The Honda F-Series engine was considered Honda's "big block" SOHC inline four, though lower production DOHC versions of the F-series were built. It features a solid iron or aluminum open deck cast iron sleeved block and aluminum/magnesium cylinder head. This engine was used in the 1998-2002 Honda Accord LX, EX, and SE, LEV models, and in the Acura 2.3CL in North America.
Acceleration (0-60) for the 4-cylinder models is improved (around the mid-9-second mark), with comparable fuel efficiency to its predecessor: 23 mpg/city and 30 mpg/hwy for LX and EX models with automatic transmissions. Emissions of Non-Methane Organic Gases (NMOG), also known as unburned hydrocarbons, produced during engine warm-up are considerably lower. The LX and EX engines produce less than 0.0075 grams per mile, qualifying them for California LEV (Low-Emission Vehicle) status. In California, the Accord EX with the available automatic transmission will produce less than 0.003 grams per mile of NMOG, qualifying it as the first gasoline-powered vehicle to reach ULEV (Ultra-Low Emission Vehicle) status. The five-main bearing block is high-pressure die-cast from aluminum alloy. The walls of the block extend below the centerline of the crankshaft, which helps stiffen the bottom end. FEM (Finite Element Method) computer analysis was used to arrive at optimum thicknesses for the block ribs and walls in order to minimize engine vibration. Additional bottom-end rigidity comes from a larger, stronger bearing-cap beam that ties directly into the cylinder-block skirt. An aluminum-alloy stiffener has been added between the transmission case and the block, just behind the bearing carrier. The stiffener serves to tie the block and transmission together into a single, reinforced unit. FEM was also used to design this stiffener so that it would not only stiffen the area, but also help minimize high-frequency engine vibration. Finite-element analysis of the Accord's piston design by Honda engineers yielded a new ultra-short, lightweight skirt design, which is very rigid and resistant to vibration and piston slap. Like the V-6 engine the pistons are gravity-cast aluminum alloy and utilize full-floating wrist pins in order to minimize noise. The engine's drop-forged single-plane steel crankshaft and connecting rods have been designed to be stronger and operate with less friction, much like the V-6 components. The I-section, drop-forged steel connecting rods have a completely new design and are considerably lighter than their predecessors (475 g vs. 578 g), which helps to minimize vibration. Pin-journal (big end-bearing journal) diameter has been reduced from 48 mm to 45 mm. Rod thickness is down from 24 mm to 20 mm and the bolt size is smaller. Like the V-6 rod bolts, those of the 4-cylinder engine are torqued to the plastic region of the bolt material in order to ensure a solid union between the bearing cap and the connecting rod. The engine block incorporates the Honda-designed second-order balance system that cancels the inertial forces common to large-displacement 4-cylinder engines. The system consists of two parallel shafts on either side of the crank-shaft, 81 mm (3.19 in.) above its centerline. Driven by a toothed belt, the balance shafts rotate in opposite directions at twice engine speed. Eccentric weights built into the shafts generate inertial forces that counteract the second-order forces created by the motion of the pistons and connecting rods. This Honda system minimizes vibration in the entire rpm range.[WIKI]
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