Understandable, but what happens when more magazines run dyno tests and get the same results? Moreso, when other international magazines are starting to accept their tests as "proof" (points to Top Gear)?
It by no means makes it the final word, but when they've tested two different cars at different times of the year and get the same 500+ BHP rating, that tends to say that something is up. There isn't anything wrong with putting more power in the car, but it'd be nice to have Nissan be honest with us.
C&D has tested two of five cars to make 420 whp on the Mustang. Others have tested 400 flat on the Mustang... others have tested 415-420. Some even claim 500 whp from the Mustang with a GT-R. The only way to "prove" anything is to put a stock GT-R on the same dyno as a stock Porsche GT2 and show that it makes as much power at the wheels... or up against another Turbo and show more power, this time.
Of course, I've discussed dynos in-depth... and this quote from another forum is another suport for my argument on the futility of bench racing:
http://www.nagtroc.org/forums/index.php?showtopic=24253&st=0&p=347825&#entry347825
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Twice now C&D have alluded to using "corrections" for their results but they
have made more than a concerted effort to hide their methods and the raw uncorrected figures
they obtaned.
Edmunds have also dyno tested a GT-R and produced a great write up about why the GT-R's dyno results
should NOT be corrected. The GT-R runs an absolute pressure controlled iterative system. For every RPM, Throttle
Position, etc. the ECU has a setpoint manifold absolute pressure. The boost is continuously adjusted up or down
to achieve the setpoint manifold pressure, which is fed back to the ECU via a manifold pressure sensor or similar device.
Since the system is governed by the absolute pressure, by default it automatically corrects for air density and air temperature
up to minimum air density/maximum air temperature combination. It is entirely unlikely that anyone will drive
a GT-R in conditions that overstep those maximum/minimum values.
This also means that comparing boost pressure is a pointless excercise as the boost is continually varied to
account for the ambient conditions. In this car the boost is just a means to an end (the required manifold pressure).
From edmunds,
SAE J1349, Section 5.5:
"... boosted engines with absolute pressure controls shall not be corrected for ambient barometric pressure."
And yet every GT-R dyno I've seen from other sources, so far, applies SAE correction.
I don't believe in SAE corrections. At all. I've seen gains of 10% or higher from SAE. I'll say it again... SAE corrections are pointless on a turbocharged engine.
The interesting argument at the moment is what the actual drivetrain loss is. Nissan claims a low drivetrain loss. In fact... 10%.
Given the
raw numbers in the test... 430 whp... correct by 10%... what do you get? 470 bhp. We should actually be carping about how Nissan is
over-rating the engine...
I don't know how people don't get how automotive technology moves over time... Let me reiterate:
drivetrain losses are an estimate. It's
not a law. That's why Honda Civics and Toyota Corollas regularly dyno higher than other cars with the same absolute horsepower... low losses. Many new cars, even with automatics, which traditionally have a 25% drivetrain loss compared to about 15-20% for manuals, actually dyno in the same region as manuals... lower drivetrain losses due to friction. It's my bane... automatics with the same bhp as my manual car dyno at the same whp because my drivetrain is an oily, rotating piece of prehistory.
Drivetrain losses are not a sliding scale, either... the extra weight of 20" wheels and extra driveshafts will
not affect a Mustang Dyno. A load dyno will only be affected by drivetrain friction and wheel traction... too little traction will cause high readings as the tires slip creates more torque against the brake... which is why a Dynapack is a great measure of absolute no-BS power... except Dynapacks are calibrated very high compared to Mustangs, so the "traditional" 15-20% calculations don't apply there, either.
But the problem with load-dynos like the Mustang is inaccuracy (Again... 500 whp?) due to the aforementioned tire slip. Dynojets seemingly give the most consistent numbers... but you can't apply the 15-20% loss calculations there, either... because they read high, too... and there's a big question amongst tuners as to the accuracy (repeatability =/= accuracy) of the Dynojet... since
changing tires or even
changing a flywheel will affect your horsepower reading on the Jet.
Changing a flywheel doesn't make horsepower. It makes for less inertia, which is why a lightweight flywheel allows for faster 0-60 times, but it won't increase your top speed, which is reliant on absolute power.
In the end, C&D's tests show that there's some differences between GT-Rs in terms of track times (but given their reliance on weather-correction for track performance may throw these numbers off)... and that there are performance differences between ECU builds... but nothing more.
That would be the one thing to really do, get a couple of customer's cars (i.e. not manufacturer provided for testing) and test them back to back, because then the dyno's actual reading wouldn't make much difference, you'd see the difference between them back to back.
...It would have been nice if it were an independent test... which time you believe will likely come down to which manufacturer you actually trust more. Wait... we're supposed to trust manufacturer information? 
