Thank you for a very interesting thread.

You can always try this too:

In a legal and safe way, make a little test run area. Mark out exactly one quarter of a mile (1320 feet). Weigh the vehicle with a full load of fuel and driver (you can do this at a commercial place that weighs trucks, or place four weight scales under each tire simultaneously, or just use a published figure and add the weight of the driver for an estimate). Start an acceleration run through this distance. When you are crossing the end line, note your speed at that point.

Now use this formula to get an estimate of bhp at the wheels:

Horsepower = Weight x [(speed/234)^3]

For example, for a vehicle that weighs 4000 lbs, and is travelling at 50 mph at the end of the quarter mile run:

Horsepower = 4000 x [(50/234)^3] = 39 bhp approximately.

Now consider the type of transmission and estimate the drivetrain losses at about 15% for a manual and 20% for an automatic gearbox. Correct for an additional 5% loss if the vehicle is four wheel drive.

So the horsepower at the flywheel is approximately 48 bhp.

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