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      12-14-2013, 02:19 PM   #81
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Drives: 2015 M3 6MT
Join Date: May 2013
Location: Seattle

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Originally Posted by Boss330 View Post
I take it you are not familiar with the turbo scene?

Modern European turbo engines are high CR, like the 991 Turbo S engine. Plenty of tuning. It's not like my old Sierra RS Cosworth with a 8:1 CR...

What specs of the S63 is of relevance in your comparison with the S55?
Which part of the N55/N54 is not relevant to the S55 since you don't think it's a good comparison of a high CR tuneable engine?

One of your previous observations was that the N55 is a low boost engine and that the S55 is high boost. But remember that the N55 is 300hp and the S55 is 430hp. For the N55/54 to go to 430hp the boost needs to be as high, or higher, as exemplified by the 20psi Switzer tune. That the N54 can achieve 600hp indicates a even higher boost level. Not sure if a 600hp N54 is possible on street gas.
Familiar or not you have physical laws and limitations. The details can be complex but the basics are relatively easy. At a certain pressure fuel of a specific octane rating self combust. 220 psi is about the highest I've seen and that is regarded quite extreme. The GT2RS as we discussed runs at 207. It's CR was lowered in relation to other Porsche TT cars to allow for the 23psi boost since boost is apparently milder than CR in the equation due to the cooling of the boosted air through inter coolers' don't ask me the details. I haven't studied them.

CR without boost is of no use. You can't say that just because one high CR car can be easily tuned all can. You got to look at the combination CR x Boost psi.

Show me a car/tune that continue to gain hp when exceeding +220 CR x psi on street gas and you'll change my view. The S55 is stock at 10.2 x 18 = 183.

The S63TU has CR of 10 and 22psi putting it right at 220. This is why I'm so interrested in that 700hp tune. Did they increase peak boost or allowed for peak boost at higher rpm? Both would gain hp but the peak boost would be highly unusual as gaining that level of hp consistently and relaibly on street gas past 220 psi.

Last edited by solstice; 12-14-2013 at 02:31 PM..