**The Cadillac CT4V: A Fuel-Efficient Powerhouse**

In the world of vehicles, fuel efficiency is a crucial factor that can make all the difference in saving money and reducing one's carbon footprint. The Cadillac CT4V is a prime example of a vehicle that prioritizes this aspect, featuring an advanced engine design that maximizes fuel economy while providing exceptional performance.

**Dual-Fluid Turbocharger: A Game-Changer**

One of the most notable features of the CT4V engine is its dual-fluid turbocharger. This technology involves two volutes - one on top of the other - which provide a unique advantage in terms of turbo response and efficiency. Unlike traditional twin-scroll turbochargers, where exhaust pulses from cylinders 1 and 4 enter the turbine simultaneously, this design separates these pulses into different volutes. Cylinder pairs 2 and 3 send their exhaust pulses to the top volute, while cylinders 1 and 4 send theirs to the bottom volute. This separation ensures that there is no overlap between positive pressure from one cylinder's pulse and another, resulting in better response, lower end torque, and improved efficiency.

**Advantages of Dual-Volume Turbo**

The benefits of this design are multifaceted. By separating exhaust pulses, the engine avoids valve overlap, which can lead to decreased efficiency and reduced performance. Additionally, the unique geometry of the dual-fluid turbocharger allows for a closer proximity between the turbine housing and the turbine itself, enabling more efficient energy transfer. This results in faster turbo spool-up times, with the CT4V engine reportedly reaching peak torque in as little as 2 seconds at low engine speeds.

**Comparison to Other Turbochargers**

The dual-fluid turbocharger is often compared to traditional twin-scroll designs. While both share similar principles, there are key differences in their implementation and performance. The twin-scroll design typically allows for a closer proximity between the turbine housing and the turbine blades, but this can also lead to slightly reduced efficiency due to the overlapping exhaust pulses. In contrast, the dual-fluid turbocharger's unique geometry enables more efficient energy transfer and faster turbo spool-up times.

**Highway Fuel Economy**

When it comes to fuel economy on the highway, the CT4V engine delivers impressive results. According to Cadillac specifications, this engine achieves an estimated 20 miles per gallon in city driving and 29 miles per gallon on the highway. While these figures may not seem particularly exceptional on their own, they are noteworthy when compared to similar engines, such as the 5.3-liter V8 found in the Chevrolet Silverado.

**Engine Block Design**

The engine block itself is an integral part of the dual-fluid turbocharger design. The exhaust manifold is integrated into the engine block, allowing for a more compact and efficient design. This pairing of cylinders (1 and 4) with another pair (2 and 3) creates a unique firing order that ensures optimal timing between exhaust pulses. By alternating these pulses, the engine avoids the negative effects of valve overlap and can achieve better response, lower end torque, and improved efficiency.

**Chevrolet Silverado Comparison**

To put this engine's performance into perspective, consider its counterpart in the Chevrolet Silverado - a 5.3-liter V8 that also features twin-scroll turbocharging. While both engines share similar principles, the dual-fluid design of the CT4V provides several advantages, including faster turbo spool-up times and improved efficiency. The Silverado engine achieves an estimated 24 miles per gallon on the highway, which is not significantly better than the CT4V's 29 miles per gallon.

**Conclusion**

The Cadillac CT4V represents a significant leap forward in fuel-efficient powertrains. By incorporating advanced technologies like the dual-fluid turbocharger, this engine delivers exceptional performance while prioritizing fuel economy. Its unique design and benefits make it an attractive option for drivers seeking a balance between power and efficiency.

"WEBVTTKind: captionsLanguage: enhello everyone and welcome in this video we're going to be talking about a massive four-cylinder engine and a very cool turbo charger a dual volute turbo that goes along with it but first i need to do a little trash talking because as an engineer it is my duty to combat confusing marketing messages so the engine we'll be discussing in this video is gm's l3b engine gm describes it as developed specifically for truck applications they say it is designed as a truck engine they say this engine is a clean sheet design for chevrolet and was developed from the outset as a truck engine they say the long stroke design will help generate the strong low-end torque customers expect in a truck a fine summary is simply to say all elements of the 2.7 liter turbo were designed for the demands of turbocharged performance in a truck environment if you were to ask me i would probably guess that this engine is for trucks and here's what you'll find it in oh goodness wait wait this isn't a truck or is it if mercedes can call a four-door suv a coupe well then maybe a cadillac sedan can be called a truck i don't know the rules anymore regardless this is a very cool engine and it has a very cool turbo so that's what we're going to be talking about so the l3b engine is an inline four cylinder it has a stroke of 102 millimeters and a bore of 92.25 millimeters which gives it a total displacement of 2.727 liters which i believe is the largest gasoline-powered four-cylinder in a road car sold today historically there definitely had been some larger gasoline four cylinders and there are definitely larger diesel four-cylinders sold today but i think that is the largest gasoline one uh let me know if you do know of one out there i think the next closest is the toyota tacoma which has a 2.694 liter uh inline four-cylinder engine but as far as gasoline engine inline four cylinders goes this is quite large and the reason for that really comes down to two things packaging as you start to get larger you might as well just use more cylinders and then because the space won't be all that different and then from a vibration standpoint inline four cylinders start to get quite noticeable vibration as you get larger in size so what gm does to combat this is they have two balance shafts underneath the crankshaft above the oil pan below this engine and so this is to combat secondary vibrations if you want to learn more about how balance shaft works i have a video which i will link in the video description which you can learn all about why they have these balance shafts in there but basically that eliminates the secondary forces that the pistons will be creating so you will have two balance shafts located underneath that crankshaft and these are rotating at two times the speed as the crankshaft so the l3b engine is used in two different applications by gm currently it is used in the cadillac ct4v and it is used in the chevy silverado which is a truck in the cts4 v it makes 325 horsepower 380 pound-feet of torque using premium gas in the silverado it's making 310 horsepower 350 pound feet of torque using regular gas now one of the really cool things about this engine is that it uses a three position cam shaft so if you've watched my video on variable valve lift then you've seen a very similar mechanism in a volkswagen engine where they use a cam slider to give different profiles that lift and close the intake and exhaust valves and so in this engine there are three different profiles for those intake valves right here what we're looking at is two of these sliders for one individual valve so really there's going to be two valves with each of these sliders and this is going to be mirrored over for each of the four cylinders and so you have these different profiles you've got the slider here in this darker blue and then these three different profiles which the intake valve can follow so it's got this one on the left here that is a high lift high duration profile that's going to give you the most power for those high load uses when you're flooring it things like that then in the center if you look at this one here you have a lower valve and a lower duration and that's kind of for your medium load area where you're going for more efficiency and optimizing airflow at lower rpm and then finally you'll notice that the third profile is different for this intake valve versus for this intake valve and so what's happening is for this third section of this cam slider you're actually disabling the center two cylinders so it's only running on cylinders one and four and so for the second cam slider it's going to go to basically an off position so it doesn't open or close that intake valve same with the exhaust the exhaust valve is going to have two sliders for just the center cylinders so that it will shut off the exhaust valves for these two center cylinders so these will operate like normal one in four your firing order being one three four two so you're alternating between one and four and the center two will basically just be air springs with that piston moving up and down so this two cylinder mode can be useful when you're just cruising on the highway and trying to maximize your fuel efficiency so what kind of highway fuel economy are we talking about here well in the ct4v you're getting 20 miles per gallon in the city 29 miles per gallon on the highway in the chevy silverado this engine is giving you 20 in the city 23 miles per gallon on the highway now 23 miles per gallon may not sound all that impressive but consider what fuel economy the 5.3 liter v8 that also goes in the chevy silverado gets on the highway it only gets 24. 24 miles per gallon on the highway to recap so far a cadillac sedan is a truck a mercedes genuine suv is a coupe and if you want the best fuel economy on the highway get the v8 now regardless of whether this engine actually makes any sense or not it does have a very cool turbo charger a dual fluid turbo so what is a dual volute turbo well it simply means that it has two volutes one on top of the other you may have heard of twin scroll turbochargers these are fairly similar in principle but they have two scrolls side by side rather than one volute on top of the other so what's the advantage of doing something like this and what's the difference versus a twin scroll as far as advantages are concerned so looking at the engine block itself the exhaust manifold is actually integrated within it so you've paired up cylinders one and four and you've paired up cylinders two and three so cylinders two and three send their exhaust pulses to that top volute and then cylinders one and four send their exhaust pulses to that bottom balloon and your firing order is one three four two and so you're alternating between which fallout is actually getting that exhaust pulse so if you look at a simplified drawing over here where we've stretched out that exhaust manifold your firing order being one three four two and you can see that first cylinder has fired the second cylinder is in the other dilute and so its pulse is over here and so the whole idea and why you're doing this is you're separating those exhaust pulses so they don't interfere with one another so that you don't have positive pressure from one of these going back into one of the cylinders that's opening up next so you split them up one three four two and then you don't have to worry about that valve overlap and as a result you get better response you get better low end torque and you get better efficiency out of this dual velo turbo now whether it's a dual volute or a twin scroll turbo both of them use this exact same strategy here of splitting the cylinders to optimize turbo response when you press down on that accelerator pedal how long does it take to actually get that turbo spooled up and so the difference here is how these exhaust gases are entering and hitting that turbine and spinning up the compressor wheel and so with this dual volute you're entering on opposite sides of that turbine versus with the twin scroll turbo you're actually entering together to hit that turbine and so you have a little overlap here where exhaust pulse from one can travel into the other chamber and so there's a bit of an inefficiency there where this is going to allow more energy to actually reach that turbine and spool it up so typically it's going to have better response because you're splitting where it actually enters that turbine where it's hitting it and where it's rotating from another difference is the distance from this turbine housing to this turbine itself so with this dual loot turbo you can bring the edge closer to that turbine wheel because you're not splitting that area right in the middle and so these will with twin scroll turbo chargers be about five millimeters from the turbine blades versus here with this dual volume design apparently you can get about one millimeter away from that turbine blade and so as a result it's going to be more efficient better response you're getting more of that energy to hit it and so as a result the turbo spools up faster and you get your torque sooner so how much sooner well chevy says with the silverado engine if you're at 1500 rpm and you floor it it takes 1.93 seconds to get to 90 percent torque so you're getting nearly peak torque in about two seconds at 1500 rpm which is a very low engine speed so it is impressive that it's able to spool up that quickly at such a low rpm however is it impressive versus say a chevy bolt which can get peak torque like that perhaps not so i don't know why i'm excited about this engine but it is very cool the technology involved and the improvements that it creates thank you all so much for watching and if you have any questions or comments feel free to leave them belowhello everyone and welcome in this video we're going to be talking about a massive four-cylinder engine and a very cool turbo charger a dual volute turbo that goes along with it but first i need to do a little trash talking because as an engineer it is my duty to combat confusing marketing messages so the engine we'll be discussing in this video is gm's l3b engine gm describes it as developed specifically for truck applications they say it is designed as a truck engine they say this engine is a clean sheet design for chevrolet and was developed from the outset as a truck engine they say the long stroke design will help generate the strong low-end torque customers expect in a truck a fine summary is simply to say all elements of the 2.7 liter turbo were designed for the demands of turbocharged performance in a truck environment if you were to ask me i would probably guess that this engine is for trucks and here's what you'll find it in oh goodness wait wait this isn't a truck or is it if mercedes can call a four-door suv a coupe well then maybe a cadillac sedan can be called a truck i don't know the rules anymore regardless this is a very cool engine and it has a very cool turbo so that's what we're going to be talking about so the l3b engine is an inline four cylinder it has a stroke of 102 millimeters and a bore of 92.25 millimeters which gives it a total displacement of 2.727 liters which i believe is the largest gasoline-powered four-cylinder in a road car sold today historically there definitely had been some larger gasoline four cylinders and there are definitely larger diesel four-cylinders sold today but i think that is the largest gasoline one uh let me know if you do know of one out there i think the next closest is the toyota tacoma which has a 2.694 liter uh inline four-cylinder engine but as far as gasoline engine inline four cylinders goes this is quite large and the reason for that really comes down to two things packaging as you start to get larger you might as well just use more cylinders and then because the space won't be all that different and then from a vibration standpoint inline four cylinders start to get quite noticeable vibration as you get larger in size so what gm does to combat this is they have two balance shafts underneath the crankshaft above the oil pan below this engine and so this is to combat secondary vibrations if you want to learn more about how balance shaft works i have a video which i will link in the video description which you can learn all about why they have these balance shafts in there but basically that eliminates the secondary forces that the pistons will be creating so you will have two balance shafts located underneath that crankshaft and these are rotating at two times the speed as the crankshaft so the l3b engine is used in two different applications by gm currently it is used in the cadillac ct4v and it is used in the chevy silverado which is a truck in the cts4 v it makes 325 horsepower 380 pound-feet of torque using premium gas in the silverado it's making 310 horsepower 350 pound feet of torque using regular gas now one of the really cool things about this engine is that it uses a three position cam shaft so if you've watched my video on variable valve lift then you've seen a very similar mechanism in a volkswagen engine where they use a cam slider to give different profiles that lift and close the intake and exhaust valves and so in this engine there are three different profiles for those intake valves right here what we're looking at is two of these sliders for one individual valve so really there's going to be two valves with each of these sliders and this is going to be mirrored over for each of the four cylinders and so you have these different profiles you've got the slider here in this darker blue and then these three different profiles which the intake valve can follow so it's got this one on the left here that is a high lift high duration profile that's going to give you the most power for those high load uses when you're flooring it things like that then in the center if you look at this one here you have a lower valve and a lower duration and that's kind of for your medium load area where you're going for more efficiency and optimizing airflow at lower rpm and then finally you'll notice that the third profile is different for this intake valve versus for this intake valve and so what's happening is for this third section of this cam slider you're actually disabling the center two cylinders so it's only running on cylinders one and four and so for the second cam slider it's going to go to basically an off position so it doesn't open or close that intake valve same with the exhaust the exhaust valve is going to have two sliders for just the center cylinders so that it will shut off the exhaust valves for these two center cylinders so these will operate like normal one in four your firing order being one three four two so you're alternating between one and four and the center two will basically just be air springs with that piston moving up and down so this two cylinder mode can be useful when you're just cruising on the highway and trying to maximize your fuel efficiency so what kind of highway fuel economy are we talking about here well in the ct4v you're getting 20 miles per gallon in the city 29 miles per gallon on the highway in the chevy silverado this engine is giving you 20 in the city 23 miles per gallon on the highway now 23 miles per gallon may not sound all that impressive but consider what fuel economy the 5.3 liter v8 that also goes in the chevy silverado gets on the highway it only gets 24. 24 miles per gallon on the highway to recap so far a cadillac sedan is a truck a mercedes genuine suv is a coupe and if you want the best fuel economy on the highway get the v8 now regardless of whether this engine actually makes any sense or not it does have a very cool turbo charger a dual fluid turbo so what is a dual volute turbo well it simply means that it has two volutes one on top of the other you may have heard of twin scroll turbochargers these are fairly similar in principle but they have two scrolls side by side rather than one volute on top of the other so what's the advantage of doing something like this and what's the difference versus a twin scroll as far as advantages are concerned so looking at the engine block itself the exhaust manifold is actually integrated within it so you've paired up cylinders one and four and you've paired up cylinders two and three so cylinders two and three send their exhaust pulses to that top volute and then cylinders one and four send their exhaust pulses to that bottom balloon and your firing order is one three four two and so you're alternating between which fallout is actually getting that exhaust pulse so if you look at a simplified drawing over here where we've stretched out that exhaust manifold your firing order being one three four two and you can see that first cylinder has fired the second cylinder is in the other dilute and so its pulse is over here and so the whole idea and why you're doing this is you're separating those exhaust pulses so they don't interfere with one another so that you don't have positive pressure from one of these going back into one of the cylinders that's opening up next so you split them up one three four two and then you don't have to worry about that valve overlap and as a result you get better response you get better low end torque and you get better efficiency out of this dual velo turbo now whether it's a dual volute or a twin scroll turbo both of them use this exact same strategy here of splitting the cylinders to optimize turbo response when you press down on that accelerator pedal how long does it take to actually get that turbo spooled up and so the difference here is how these exhaust gases are entering and hitting that turbine and spinning up the compressor wheel and so with this dual volute you're entering on opposite sides of that turbine versus with the twin scroll turbo you're actually entering together to hit that turbine and so you have a little overlap here where exhaust pulse from one can travel into the other chamber and so there's a bit of an inefficiency there where this is going to allow more energy to actually reach that turbine and spool it up so typically it's going to have better response because you're splitting where it actually enters that turbine where it's hitting it and where it's rotating from another difference is the distance from this turbine housing to this turbine itself so with this dual loot turbo you can bring the edge closer to that turbine wheel because you're not splitting that area right in the middle and so these will with twin scroll turbo chargers be about five millimeters from the turbine blades versus here with this dual volume design apparently you can get about one millimeter away from that turbine blade and so as a result it's going to be more efficient better response you're getting more of that energy to hit it and so as a result the turbo spools up faster and you get your torque sooner so how much sooner well chevy says with the silverado engine if you're at 1500 rpm and you floor it it takes 1.93 seconds to get to 90 percent torque so you're getting nearly peak torque in about two seconds at 1500 rpm which is a very low engine speed so it is impressive that it's able to spool up that quickly at such a low rpm however is it impressive versus say a chevy bolt which can get peak torque like that perhaps not so i don't know why i'm excited about this engine but it is very cool the technology involved and the improvements that it creates thank you all so much for watching and if you have any questions or comments feel free to leave them below\n"