WHP Or CHP: Which Should You Trust? - Dynojet

Companies love to tout horsepower claims, but how do you know how much power your vehicle is really generating? There’s a lot of confusion around how horsepower is measured and advertised these days, and it really boils down to two very different metrics. 

There are two main ways of measuring how much power a vehicle generates: wheel horsepower and crank horsepower 

Defining CHP & WHP 

Crank horsepower (also commonly known as flywheel or engine horsepower) is the amount of power that an engine can make without the drivetrain connected, measured at the flywheel. Wheel horsepower is the amount of power an engine generates when connected to the drivetrain, measured at the wheels. 

Simply put, crank horsepower isolates the engine, so you can know how much horsepower the engine alone generates without the drivetrain or any modifications. CHP is measured on an engine dynamometer. Wheel horsepower is the vehicle’s total measurement of power, measured on a chassis dynamometer.  

Dynojet’s R&D Manager, Carl Chastain, breaks down the differences between WHP and CHP: 

Why CHP is Popular 

The simple reason why CHP is often most popular is that the number is almost always higher than WHP. Vehicle manufacturers make horsepower claims using CHP, knowing it’s the bigger number.  

CHP doesn’t take into account power steering or your transmission, as well as power used by other components. 

CHP is a metric that measures what an engine can do, but it doesn’t really give you the true and accurate depiction of a vehicle’s power. CHP may be the big flashy number that the dealer gives you, but when you put the vehicle on a chassis dyno, you’ll be able to measure WHP and see how much power your vehicle really puts down to the ground. 

Many people feel that their vehicle “loses” power when they do a dyno run, but that’s just a misconception. WHP, as measured by a chassis dyno, shows what your vehicle is truly capable of — not just the engine’s performance. 

Why Dynojet Trusts WHP 

From day one, “Truth in Power,” has been more than a Dynojet slogan. It’s core to our mission as a company.  

We don’t believe in gimmicks or inflated HP numbers. When testing and promoting our products, we measure everything in WHP.  

You can test your vehicle on a Dynojet dyno anywhere in the world, and know that the numbers you’re seeing represent the power at the wheels. 

Tuning Dynamometer Wheel Horsepower Crank Horsepower Horsepower

Posted in Testing and Tuning

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