View Single Post
      01-24-2010, 02:35 PM   #9
cstavaru
Brigadier General
 
cstavaru's Avatar
 
Drives: 2009 335i M Sport Sedan 6MT
Join Date: Aug 2008
Location: Bucharest, Romania

Posts: 3,235
iTrader: (0)

Quote:
Originally Posted by stressdoc View Post
Twin scroll is another way of getting boost at low rpm/pressure -- a small impeller with little inertia, and then a big one for serious boost (like the turbo in the diesel).
Sorry but this is not true. Twin-scroll just means that exhaust gases (from the six cylinders in this case) are split in two separate streams of flow (one flow from each 3-cylinder bank) which enter the turbine separately and spin the same impeller which has two sets of fins, one for each flow. The advantage is the higher pressure in each flow and the alternating exhaust pulses in each flow path (after a cilinder fires the exhaused gas from that cylinder creates and exhaust "pulse") which create the high turbine RPM faster than a single flow.
cstavaru is offline  
0
Reply With Quote