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Calculate Power from Torque – Power Calculator

Calculate power from torque by entering your numbers below.

Why Calculate Power from Torque?

My thinking behind this calculator was to help me decide if and how much benefit there would be by fitting bigger camshafts and/or turbos. How much extra power could I get if I increased the size of the turbo. If I can move the torque farther up in the rev range, what benefit would there be?

Turbocharging

Small Turbos

Generally speaking, turbos fitted to engines from the factory are woefully small. Car manufacturers usually design their engine to make torque low down to make them feel fast on a test drive. The problem with small turbos is they choke the engine at higher RPM. By fitting a bigger turbo we can increase the power of the engine without increasing the stress on the engine because we are keeping torque the same. We are just moving the torque up the rpm range.

I have done an example here looking at 1.8T big turbo selection. VW/Audi/Seat/Skoda fitted their 1.8T 20V motor with very small turbos. We can increase the power of the engine massively while keeping torque the same if we fit a more suitable turbo.

Big Turbo Downsides

Boost Threshold. ie the RPM at which the turbo can make boost. Fitting a bigger turbo increase the boost threshold. If for example we could make full boost at 2000rpm with the stock small turbo, a turbo which can sustain torque to redline might not make boost until 3 or 4000 rpm.

Bigger Cams

Same story as with factory turbos. A lot of the time car manufacturers will choose a camshaft that will make good power low down, the problem being the engine loses top end power.

If we find the peak torque number we can compare that to bigger cams which make the same torque at higher RPM. Cam manufacturers like Piper tell us where the power band is for their camshafts.

If we take that peak torque number and move it to a higher RPM we can see how much power we can make from the engine.

Camshaft example

An engine gives 150lbs/ft of peak torque at 2000rpm and it makes 130hp peak. If we move that 150lbs/ft number to 5000rpm we get a new peak power figure of 142hp. Moving it to 6000rpm we get 171bhp.

No Stress

The great thing about moving the torque further up the rev range is that we do not increase the stress on the engine. We will probably lose torque at the low end but we make more power from the mid range to redline.

Try It – Calculate Power from Torque

Find how much potential power your engine has. Find it’s peak torque and move it higher in the RPM range. How much extra power can your engine make?

And if we don’t mind increasing the stress on the engine a little bit, add 20-50% to your peak torque number and see what they gets you.