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A 600 hp Cobra is not a 600 hp Cobra, is not a 600 hp Cobra...

The major MFRs (including Porsche) measure flywheel hp waaaaaayy different then the engine builders we've known and grown to love do. Our guys "optimize" everthing possible, great flowing headers/exhaust, pretty much zilch on parasitic losses and other misc HP producing tweaking. It's all about the bragging rights... and sales. Athough their measurement is "corrected", it's not corrected to the extent that the major automotive manufacturers do. GM started it all off by complying with the new SAE J1349 rating system. Under the new, more stringent system rated HP has dropped a significant amount. I believe Porsche has switched over to a similar, if not the same rating system.

Case in point ... When my C6 Z06 was bone stock it put down 450 rwhp, SAE corrected. (pretty much the average rwhp for similar Z06s) At 505 MFR rated hp that equates to a 11% parasitic loss. That seems to be repeatable by the majority. It would appear that most Cobras suffer a 20% to 30% parasitic loss, with a few on either side of the percentages. In a lot of cases your "600 hp" Cobra will put down around 450 rwhp, with an average set of decent flowing headers/sidepipes.

So, along with better suspension, stickier tires, 4wd, electronic HP enabling nannies add an accurately rated hp engine to the mix. It's no wonder the Porsche has better stats.