A dyno, short for dynamometer, measures an engine’s torque and calculates its horsepower across the rev range. A chassis dyno measures at the wheels with the car strapped down on rollers; an engine dyno measures at the crankshaft with the engine out of the vehicle. A dyno test shows power and torque curves, and often the air-fuel ratio, so you can see what a modification really changed.
Types of dyno
- Engine dyno: the engine is bolted to the dyno directly, giving crank figures without drivetrain losses. Engine builders use them to break in and test engines.
- Chassis dyno: the vehicle drives rollers, giving wheel figures; see horsepower vs torque and wheel vs crank horsepower.
- Inertia vs load-bearing: inertia dynos measure how fast the car accelerates a heavy drum; load-bearing dynos apply a brake to hold or load the engine, which suits steady-state testing. The two types often read differently for the same car.
What happens in a dyno test
- The vehicle is strapped to the dyno and cooling fans are placed in front.
- The operator warms it up and checks fluids and tire pressure.
- A run is made in a gear close to 1:1 from low engine speed to near redline.
- The software records torque, calculates horsepower and plots the curves, often with air-fuel ratio and boost.
- Several runs are averaged, and the results are corrected to standard weather conditions.
Why dyno numbers vary
- Different dyno types and brands read differently.
- Correction factors (SAE, STD and others) change the reported number.
- Heat soak, air temperature, altitude, tire pressure and strapping all affect results.
The most useful comparison is before and after on the same dyno, on the same day if possible, with the same correction factor and gear.
What a dyno test is used for
- Measuring gains from parts such as a supercharger kit, intake or exhaust.
- Setting up engine calibration safely under load.
- Diagnosing a loss of power, for example a failing turbo or a fuel delivery problem; see fuel pump symptoms.
Dyno results quoted in our listings
Several makers quote dyno results. East Coast Supercharging lists a dyno result for a stock 2016 Camaro SS automatic with its Novi kits of 550 hp and 510 lb-ft at the wheels, and AWE lists measured gains for its WRX and STI Track Edition cat-back. See our Camaro supercharger kits, cat-back exhaust systems and how much horsepower does a supercharger add?
Shipping is a flat $80.00 per order to US addresses, with 15-day free returns. Questions? Ask a parts specialist.