Honda 2.4L DOHC I-4

Honda proves a bread-and-butter engine, its all-new 2.4L direct-injection 4-cyl. in the Accord, is more like a piled-high deli sandwich.

January 7, 2013

3 Min Read
Honda 2.4L DOHC I-4

Bread-and-butter engines make the auto industry go ’round, but they rarely dazzle us with superb refinement or sportiness.

These types of high-volume engines are in affordable cars, and their mission is simple: Deliver the occupant reliably from Point A to Point B and blend into the woodwork.

Only a handful of these unsung heroes have earned Ward’s 10 Best Engines honors over the years, and 2013’s standout among this segment is Honda’s all-new 2.4L direct-injection 4-cyl. in the Accord.

Honda’s first DI engine in North America, branded as “Earth Dreams,” is loaded with compelling technologies, including a forged-steel crankshaft with journals micropolished to reduce friction and a pair of chain-driven counter-rotating balance shafts located in the oil pan to offset harmonic vibrations inherent in 4-cyl. engines.

The addition of fuel being injected directly required a completely re-engineered combustion chamber and a new “dished” surface for the piston crowns to enable stable combustion and proper distribution of the stratified fuel charge.

The flatter, more compact combustion chamber reduces unburned hydrocarbon emissions and contributes to a higher compression ratio of 11.1:1, up from 10.5:1 on the previous 2.4L.

Within the cylinder, engineers set out to reduce sliding friction by offsetting the bores from the crankshaft by 0.3 ins. (8 mm), which gives the connecting rods a more favorable angle during each power stroke, boosting efficiency.

Mass was taken out wherever possible, resulting in a 3.5% reduction in overall engine weight compared with Honda’s previous-generation 2.4L.

Part of that weight savings comes from eliminating the exhaust manifold – an emerging trend for a number of new engines – and incorporating exhaust passages directly into the cylinder head.

This new design allows the close-coupled catalyst to mount directly to the cylinder head, on the front side of the engine, enabling it to heat up faster for reduced emissions. The transversely oriented 2.4L also stands more upright now, whereas the previous engine vented on the back side and slanted rearward 15 degrees.

All this technology adds up to an engine that caught WardsAuto editors off-guard for its power and smoothness.

Over the course of a 537-mile (864-km) test drive, two editors exceeded 33 mpg (7.1 L/100 km) in this generously proportioned sedan that gets up to speed with no problem thanks to 189 hp, ample low-end torque and a wonderful mid-range punch.

“Honda proves once again it isn’t about the numbers,” WardsAuto editor Drew Winter writes on his score sheet. “This engine is fun and sporty. It’s an excellent, practical engine that delivers both performance and fuel economy in unassuming fashion.”

Under a heavy boot, as engine speed builds past 4,800 rpm, Honda’s well-established VTEC variable valve-timing system transitions to a high-lift, long-duration intake cam profile for outstanding high-rpm engine power. And it all happens with regular unleaded gasoline.

Worthy of a shoutout are two new transmissions that help this 2.4L engine truly shine.

A 6-speed manual in the Accord Sport amps up the fun quotient, and driving enthusiasts also will eagerly accept the all-new continuously variable transmission, developed internally to demonstrate that CVTs aren’t just for poky hybrids.

With excellent transmissions, Honda’s 2.4L DI engine isn't just a bread-and-butter 4-cyl.

Now it's a piled-high deli sandwich.

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