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      12-14-2013, 04:32 PM   #92
Boss330
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Quote:
Originally Posted by solstice View Post
What is the psi with those tunes?
I suspect that gains are mainly made by less tapering and not by pushing peak bost. The question is, can the S55 stock turbos support less tapering?
A pure guess from me is, not much. Reasons being that minimum lag and high rpms are both M trademarks leading me to think that BMW selected small turbos and utilized most of their ability to pump air at high rpms already.

I do think they have left enough room for about a 5% or ~25hp power bump with the comp. pack. utilizing mainly peak boost ~4psi but this is just speculation.
Minimum lag is taken care of via the "anti-lag" system explained in a different thread that keeps the turbos spinning at 100.000rpm even when coasting (when in "M-modes"). So, not that critical to have small turbos. But just as you, I don't know any details of the turbos so they could be on the small side and not have a lot of room for more Power. But I find it unlikely that BMW has chosen turbos that operate at 95% of full capacity...

Let's take a different example:

Audi RS6 with the 4.0 V8 TFSI engine.
It has a 10.1:1 CR and max boost of 1.2 bar

Quote:
An unthrottled intake system supplies the four-liter V8, which has a specific engine management system, with air; the Audi FSI direct injection metres the fuel. Switchable flaps in the intake ports mix the incoming air in a cylindrical motion to enhance charging and combustion. The directly injected and intensively swirled fuel cools the combustion chambers. This method enables the high compression ratio of 10.1:1.
Two turbochargers generate up to 1.2 bar of relative boost pressure.
http://www.ausmotive.com/downloads/A...t-July2013.pdf

MTM has developed several stages of tuning with the highest output being the 722hp version. Similar output to the Manhart and G-Power versions of the F10 M5.

http://www.mtm-online.de/en/Audi/RS6...FZID=RS6C7412q

I find it unlikely that BMW has left so little safety margins in the S55, when the S63 hasn't and other manufacturers also have high CR engines that can achieve a 25% boost in power. You really don want a turbo setup that runs at 100% in Competition Pack mode. That would very likely not be up to BMW quality standards and needed longevity of components (warranties etc).

If, BMW has built in so small margins, then I suspect that will allmost be a world first...
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