Dyno results: reliable or BS?

Gardus350z

Hi guys, I'm new here...I'd like to know what's the general view around here about dyno testing.

I'd also like to share my experience as I've seen a lot of dyno runs...

First of all, I think all dyno testing on an inertial dyno are pretty much useless.
I've see a lot of charts on this forum, and usually there are no data about the weather condition, or the power loss, engine data acquired from the OBD port etc.
They could probably be used only to measure the difference between different configurations on the same car, but at the same time, even correcting the values with the EWG correction factor (the DIN is obsolete), this doesn't take into consideration the variation in tyre pressure and temperature, the trasmission absorption that can vary with the oil temperature.

For what I know, the only dyno reliable in absolute terms are the brake dyno that measures the power loss every run, and use all the data available (air intake T, ambient T, ambient P, humidity) to correct these values, and when you compare the charts you need to know everything about the conditions of the run!

I'm going to post the charts of my friend's 370Z on a MAHA dyno as soon as I can, both standard and with the catback.

For the 350z 313 hp i think these are a good example:
stock

full exhaust (headers, HJS cats, catback)

VS


There's so much more information than the usual chart with just power and torque compared!
For the non-german speaking:
Norm-leistung: Crank HP corrected
Motorleistung: Crank HP non corrected (just WHP+Power loss)
Radlesitung: WHP
Schleppleistung: power loss
Zundung is ignition timing or spark advance
T ansaugluft: intake air temperature
V Luftmenge: air mass flow
Dampfdruck: relative pressure
Others are self-explaining.