, engine, transmission (manual or automatic), features, and aesthetics are all the majors that people look for. Most of these aspects can easily be compared with the other cars, except the engine, and its vital stats. So, how can we compare two cars? This is where the term power to weight ratio drifts in.

era of turbocharged vehicles
The era of turbocharged vehicles

So, to make buying a car less of a hassle, today we’ll clarify how to compare 2 or more cars on the basis of their engine performance.

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What Precisely is Power to Weight Ratio?

To understand the concept of power to weight ratio we need to know some little basics and a pinch of obvious facts. All the cars on the road produce different power figures (unless they have the exact same engine with the same tuning) and their weight also varies. Let me break it down, Ford Figo is a really sweet little hatch that generated 95hp of max power from its 1.2litre petrol engine and weighs 1067kgs (tentative).

Ford Figo
Ford Figo

Whereas, in the same segment, Tata Altroz with its 1.2-litre turbo petrol engine generates max power of 100hp and weighs 1130kg (tentative). Here both the engines have similar displacement but different power figures. Now which one is better or which one to pick?

Tata Altroz Turbo Petrol Launching 13th January
Tata Altroz Turbo Petrol

To judge the car on the basis of performance we require a number that should be independent of the weight or the mass of the vehicle. So, now if we divide the power of the vehicle and by its weight, et voila, we have the vehicle’s power to weight ratio. Usually, the unit used to denote power to weight ratio is bhp per ton.

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After this calculation, if a car has a higher numeric value it means the engine can deliver more power to pull to push that 1 ton of mass or weight (the car). This is one of the reasons a motorcycle has super-duper high power to weight ratio figures and can accelerate in just a blink of an eye.

How to calculate the power to weight ratio of your vehicle?

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BS6 Ford Figo: Reliable Cars In India

Here is a detailed step guide to calculating the power to weight ratio of your vehicle.

Step 1: You need to know your car’s power output

The carmaker mostly mentions these figures on the front page of the vehicle’s brochure. Still, if are deprived of that you can also look for it on the internet. But the catch is, the manufacturers mention the maximum power the engine can produce. However, the car will not make that high power on daily basis. Still, the max power figures are enough to get a gist of it.

Step 2: Check how much your car weights

Like the power figures, finding out the weight of the vehicle can be a little tricky. At times, you can find the numbers on either the manual or the brochure. But it not, the internet is the only option, but you’d not be able to get the exact figures. That said, the curb weight is the weight of the car without the driver, passengers or luggage.

Step 3: Here goes the formula

Power to weight ratio = Power/weight

Note: before calculating, do remember the power of the vehicle is in horsepower (hp) and the weight in (ton).

Let’s put the equation to the test

Drag Strip
Drag Strip | Image Source (1)

Earlier we talked about the power figures and weight of Ford Figo and Tata Altroz.

Ford Figo: Power = 95hp, Weight = 1067 or 1.067ton

Tata Altroz: Power = 100hp, Weight = 1130 or 1.130 ton

Clearly, Altroz is heavier but also, it is powerful. On its other side, is Figo which is a little down on power and weight. Which one has the higher performance considering its weight?

Power to weight ratio (Figo) => 95/1.067 = 89.03hp/ton

Power to weight ratio (Altorz Turbo) => 100/1.130 = 88.49hp/ton

Ford Figo has a better power to weight ratio than the Tata Altroz but not by much. But still when driving fast every second matters. Hence, Figo will accelerate faster compared to the Altroz, but the difference will not be huge.

So, this was everything about the power to weight ratio. Let us know what is the power to weight ratio of your vehicle?

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Also, read: 10 Car Manufacturers And Their Most Fuel-Efficient Engines

Utkarsh Bhardwaj
Technical Content Strategist at GoMechanic | Big Time Petrolhead with the passion for building cars and driving those beauties.


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