The direct torque aproch is way to pricey
The g-tech performance meters claim +/- 1%. For $200 + all the other features :dance:
(still not as cool as making your own)
Building your own is educational, that's for sure.
If I were you I would do the following assuming petrol car!:
- Take a note of my cars peak horespower and at what RPM (this will give you an idea of whether you are in the right ball park!)
- Using MAF or speed density (depending on available PIDS) obtain mass airflow g/s
- Calculate fuel flow g/s assuming lambda = 1 (14.7 parts air to one part fuel by mass)
- Assume for now that your vehicle does not run rich under high load, this is entirely possible- I know some ECUs are mapped to avoid running rich at all costs (maintain emissions...)
- multiply the chemical energy stored in the fuel by 0.3 (approx ICE efficiency)
- I have done this and it worked nicely for me!
If anyone is interested in taking this approach I am happy to do a bit of legwork and provide a walkthrough on how to do the above?
The other approach mentioned a few times in the post was essentially F=ma assume you know mass calc acceleration you get force this equates to useful power at the wheels. Assuming you do multiple runs for wind on a flat road this is a more true figure of your vehicle's power.
I don't want people to be put off this technique based on your speculative comments. As I already said in my post, I have tried it and found it provided a reasonable estimate of manufacture quoted figures (on more than one vehicle). I would say within 2-3% error.
I just wrote a post, giving an overview of the maths involved, even for those without a MAF signal. Chemical energy of petrol is approx 43MJ/kg. Check out the post here
---------- Post added at 07:08 PM ---------- Previous post was at 06:59 PM ----------
2 gallons / hr = 7.571 litres/hr
density of petrol = 749.5 g/l
mass of 2 gallon/hour = 5674.46 g/hr
fuel flow = 1.576 g/s
Power = 0.33 * 1.576 * 43 [kW]
P = 22.36 kW
P = 30.4 hp