Parallel vs. Sequential vs. Compound - Twin Turbo systems explained - Boost School #11
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In today's episode we're talking about twin turbo setups and we will be doing a detailed explanation and comparison of three different setups. Parallel, sequential and compound twin turbo setups. No, sequential and compound turbo are not the same thing and I will explain how the two differ.
But first, the basics. Why would you ever use two turbos over one? After all a single turbo does the job just fine. It hooks up to the exhaust manifold where it relies on the heat energy of the engine's exhaust to spin up the turbine wheel which is directly connect to the compressor wheel which suck in air compresses it and sends it into the engine to be burned together with the fuel.
But as with most things in life, there's a compromise and that's the turbo size choice. Naturally you would assume that a larger turbo makes more power than a smaller turbo, all other things being equal, and you would be correct. But a larger turbo also needs more heat energy to be spooled up to generate it's maximum boost.
Although it may sound weird a parallel twin turbo setup is in reality very similar to a single turbo setup, just with twice the turbos. You will find parallel turbo setups most often on v6 and v8 engines. A classic and well known example is the twin turbo V6 engine on the Nissan GTR R35.
A parallel turbo features two turbocharger of equal size operating completely independently. This means that each is hooked up to a separate exhaust manifold and each has it's own waste-gate. Exhaust gasses are not diverted from one turbo to the other in any scenario. Each turbo also has it's own intake piping. The intake piping from the two turbos may join before or after the intercooler or it may not join at all, instead each turbo may be feeding a separate intake manifold.
Now when it comes to V6 and V8 engines a parallel setup has many benefits. The first benefit is that dramatically simplified and reduced exhaust piping.
So then why are all the 2jz, RB, LS and other engines which are often used for making big power all running big single turbos and not twin turbos? Well the main reason behind this is that OEMs have incredible R&D capabilities at their disposal and prioritize driveability whereas car enthusiasts do not. What I'm trying to say is that the big single is the easiest setup to get right when chasing big power.
However, twin turbo setups still face the same compromise of the single turbo. While they ease packaging costs and help preserve responsiveness and efficiency by allowing shorter and simpler piping they ultimately can't escape the turbo size choice compromise, they're just splitting it in half.
But a sequential twin turbo setup promises to achieve both, a very low boost threshold and great low rpm performance together with power at the top. Originally invented for the Porsche 959 to get rid of the sudden onslaught of boost present in previous Porsche Turbo models the sequential system gets rid of the compromise by spooling up the turbos in sequence, so one after the other instead of both at the same time.
A common misconception is that a sequential turbo system consists of one small and one large turbo. This doesn't have to be the case and a sequential turbo system can feature two turbos of the same size. What makes a system sequential is not the size of the turbos, but rather the fact that they are spooled and after the other and not at the same time as in the parallel system.
Now this is where all the confusion begins because the terms compound and sequential are often used interchangeably and they're really not interchangeable because not every sequential system is compound but every compound system is sequential.
The way to differentiate between the two is this. In a system that is only sequential we have one turbo spooled before the other but both turbos feed into the intake manifold of the engine. In a sequential compound system one turbo is spooled before the other but one turbo also feeds into the other turbo, and one turbo is always larger than the other. Proper compounding cannot be achieved with two turbos of the same size.
So how does the system work? Well we have two turbos, one small and one large different people will call different turbos primary and secondary so you can largely ignore that distinction. What you have to remember is that the smaller turbo is always the high pressure turbo and the large turbo is always the low pressure turbo and the large turbo always feeds into the smaller turbo.
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#d4a #boostschool #twinturbo
00:00 The problem with singles
03:06 Parallel
09:39 Sequential
15:00 Compound - ยานยนต์และพาหนะ
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Thank you.
I have twin gt15 turbos I want to setup.
But I have real work to do unfortunately.
Or fortunately.
Now you should do variable turbos.
There’s a guy on Tdi club who took a stock 1.9 vw Tdi.
Used the stock variable turbo as one of a compound system and had very good results.
But I still love you my brother man for whatever you choose to teach us.
You are a tremendously amazing friend/teacher.
Thank you ❤❤❤❤❤
Excellent , well researched Video . As Usual . You're quite good at this stuff Young Man .
@@fastinradfordable sweet what do you plan on putting them on
As a civil engineer that started out as a mechanical engineer. This guy is phenomenal. His explanations are so engineer processed. Thorough through, and through, step by step, and still technical but not confusing. To me it’s like intellectual crack for my brain.
and the way he express his ideas are simply profecient,
how i would love to go to school once again if the teachers would be same as him
Really? So it’s the heat energy from the manifold that spins the turbo, not the air flow/pressure? Hmm, interesting!
@@shane888davies6 "even I know heat has nothing to do with it" where do you think the pressure comes from? It's heat. The explosion in the engine primarily generates HEAT, which is deposited primarily in the exhaust gases, which exit the engine at high pressure CAUSED BY the heat. Heat makes stuff move more, which is what generates pressure in matter. You get more pressure with less molecules if the heat is higher. If you reduce the exhaust gases to like 100 degrees celsius, they'll be at a very much lower pressure than when the exact same number of molecules exit the engine. An explosion generates neither matter nor energy - it transforms chemical energy into thermal energy, causing the resulting gas mixture to expand rapidly and violently, pressing on the piston, then exiting the engine in a still compressed and scorching hot pressure wave.
In short, the heat is the cause of the actual pressure of the gas. If you ran an intercooler on the exhaust gases of the engine, then into a turbo, you'd lose all the turbo pressure, even in a magical reality where the impedance of flow created by the cooler caused no reduction in gas weight outflow from the engine.
@Shane888 Davies ooh look, its one of those "tell me you don't understand thermodynamics without..." kinda moments 🗿
Babe wake up D4A posted about turbos
I LOVE THE DIESEL CONTENT. So hard to find modern, reliable info with this level of technical detail.
Ever wondered who the creator of this is universe is?
I present to you, my God and my Father
The Lord God, and my Lord and Saviour Jesus.
My life changed forever because of him.
God wants to have a relationship with you. He loves you so he didn't spare his own Son Jesus Christ for that reason(John 3:16)
that died for your sins.
He is not religious.
He isn't about religion.
He wants a relationship.
*Even though you sinned awfully against him and he would have to send you to hell, but he is A God of love as the Bible says.*
He wants to be your friend.
If you'll accept him.
I learnt it that way.
We all have our own beliefs
and that's why we have to trust the only usable source: the Bible, the Word of God
. He didn't put a bunch of rules you have to follow,
It was people that did.
Those are false.
Only way you can come to God
is you coming to his Son, Jesus.
His only Son died on the cross of Calvary,
For YOU.
So you may come to God
and go to heaven, to be with him.
God *focuses on the individual* ,and you are that one today.
He loves you so much,
He created you,
He shaped you,
He formed you.
Why don't you accept his love today?
All you have to do
is to come to the cross
Ask Jesus for forgiveness by saying you're sorry for your sins.
That's where the journey of passing from death to life begins!
*He loves us enough to give us a choice: we can ask him to be part of our lives now, and so avoid hell and look forward to enjoying his perfect eternal kingdom, or not.*
We Christains need to speak out.
If you're a Christian let's speak up for our faith already. We know what is going on in this world is sin, abortion, homosexuality, prosperity gospel...
Let's do it brethren already.
If you reject Jesus, I am telling you, you will face the biggest amount of punishment in hell, more than murderers, adulterers, liars constantly gossiping, the proud and the wicked. If you reject Christ God cant forgive you of it until you come truly to Christ.
Take it seriously, Amen.
10 at the name of Jesus every knee should bow, of those in heaven, and of those on earth, and of those under the earth, and that every tongue should confess that Jesus Christ is Lord, 11 to the glory of God the Father.
Philippians 2:10-11 NKJV
Watch: th-cam.com/users/shortsRCANXQjDCm8?feature=share
looking to youtube from professional shit makes no sense. youtubers arent pioneering anything
@@nomercyinc6783 they are pioneering how we get information. I learned a lot of stuff about engines, guns, and you name it, easier than I did reading it out of a book. So yes, they are pioneering how we get information, not the information itself.
@@nomercyinc6783 everyone in the automotive world knows that REAL insightful information comes from experience. It’s also common knowledge that wherever you go for information you’ll have to wade through bullshit before you find what you’re looking for. TH-cam is nothing more than documented experience in an easy-to-find format. I’d say you’re the one behind by not using every resource and reference tool that you have. Hanes manual open in front of me, I still TH-cam almost everything just for that one piece of insightful information that makes the entire job less of a headache.
@@nomercyinc6783 You don´t know 2stroke stuffing
Video suggestion: guide to tire dimensions and their effect on grip& performance.Many youtubers will simply say wider tire=more rubber contacting the ground which means more friction and grip.But friction doesn't depend on the contact area because a smaller area will have more pressure and a bigger one will have less,so the overall friction will be the same for both considering mass of the vehicle doesn't change.I would like to hear an explanation from you
I'll do a video on something like that, because the same thing applies to bigger brakes too.
Your explanation is totally incorrect. For pneumatic rubber tyres, friction is absolutely 100% dependent on the size of the contact patch. For very complicated reasons, as the shear stress acting on a tyre increases, the coefficient of friction drops. Increasing the tyre size reduces the amount of shear stress a tyre expriences and therefore increases grip. For the exact same reason this occurs, a heavier car will have less performance than a slower car given equal tyre sizes. It is also the basis of many aspects of chassis tuning (e.g. making the rear suspension stiffer will increase the grip on the front and vice versa).
There are a bunch of free resources online for you to learn about this phenomenon but I recommend watching this video (th-cam.com/video/bYp2vvUgEqE/w-d-xo.html) on general vehicle dynamics. The information you're looking for is at 52:55 or so, but I highly, highly recommend watching the whole thing if you're the least bit interested in this sort of thing. It's super dense and well explained, and while it's not 100% correct, it'll give you a rough idea on what to look out for if you wanna do some further reading on your own.
u r right, friction indeed only depends upon weight and coeff. Of friction and not on contact area however key here is there must be direct contact between surface and tyre which is not always possible. sand, debris and other things present on the road could easily break the contact and so does the friction. wider tyres increases the probability of a direct contact over broad spectrum compare to skinner tyres.
You are oversimpilying one of the most complicated aspects of vehicle dynamics.
Whole books have been written about tyres.
@@petrolheadJJ Dude I know friction of a tire definetly depends on its width and I didn't simplify anything about tires,read my comment again.What was in my mind was a solid block sliding across a surface.Anyways all I want is to understand how this complex phenomenon works
interesting note on compound turbo setups, you can do it using the same size turbos, but you need 3 of them; 2 to act as low pressure turbo, 1 to act as high pressure.
Interesting!!!
Yup, cuz best sizing is to low boost turbo is twice size of high boost turbo....
I know a guy with a triple turbo Cummins. It’s fucking rowdy.
in case of an L6 can you have each turbo fed by two cylinders?
@@Jacob-W-5570 too complicated for parrallel and not efficient for sequentials or compund
Loved the video! I’d love to see one now on “twin charging” or using both a supercharger and a turbocharger.
Really like that you mentioned cylinder mixing/interference being better avoided in some configurations for turbo response and engine efficiency. I would argue that is a large factor that many people skip over when looking at mid/low rpm power/spool differences
@Matt Morison Ever wondered who the creator of this is universe is?
I present to you, my God and my Father
The Lord God, and my Lord and Saviour Jesus.
My life changed forever because of him.
God wants to have a relationship with you. He loves you so he didn't spare his own Son Jesus Christ for that reason(John 3:16)
that died for your sins.
He is not religious.
He isn't about religion.
He wants a relationship.
*Even though you sinned awfully against him and he would have to send you to hell, but he is A God of love as the Bible says.*
He wants to be your friend.
If you'll accept him.
I learnt it that way.
We all have our own beliefs
and that's why we have to trust the only usable source: the Bible, the Word of God
. He didn't put a bunch of rules you have to follow,
It was people that did.
Those are false.
Only way you can come to God
is you coming to his Son, Jesus.
His only Son died on the cross of Calvary,
For YOU.
So you may come to God
and go to heaven, to be with him.
God *focuses on the individual* ,and you are that one today.
He loves you so much,
He created you,
He shaped you,
He formed you.
Why don't you accept his love today?
All you have to do
is to come to the cross
Ask Jesus for forgiveness by saying you're sorry for your sins.
That's where the journey of passing from death to life begins!
*He loves us enough to give us a choice: we can ask him to be part of our lives now, and so avoid hell and look forward to enjoying his perfect eternal kingdom, or not.*
We Christains need to speak out.
If you're a Christian let's speak up for our faith already. We know what is going on in this world is sin, abortion, homosexuality, prosperity gospel...
Let's do it brethren already.
If you reject Jesus, I am telling you, you will face the biggest amount of punishment in hell, more than murderers, adulterers, liars constantly gossiping, the proud and the wicked. If you reject Christ God cant forgive you of it until you come truly to Christ.
Take it seriously, Amen.
10 at the name of Jesus every knee should bow, of those in heaven, and of those on earth, and of those under the earth, and that every tongue should confess that Jesus Christ is Lord, 11 to the glory of God the Father.
Philippians 2:10-11 NKJV
Watch: th-cam.com/users/shortsRCANXQjDCm8?feature=share
Would be good to see the twinscroll/single scroll differences highlighted. As far as setups go, it's an interesting middle ground.
@@jonowichert787 We've seen reducing cylinder to cylinder mixing (more pronounced with longer duration/overlap camshafts) being one of the larger factors in why a divided setup acts like a larger engine in the earlier rpm range, and also interestingly, a parallel turbo inline 6 with the front 3 to one single scroll turbo and rear 3 to another single scroll turbo has the same beneficial effect of reducing cylinder mixing as a divided setup. Probably better from the engine's view since there isn't any possibility of cross talk across the divider in the turbine housing, and have seen that it doesn't take much of a path (like a single wastegate divided setup that isn't divided all the way up to the wastegate valve face) in order to make a divided setup act more like an open setup and lose much of the spool/response/VE gains
I'm a huge car guy and also big into physics and I like this channel a lot because it gives me the fundemental detail I'm looking for. Love the comments the discussions and the overall community here.
how are you big into physics ts is too hard
As someone who works as a diesel engine developer, I love the way you explain this topic.
The only thing you're kind of missing (propably due to not confuse the heck out of your viewers LOL) is that modern compound setups use a bypass valve for the high pressure compressor, which will "turn off" the high pressure turbo at high pressure ratios, making the system practically function as a single stage turbo only (the low pressure turbo).
I am an educated car guy, but I still learn. And you help me to tell people such things in a quite easy way. Thanks!
That's the idea that being able to relate an idea to a layperson is the final step of fully understanding it yourself. I love it. This guy has a particular talent for it.
Great video as always! I feel like I have a good understanding of single and twin turbos but sequential and especially compound turbos, I did not understand as well. I always thought the smaller turbo in a compound set-up fed the larger turbo. I did not realize that a smaller turbo can still increase boost from a larger turbo feeding it. Thanks again for the video!
Ghost your not alone bud. I used to work on jet engines and was right with you on that compound thought I thought smaller woke up quick and fed the larger already compressed air waking it's ass up with fury but then I would think the smaller being the only thing the larger has to breath through it would choke as it woke up and although I kinda see his point I'm still confused on the compound theory and have so many more goddam questions lol.
@@chriss6154 I think it's easy to envision these things as "blowing" air (hence the supercharger nickname of "blower") but really what they're doing is compressing it. In other words, it's not like a bathroom exhaust fan that just pushes air along a pipe, these things are actually grabbing air and squeezing it into a smaller space in order to create boost. That's why they create so much heat. The exhaust fan might have some difference in pressure between the intake and exhaust but if you try to actually run it fast enough to create boost it'll stall and choke itself and won't move much air at all.
I think jet engines are actually a good example of compound boost. Most of them have two stages with the first one having larger diameter compressor blades that lead to a second stage with smaller blades and an increasingly smaller throat for the air to flow through.
Gotta admit, I thought I had a decent understanding of these things but it wasn't until watching this vid and reading your comment that it all clicked. I think part of the problem of being a petrolhead is you don't get exposed to diesel stuff, and diesel and jet fuel are pretty much the same stuff so it's pretty much the same concept, it's just one's purely axial while the other has a reciprocating engine in between all the boost-creating devices lol. Kinda reminds me of people making jet engines out of old turbochargers haha.
Also for some reason reminds me of Scott Manley's vid on supersonic wind tunnels and how they work. /watch?v=v0Z_4VyuzcA
This is why i love this channel, he just made the idea much clearer than i had thought
Same. I realized that my D5 Volvo doesn't have a normal sequential turbo, but a compound turbo.
@@chriss6154 The trick is to remember that air has mass, and that mass is what we're actually worried about. Only the outermost point in the system can actually bring MORE mass to the system, so the outermost has to be the big one in order to bring more mass in. Once we're inside the system, we cannot grab more mass, only cram it closer together, so we must get smaller as we go deeper into the system.
FIAT/Lancia triflux was also an inline 4 with radial valve setup that had parallen twin turbos each located on the opposite sides of the engine. There was both intake and exhaust on both sides of the engine due to the radial valve setup effectively "turning the inline 4 into a v8" as far as intake and exhaust piping goes
You're partially right, it got the name tri-flux because it's frontal silhouette looked kinda like a Y. It had 3 areas for intake/exhaust, 2 for exhaust (sides) and 1 for intake (on top).
@@tbkriley yes i worded it wrong. By intake being on both sides i meant it being on each side of the head due to the radial/cross valve setup. The intake manifold itself feeds from the top as you said. Which is pretty close to a v engine with top intake manifold and exhaust manifolds on each sides
Frikking love it how you explain things!A perfect learning curve from simple into more complex examples,no unnecessary bs or dumb jokes and no ego sauce either! Thank you
@driving4answer @TELEGRAM TO CLAIM PRIZE fucking scammers
....... but I like dumb jokes, and he makes them from time to time.
instead of mufflers just keep adding compound turbos until every last bit of exhaust energy is captured!
🤣🤣
This also solves emissions since a particle with no energy cannot move. Genius!
@@d4a I wrote a big long reply and lost it RIP. But I was basically saying that jet engines are like turbos but with a lot of compound stages which makes them way more efficient.
I'm thinking 5 turbos would be a good starting point to experiment with. Primary turbo would be normal size to match the engine, second would be 12% larger, third would be 24% larger, fourth would be 50% larger, and the final one would be 100% larger than the primary, just like the normal final stage compound turbo size.
I want to find some CFD software to model this and see how well it might work. The plumbing would be a nightmare, it's too bad they don't make axial flow turbos, but at that point it's pretty much a jet engine eh?
I mean honestly, with 5 turbos and a straight through turbo style muffler and resonator I think the car would be pretty quiet, and theoretically should be much more efficient than just 1 turbo (or turbine stage).
@@igornoga5362 Actually you just gave me another genius idea! Make the hot side turbine blades out of cat material so you actually get 5 stages of CAT turbos that would probably make a decent improvement on the emissions. It might be tough though to make a blade out of cat material that is still strong enough to be a hot side turbine.
Another awesome video from D4A! I always learn something new from your videos. Congrats on 500k subscribers! You've earned it! You'll hit 1 million in no time if you just keep up the good work. Thank you for keeping your content efficient and to the point, without fluff, filler or excessive ads
Absolutely awesome video, as usual.
One thing I'd like to see everyone - not just you - embrace though, is clearly stating "peak power" instead of "power"; because - for example at 7:38 - two setups with "the same power" probably only make the same *peak* power, but one has greater area under the power curve overall (e.g. higher power at some RPM that isn't the peak), meaning it actually makes more power overall- many people don't seem to realize that's a thing.
Excellent break down of how both turbo systems in general work, and how the difference between the various combinations of multi-turbo systems work!
The way that you explained this video is truly amazing, the way it was described so simply yet so detailed is beyond amazing. Thank you Mr D4A
It's a scam
THANK YOU for using the term boost threshold, and not turbo lag. So tired of seeing these terms getting confused...
Very cool. I didn't really know about sequencial turbo set-ups. And the details to distinguish the different set-ups are undeniable. Thank you for another very thorough and amazing video!
This was another excellent video! Boost School is one of my favorite D4A video series! I would love to see a future video entirely about the effects of heat (pros and cons) within a turbo system--especially how it relates to producing boost. Thanks so much, and keep up the excellent work!
This is a scam
Interesting fact about compound turbo systems: In these, the air reaches the bigger turbo first, as he said. But the smaller turbo actually spools up first. What that means is that the small turbo can actually suck air through the big turbo in order to get boost going in a hurry.
Great video!
I actually said all that in the video
@@d4a Sorry, got called away before the end. Great video as always!
His description was good, but his definitions... need work. His compound turbo is sequential, not compound as compound turbos are tied directly to the crank shaft, otherwise it was well done.
@@w8stral You are thinking about the turbo compound engine, not the compound turbo. This was a series of radial aircraft engines built by Curtis-Wright called the R-3350 which featured "blow down turbines", which added power to the crank via a fluid coupling. They were tricky to operate, and I'm pretty sure this was the only production engine of this type. A compound turbo the way I've always understood it is more than one turbo mounted in series so that one blows into the other. The turbos are different sizes so that one spools quickly, while the other handles the large amounts of air necessary at high rpm. They supercharge the engine, not directly add power to the crankshaft.
Yes, his verbiage is sometimes odd. To his credit, English isn't his first language so he gets a little bit of a pass...
This channel is INCREDIBLY good.. worked a lot w/ all kinds of race cars, alcohol funny cars top fuel, sprint cars, tractor pulling, etc.. I'm not saying I'm a master of all these things but what I am saying is I still learn a lot and to have experience in these things, and I can still tell you for whatever it's worth, that this channel is incredibly, INCREDIBLY good, probably one of the best!
Another thing I love is that there is no way you are not getting people for getting people into learning and critical thinking, as well as getting them into stuff like racing, fixing their own cars and so on, awesome, awesome stuff!
🤘🏻
7:30 This reminds me of this RCR video on a Subaru Impreza with a single turbo 2JZ swap. IT WAS A MESS TO DRIVE, they were struggling to get the turbo going on the street. He described it as "If a can of Four Loko were a car"
I just finished your boost school playlist this morning, and i dont have to wait for the next episode haha
The (tier IV) diesel engines in the snowcats I work on have variable geometry turbos. They change the internal dimensions of the compressor depending on the required boost. It's a high tech alternative to waste gates. You should do a video on them if you haven't already.
I think I remember Car and Driver magazine talking about Porsche using those in the 911 a few years ago too. Interesting stuff.
a 1994 TDi with 110hp has this. Nothing new
@nthgth ya, Porsche designed them and it changed a lot of the engineering behind them. But they are expensive, complex and are designed for a specific engine. And can't really be modified out of spec
Man the fact that I was totally focused throughout the whole vid makes me feel like a liar when I don't focus on studying
i really respect and look up to you man. "get lost and you shall find what you are looking for" was beautiful
Thank you so much, I'm honored
Thanks for watching and commenting❤️ you have been randomly selected from comments as winner of today’s giveaway hit me up via the digits above to claim prize......🎁🎁
Wow!! I had no idea you can route twin turbo applications in different ways!
Thank You so much for this video!!!
Dude....friggin AWESOME explanation and graphics! Loved it!
Almost didn't watch this thinking "oh this is simple, it's obvious enough from the names what they are and what the advantages are"
But it was much more interesting than I expected. For example I never actually realised the 2JZ's turbos are the same size and just come on separately. The assumption was just that since they are "sequential turbos" that meant it has a smaller one that spools faster and a larger one that spools slower.
Another brilliantly produced and presented video! Fantastic and very accessible information here, as always. Great integration of graphics, photos, and constituent videos!
Fun fact, the 2nd-gen Saab 9-3 was available with a twin-turbo diesel I4 and a single-turbo gasoline V6 (the turbine was fed by a single bank but the compressor acted on both)
Edit: the asymmetrical V6 turbo was actually the 3.0 used on the 1st-gen 9-5
I believe these 54 degree V engines used very low boost. Low boost turbocharged engines actually gain fuel efficiency due to the increased compression. It's funny you brought that car up because I was just thinking of these when I read your comment.
@@Flies2FLL wasn’t SAAB one of the first manufacturers that turbocharged their cars for fuel efficiency instead of power?
@J M when i eventually get my hands on a 240z i'll drop an i5 turbo engine and awd drivetrain. just about every manufacturer that made a sporty i5 engine made them REALLY good.
@@devandrasimanjuntak1646 I think it was for power. The V6 cars used an Opel engine.
@J M The SAAB four cylinder engine was actually a British design from Triumph. SAAB made it reliable by redesigning the cylinder head. The GM 3.8 liter V6 was not a Chevy engine, it was a Buick engine that actually started life as a 3.5 liter V8, was bought by Rover, and then repurchased by GM and cut down into a V6. But I agree with you on SAAB longevity; If you keep oil in them they run forever.
Glad to see u come back with another Boost School😍😍
got recommended here for some reason, stuck till the end. clear and good explanation, keep it up dude
Great presentation-I thought compound turbo's worked opposite of what you said. But now that you showed how they work-it makes sense. Thanks for your video!
This is phenomenal. Not sure if this is talent or honed skill, but you are great at teaching.
Compound charging was fairly common in WW2 aircraft engines, but was typically used with centrifugal superchargers rather than proper turbos for most engines and aircraft, save for the P-47
Both the P-47 and the P-38 used superchargers and turbosuperchargers in a sequential set up.
That's not really a compound turbo setup, that's generally referred to as twincharging.
Awesome explanation, thanks for sharing it! =)
In Brazil we had a tuner that made one EA211 1.0 three cylinder engine with compound system... peak pressure was above 3.0 bar and the engine developed 250+ HP on 100% ethanol fuel.
Other setups with just one bigger turbo could reach 200+ HP but sacrificed the low-end RPM (spooling just over 3k RPM), which is extremely critical for such tiny engine.
It was a complex but beautiful design.
Best easiest most detailed explanation have ever found!! You really know your stuff bro! No complicated terminology just straight forward love it! Liked subscribed n shared! When I want to build my s15 your going to be my go too guy brother ❤
Thank you D4A! Excellent work on the video! The way you explain how things work is amazing!
Thanks for watching and commenting❤️ you have been randomly selected from comments as winner of today’s giveaway hit me up via the digits above to claim prize.... 🎁🎁
This is a scam
Another good one. Love to see one about twin scroll turbo systems
thank you AEM for supporting this channel!!! and thanks D4 another great vid bud!
Excellent video and really interesting. And this is how to do sponsorships! It's actually relevant to the content and you tied it in at appropriate points to show how the sponsor's products can be used in context. Keep up the great work!
Really great video!! Was watching some of the boost school last night and had to watch when I saw this posted! Thank you and have an awesome day D4A!
Great content and explanation as usual.Thanks!
Thank you so much for posting this! I'm a university student taking part in Formula SAE and learning about engines, turbos, whatnot is truly exciting stuff! Hopefully, I can contribute to the team with this knowledge soon enough! Cheers!
YT suggestions are sometimes good: you're good! I saw some of your videos today and I'll be watching more. Thanks for the great quality, keep it up.
I'm a Diesel mechanic from Iran. I have never worked on anything remotely "advanced", because they don't exist in our country or at least are not frequent. But I always had a theory: if small turbo --> lower RPM activation + lower boost and large turbo --> higher RPM activation + higher boost, why we don't invent a system that I call "a turbo for a turbo". It works in a way that we put a tiny and very sensitive turbo that will spin immediately with the lowest amount of exhaust gas before a larger main turbo. That small turbo won't feed the compressor side of larger turbo, but the exhaust side of larger turbo. The large turbo will suck the air from air filter in traditional way. The exhaust side of larger turbo will be also fed by exhaust manifold. There will be a shut-off gates before exhaust sides of both turbos. This system will work this way: we step on fuel pedal, engine revs slightly, small turbo goes crazy and will feed the larger turbo with high air pressure (the exhaust manifold that feeds the same spot in larger turbo is closed now to prevent back pressure) so that it starts to spin before the engine would spin it at normal conditions. Now that the large turbo is kicking in and exhaust pressure is going up, the exhaust manifold that leads to small turbo will be shut (to prevent the turbo from exploding) and the valve before the exhaust side of big turbo will open and big turbo which has enough speed now will be fed by the exhaust fumes as it was intended. But there will be no lag, because the big turbo is already spinning. Please let me know what you all think about this
Behrooz- Well done my friend and greetings from the US. I had to draw out your plan so I can grasp it but it sure sounds like it checks all the boxes. I've often had similar thoughts but wondered about using maybe a very small electrically powered micro turbo to produce the boost for the larger turbo just as you described. I always wished I had the money to have a small shop and work with someone like yourself to test these ideas. I could work for hours on ideas like that.. Oh well, until then.. Take care my friend.
you're missing one important piece, this setup doesn't actually add any extra energy to the exhaust stream to spool the second turbo. You need to burn fuel for that to happen, and inside the engine is generally the best place for that. Which turns the idea back into a regular compound turbo setup. :)
@@giggiddy thanks man. It makes me happy to see people like you, curious and dedicated to their ideas. I'm poor, here in Iran I only make 150 USD per month. I can't afford to test any of my ideas. Currently I'm applying for University in Canada for Neuroscience Masters. If I make it, I plan to become a Neuroscientist, make money and then attack automotive world with free hand and mind. Wish me luck. You too stay safe and curious.
You would need full control of the valves/gates, perhaps you could use a fancy electronic wastegate like the new turbo smart one to control the transition.
@@AlexanderBurgers I don't intend to add any more energy to the system. This is a solution to reduce lag for big turbo engines.
What about a VNT or superchargers driving turbo's?
Love the content, thanks! Definitely among the best information available. I just wish the boost school videos could be more frequent.
The thing about Turbo is that the bigger the turbo is the laggier it gets and the placement of it can significantly either response fast or too slow sometimes the weirdest one i've seen is Nissan Z with turbo on the back
The turbo on the back engine in the front stuff is honestly a bit of a stupid trend..very little benefits and many downsides on that one.
Great video, but a tiny mistake @ min 17: Having different diameters when comparing the outlet of turbo 1 and the inlet of turbo 2 does not cause a changing volume in the pipe connecting them, as a given pipe does not change its volume. However, a change in diameter in the piping will result in a change of the pressure inside: increasing the diameter decreases the pressure when comparing before and after the expansion. This results in wasting some of the energy, the first turbo had transferred into the compressed air, in other words: a loss of efficiency. Vice versa, decreasing the diameter in the piping will result in a increased pressure in that part of the piping behind said restriction at the cost of loosing efficiency on the first turbo: it has to work harder.
Basically, the result stays the same: loss of efficiency due to mismatched sizing of the turbo chargers. But from an engineering point of view, the difference matters: in this application, we are talking about flowing fluids (compressed air), which are in the realm of Bernulli´s law and the Navier-Stokes equation.
Interesting side fact: in the aircraft engines of WW2, there were several stages of compression (e.g. combination of turbo and supercharging) in series. Since it is more efficient to compress colder air, there were cooling stages after each compression stage. Funny thing: the cooling in between the compression stages was defined as "intercooling", whilst the cooling behind the last stage of compession was called "aftercooling". Therefore, the term "intercooling" is actually use in a wrong fashion when it comes to cars: no matter what combination of chargers are used in cars, in almost all cases, the cooling of the air only happens behind the last compression stage before entering the inlet valves of the piston engine. Therefore using the expression "intercooler" when it comes to cars, is actually wrong: it is always aftercooling.
There are automotive examples of it. The Lancia Delta S4 used a series configuration (turbo to supercharger) with an intercooler after each stage.
@@leoarc1061 "...no matter what combination of chargers are used in cars, in almost all cases, the cooling of the air only happens behind the last compression stage before entering the inlet valves of the piston engine."
Plus, the Delta S4 as one of the most powerful Group B vehicles can hardly be called a regular car - or have you seen a Champcar cruising along the streets lately? ;)
@@RageDavis I wasn't negatively criticizing your input. Simply adding to it.
You are correct. Terms like "intercooling" and "aftercooling" are often misused.
In regards to the Delta S4, what is your opinion on its configuration? Could've Lancia done better with turbochargers alone? Or, could've a centrifugal supercharger been a better option than the roots?
This has got to be my favourite TH-cam channel, I was LITERALLY thinking about this today at work and you answered everything + some
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Thank you for this. You deserve waaaaay more subs dude. I learn something new every time I watch one of your videos!
As usual, a video that has blown me away :D
I can sleep now, thank you
Thank you! So interesting. I just love learning all this stuff. Maybe one day I can build something cool :)
Hell yes!!! I've been waiting for you to do a turbo video like this. I can't watch yet as I'm at work, looking so forward to watching.
another great turbo video. Had no idea a compound system was working this way. I've always had at least 1 turbo car since the last 20 years. I just love em.
Would love to see your take on "hot vee" engines, (i.e. advantages, packaging & examples).
Twin charged engines are kinda cool too, and although not entirely practical, I might twin charge my car in the future 😁
The Delta S4 used twin-charging to have anti-lag before anti lag was really a thing.
Screw practicality that would be dope to see you build a twin charged car
Best TH-cam car enthusiasts technical teacher right here!
WOW. So much information in a single video. This is fantastic content and he is an excellent educator. I'm a huge fan of turbos!
I'm guilty for not studying math but studying on how turbos work
Time well spent
Can u explain about Crank offset? I've a bit confussed over its actual usage. Some says it reduces the vibrations while others expressing how it increases the effectiveness of the power stroke. It's also have been Heard that it gives more freedom to set valve timing since piston spend more time in BDC and TDC.
Nothing can make an engine ‘spend more time at tdc
The 'Goldilocks' turbo is "the most rational compromise" - masterfully put.
Great work! I’ve been building forced induction engines for years. Mostly smaller stuff like snowmobiles, sxs, atvs, etc etc. However, I’ve also built quite a few larger engines for sand cars and off road racing buggy’s/trucks with everything from Honda 3.5 v6s, Rotary’s, GM small/big blocks, Subaru’s and of course my little VW bug street cars. It’s a lot of fun getting 300-400hp out of a VW. I also own and am I heavily involved with turbocharged aviation engines (that is a whole different story). Anywho, you did a great job explaining the basics of these systems. The one thing the vast majority (especially the rice burners) doesn’t understand is....more boost does not always equal more power, especially in gasoline vehicles. The key is air density. This is achieved by turbos being properly sized like you mentioned and even more importantly in the meat of the compressor map. Most people don’t even know what a compressor map is, let alone how to read one. What I’m getting at is forced induction is a science and requires many many hours of R&D and a vast knowledge of how these systems actually work and what the actual goal is. Never is higher boost the number one goal like many will think or try. Air density is the number one goal which involves a vast amount of different parameters included but certainly not limited to temperature, humidity, barometric pressure, elevation or altitude, drive pressure, etc, etc. Creating actual boost pressure is the easy part, but without paying attention to all of the other factors you will never be successful. Thanks for sharing!
Compound Question? Is there any benefit to intercooling the air after it leaves the large turbo to reduce the inlet temps on the small turbo? Basically two intercoolers.
Pretty sure this is where the term intercooler came from since technically most setups are an "aftercooler"
Thank you, your skills explaining complex stuff are legendary. Suggestion: can you do a topic on turbo’s with variable turbine wheels, like Porsche use or have been using?
What about compound turbos vs superchargers for diesels?
A med/large centrifugal supercharger blowing into a small/medium turbo in a compound setup would give a unique dynamic. You may have to put a wastegate on the supercharger's output to limit boost during higher rpm throttle/load transients to limit boost spikes and potential surge on the supercharger.
@@johnnymac1976 I like that idea
Let's say your girlfriend left you...AEM infinity can handle all of that and more
The details of this topic has eluded me for a very long time. You spell things out so clearly. Thank you.
👆👆👆
So many people forget about exhaust scavenging. You don’t want more than 3 cylinders per turbo, because there’s no exhaust scavenging. It’s more important for NA engines, which is why going too big on your exhaust will actually lose power. But it still provides more power in boosted engines.
Thanks man, I learn so much from your channel. You have the ability to explain things perfectly.
I know nearly nothing when it comes to cars but it has always fascinated me, I love these videos
Iam a diesel technician and I work with this systems all the time. Really enjoyed this video. Thank you
Learned a lot from this super informative video. This answers a lot of questions and confusions I have had about these setups.
To add to your explanation of compound turbos...
The small turbo pulls air all the way from the large turbo inlet, this force is acting on the vanes of the large turbo, as well as the exhaust gasses that are flowing past it after the small turbo. The large turbo spins almost all the time the engine is running (depending on the setup) but not fast enough to compress. Once the small turbo builds a little pressure, the intake pulls on the intake, and the exhaust pushes on the exhaust from small to big, pushing the big even faster. Thus, the big turbo is behind the small one, but not a lot. Once the big one kicks in some compression of its own, it becomes a cycle of increasing pressure where both turbos will continue to spool faster until they reach their limits (or gas is no longer applied to the combustion process and exhaust pressure drops)
Loved my 1JZ parallel setup!! What a great engine!
wow, this is much more in-depth than i first suspected. nice job doing your homework. thanks man
This is the best turbo explanation ever! The quality of the video and the explanation is so high that I can't believe I'm watching this for free
Dude, you always do a great job with your explanations and videos. I've learned a lot from you.
This is a scam
Another absolutely brilliant video. Thank you again. Your explanations are excellent and the way that you make it simple enough for anyone to understand the engineering, is second to none.
This is a scam
He's BACK! Great to see another educational video on performance mods. 👏 missed these!
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Some diesel-electric locomotives use what I learned as a compound turbo, but this was setup with a belt-drive on low RPM and a clutch releasing the belt-drive for being exhaust-driven on higher RPM. This seems to be a system that reduces spool-up time and gives a good torque on low RPM.
Thank you for the excellent explanation of the inner workings of forced induction systems. It’s a breath of fresh air. 😬😉
I have always been confused about compund turbo systems but you explained it very well and it all makes sense now, thanks.
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Great video as usual! Thanks for the always useful information that you provide.
BTW, at 1:29 Mazda Skyactive-X is the sole exception I know
Fantastic explanation of different turbo layouts. Now explain how variable geometry turbos work in different circumstances please.
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Great video! I never found someone who explained this in a way I could understand until now
Why haven’t I described to your channel until now? This was an amazing video!! Thank you 🙏🏼
I thought compounds and sequential were the same but now I know different. Thank you! Your really good at this. I remember when compounds were being developed for diesel pick up trucks. I knew a few guys that were hand building them. They had all these boost leak problems running 80-90psi boost. Blowing boots all the time. Now everyone has a kit, which is awesome, more competition makes the quality stand products stand out. What really blew my mind was how much cooler the egt was with compounds. 200-300 deg cooler across the whole power band. I think they said it’s because there is next to no drive pressure with the compounds on a diesel. They still seem finicky in the long run to me, I’d rather have the head ported, valves done with mild cam and a matched turbo for durable results.
As always, another informative and well researched video. Surpassed only by your usual flawless presentation. Just don't try it after a few drinks lol Tahnks agin maate.
What a fantastic and informative video.
I do think that there is another variable to the equation that wasn't specifically addressed though: turbo location. There's an uncommon turbo configuration called the "rear mount" where the turbo(s) can be placed near the exhaust rather than inside the engine bay. This has a significant difference in power delivery characteristics that should be addressed, too.
With the rear mount turbos, you'll obviously have more turbo lag than conventional locations. But it is also more consistent in the buildup of body pressure, doesn't drop body as quickly when reading the throttle, and allows the compressed air to cool more by the time it goes into the engine.
Great topic, great explanations, great drawings, great accent for people around the world to understand without the need of subtitles.
Great video overall!
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Love this man I genuinely Lear a lot, he explains everything so well
Fantastic.. from a lay man Camry driver...thanks so much!
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Best explanation of this topic!!! I never properly understood up until seeing this
thank you very much for this very important lesson, I have been looking for various sources that are complete and easy to understand, this is what I found to have both.