Continental Car Lab | Does air conditioning affect engine power?

Today on Car Labs –the true power of air!

Have you ever heard the myth air conditioning slows you down? Maybe your uncle turned it off when overtaking trucks on family road trips.

Or maybe you had a mate who swore his Hyundai Excel could not climb a hill with it on!

There is a theory behind this. Air conditioning relies on a belt attached to your engine to drive its systems, and that’s why many believe it saps precious power.

But if it’s only a kilowatt here or there, then it probably isn’t worth worrying about. So we’re tackling this myth with some real-world science…

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We headed out to Herrrod Performance’s dyno room. It’s where expensive and complicated equipment measures a car’s engine power.

So, that’s what we’re going to do with this Mazda MX-5. It’s a bit slicker than a Hyundai Excel, but its small capacity engine should make any power drain obvious.

We’ll run three times with air con off and then another three times with it on, then compare the averages to see if the theory is all just hot air!

Now, dynos work in different ways, but they all apply some resistance to the car’s wheels and then measure how easily, or slowly, the engine overpowers it.

Given that the myth suggests air conditioning robs power, our MX-5 should make more when the air conditioning is turned off. So, let’s find out…

Before I reveal the results, it’s worth mentioning that the most advanced hybrids today run air conditioning off battery power - costing the engine nothing!

But for the majority of cars like this MX-5, well, there is a difference.

With the air conditioning on its highest setting the car lost 2.5kW, or around 2 per cent of its overall power.

That might not sound like much until you look at its torque figure, that shows a much larger five per cent difference. And that’s something you’re going to feel in the tight and twisties - especially in your mate’s Hyundai Excel...

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