How power is measured: engine dyno vs chassis dyno vs hub dyno
If you've seen the latest MCM episode (CLICK HERE) then you will have seen MOOG's UP! GTI get strapped to the dyno and turned to 11. Some of you may be wondering why this dyno is different to the dyno our mates at Haltech use and there is a good reason for this.
There are three basic types of dyno, and these aren't just used to measure your llamathrusts - they're actually a tuning device so you can safely run the car through its paces without risking everyones' safety on the street, or oiling down your local track (it's never fun to drive over your own crankshaft after too many PgUps).
The types of dyno are: hub dyno, chassis dyno, and engine dyno. The term "dyno" is actually short for "dynamometer" and while there are dynos for measuring hand strength or shock absorber performance, the ones we'll be discussing today are all about showcasing an engine's health through a horsepower and torque readout.
The most common form of dyno is the chassis dyno, where a car turns large steel rollers against a brake, to ascertain how much power it makes. Normally the dyno operator is connected to the car's ECU or is monitoring the car's air:fuel ratio while this is happening to ensure everything is operating as it should, and no damage is being done.
Chassis dynos can be two-wheel-drive or four-wheel-drive, and they can be adjusted for cars of varying size as, for example, a GT-R Skyline needs more space between the rollers than a GTi-R Pulsar.
The car will generally be strapped down to the rollers so there is no risk of the tyres spinning on the rollers as it moves forwards under acceleration. Strapping the car also prevents it from "climbing the rollers" which is a terrifying moment as the car will try to drive itself off the dyno at full speed and power.
The next style of dyno avoids that last issue. Hub dynos are becoming increasingly popular as cars make ever-increasing amounts of power. However, a bit more work is required to get the car onto the dyno, instead of simply driving on like with a chassis dyno.
On a hub dyno the car is jacked up and driven wheels are removed, adapters are fitted so the car can by physically bolted to the drums which will measure the car's output. This removes any chance of tyres slipping, which affects the final reading, but some critics also say it isn't a true reading of a car's power as the car doesn't need to turn its wheels and tyres (which does make a difference with large-diametre wheels).
If you like big power cars, FOLLOW THIS LINK to watch my mate Bubba's 7-second Holden Commodore street car make over 2200hp at the hubs.
The final way power is measured is more difficult to find today; an engine dyno. This removes the transmission and driveline from the equation and simply tells you how much power this particular engine can theoretically produce. Engine dynos are traditionally how manufacturers come up with power figures for their cars, and are commonly used by racing teams to test modifications and changes in combinations.
Large scale engine builders will also typically have access to an engine dyno for testing and to run engines in - running engines in (including "breaking in" camshafts) was more common in older years when carburettor, ignition system, and ECU technology was lower tech. Very spicy engine combinations will often still be spun up on an engine dyno to test them before being fitted to the car.
The engine dyno is largely the same as the other types of dyno, except it is commected via an adapter to a single drum. This photo below comes from our mates at Haltech, who have this awesome post about dynos HERE which can explain more
Ultimately, the best type of dyno comes down to what you want to do and the car you want to do it with. If you need to check the health of a freshly built engine, see if you have an engine dyno handy. Want a tune done? A chassis dyno will be simplest. Or, if your car has A LOT of power, you'll probably need a hub dyno.
