Roman,
I agree with what you're saying and I agree that allot of club dyno runs seem to just add on 20% or 15% on an ad-hoc basis with no explanation. This is a "plucked" figure -no mistake and the most effective way for f/wheel power is on an engine dyno but that's allot of work and you can maybe accept an inacuracy measuring it another way. Perhaps my own mis-interpretation but I've extracted this from the Dastek web site page.
Quote:
I understand that you use a coast down test to determine flywheel power. Why, when wheel power is what makes you go?
The problem with measuring wheel power only, is that many factors can affect the wheel power output - tyre design, temperature and pressure, wheel alignments, gear box oil, viscosity temperature and level, wheel speed, final drive ratios etc.
As an example; take two very similar cars with similar modifications, both are tested on a 'wheel horse power only' dyno, Car A has 12 Bhp more at the wheels than Car B. The owner of Car B and/or the dyno operator begin looking for problems with the turbo chargers, ECU calibrations, CAM timing etc. If the test had been carried out on the Dastek Dyno, the coast down test would have revealed the transmission loss would have appeared excessively high, thus taking the focus away from the engine fault and pointing us in the direction if the drive line problem. The fault was in fact a partially seized brake caliper, which was converting the power into heat.
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Dastek Dynamometers - Frequently asked questions
...now if this is crap then fair enough but I have read the theory in better detail ages ago and seemed OK engineering wise at the time.
I'm just back from Cambridge and spoke to Patrick at Rogue yesterday afternoon about finding a competent dyno centre to do some proper work. I think there's a place in Tewkesbury which has a Mustang dyno which I think is highly rated. I'm thinking a 1,200 mile round trip there early next year is better than faffing about on others. I believe this can simulate a Dastek dyno also, so I can look at tuning some mods, then doing a final "Dastek" power run to see a comparison from my first run a few weeks ago.
...My comment still stands -and this is what I think we should be clear on is are we considering the same units, PS doesn't equal Bhp but I can't find a conversion figure yet (surely we shouldn't quote 200Bhp for the BEAMS -it's 200PS or about 197-198Bhp?) . And what on earth's an HK -I'm an engineer and never heard of that unit before, I can't find it searching the internet so far?