Honda 1.5-Liter Turbo Engine

• The 1.5-liter Turbo engine is part of the “L-Series” engine family, which has been produced in various forms worldwide since 2001.
• The 1.5-liter Turbo engine debuted in the U.S. in the 2016 Honda Civic and is currently available in multiple Civic, CR-V and Accord models
• Honda has sold more than 3 million cars and light trucks in the U.S. powered by this engine since 2016

One of the latest in a long line of Honda engines renowned for its power, efficiency, and reliability, the 1.5-liter turbocharged 4-cylinder is part of the “L-Series” engine family, which has been produced in various forms worldwide since 2001. Since the 1.5-liter Turbo engine debuted in the U.S. in the 2016 Honda Civic, eight versions of the engine have been available with outputs ranging from 174 to 205 horsepower (SAE net) in various applications, and more than 3 million have been sold.

Common features across all seven versions of the engine include a double overhead cam (DOHC) cylinder head, dual Variable Timing Control™ (VTC™), direct injection, and a low-inertia mono-scroll turbo system that uses an electric wastegate to control boost pressure. Today the latest versions of the 1.5-liter Turbo are found under the hoods of Civic, CR-V and Accord models.

Engine Internals
To minimize weight, the engine block is die-cast aluminum. Individual reinforced main bearing caps add strength. Cast-in iron cylinder liners provide long-lasting durability. Each journal on the lightweight forged-steel crankshaft is micropolished to reduce internal friction.

The connecting rods are made of a lightweight, high-strength steel, heat-forged in one piece and then “crack separated” to create a lighter and stronger rod with an optimally fitted bearing cap.

Lightweight pistons use “cavity-shaped” crowns, to provide a high-tumble intake charge that further enhances combustion efficiency. The piston’s carefully optimized skirt is designed to minimize reciprocating weight, reducing vibration and increasing operating efficiency. Twin oil jets directed at the underside of each piston crown keep the pistons cool to help prevent detonation, and ion-plated piston rings help reduce friction for greater operating efficiency.

DOHC Cylinder Head and Valvetrain
The lightweight DOHC cylinder head is made of pressure-cast aluminum alloy, with the exhaust manifold cast directly into the cylinder head. This eliminates the need for a separate exhaust manifold, reducing weight and complexity. Additional weight reduction measures are used throughout, such as smaller M12 spark plugs, and thin-walled hollow camshafts.

A low-friction, silent chain drives the dual overhead cams, and the cam drive is maintenance free for the life of the engine. Sodium-filled exhaust valves are cooled by the exhaust port cooling jacket, rather than an enriched fuel mixture used in many turbo engines. This enables a leaner mixture, reducing emissions, increasing fuel efficiency and power.

Variable Timing Control™ (VTC™) varies the phase of both the intake and exhaust camshafts independently, optimizing cam timing to suit driving conditions. Under light loads, valve overlap can be increased to reduce pumping losses and improve fuel efficiency. When engine speed is low and engine load is high, such as during initial acceleration, the amount of overlap is increased to boost the scavenging effect, which improves torque and responsiveness. When engine speed is high and engine load is also high, such as during full-throttle acceleration, the amount of valve overlap is reduced to increase engine output by improving both intake and scavenging.

First introduced to the engine on the 2018 Accord, Variable Valve Timing and Lift Electronic Control (VTEC®) has since been adopted for other versions of the engine. Working in conjunction with the VTC™ system, VTEC® alters valve lift, timing and duration of the exhaust valves. The increased valve lift from VTEC® operation varies to improve gas scavenging at low rpm, part throttle conditions, as well as higher rpm, full throttle operation, helping to improve performance across the engine speed range.

Fuel Delivery
Supplying fuel is a direct-injection system featuring a compact, high-pressure, direct-injection pump with high fuel flow, pulsation suppression and variable pressure control to optimize injector operation. The multi-hole injectors deliver fuel directly into each cylinder, optimizing fuel atomization for more efficient combustion.

Thanks to the precise control the system enables, the multi-hole injectors can create the ideal stoichiometric fuel/air mixture in the cylinders for good emissions control, adjusting its function for the best performance based on operating conditions.

For example, on cold engine startup, fuel is injected into the cylinders on the compression stroke. This creates a weak stratified charge effect that improves engine start-up and reduces exhaust emissions before a normal operating temperature is reached.

Once the engine is fully warmed up, fuel is injected during the intake stroke for maximum power and fuel efficiency. This also helps create a more homogeneous fuel/air mix in the cylinder. Aided by the high-tumble intake port design, this improves volumetric efficiency and reduces knock thanks to the cooling effect of the incoming fuel.

Turbo System
For maximum responsiveness, a small-diameter MHI TD03 turbo is used. The single-scroll housing design helps the turbo build boost even at relatively small throttle openings and low engine speeds. The electrically actuated wastegate enables precise control of boost pressure.

Cooling the intake charge is a large low-restriction intercooler, in all cases positioned low in the front of the car where it receives essentially unobstructed airflow when the vehicle is in motion. As intake air is compressed by the turbo, it heats up, and the intercooler helps reduce that temperature, making it denser and improving performance. Lightweight resin composite inlet pipes carry air to and from the intercooler to reduce the overall weight of the turbo system.

10th-Generation Civic (2016-2021)
For the U.S. market, the 1.5-liter Turbo (L15B7) was first introduced on the 10th-generation Civic Sedan and Coupe in EX-T, EX-L and Touring grades. Running 16.5 psi of peak boost, the engine produces 174 horsepower (SAE net @ 6,000 rpm) and 162 lb.-ft. (SAE net @ 1,700-5,500 rpm) — a significant upgrade of 16 horsepower and 24 lb.-ft. of torque over Civic’s standard naturally aspirated 2.0-liter engine.

All grades of the 10th-generation Civic Hatchback were also powered by the new turbocharged engine. However, the Sport and Sport Touring models were equipped with a variation of the engine (L15BA) that produces 180 horsepower (SAE net @ 6,000 rpm) running at the same boost levels. This is due to a freer-flowing center-exit exhaust system and upgrades that benefit from higher octane premium fuel. When equipped with a manual transmission and running on premium fuel, the engine also received a bump in peak torque to 177 lb.-ft. (SAE net @ 1,900-5,000 rpm).

Introduced for the 2017 model year, the Civic Si Sedan and Coupe were powered by a 205-horsepower version of the 1.5-liter Turbo (L15B7 High Output) paired exclusively with a manual transmission. The horsepower improvement was due largely to an increase in boost to 20.3 psi which also required premium fuel.

5th-Generation CR-V (2017-present)
Introduced for the 2017 model year, the redesigned fifth-generation CR-V also featured the turbocharged 1.5-liter engine (L15BE) in EX, EX-L and Touring trims. Since the 2020 model year, the engine has been standard in all non-hybrid versions of the compact SUV putting out 190 hp (SAE net @ 5,600 rpm) and 179 lb.-ft. of torque (SAE net @ 2,000-5,000 rpm. 

In this application, the pistons feature a reshaped crown, which lowers the compression ratio from 10.6:1 in Civic to 10.3:1. The reshaped 9-blade turbine impeller inside the turbocharger is also used. This change allows boost pressure to be increased to 18.5 psi while still using regular unleaded fuel. Finally, the induction system includes a 4% improvement in overall flow, which also contributes to the higher output.

10th-Generation Accord (2018-present)
When it debuted for the 2018 model year, the 10th-generation Accord featured the 1.5-liter Turbo in LX, EX, EX-L, Touring, and Sport grades. In 2022, it is available in the Accord LX, Sport, Sport SE and EX-L.

The 1.5-liter Turbo used in the Accord (L15BE with VTEC®) is similar to the version powering the CR-V. It features numerous updates including 20.2 psi of turbo boost and VTEC® variable valve lift technology on the exhaust side. This is the first time VTEC® was used on the 1.5-liter Turbo. It improves performance across the rev range by working in conjunction with VTC™ to enable improved gas scavenging.

Additional modifications to the engine include a new “4 into 2” exhaust manifold design cast into the head. This groups the exhaust from the 1 and 4 cylinders and 2 and 3 cylinders, with each group using a separate exit port to the turbocharger. This design helps smooth exhaust flow to the turbocharger for more efficient operation and better low-rpm response.

The result of these changes are ratings of 192 hp (SAE net @ 5,500 rpm) and 192 lb.-ft. of torque (SAE net @ 1,600-5,000 rpm) on regular unleaded gasoline.

11th-Generation Civic (2022-present)
Powering the new 11th generation Civic Sedan EX and Touring grades, as well as the Civic Hatchback EX-L and Sport Touring is the latest of the 1.5-liter Turbo (L15B7 with VTEC®). Compared to the versions of the engine used in the 10th generation Civic, multiple updates have been made to improve output, fuel efficiency and emissions.

The most significant was the addition of VTEC® to the exhaust cam, improving exhaust efficiency and optimizing valve overlap. The new Civic engine also uses a “4 into 2” exhaust manifold design, similar to the one used on Accord, and a 10.3:1 compression ratio.

In the latest Civic the engine also uses a reshaped 11-blade turbine impeller design in the turbocharger, and it combines with a new flow path to enable the turbocharger to generate pressure in a wider range and more efficiently. Exhaust channeled to the turbo now enters the turbine wheel diagonally, rather than from the side as before.

Moreover, by reducing the curvature of the intake air entry to the compressor housing and the high-pressure side pipe, which leads to charged intake air discharge, the pressure drop is reduced. This increases efficiency by approximately 5% in all areas, resulting in high responsiveness and high output. With these changes the engine’s peak output of 180 hp (SAE net @ 6,000 rpm) and 177 lb.-ft. of torque (SAE net @ 1,700-4,500 rpm) are possible at 16.5 psi of boost on regular unleaded fuel, instead of premium in the 10th-generation Hatchback.

The new high-performance 2022 Civic Si is equipped with a 200 hp (SAE net @ 6,000 rpm) version of the engine (L15CA) that features the reshaped 11-blade turbine impeller design, 17.8 psi of boost, VTEC®, a 10.3:1 compression ratio, and significant power delivery improvements. It now maintains more output between its 6000-rpm power peak and its 6600 rpm redline than it did in the previous Si models (L15B7 High Output) and its peak torque of 192 lb.-ft. arrives at 1800 rpm, 300 rpm sooner than before, for quicker punch off the line and out of tight corners.

6th-Generation CR-V (2023)
An updated and refined version of the direct-injected 1.5-liter turbocharged 4-cylinder engine is under the hood of the 2023 CR-V EX and EX-L models. The engine has received multiple enhancements to provide a more refined driving experience and enhanced power delivery.

Running on regular unleaded gas, the engine produces 190 horsepower @ 6,000 rpm (SAE net) and maintains peak power over a broader range at high revs than before. Its 179 lb.-ft. (SAE net) peak torque spans 1,700-5,000 rpm, arriving 300-rpm earlier than before for a more responsive feel.

VTEC variable valve timing is now used on the exhaust side of the twin-cam head. This helps improve exhaust efficiency and optimizing valve overlap, efforts that contribute to improved fuel efficiency. It also helps lower the engine speed for peak torque. More information about the benefits of VTEC is available here.

For emissions, a new catalytic converter that minimizes the use of rare metals is used, helping CR-V achieve LEV3 SULEV 30 emissions certification (ULEV 50 with AWD). Further aiding fuel economy and reducing emissions is a new idle-stop system that turns off the engine at stoplights.

Improving acceleration response is a high-efficiency high-response turbocharger and low pressure-loss turbocharger piping. The turbocharger now routes exhaust gas diagonally to the turbine wheel, and the turbine blades also have been reshaped, helping the turbocharger generate pressure in a wider range of engine speeds and more efficiently.

The exhaust manifold is now a 4-into-2 design, which consolidates the exhaust from the number 1 and 4 cylinders into one port, and the number 2 and 3 cylinders in a separate port. This reduces exhaust pulse interference, improving intake and exhaust efficiency, especially at low engine speeds.

Engine noise has been significantly reduced by a new high-rigidity crankshaft and oil pan, and a new intake cover. Further noise reduction measures include noise-insulating engine mounts and a new muffler redesigned from a J-turn internal structure to an S-turn.

Honda 1.5-Liter Turbo Applications

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