2004 Honda S2000 -- Powertrain Part 1

Powertrain

Overview

The S2000 powertrain uses a front-engine/rear-wheel-drive layout. The longitudinally mounted engine is mated to a 6-speed, close-ratio manual transmission. A propeller shaft carries the output of the transmission to a frame-mounted limited-slip differential. The differential drives the rear wheels via separate axle shafts.

The 2.2-liter, aluminum-alloy, inline 4-cylinder S2000 engine produces 240 hp @ 7800 rpm and 162 lb.-ft. of torque @ 6500 rpm. The cylinder head is also made of aluminum alloy and features dual overhead camshafts, 4 valves per cylinder and VTEC (Honda's variable valve-timing system) on both the intake and exhaust valves. Fuel induction is via Honda's sequential, Multi-Point Programmed Fuel Injection (PGM-FI) and the ignition system is a high-voltage, computer-controlled direct type with individual spark coils for each cylinder. The engine's exhaust emissions qualify the S2000 as a Low-Emission Vehicle (LEV) in California.

New for 2004

Objectives for enhancing the 2004 S2000 powertrain focus on improved power delivery at low and mid-range rpms while maintaining the high-revving, race bred nature of the S2000 engine.

Mechanical improvements have been made to many components of the engine and transmission to enhance everyday street driving appeal and the S2000's capabilities on the track. More torque is available at lower rpms while the overall enhanced power band increases dynamic transitional capabilities, i.e. exiting corners faster. Significant changes include:

  • 2.2-liter engine displacement (increased from 2.0 liters)
  • Horsepower and torque band increased 4- to 10-percent between 1000 rpm and 8000 rpm with useful high performance power now starting at 3000 rpm.
  • Transmission gear ratios revised (4% lower on gears one through four)
  • Transmission efficiency and direct feel improved with carbon synchronizers

2004 S2000 vs. 2003 S2000

Between 1000 rpm and 8000 rpm, available torque and horsepower increase between 4 and 10 percent. Additionally, useful power for high performance acceleration begins at about 3000 rpm compared to about 6000 rpm on the 2000 - 2003 models. The performance improvement at lower rpm ranges can be attributed to the increase in displacement and revised valvetrain tuning. Lower gear ratios on gears one through four further magnify the new performance characteristics of the engine.

The enhanced powerband benefits acceleration response at lower rpms and improves the overall "powerful feel" of the car in everyday driving. To increase the engine displacement, powerband, and direct transmission feel of the vehicle, the following specifications and components have changed:

2004 2003 Change/Notes
Engine
Engine 2.2-liter DOHC VTEC 2.0-liter DOHC VTEC + 0.2 liters, attributable to engine stroke change
Horsepower 240 @ 7800 rpm 240 @ 8300 rpm + 0 hp @ -500 rpm, same peak horsepower with overall powerband characteristics strengthened by 4% to 10% between 1000 and 8000 rpm
Torque (lbs.-ft.) 162 @ 6500 rpm 153 @ 7500 rpm +9 lb.-ft. @ -1000 rpm with improved powerband characteristics strengthened by 4% - 10% between 1000 and 8000 rpm. Max torque increases 5%.
Rev Limit / Fuel Cutoff) 8000/8200 8800/9000 Piston travel configuration decreases rpm limit by 9% because of piston speed increase.
Compression Ratio 11.1:1 11.0:1 +0.1:1
Bore x Stroke (mm) 87.0x90.7 87.0x 84.0 0.0x+6.7
Crankshaft Half Stroke (mm) 45.3 42.0 +3.3 (Crankshaft determines stroke length and creates displacement change)
Connecting Rod Length (mm) 149.65 153.0 -3.35 (Calibrated for crankshaft half stroke)
VTEC (low-speed profile) Reconfigured
-
Low-speed intake duration decreased and exhaust duration increased for more torque
VTEC (high-speed profile) Reconfigured
-
High-speed intake and exhaust duration slightly decreased for torque and top horsepower
Transmission
Transmission Ratios Reconfigured
-
Gears 1-4 = 4% lower for performance
Gear 5 = 1% lower
Gear 6 = 2% higher
Synchronizers Carbon (Double carbon single cone on 1-2 and single carbon cone on 3-6) Brass (Triple Cone or double cone on gears 1-4) Carbon material reduces mechanical loss and increases capacity of synchronizer

2004 Powertrain Main Features

The following are the main features of the S2000 powertrain:

2.2-Liter (2178 cc) VTEC Engine

  • 8000rpm rev limit
  • 240 hp @ 7800 rpm
  • 162 lb.-ft. of torque @ 6500 rpm
  • 0-60 mph acceleration in less than 6 seconds
  • Compact, lightweight engine design aids in ideal (50/50) weight distribution
  • FRM (Fiber-Reinforced Metal) cylinder liners
  • 87.0 mm bore X 90.7 mm stroke contributes to increased torque band
  • Rigid aluminum (ladder-type) main bearing support, with cast-iron bearing inserts, enhances engine durability
  • Lightweight forged-aluminum pistons and heat-treated (carburized), forged-steel connecting rods add durability
  • Full-floating piston pins eliminate piston noise during warm-up
  • High-volume oil pump with silent chain drive
  • Compact, high-efficiency oil cooler
  • Cast-aluminum oil pan helps minimize engine noise and enhances oil cooling
  • 11.1:1 compression ratio
  • Compact, DOHC VTEC cylinder head and valvetrain
  • Lightweight, MIM (Metal-Injection Molded), sintered-steel rocker arms
  • Low-friction roller-bearing cam-followers
  • Compact, 2-stage cam-drive with silent chain, scissors gears and fully automatic tensioner
  • Hollow camshafts function as lubrication path for VTEC valvetrain
  • Sequential, Multi-Point Programmed Fuel Injection (PGM-FI)
  • Intake system with straight inlet ports and low-back pressure exhaust system
  • Electric-motor-driven, multi-port secondary air-assist injection system helps lower hydrocarbon emissions
  • Meets California's stringent Low-Emission Vehicle (LEV) standard
  • Compact engine ancillary drive system uses a serpentine drive belt with automatic tensioner
  • Compact engine ancillaries, such as air-conditioning compressor and water pump, save weight and take up less space
  • Direct-ignition system with long-lasting platinum-tipped spark plugs
  • Low back pressure, metal-honeycomb catalytic converter

Transmission

  • Longitudinally mounted 6-speed manual transmission
  • Transmission lubrication pump enhances durability
  • Reduced shift effort and direct feel from carbon synchronizers on gears one through six
  • Short-throw, direct shift linkage
  • Compact pull-type clutch mechanism and high-performance clutch
  • Propeller shaft uses highly durable constant-velocity joints
  • Torsen limited-slip differential
  • Highly rigid axle shafts utilize stronger flanged ends in place of splines
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