Acura 1.5-Liter Turbo Engine

  • Part of the “L-Series” engine family, the 1.5-liter Turbo engine makes its Acura debut in the all-new Acura Integra, creating the first-ever factory-turbocharged Integra
  • Integra’s 1.5-liter Turbo features Variable Valve Timing and Lift Electronic Control (VTEC®)
  • Latest version of the 1.5-liter Turbo (L15CA) delivers 200 hp1 and 192 lb.-ft. of torque2

Produced in various forms worldwide since 2001, the 1.5-liter turbocharged 4-cylinder is a member of the “L-Series” engine family. In 2022 it makes its Acura debut under the hood of the all-new 2023 Acura Integra, creating the first-ever turbocharged Integra from the factory.

A performance 5-door liftback, the new Integra marks the return of the iconic nameplate to the Acura lineup and continues the Integra tradition of offering unmatched premium performance at an attainable price point. To deliver 200 hp1 and 192 lb.- ft. of torque2, its turbocharged high-output 1.5-liter VTEC® engine features 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.

Engine Internals
To minimize weight, the engine block is die-cast aluminum, and uses individual reinforced main bearing caps for additional 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 increasing 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.

Variable Valve Timing and Lift Electronic Control (VTEC®) is also used on the Integra’s 1.5-liter Turbo. Working in conjunction with the VTC™ system, VTEC® alters valve lift, timing and duration of the exhaust valves opening. 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 with a 11-blade turbine impeller 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, positioned low in the front of the car where it receives 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.

2023 Integra (L15CA)
Powering the new Acura Integra is the latest version (L15CA) of the 1.5-liter Turbo engine which has received multiple updates, including VTEC® variable valve lift technology on the exhaust cam, that collectively extend peak output across a wider rpm range and improve fuel efficiency, emissions and drivability. VTEC® improves exhaust efficiency and optimizes valve overlap to better performance across the rev range by working in conjunction with VTC™ to enable improved gas scavenging.

The engine, which features a 10.3:1 compression ratio, also uses a “4 into 2” exhaust manifold design that is integrally cast into the cylinder 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.

Peak boost is 17.8 psi. Reshaped turbine wheel blades inside the turbocharger combined with an optimized flow path enables the turbocharger to generate pressure in a wider range and more efficiently. Exhaust channeled to the turbo enters the turbine wheel diagonally, rather than from the side as in earlier versions of the 1.5-liter turbo.

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, which increases efficiency by approximately 5% in all areas, resulting in high responsiveness and output.

The results are output of 200 hp1 and significant power delivery improvements over previous variants of the engine. More output is maintained between its 6000-rpm power peak and its 6600 rpm redline and its peak torque of 192 lb.-ft.2 arrives at 1800 rpm, 300 rpm sooner, for quicker punch off the line and out of tight corners.

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  1. SAE net @ 6,000 rpm
  2. SAE net @ 1,800 - 5,000 rpm