[D CHOI]

If I'm in 1st or 2nd gear driving moderately and decide to floor it I hear a turbo spooling and then quickly stops and resumes and car then starts pulling harder. (all happening maybe around 3-5 rpm) This is felt more in comfort and less in sport. I also lose traction sometimes which explains why it may stop spooling but sometimes I don't and it still has that double spool stop and go or is it that how the twin scroll turbo works?

[mjsaville]

Nope...

[J.M]

That's just the traction control system intervening, and it does intervene more in confort and sport than in sport+.

[D CHOI]

Originally Posted by J.M

That's just the traction control system intervening, and it does intervene more in confort and sport than in sport+.

I'm thinking that too but I guess sometimes the DSC light doesn't flash and only flashes if it's a more serious intervention. I find the best way to avoid this is to gradually step on the throttle so it becomes more smooth with power delivery. Especially holding the rpm around 4-5k RPM in 2nd gear and then flooring it got me like

[Aronis]

Originally Posted by D CHOI

is it that how the twin scroll turbo works?

Twin scroll turbo refers to the input path to the turbine side of the turbo. With older turbo designs the exhaust gases from each piston simply joined together in the exhaust manifold and moved onto the turbine on the turbo. This has issues with the pulsatile nature of the exhaust output and is less efficient.

The twin scroll separates the exhaust path of each piston so that 1/2 goes to one path and the other half to the other. The two paths then hit the turbine at two separate surfaces on the same turbine, just side by side. This smooths out the flow of hot gases to the turbine and makes the spinning of the compressor side more constant and smooth. It also removes some of the pulsatile nature of the exhaust flow.

The M3/4 have two turbos so the exhaust gases from each of the 6 cylinders are split between each turbo but again with two separate paths to the turbine.

I think I read somewhere that there are also some turbos that have variable angle turbine fins.

Also other turbo designs use two different sized turbos in parallel to take advantage of the different characteristics of exhaust gas flow at various engine RPMs.

Mike

[DKX4///M]

I get the same thing like the boost builds too quickly and the dv, releases the boost and it has to build back up...it's a pita . ..I'd like to get to the bottom of it too...

[D CHOI]

BTW it doesn't help that my car came with them stankin contis...