A Dyno (dynamometer) is a device which CAN measure the forces generated by your engine. There are many different types and they work in different ways. One type measure the power generated by your engine by resisting the engine (often, using some form of oil pump and then restricting the flow of that oil. The engine can then be put on FULL throttle but held at various revs. Basically, at FULL throttle, you restrict the oil flow until the engine revs are held a specific value. Measurement is then done at a series of 'steps' in the rev range... e.g., power at 5,000, then at 6,000, then at 7,000... etc.. The 'power' generated in each 'rev range' is calculated by seeing the amount of force (restriction in the oil flow) required to PREVENT the engine from accelerating PAST X,000 revs..
Another type uses a flywheel and can be used to measure the rate at which the engine accelerates. It then is used to record the time that it took to get from (e.g.) 6,000 rpm to 6,100 rpm. Because you know the mass of the flywheel, you can calculate how much 'power' it took to accelerate the engine from 6,000 to 6,100. In a single 'acceleration from (e.g.) 2,000rpm to 18,000rpm, you can calculate the power of the engine THROUGHOUT the rev range. In my opinion, the flywheel dynos are the one which measure the REAL performance of the engine because it closely matches how you WANT to use your engine. However, others disagree...... to put it mildly!
However, you have to know that although there IS an exact 'BHP' generated by your motor at various ranges, the dynamometers ONLY 'display' the BHP depending on how they are calibrated....... and that calibration CAN be....... adjusted.....
Why would anyone want to show a higher BHP for their tuning work than shown by other 'tuners'......? Do I need to ASK??????
Secondly, ALL dynos ONLY measure the 'power' of the engine ON THAT day, at THAT temperature, in THAT humidity, in THAT barometric pressure, with THAT exhaust pipe on THAT fuel, etc., etc., etc.. Thus, it's almost IMPOSSIBLE to compare motors (realistically) that may have been 'dyno-ed' by two separate machines/tuners in different locations on different days!
They are MOST useful at comparing the effects on (for example) the Exhaust you are using where you can test the motor with exhaust A, and then quickly swap to exhaust B and re-test the engine. You could also use it to compare Motor A with Motor B..... if you can swap them reasonably quickly on the same day, on the same dyno.
Put crudely, they are GREAT for some jobs but you MUST NOT rely on the figures you are given..... they are COMPARATIVE, not ABSOLUTE!
Obviously, for the 'techies', I have simplified this stuff and I am aware that I am generalising here!
Ian
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Dyno explanation by 'Dubzy1981' (18 Oct 2015 @ 15:22)
