Twin Scroll Turbos - GT-R Register - Official Nissan Skyline and GTR Owners Club forum

Jez · 1st May 2003, 02:07 PM

I have been reading the reviews on the new Impreza 'Type C' and it appears to be using a twin scroll turbo setup.
This is also used on the MR2 Turbo according to other forums I have looked at.

Does anyone have a good (fairly basic) explanation on the differences between these and a traditional turbo set up and why they produce a lot less lag ?
Mycroft has been quiet for a while, this looks like the sort of thing he would know

Are there any twin scroll setups available for aftermarket tuning ?

Jez

hipogtr · 1st May 2003, 02:38 PM

Here's my shot at a basic summary...

A twin scroll turbo uses a turbine wheel that has two varying scrolls instead of one (ie. picture two turbine wheels joined together in a slight offset and resized to fit into a split entry turbine housing). The twin scroll turbo utilizes the staggered (read odd) exhaust energy pulses from the engine more efficiently by removing interference. That is, each pair of exhaust pulses are sent down a separate path and hit their own individual part of the twin turbine scroll unimpeded. This makes for a more efficient conversion of the exhaust pulse energy into rotational force. Ultimately, you can get quicker spool up, earlier torque production, etc. (ceteris paribus) than what is achieved with a single scroll (and single entry) turbo.

Cya O!

Mycroft · 1st May 2003, 03:05 PM

Not much to add really, hipo has covered most of what you need to know...

Some details to fill in...

They have real value in 4 cylinder where the distances and pulses that strike the blades can be rather congested so twin entries mean you can combine the pulses from C1 and C4 to one side if the scroll and C2 and C3 to the other... by doing this you can minimise the detrimental effect of having pulses arrive at 180 degree intervals ± the pipe length effect... pipe length becomes increasingly important as the revs rise and the comngestion occurs....

1st May 2003, 02:07 PM	#1 (permalink)
Jez GTR Register Member Join Date: Oct 2001 Location: South Coast Posts: 338	Twin Scroll Turbos I have been reading the reviews on the new Impreza 'Type C' and it appears to be using a twin scroll turbo setup. This is also used on the MR2 Turbo according to other forums I have looked at. Does anyone have a good (fairly basic) explanation on the differences between these and a traditional turbo set up and why they produce a lot less lag ? Mycroft has been quiet for a while, this looks like the sort of thing he would know Are there any twin scroll setups available for aftermarket tuning ? Jez

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1st May 2003, 02:38 PM	#2 (permalink)
hipogtr GTROC Member Join Date: Feb 2002 Location: Land of the Rising Sun Posts: 1,985	Here's my shot at a basic summary... A twin scroll turbo uses a turbine wheel that has two varying scrolls instead of one (ie. picture two turbine wheels joined together in a slight offset and resized to fit into a split entry turbine housing). The twin scroll turbo utilizes the staggered (read odd) exhaust energy pulses from the engine more efficiently by removing interference. That is, each pair of exhaust pulses are sent down a separate path and hit their own individual part of the twin turbine scroll unimpeded. This makes for a more efficient conversion of the exhaust pulse energy into rotational force. Ultimately, you can get quicker spool up, earlier torque production, etc. (ceteris paribus) than what is achieved with a single scroll (and single entry) turbo. Cya O!

1st May 2003, 03:05 PM	#3 (permalink)
Mycroft Banned Join Date: Apr 2002 Location: Up someones nose, apparently Posts: 3,561	Not much to add really, hipo has covered most of what you need to know... Some details to fill in... They have real value in 4 cylinder where the distances and pulses that strike the blades can be rather congested so twin entries mean you can combine the pulses from C1 and C4 to one side if the scroll and C2 and C3 to the other... by doing this you can minimise the detrimental effect of having pulses arrive at 180 degree intervals ± the pipe length effect... pipe length becomes increasingly important as the revs rise and the comngestion occurs....