Does accurate HP mean anything? The only thing that matters is relitivity. Lets say the thing is off. Lets say your ski has 50 hp stock and that machine says you have 75. If you put a B-pipe on and the HP goes up, you can see a relitive improvement. If you see it go down, you see a relitive disadvantage.
It's just like the compression gauges most of us use. The callibration of the gauge doesn't matter for someone like me with a stock engine. The only thing that is truely important is that the compression stays the same. It may be 150 and the gauge says 160. As long as it says 160 every time I check it... who cares if it's right? It only matters that it's the same.
There's nothing wrong with an inaccurate dyno when you're simply trying to compare. A good example is people who "test" water boxes. A change in sound can make people think they are going faster. It doesn't always matter what the true torque number of the machine is... as much as it may matter that you simply have more or less torque relitively.
