Variable Twin Scroll Turbocharger - The Future Of Gasoline Turbos?

Variable Geometry Turbochargers and Twin Scroll Turbochargers each have their own unique advantages, but what if you could combine the technology together? Borgwarner has developed a turbocharger concept where a twin scroll turbocharger has a valve which can redirect exhaust airflow into just a single scroll, or vary the amount the valve opens and allow for the gases to completely split between the two scrolls.
The disadvantage of variable geometry turbochargers is that they are too expensive for gasoline applications because the materials have to be strong enough to withstand the high exhaust temperatures resulting from gasoline combustion. Diesel applications tend to have lower exhaust temperatures so the technology is far more common with diesel engines. By implementing a valve with the twin scroll turbo, it can act very similarly without worrying about exotic materials to make it work in gasoline engines.
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Twin Turbo Diesel - • How Turbo Diesels Work...
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[@diltzm]

I remember seeing something similar as a stand alone piece between the exhaust manifold and turbo inlet. It was called a qsv for quick spool valve. You can add it to any t4 twin scroll application and get the same effect. It's cool to see someone finally integrate the idea into the housing itself.

[@oliverscorsim]

See thats what im talking about lol but not the same iv been cutting twin scoll housings for years for a reason. Qsv you have a collector behind the qsv this and what iv been doing and i didnt come up with it keeps those two wave systems if you will separate all theway through. Means better top end if things are done right.

[@tomfanshawe6947]

Great video. Your videos are extremely good, very informative, been watching them for a while now and very impressed. Keep it up!

[@EngineeringExplained]

+Tom Fanshawe Thanks, happy to hear it!

[@aijii]

agreed. Now if only you could answer my question, which is where the hell do I throw my money to buy one of these ?

[@nicenow25]

+aijii twinscroll has been able to allow manufacturers to have smaller more compact engines. if they don't utilise this best of both ideas the vgt and twinscroll then how are they allowing the twinscroll to develop

[@mikeguitar9769]

+Engineering Explained I agree this could be significant for turbo design. You've done an amazing job explaining this. So Borg Warner showed this at SEMA but apparently there's nothing else on youtube about it?

[@markcray5164]

I've only just seen EEs videos, really good info, well explained too.

[@toma3397]

That's really smart.

[@Valtra103]

+Toma Turcu I wonder how inline 6 like 2jz or rb26 would perform with huge twin scroll. 1000hp with good low end on best sounding engine... Real dream for me :D

[@toma3397]

Valtra103 it would be amazing getting best of both worlds low end and high boost at the higher rpms

[@Crazylalalalala]

+Toma Turcu while watching the variable turbo video I was wandering why they don't just do this instead. I guess they do..

[@211crod]

+Valtra103 most of the guys with 2jz motors that have big turbos use an item from sound performance called a quick spool valve. it is similar to what this video showed just not built in the turbo.

[@Valtra103]

211crod I wonder if this is more effective than valve?

[@ValExperimenter]

I thought of doing this with a dual entry turbo in the 80's, they were called dual entry rather than twin scroll back then. From memory I sent all the exhaust to the rear scroll (one nearest the bearing) at low boost pressure and used an actuator to swing the vane just like in this one except the vane was in a rectangle section duct immediately upstream of the exhaust flange because it was designed to use a standard turbo . Variable geometry turbos were research only items and most turbos installations at the time used carburetors. Good to know the idea was sound.

[@munmunyee]

Would love to see you do a video on Koenigsegg's twin VGTs

[@arjuhama]

This turbo system's not going to die out now that you've explained its usefulness.

[@flakey7832]

i thought about this like a week ago and this pops up in my recommended... damn it, i actually believed i came up with something once in my life

[@danielpowers4787]

this is genius. I'd love to see it applied and tested

[@supramaniac502]

This has been done before, just not as an integrated part of the turbo housing....its called a quick spool valve, and it is an extra part that sits between the manifold and the turbo. Sound Performance Engineering is known for making quality versions of these, though I bet you could find others if you did some digging. Only thing about this that is different is the integral packaging....

[@meetthecarolinas9638]

This “technology” is nothing new. As mentioned, aftermarket Quik Spool valves have been around for a while. But even more impressive, Mazda did this in the 80’s on the FC RX7’s. The valve was located in the exhaust manifold.

[@LightningSe7en]

HELLO FROM THE FUTURE

[@raptor31able]

Beans Diesel bd diverter valve.

[@chippyjohn1]

@@supramaniac502 Their quick spool valve blocks one port on a twin scroll, it doesnt actually utilise twin scroll manifolds. Its a poor design.

[@MakingCentsInTrucking]

Thank you for explaining. International used this technology on its 12.4 liter maxxforce diesel engine. It makes the engine very responsive and eliminates turbo lag. They are now switching to vgt for some reason and are claiming to have better results.

[@UncleDoug]

Very well explained. Thanks !!

[@kenGPT]

Got curious on twin scroll turbos and used KZbin search. No better person to explain this than him. Thank you!

[@TheBlissPhuket]

my car has 5 cyl, so...gotta stick with single scroll

[@Delibro]

I own a car with that Twin Scroll Turbocharger since five years, a Peugeot 308 GTi 200 THP. So, even in cheaper cars this is available at least since 2010. I love the evenly spread power along the rev range from 1900-6000 rpm. And it is quite quick in response time. Its really fun to drive especially on a day to day use. For durability reasons, the car is now 9 years old and I had no issues with the turbo, but cylinder valves, oil leak and gasoline pump.

[@XxChuyoxX]

Hey Jason! Have you ever thought about reviewing older vehicles? (Mainly performance oriented cars) I know it wouldn't benefit you as much as reviewing newer cars, but it would be interesting.

[@EngineeringExplained]

+XxChuyoxX Comes down to two things really. First is risk; by driving manufacturers cars I've already handled all of the insurance side of things. If I get into an accident, the outcome is clear. If this were to happen with a viewers car, it puts me in a bad situation. Second is time, I'd have to spend time reaching out and organizing times and locations to get into these vehicles, which currently is all a very streamlined process with the manufacturers. As I do all of this solo, I have to make sure I'm efficient with my time.

[@XxChuyoxX]

+Engineering Explained Completely understandable. I figured there were reasons why haven't done it. Thanks for the response

[@buckethead560]

+XxChuyoxX check out the channel "regular car reviews." They kind of do that: except he tends to be part informational, part comedy, and part weirdness. Worth a look.

[@Scouter98]

+Evan Cotton most of his "reviews" are shit. Some are bang on though.

[@grahamthompson4999]

+Joe Barbaro The reviews done by Regular Car Reviews are not made to be spot on, their satire poking fun at the car and the people who drive the cars in some cases. If you take the reviews that they do seriously there is no fun in them but if you view them as they are intended to be viewed you'll have a good time.

[@chippyjohn1]

I thought of this 4 years ago, its a pretty simple concept!

[@EJL2004]

Thanks again Engineering Explained, I love your channel! I'm curious to know what you do as a career besides your fantastic KZbin presentations. You could be a professor as far as I'm concerned as you're clearly passionate about educating and the science and engineering behind all of these mechanical pieces that make us love our rides. Keep up the fantastic work!

[@CarsnStuff]

Very interesting. Seems similar to SP engineering's "quick Spool Valve " Except with it you can run it on any twin scroll turbo charger. Its nice because if anyone runs a huge turbo the quick spool valve essentially blocks off one side of the scrolls so all the exhaust pressure is doubled through a smaller area resulting int much faster spool. Its sort of like if you take a hose and hold your thumb at the end and the pressure seems to rise. now imagine doing that to alittle fan blade with that higher pressure from blocking it off.

[@TheBeerBox80]

This makes a lot of sense, I see this as definitely the future of turbos for street cars. Thanks for posting.

[@amdisthebest]

Integrated quick spool valve! Borg Warner doing very neat things with these EFR turbos.

[@ericanker9049]

Very nice videoes mister. Just enough details, not to much repeating (which makes many youtubevideos boring), and correct pace for these short videoes. I know something about engines but by watchin these, small gaps here and there are beeing filled. Keep it up please! Greetings from Norway.

[@Hatredkopter666]

Such a simple solution to the air flow issue, surprised they didnt think of it earlier.

[@theotherdave2005]

I genuinely hope this takes off. Turbocharging small-displacement motors is clearly going to be the OEM strategy for hitting CAFE targets in the short term, so a simple setup that extends the powerband for reasonable money is fantastic IMO.

[@zensation4871]

I work on turbos for semis and the variable geometry ones always seem to fail. You should do a in depth explanation of an HX35v

[@peterwinson8476]

1998 I bought my first car with a variable turbo, a VW T4 with 150 hp. Was a great experience back in the day :)

[@johnnyboy2459]

Can you explain how to read a turbo Airflow chart/graph?

[@lamazver]

Its sad that borg Warner didn't offer this already

[@AbcdEfgh-sq2tf]

3 years late but Borg Warner was too late when they released that. If they did this 20 years prior, it would be considered almost revolutionary.

[@AbcdEfgh-sq2tf]

Also the twin scroll turbos by themselves significantly reduces turbo lag to a point where most manufacturers and customers felt satisfied. So adding a VGT vane just adds weight and cost to the whole package.

[@boarderboi7]

It's a great idea, the only problem is those with normal turbo set-ups would need a completely bespoke header set-up, which is also not cheap

[@cnjconsulting]

Variable geometry turbos have been used on diesel engines for 15years. This is actually a diverter valve set up. A true variable geometry set up has adjustable vanes in inlet housing for the turbine.

[@pec1739]

woah 5 years ago i already have this design, now they making it real :D

[@kcm732]

its basically the same-ish idea behind variable runner length intake manifolds. very cool, and I can totally see this catching on.

[@rhkips]

That is ingeniously simple! Low failure rate, cheap to manufacturer and implement, better performance, and the ability to control both economy and performance? Sounds like a winning combination to me! Here's hoping this hits the market soon! :D

[@Boostedlifestyle]

sound performance has been doing this with a "quick spool valve" for years already

[@sachideshmane5088]

This is called a quick spool valve. Mazda did it on the turbo rx7 in 1985.

[@lukerogers78]

Borgwarner, please put these into production. Hurry up and take my money.

[@galpinspeedshop2591]

This concept has been out in the diesel world for years in the aftermarket. BD diesel makes a diverter flange that does exactly what you are talking about. It goes between the manifold and turbine housing.

[@felixarbable]

it would be great to here a thing about koenigseggs free valve technology

[@uhrwerks]

Felix, I hope I'm proven wrong, but my gut says that "camless" system is going to either stay a prototype or possibly just end up on $2mil "Supercars." I like the idea, but it's complex & costly. You basically need a servo for each valve & a system to control it. Take airplanes, "fly by wire" is becoming the standard, but hydraulics are still involved for some things or at least back up.

[@theslimeylimey]

+uhrwerks As with just about all technology, with time the price will keep falling until it basically becomes a commodity. Just think how much it would have cost to make a mid range car of today in 1980 with its ABS, traction control, electronic differentials, air bags, seamless glass windows, bonded composites, LED lighting, engine ECU, Variable valve timing etc. The technology to make those things existed back then but manufacturing tech in the automotive field had not advanced to where it was economically feasible.

[@samr1321]

+felix pinto Koenigsegg's free valve technology? since when the "free valve" become Koenigsegg's technology? The first company to patent the technology was FIAT in 1999. The same tech has been in use since 1960s by renault, ford, bmw, fiat...etc Fiat have been using the same technology in their MultiAir engine that is used in Fiat Panda and Fiat 500. lmao Koenigsegg fanboys are so deluded!!

[@felixarbable]

Sam R iirc those you mentioned still have camshafts

[@samr1321]

felix pinto It doesn't have camshaft for the intake valves. The reason for that is because the system is extremely sensitive to high temperature. lol The system have been in use since 1960. Koenigsegg has had ZERO part in invention of the system. Also, the original electro-hydraluc valve (invented by Renault in 1960s) was for both intake and exhaust valves. Koenigsegg fanboys, get a clue!

[@schuttrostig5729]

The turbo also has an integrated bypass, which is another cost saving feature as it saves a lot of additional tubing and space.

[@Rexus5]

Another excellent video! Absolutely love learning the differences between turbos!

[@boostedbuiltgarage]

I definitely think this setup will start appearing on newer cars for sure

[@nestnortheastsustainablete9230]

That was very easily explained. Amazing job buddy. I was thinking it would take years for me to learn about twin turbo engines.

[@MrTRESTOON]

So this is similar to the Sound Performance Quick Spool Valve. It uses the same principle as this new turbo design, but is not as complicated/expensive as it requires a open scroll exhaust manifold and twin scroll turbine housing to operate.

[@turbotoaster1984]

+Florida Street Project I was just about to type the exact same thing as soon as I saw it, looks like they have seen them and thought they could integrate that into there turbine housings, ive been thinking of getting one myself to give my little 4 cylinder a wider power band as i run an open manifold

[@arthurjennings5202]

It seems the 2016 Buick Encore uses the twin scroll turbocharger on its 1.4 Liter engine. The engine acts like a larger displacement engine in that its low end torque is high, while still having some high end power. It also has two scrolls with a large vacuum/pressure actuator moving a vane in the exhaust passage. Thanks for the explanation of how it works.

[@DC-rn1fc]

Actually, if there is only ONE actuator, it certainly is a wastegate. These here require two actuators, as this system may very well get some of the advantage of a VGT, but won't allow to skip having a wastegate. Depending on the actual engine, some gasoline engines will even still need a wastegate when a VGT is applied, while Diesel ... nearly always VGT nowadays ... has been the standard for some 20 years now. But this still is great, as the low efficiency of a bypassed but still active turbine is pretty low ... imagine, all the gases see the same pressure upstream and downstream, but only what goes through the turbine will do any work ... in a peak power situation, you can very well have like 60, 70 % of exhaust gas going through a wastegate, maybe even more and not likely much below...

[@longfade]

I’ve watched dozens of your videos and I think I’m at about a 10% comprehension level. Next month I hope to be at 12%.

[@bradcomis1066]

This certainly seems like it would be something easy to adopt into new engine designs. The packaging requirements are pretty similar, just add the mechanism to drive the flap and program the engine computer to use it. An easy win. Hopefully it'll be rolled out soon. @engineering explained- It would be cool to hear your thoughts on the Achates engine, which will hopefully be making its way into productions cars this decade. It sounds like a real break through.

[@91ludesit]

6 years later and still no available variable twin scroll housings on the market.

[@michaelovitch]

greater rotating mass = lag those things will not be used,except on diesel engines. more air =more gas ,as i know ,the manufacturers are searching to reduce emissions and increase mpg,not the opposite.

[@MrAcat1988]

I've learned so much from all your videos! thanks love the channel and please upload more great content!

[@pito21211]

Something like this has already been done. Sound Performance has quick spool valve that has worked wonders for some of the supra guys.

[@Windforce7]

I have a question for you. Acura says: TLX Type S features a dual-scroll turbo V-6 engine that delivers 355-HP116 and 354 lb-ft116 of highly responsive torque. Do it mean it'll have a twin scroll turbo or variable twin scroll turbocharged engine?

[@Cjudd001]

I designed the same concept about 20 years ago on rhino cad. the difference with my concept was the valve directed gas to front the front scroll to get all flow across the whole turbine wheel. It never went further than cad.. dreams hey.

[@Cjudd001]

Same design... your drawing is wrong.

[@heikopanzlaff3789]

What is the difference of this new Borg Warner system and the 2-way-system I have in My RX 7 FC Turbo from 1988 made by Hitachi ?

[@smminco]

you have 2 turbos.

[@WholesaleTurbos]

Heiko Panzlaff nothing, they scrapped it in the s5 rx7 for a larger unit that had the same lag/responce

[@Olliebobalong]

Love you videos buddy. Regarding turbos, I can see the future, in lower powered passenger cars anyway, being electronically actuated turbo chargers, which use electric motors to spin the turbo up when there is no pressure, then when the RPM of the engine is at its peek, the exhaust pressure takes over as in a regular turbo. Used in F1 initially, they can even hook the turbo up to act as an electricity generator off throttle to feed electric back into the cars power systems, saving energy. Very clever stuff.

[@oliverscorsim]

Nsx has that

[@garyoaksify]

another great video well done mate your videos make so many things easy to understand keep up the good work

[@wazza33racer]

the experience on heavy truck engines is that VGT turbo designs seize up. However, with a simple flapper mechanism maybe that idea would be more successful.

[@LuckierVini1]

The concept has been around for a while, Sound Performance sell their quick spool valve that does the same thing

[@brett6459]

Great Video, made it very simple to understand. Enjoy watching the videos. keep it up!

[@HanksDeuce]

[Rant On] Homework for your next assignment. Write 1000 times on a chalkboard the following, "RPMs is not a word." RPM = Revolutions Per Minute. RPMs doesn't make sense. Revolutions Per Minutes? Go back in your video and anytime you stated RPMS you could replace it with Revs. Sorry for the rant, but it's like nails on a chalkboard to this engineer each time you say it. [Rant Off] I have no other issues with anything else you've ever done. Love the channel and what you are presenting. The whiteboard explanations are a nice touch. Us engineers need to explain things visually most of the time anyway. Kind of hard to explain pretty much anything engineering related without a whiteboard or a physical demonstration. This really is phenomenal turbocharger technology though. I wonder which manufacturer will be the first to put it into use on one of their vehicle lines? Ford? GM? Dodge? Or an import?

[@Incognitodemons]

So Mazda did something very similar in the rx7 turbo 2. It was a twinscroll turbo and one of the models was obvious as the runner sizes on the turbo where obviously different ar when you looked at them. But in their cast manifold they had a flap or door similar to what Borg Warner is doing now. All based off psi ofcourse.

[@lesnordman1387]

I really like this video: thanks for posting it! Question: in the video you said that variable turbochargers require "exotic materials like this" but you did not have those materials listed on the white board. Which materials are you referring to? Thanks! :-)

[@CJ-ty8sv]

Good Video but a tad bid misleading. The A/R Ratio of the two volutes (Scrolls) is the same. In the video is seems that its implied that the two volutes are of different A/R ratio's (or at least that what I gather based on many comments / questions being ask). Whats changing is the overall area as the 2nd volute starts to become in use. Think of it like a progressive 4 barrel carburetor, at idle and low throttle, you are only using 2 of the 4 barrels and then as you push further on the throttle, you start to progressively open the 2nd set of barrels. While the Geometry of the two volutes is slightly different, the "ratio" is the same (or extremely close two if not identical) and the flow potential of each individual volute is the same. If it wasn't, there would be an intentional flow potential difference between cyl's 1&4 and 2&3 once the diverter plate was fully open (i.e., both volutes in use at have the exhaust flow each) and that is not something that any engineer for Borg Warner would intentionally do Ironically though, this isn't really anything new. This idea has been used on both Gasoline and Diesel turbocharger setups for years. Just in the past, its been done in the manifold or as a sub plate between the turbo and the manifold. The Sub plate setup however was not identical as it did not keep opposing cylinders grouped properly and was more like a throttle plate in a single bore (like a throttle body)... Basically you used a "all into one" manifold / collector design but use a twin scroll turbine housing on the particular turbo. Then the sup plate (between the turbo and the manifold) had a butterfly valve in one of the volute entries which would block that volute from being used so all the exhaust had to though one volute. Then the valve would open and the exhaust gasses could pick which volute they went down . The same idea as shown in the video can (and has been) implemented into the manifold (in the collector), and thus you can have the same setup with ANY Twin Scroll turbine.

[@ThisClarkDude]

There needs to be some form of sensor on the flap that sends Information to the ecu to make tuning easier.

[@recpro7847]

Thank you for making that simple.

[@sammcevoy5338]

Great video as always it seems like a much more simple solution to other turbo designs in the past (I drive a subaru sequential twin-turbo) that has sooooo much more R&D/more to the system to be happy and still would not be as efficient as one of these turbos (correctly sized) and i could not see this costing that much more that it could not be made on a production basis awesome stuff!

[@scadieee]

Correct me if I'm wrong but doesn't a quick spool valve perform very similar to this ?

[@MrTRESTOON]

Yes, yes it does

[@ForestTDI]

+Scadieee Not "very similar". In QSV way, you have valce, which is in the way of exhaust gases but in this way, valve gets hidden and does not may any restrictions. Also, QSV pushes turbocharger a little bit longer from head so thermal and kinetic energy is a little bit lower. Also QSV is another "steel" which needs to be heated (consumes thermal energy). Everyone who uses thermal heatshield on turbine housing knows betefits of that. PS: I am sorry for my english I hope you understand

[@SeikuroS]

A quick spool valve can't have a divided exhaust. This one outputs specifically in a twinscroll when the valve is open, meaning each of the exhausts have a specific place they need to be. When it's closed, it acts as a divided exhaust.

[@ForestTDI]

This is perfect video and let me wrtie "Hats off" to producer. But, there is huge misleading failure on blackboard: drawing is presenting valve reducing flow into inner scroll (closer to centre of CHRA), also it is said wrong (time 1:21). But as everybody can see (time 2:23), in low RPM reduced scroll is that outer scroll. Reason is logical: inducer of turbine rotor has bigger diameter that exducer. So lever effect works for higher spool up.

[@ztech-consulting]

I've read that the future of turbos will be electric turbos. Basically an electric motor spins the turbo at low RPM where the exhaust gases are not enough, and once the engine can run the turbo at higher RPM's it basically shuts off the electric engine. Kind of like torque fill.

[@Teth47]

+Z Vaper The problem is that motor needs to put out a huge amount of power at ridiculous speed, so it's big and expensive, and power hungry, so you need a beefy electrical system, which is very expensive, not to mention the driver for the motor, and a battery capable of dumping massive amounts of power, that's gonna be a lithium ion, really expensive, the list goes on. It might be the future of turbos, but it's the distant future of turbos, and by then we'll probably just put a bigger motor under the hood instead of bothering with the gas

[@joaosoares3719]

+Teth47 Dude, read about Audi electric turbochargers and their 48v system; pretty much everything you said is wrong. The future of turbos is obviously electric torque filling, either in the form of mild-hybrids like those Audis or PHEVs. I have no idea why Jason doesn't cover these systems...

[@doctorzaius4084]

+João Soares Agreed 100% - boost + electric motors are a match made in heaven!!

[@Teth47]

João Soares An electric turbocharger is nothing more than a pointlessly inefficient supercharger, unless you use a much more complex system with a turbine attached to a generator to scavenge energy from exhaust gases, otherwise it's parasitic load, because second law of thermodynamics.

[@doctorzaius4084]

Teth47 If you were looking ONLY at peak output, then yes, you're right... but the benefit of an electrically driven turbocharger is primarily in reducing lag and/or recovering waste energy, as in the turbine-generator model you mentioned above. Is this more expensive and complex? Yes, but the future is already here... see Audi's new SQ7 TDI. Obviously they believe the losses incurred with a step-up to 48V are more than offset by the benefit of having peak torque available from 1,000rpm! More to the point, though... the pancake-style electric motors utilized in most parallel hybrid systems are the *perfect* match for boosted, high-revving engines. When you've got a secondary power source that can produce 100% torque from 0rpm, then lag and diminished power at low engine speeds are wholly much less of a concern. IMO, even on non-boosted engines, this is very clearly the future. Pound for pound, no internal combustion engine can match the thermal efficiency of its gas-electric or diesel-electric hybrid equivalent. In the near future, I believe we're going to see hybrid systems go from being a luxury or novelty item to being, essentially, the modern replacement for the torque converter. Engines will get much smaller as turbos and batteries grow.

[@JustforFun-cb7bo]

This is a very clever system, i think it's gonna have a say in the near future.

[@Aglai76]

*3 years later* So uh... where tf can I buy one?

[@ssllhh100]

@@Aglai76 they scrapped it in favor of their dual volture design

[@Aglai76]

@@ssllhh100 tl;dr me on that?

[@Al0011235813]

It’s not really a traditional VGT is it? It doesn’t have a linear actuator and the vanes don’t pivot. It’s more like an upgrade on a twin-scroll design. I doubt it performs as well as a VGT over a wide rpm band, but it should be cheaper and better suited to petrol engines with hot exhausts.

[@yfz450rider39]

Soo this is like having the benefits of a twin turbo setup with only one turbo? Neat!

[@ricardolourizela5961]

Great video, as usual! But why don't you ever talk about systems that eliminate turbo lag? You know, electric engines acting as torque fillers (mild-hybrid systems like the 48v Audi system, PHEVs), Volvo's Power Pulse technology, etc... Turbo lag is one of the most annoying consequences of this turbocharging mania and somehow you don't seem to ever address that point. Cheers.

[@joaosoares3719]

+Ricardo Lourizela They're not exactly easy to understand or to explain. Also, I think this guy secretly loves turbo lag and poor throttle response.

[@DirtDude117]

I would love to have one of these top mounted on my N54. Right now the options are either twin turbos that don't last or single turbos that don't make low or really high power

[@gusbisbal9803]

How they graduate this would be interesting. As the valve opens the airflow turbulence produced when the value is only partially opened (into the larger scroll ) would dramatically change as it fully opened. So a 10% opening would not produce 10% increase in pressure. But I guess that calibrating it according to turbine RPM would solve all of that. After all thats the only thing that really counts.

[@sasjadevries]

1:25 I'm wondering how much turbulence it will generate since there are some flat faces so that part of the exhaust pipe is not round at all, which is undesirable. Secondly just try to imagine how crazy the airflow will look like when looking at 1:25. One solution I would come up with is making something like an x-pipe where one leg of the x can be closed with a valve.

[@mateuszodrzywoek8658]

carbon fibre for the cold part of the turbo forged steel for the hot part of the turbo this way you can optimize it

[@LifesVoyager]

I tried this experimentally over 30 years ago. Shame I didn't pursue it. i was puzzled at the time that the turbo makers hadn't done it

[@jackbates5790]

At 2:55 you explain that the lever opens gradually until both scrolls are fully open. I understand why its closed in the first place so the smaller turbo gets all the exhaust gases at low rpm causing it to spool quicker and deliver more power on the lowerband then when you explained that the bigger turbos provide boost at higher rpms. My question is, why dont they close the smaller scroll off when at high rpms so the exhaust gasses from the 4 cylinders only feed the bigger turbo? Rather than supplying exhaust gasses to the smaller turbo at which point you are in the high rpms causing the smaller turbo to be redundant. So why is it still being fed exhaust gasses?

[@soraaoixxthebluesky]

typically it's a continuously variable type turbo. simple yet genius

[@joseolvera2060]

I've always had one in these in mind. And I'm definitely getting one once they improve in a couple of years

[@danekeeper1]

Jason .I have a diesel bmw wagon..twin turbo, one is excited at low rpm and the second at about 2100 rpm but the borg warner system in this car uses the ebp valve to throttle the small turbo at high rpm, so it is similar to their newer one except the throttling is done on the other side of the power band and on the other side of the exhaust stream...

[@DesuVR]

Theoretically, this sounds like the solution to end all solutions in a turbocharged car!

[@bmarcy86]

Love your videos. I would like to see this concept come to wide use in today's stock and aftermarket applications. A "simple" design to create max boost across a high rpm range? Yes please, it has 4 cylinder high revving engines written all over it.

[@vopall]

Great video. I'd love to see these become the norm

[@saigoneze4465]

another excellent short concise explanation for us layman car lovers .Can you do more vids regarding the 2015+ wrx and the engine it uses

[@JohnsonMac]

The current EFR 7670 IWG .92 A/R spools insanely fast already... 26psi by 3500RPM on a 13B rotary engine. This takes it a step further!

[@Adrianzx]

they have been doing this with larger turbo and call it a quick spool valve. Most sit sandwiched between the manifold and turbo but don't see to have to progressive opening the BW turbo dose.

[@atubebuff]

Great info. FYI, you might want to adjust the zoom or the hood on the lens to remove the vignetting on the left side corners.

[@Toastmaster_5000]

honestly I'm surprised something like this wasn't done years ago. I feel like such a design is kind of obvious to use.

[@peteyates]

It would be interesting to see the formation of the twin scroll. Are they totally separate or do they bleed together the exhausts. Do they need to be the same size or can it work with large and small. You still have the inertia of a large air flow section so would it not be better to operate with two separate turbochargers to really optimise the flows. And mention the new generation of electric turbos that are starting to be seen. This would seem to be the best of all worlds simplifying the whole engine by allowing the two flow paths to follow completely optimum routes rather than coming together at the turbo. Electric transmission can potentially run in the high 90 percents so the loss from the electric transmission will more than be made up by the improved mechanical efficiency. Pete

[@kaktotak8267]

So it's not actually a combination of VGT with twin scroll, it's a combination of sequential twin turbo with twin scroll in just one clever modification to the twin scroll.

[@Procharged32]

U need to revise this video again explaining the difference between the two turbos and the pulsating of the engine why the twin scrolz are beneficial.

[@peterkaraferis]

Basically, twin turbochargers are combined to one turbocharging unit. The only difference is that "lever" in the exhaust manifold which is adjustable. Very sharp idea, I like it. If it can be programmed by the ECU and be manipulated by it, it should make turbo lag disappear. Nice! But then, all the turbo-drama goes....

[@ENFEbbnFlow]

I have a question, why wouldn't the variable valve open completely, to let all of the high rpm exhaust into the high velocity scroll, instead of opening half way to let half of the exhaust be waisted into the low velocity scroll? Wouldn't you receive more power with 100% of the high rpm exhaust gasses flowing into the high velocity scroll for maximum air volume? Thank you.

[@timruddell125]

This probably wouldn't that expensive for Borg Warner to research further, it's pretty much an adaptation of the internal wastegate. They already have the know-how to ensure the system can handle the heat, it's probably just a matter of optimising the flow of gas around the valve and reducing weight and cost. What sort of parameter would this system be controlled by, solely RPM or would engine load also be factored in?

[@BornslippyZ]

Really cool lesson and technology!

[@Sibsko21]

Are there any downsides to this type of turbo?

[@srtneonalex]

price

[@ChucksSEADnDEAD]

Size, didn't get a real sense of scale but it just looks bulky.

[@ChucksSEADnDEAD]

+Filipe Amaral And I guess that when only the "red" turbo is connected, the "orange" is extra mass that introduces parasitic losses.

[@billyp4850]

+Filipe Amaral There is only one turbine wheel! The losses will be less than a normal twin spool turbocharger because all of the exhaust gases are hitting the turbine wheel at the optimal angle. The weight associated with having two exhaust passages is no different to a twin spool turbo.

[@billyp4850]

+Filipe Amaral There is only one turbine wheel! The losses will be less than a normal twin spool turbocharger because all of the exhaust gases are hitting the turbine wheel at the optimal angle. The weight associated with having two exhaust passages is no different to a twin spool turbo.

[@Humance]

why not close the valve all the way so the exaust gasses can flow all in the bigger A/R scroll when the motor is running in high rpm?

[@EngineeringExplained]

+Daniele Dal Col That would reduce the A/R ratio, both scrolls are greater than just one.

[@Humance]

Rade2112 u didn't understand what i asked

[@apache249]

+Daniele Dal Col There is no "bigger scroll". Both scrolls are the same size. Opening up both of them is what effectively "doubles" the size.

[@billyp4850]

+Rade2112 No, to get the greatest boost you need the greatest mass flow, requiring the largest volume, i.e. both scrolls open. The idea behind a twin scroll turbo, and this turbo is to get the gasses to hit the turbine wheel at an optimal angle, this angle changes as the exhaust volume and turbine rpm change, hence the valve moving. Pushing all the gasses into one scroll isn't generating more power, its just using what you've got in a more effective manner.

[@billyp4850]

Rade2112 Well yes the angles are different, that is the point of a twin scroll turbo, two different exhaust passages at different angles to the turbine wheel. But to get the greatest boost you need the greatest volume, no point closing one passage off, that's like having a smaller turbo!

[@JonathanFC229]

the twin scroll on my old 88 RX7 TII had quite a bit more lag than the variable geometery VNT turbo on my Jetta tdi...

[@canddmeyer]

I just purchased a Fusion with a turbo. The flapper in the video is just another thing that'll break in my opinion. But if these hit the market and the flap isn't proven to be a weak point, then bring it in.

[@hismonstrousness2478]

I know hindsights 2020 but I feel like we should have already been using these. I don't think it will fizzle out. I don't know what the downsides to this setup would be in comparison to a twin setup. Ultimately that would be the deciding factor I'm sure. The more I think about it though, this prototype is going to be the future for my gasoline engines. Simplicity is always the way to go.

[@konstantinos_iliadis]

Jason, first of all i had to watch this video only once to understand what you are explaining so thumbs up to that ! second of all, for me this was the most interesting car-tech video in 2015 ! and a question, does the focus rs mk3 have a twin-scroll turbo?