I certainly wasn't calling anyone a liar, just in my experience rolling road figures are pretty pointless to use to start claiming flywheel figures, and here's why:
-there are many different types of rolling road. You get inertia drag brake types and you get eddy current types. The latter can load the engine more by increasing the drag weight (either hydrolic or electronic). Static inertia system simply use a big heavy weight which can't increase it's drag on the engine. The result of this is, different types of rolling road dyno can produce significantly different results. Both are correct in terms of how they are achieving the figure, but they are not directly comparable to each other, let alone comparing to manufacturers engine dyno figures.
-along with the different types of dyno you also get different makes. These can vary results too, more so if it's a hub mounted rolling road
-correction factors. When manufacturers dyno an engine they have to conform to very strict guidelines on ambient temperature, fuel, ancillaries, humidity, DA and a host of other values. These are usually defined as standards, SAE Net (Society of Automotive Engineers) is one example, although DIN and a few other standards are used in the EU and Japan.
There are a host of calculations that can be applied to "correct" to a standard. Not doing so can show massive differences in output, e.g. a 300rwhp V8 muscle car can show a variance of 20-30rwhp by correcting to SAE or not
-Metric/Imperial. There are both metric horse power (PS) and imperial (HP). They have slightly different values, so knowing which one is being used is rather important
-Drivetrain loss. This is really the biggy here. It's all guess work!. Sure some dyno's might measure coastdown, but that doesn't tell the entire story. Deriving flywheel figures from wheel figures is vague at the best. For normal rwd cars some will say 12% + 10bhp, others 15%. Yet there are loads of theories......
4x4's, well some claims 25%, others nearer 18%. Nissan will have you believe their GT-R is nearer only 6% drivetrain loss, which frankly is pure science fiction.
-Graph smoothing, to little graph smoothing will usually show false PEAKs giving artificial PEAK numbers.
-Operator error, either by accident or design. This occurs on both the correction factors and drivetrain loss. Most dyno's allow the operator to input the values for these manually, so they easily have the ability to manipulate the figures.
So I'm more than happy to see a dyno plot, in fact the plot and under the curve performance is far more interesting to me than out right PEAK figures.
I suppose what would be ideal is to have a base line 'before' whp plot, then on the same dyno an 'after' whp plot. That way it'd show the actual gains made over stock.
And bearing in mind many 4.6's don't make 225hp stock anyhow. (think LR faced legal action in the States over it).
