Specs We Need
- Weight of vehicle
- Gear ratio
- Final drive
- Tyre size
You can find this data here
We also need to know the
- Acceleration time
- Coast down time
How to use this engine horsepower calculator
1.Choose a start speed and end speed of your acceleration run
2.Record the time it takes the car to accelerate between these speeds
3.With car out of gear, record the time the car takes to decelerate between these speeds, on the same piece of road as the acceleration run in the same direction. This time will compensate for wind resistance, wind direction and speed, rolling resistance of tyres and the gradient of the road
This engine horsepower calculator is designed to give you an easy way to calculate the horsepower of your engine just by using a stopwatch and some simple specs of your car.
Quick and easy and no need to do runs in both directions!
Any questions? Leave a comment below!
Real World Example
We have tested this calculator on a Ford Focus MK1 1.6. Using the data from cars-data.com. It calculated a wheel horsepower figure of 72bhp (uncorrected). We have previously dynoed this car and we got a wheel horsepower figure of 75bhp.
In short, we think this calculator is very accurate, although it does not compensate for atmospheric conditions eg temperature, humidity and pressure.
Create a Dyno Graph!
You can also make a dyno graph using this calculator.
Simply time the car over each 10mph/10kmh segment from 2000rpm (for example) to redline.
Then record the time the car takes to decelerate through each segment during the coast down.
Top Tip. Use a video camera pointed at the speedo to record acceleration and deceleration. Import this video footage into your video editing software to get precise acceleration & deceleration times.
Plot this data into excel (with RPM along X-axis and horspower on Y-axis) to get your dynograph.
Want to calculate other things? Check out our other calculators here