From sedans to SUVs, Honda uses turbocharged engines in some trims of many of its passenger vehicles. Most, like the Accord, Civic Si, and CR-V use various iterations of the 1.5-liter inline four turbo, while the Civic Type R has the seriously powerful 2.0-liter inline-four turbo. At some stage, turbos were considered powerful, but unreliable, and suffering from the dreaded turbo lag — that horrible pause between flooring the accelerator and the serious power kicking in. This is fortunately no longer the case.
While the 1.5-liter turbo is used mainly for fuel efficiency, getting more power from a smaller, lighter engine, Honda turbocharged engines are all renowned for their durability. Honda has been using turbos since the 1980s, first in its motorcycles, then in its F1 engines, and starting in passenger cars in ’88. The Civic was the first turbocharged Honda in the US in 2016. Here is a look at some factors that make these engines last so long.
Reinforced Engine Internals
Apart from the displacement, the main differences between the 1.5-liter and 2.0-liter engines are in the valvetrain system, the fuel injection and manifold design, and the size and shape of some of the components. The engineering and materials used to make these internals so durable are mostly the same.
Engine Block And Crankshaft
The engine block is die-cast aluminum to save weight. The main bearing caps are individually reinforced to add strength. Iron cylinder liners are cast in for longer-lasting durability. The crankshaft is made of lightweight forged steel, and each journal is micropolished to minimize friction. The connecting rods are made from a lightweight, very strong steel. This is heat forged in one piece, which is crack-separated to produce a lighter and stronger rod, with a perfectly fitted bearing cap.
Pistons And Camshaft
The pistons are very light, and use concave crowns to create a high-tumble intake charge — basically the optimal mixing of the fuel and air — to provide efficient combustion. The lightweight DOHC cylinder head is made with pressure-cast aluminum alloy. Both the 1.5-liter and 2.0-liter engines have the exhaust manifold cast directly into the cylinder head to reduce weight and complexity, although the design of this manifold differs between the two engines. Weight is further saved by using smaller M12 spark plugs and hollow, thin-walled camshafts. A low-friction chain drives the overhead cams, and the cam drive is maintenance-free for the life of the engine.
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Better Cooling And Less Friction
From the cauldron of the early F1 turbocharged engines, to high-revving motorcycle engines, to building generation after generation of efficient family cars and hot hatches, Honda has built up institutional knowledge on how to make good turbo engines that last. A lot of that involved increasingly sophisticated ways to improve cooling and reduce friction.
Optimized Cooling Capabilities
The first and most obvious step in keeping things cool is to use an efficient intercooler to cool the air heated up by the compression of the turbo, making it more dense for better performance and reducing the chance of knocking. The next bit of engineering involves twin oil jets spraying the underside of each piston to keep them cool and stable during combustion.
Hollow exhaust valves are filled with sodium to help transfer heat away from the valve head to the cooler exhaust port cooling jacket. This allows the use of a leaner fuel mixture, which increases fuel efficiency, lowers emissions, and boosts power. Because the exhaust ports are cast directly into the aluminum-alloy cylinder head, the surrounding water jacket efficiently cools the exhaust path.
Reducing Friction Through Various Channels
The outer skirts of the lightweight aluminum pistons have a low-friction molybdenum coating in a dot pattern to reduce friction and vibration as they move against the cylinder walls. These cylinder walls go through a two-stage machining process that creates a super-smooth surface, further reducing friction between the piston and the cylinder wall. The piston rings are ion-plated for minimum friction and maximum operating efficiency. Besides the polished crankshaft journals, low-friction cam chains, and lightweight engine internals mentioned above, the Honda engines also use a two-stage oil pump relief valve for optimum oil flow and low-friction oil seals.
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Advanced Valve Control
The more efficiently an engine can operate over a range of driving conditions, the lower the stresses on this engine, and as a result, the more durable it will be. Honda has pioneered valve timing control (VTC) and variable valve timing and lift electronic control (VTEC), which improve not only engine performance, but also fuel efficiency, and engine durability.
VTEC And VTC
VTEC is used with the exhaust valves to help control gas scavenging and improve performance across the engine RPM range. At low RPMs, a low-lift cam profile is used, improving fuel efficiency and keeping the idle stable. At high RPM and during heavy loads, VTEC hydraulically engages a high-lift, longer duration cam profile. This allows more of the air/fuel mixture into the cylinder before combustion, boosting power.
Dual VTC continuously adjusts the timing of both the intake and exhaust camshafts relative to the crankshaft. It uses the engine control unit to dynamically control valve opening and closing times, depending on the driving conditions, such as speed, engine load, and throttle position. This continuous process helps to optimize torque, particularly at low to midrange RPM, which improves general engine efficiency.
The Synergy Between VTEC And Dual VTC
The engine control unit (ECU) is the interface that allows the seamless combination of the VTC timing and VTEC opening of the valves. This interface continuously adjusts the system to allow a broad, flat torque curve, quick boost response, and high-RPM power in the turbocharged engine. This creates optimal airflow and combustion efficiency under all driving conditions, and minimizes turbo lag by optimizing valve operations to allow the turbo to build boost at even low RPMs. This leads to greater engine efficiency, resulting in an engine that will last longer.
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Maintenance Minder
The maintenance minder is an integrated system aimed at making maintenance easier and happen on time. Instead of fixed service intervals, these systems use pressure sensors, temperature gauges, and measure speed and operating conditions to determine the remaining oil life and when other services are needed. This information is displayed as specific codes on the dashboard. Maintenance minder avoids the expense of premature services, while making sure that services that become due are done on time. This is crucial for the performance of such a high-performance engine.
Any engine, particularly high-performance ones like the turbocharged Honda unit, requires regular and proper maintenance to ensure it can give so many miles of hassle-free service. Oil should be monitored continuously and changed regularly, and the engine should be warmed up properly before hard use, and preferably cooled down again afterward. The recommended grade of both oil and fuel should always be used. But Honda has made the maintenance process a lot simpler.
Durable Design
Anyone who has ever had a timing chain issue will love the maintenance-free timing chain on the Honda engines. The integrated exhaust manifold that is cast directly into the cylinder head helps to simplify the layout of the engine and improve heat management. Heat, friction, and vibration all contribute to faster wear and tear, requiring more maintenance more often. The sodium-filled exhaust valves allow running a leaner fuel mixture, which reduces engine stress. The low-friction components in the cylinders and pistons mean less wear over time, while the rigidity of components such as the crankshaft and oil pan reduces vibration and the general wear that comes with that.