Quickly Clarified - Single Scroll vs Twin Scroll Turbos | Pros & Cons

In my previous video about Equal length headers vs unequal length headers, I briefly mentioned how equal length headers allow for a twin scroll turbo setup to be implemented. However, what actually is a twin scroll turbo? In this video, we’ll be going over what that is and what are the advantages and disadvantages of such a setup.

Sections:
0:00 - 0:27 Intro
0:27 - 0:39 Sub
0:39 - 0:58 How Turbos Work
0:58 - 1:55 Single Scroll Turbos
1:55 - 3:11 Twin Scroll Turbos
3:11 - 4:03 Pros and Cons Comparison
4:03 - 4:49 DSPORT Experiment
4:49 - 5:30 Outro

Songs:
Kazem John - Cha

Kazem John - Bounce

Alainite - Explore This (prod. WISHBOI)

[muntee]

The collector is actually like a reserve bank of energy so the turbine wheel is not accelerated in a pulsing manner which means between each pulse the turbine decelerates and looses energy, the next pulse then has to re-accelerate the turbine to the prior velocity before it can accelerate it further, again wasting energy.
The idea is the same as aero ducts for cooling. As the volume of the area increases at the collector the velocity of the gas decreases but the pressure increases. This helps buffer the pulse feed into the outer, lateral section of the turbine wheel, loading it evenly with a higher pressure gas. As the gas transitions to the axial flow section of the turbine wheel, the gas is squeezed into a smaller volume which accelerates it's velocity. As the gas reaches the opening in the housing the design of the dump pipe along with the cooling gasses 'contracting' attributes, causes the accelerating outflow of gas to draw the gas behind it along with it.
That's where the correct header pipe diameter and resonator profile and placement come in, the reverberating LOW pressure wave that travels from the resonator cavity back towards the turbine should ideally reach the dump pipe / turbine immediately before the next high pressure sound wave from exhaust pulse.

That's why it's critical to place any crossovers/bridges correctly and to choose the correct diameter exhaust. *Not just for performance at maximum output, but for maximum performance where the engine needs it most.... Where it most suffers from lag where you intend to use the engine the most, with a small, compromising consideration for maximum performance. 😉
A machine is a chain of links that all must lift be able to lift the weight, so the machine is only as able as it's weakest link allow it to be. If you approach fluid dynamics and thermodynamics with this perspective, instead of simply taking at it with a bigger sized hammer (10L displacement, Nos, engine that can only function at high boost & full throttle to badly create the same performance/torque as a lesser, more harmonized/civilised engine is able too with much less parasitic losses to friction, heat, sound and vibration. (And thermo/fluid dynamic deficiencies.)

[RisitasKEKW]

my 2019 JCW Mini Cooper has a twin power turbo, or 'twin scroll turbo' - i had no idea what that meant until i watched your video. Very informative. Thank you!

[kenxiong]

Very detailed and straight to the point! Thanks

[jazzingpanda]

Late to the party, but a great video ty.

Me and my mate were trying to get our head around the power differences between a BMW 218d and 220d. Both N47 (don’t laugh) 1995cc in-line 4s.

It was only after this video we understood the Turbo common rail vs BMW “TwinPower” / variable geometry turbo.

That explains the ~40bhp difference between the two. Thank you!

[kentuckyblugrass]

I felt like I was traveling with a band of gypsy's during this video.

[jamiewilliams]

Very educational very right to the point the only issue I have is that you can't leave out Saab Saab was the leader in putting turbos into everything they have a twin scroll system that one side is bigger than the other that way at low RPM you have low and boost and at top RPM you have top-end boost its supposed to give you both and have a little bit of lag it actually is a very good

[farashgar]

I own a mark V supra and trying to educate myself. This video is amazing. Thank you. So in 911 turbo they use twin turbo setup and both of them are twin-scroll?

[zokusharuuku]

Twin scrolls spool up faster in theory but with certain cars/scenarios they don’t and can reduce the maximum amount of power you will make throughout the power band. I’ve always wanted one until I did my research and saw actual race cars that used multiple different types of twin and single scroll turbos and they found that the single scroll made more power and spooled up quicker in their situation.

[kingiggy]

It's funny, I just tuned my 2019 wrx and put a new intake, catback, ebcs, bpv and aos. For the first time since putting all the parts on and getting a proper tune done, I went wot and wondered why I didn't feel boost past 5k rpms in sport sharp and this makes complete sense. (Forgive my noobness in not understanding the difference between the two.) Also makes so much more sense as to why the wrx and sti have two different type of header setups. Thanks for the video!

[ДФҜя]

very informative and awesome editing video. Thank You

[Master_Psyper]

The graph alone should tell you that the data and cons you’re providing are not correct. I don’t see that red line going above twin scroll at all throughout that graph so the loss of power up top is not shown. Additionally the twin scroll prevents a cylinders exhaust gas being forced into an opposing open valve to an unfired cylinder. Twin scroll is definitely the way to go but with v band becoming increasingly popular for fitment and seal and reliability, it’s worthless and not practical with twin scroll ( the original reason I clicked the video) . The twin scroll splits the banks so there are no opposing forces through the exhaust cycle thus becoming more efficient draining not only lower end boost response but nearly identical if not better, top end performance.

[syntropy]

Its not because the pulses colide, its because the pusles overlap with when other cylinder exhaust values open thus reducing volumetric efficency, hence the single scroll takes longer to spool due to the engine having lower volumetric efficiency.

[Watchreviewblog]

Nice explanation, also both the Mini Cooper F56 1.5t and 2.0 use twin scroll.

[peanutheadrules]

The USDM Subaru STi is a single scroll, the JDM Subaru STi is a twin scroll with ELH from the factories

[komoru]

Good info, BUT that background music was distracting!

[NocturnalDistortion]

Don't always have room for a twin-scroll unfortunately, especially when working with larger displacement engines.

[livelifeoutdoors]

Awesome video mate. Is there anyway I can get the Subaru rumble noise on a equal length header/twin scroll turbo? I have JDM 2008 STi GRB hatch with EJ207 engine. ..

[ilvtofo]

Subscribed 👍🏼 love these informative videos

[streetangel]

The 09 jdm Subaru STI comes twin scroll as Vf49.

[Oven_Steaks]

My guy. You need to turn down the music when you talk. But this is very educational.