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      11-20-2012, 03:26 PM   #19
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NoTempoLimitN54's Avatar

Drives: E92 335i
Join Date: Sep 2012
Location: Los Angeles, CA

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Originally Posted by AndyR83 View Post
Ive read that AT holds boost through shifts while MT does not, potentially giving a performance advantage.
I debunked this myth in another thread. The DME pulls ignition timing during manual transmission upshifts to avoid cutting boost:


The potential of software functions to optimize the response of the car can be shown with the following example: After a gear shift with a manual transmission the boost pressure is normally low. In order to realize a high torque as soon as possible after the gear shift it is necessary to increase the boost pressure quickly. The decrease in boost pressure however is caused by the driver, who has not torque demand during a gear shift. So a software function has been developed which is not closing the throttle valve during a short gear shift but decreases the torque of the engine by shifting the ignition time. So the mass flow through the turbine is still high even if the driver is changing the gear. This leads to a much better torque right after the gear shift, because the turbines are only loosing a small part of their energy. The effect of this software function is shown in fig. 9.

SAE Technical Paper Series 2007-01-1560
BMW High Precision Fuel Injection Conjunction with Twin-Turbo Technology: a Combination for Maximum Dynamic and High Fuel Efficiency
Cristoph Luttermann and Werner Mährle
BMW Group
The original text must have been translated from German, which is why the grammar is poor.

For Sale: 2009 335i 6MT (E92/N54), Sport / M-Technic / no iDrive / Black Sapphire / Black Dakota Leather, ZCW, 6FL, PDC, 19" VMR VB3, Pilot Super Sport, M3 control arms + tension links (fr) S. California