Inertial Dynamometer Vroom Vroom Vroom Testing

I think it has to be tested under load...

"In most dynamometers power (P) is not measured directly, but must be calculated from torque (τ) and angular velocity (ω)^{[citation needed]} values or force (F) and linear velocity (v):

or

where

P is the power in watts
τ is the torque in newton metres
ω is the angular velocity in radians per second
F is the force in newtons
v is the linear velocity in metres per second

Division by a conversion constant may be required, depending on the units of measure used."

https://en.wikipedia.org/wiki/Dynamometer

Angular speed = RPM x 2 pi x pulses/revolution

Angular acceleration = time rate of change of Angular speed

Torque = moment of inertia x Angular acceleration

Power = Angular Speed x Torque

So theoretically, it's certainly possible.

I don't know if you will get the same answer that you would get if the engine were operating at a steady speed with a steady load.

It is certainly possible to obtain performance figures for any internal combustion engine from the equipment manufacturers directly.

The instantaneous output power would vary with a number of factors, with the instantaneous atmospheric weather conditions, ambient temperature and the barometric pressure being among them.

If your vehicle has an OBDII connector, you can purchase devices for this.

I have a wireless Bluetooth adaptor that I can monitor with my phone.

You can see acceleration, fuel mix, GPS position, 0-60 time, etc. etc.

The old fashioned way was to take it out and drive it up a steep hill with the pedal to the floor in the highest gear it can handle the hill in and time yourself between two fixed points.

From that given the known distance, elevation change and weight of the vehicle you can get a fairly good estimate of your effective at the wheel power.

That or if it's an automatic simply do a torque converter stall test (gas pedal to the floor and brakes on hard) and see how your RPMs change between different fuels.

Thanks to all who replied- the vehicle is actually a 1980 Series 3 Land Rover, so no OBDII, unfortunately- it does have a carburettor and distributor. Nothing puts a big smile on my face like driving it, nothing wipes the smile off like paying for the fuel, so that's why I'm experimenting with charcoal gasification, and I want a quick "tweak and reevaluate" check on the power. The maths doesn't look too onerous for an Arduino- it's about acquiring 3 pulses and 2 intervals in milliseconds, not microseconds, processing it, and displaying it in a friendly way.

There is no way you can do this without going on a dynamometer. All you will be measuring will be the power required to spin the engine, which bears no relation to what you want.

?????? I'm hoping to measure the power available to *accelerate* the engine, or more accurately measure the angular acceleration. Without knowing the moment of inertia of the crankshaft and flywheel, I won't be able to derive a figure in kilowatts, but it will remain constant, so I hopefully can get a key indicator from the angular acceleration.

I think you should look at published graphs for torque and power against RPM of an IC engine, e.g. here:
http://www.mpoweruk.com/piston_engines.htm
where you will observe that the lines for torque and power are not parallel.

But surely....... The torque/RPM curve won't resemble the power/RPM curve because power is proportional to torque multiplied by RPM. In a steady state dyno, the torque is measured against a brake, in a flywheel or inertial dyno, it's derived from the angular acceleration of an external flywheel:

http://dtec.net.au/inertia%20dyno%20design%20guide.htm

what I'm considering is: dispense with the external flywheel, and use the vehicle's own flywheel.

Two points. First, the product of torque and RPM is not linearly related to the power in the reference I gave. This may be within the realm of observational error, but the second point is that the vroom-vroom method involves the activation of the accelerator pump on the carburettor. The measured acceleration at, for example, 3000 rpm, may depend on whether the acceleration started from 1000 or 2500 RPM. I'm not sure how your alternative fuel supply functions.

If all you want is a quick "tweak and reevaluate" check on the power, just use a stopwatch and the same course.

I wouldn't bother with any testing, a series 3 LR will disintegrate before you complete the tests.

I had to drive them at work. After 2 years and they were demoted to internal use only, 6 years and they were scrap.

We made an inertial engine dynamometer (engine out of vehicle, on dyno) with a 600lb flywheel. It can provide the full rpm power/torque curve on a 1000 hp motor in a full throttle run lasting about 3 to 4 seconds. Repeatability is about +/- 1hp. This system, while really neat, is overkill for your needs.

Your problem is much simpler. Since you are really looking for the best tuning for your vehicle, find a flat deserted road, get moving in second gear, give it full throttle, and start your stopwatch when you hit 10mph. Continue the full throttle acceleration to a speed near redline, stopping the stopwatch as your speedo passes that speed. Do this 2 or 3 times, hoping for repeatable results, recording all test results.

Make your experimental change, and then repeat the acceleration time test. Finish the series of tests with the original settings, hoping to repeat the original results.

The types of errors you are limiting with this testing process are:

Wheel slip (second gear)

Air friction (not going too fast)

Specific peak anomalies (wide range of engine rpm)

Human stopwatch errors (multiple passes achieving similar time results)

Terrain effects (starting at the same place with data taken over a similar path)

Human judgement effects (human senses can be easily fooled by non-obvious cues)

I performed a similar set of tests to find the best jetting for a motorcycle, many years ago.

later,

Carl