Technical Specifications For The 1991 Nissan 240sx Hatchback

Alright, let's dive into the nitty-gritty of the 1991 Nissan 240SX Hatchback. This is a popular chassis for a reason, so understanding its technical specs is key whether you're planning on basic maintenance, serious modifications, or just want to appreciate it for what it is.

Engine Options & Specifications

The '91 240SX Hatchback primarily came with two engine options, both inline-four cylinder designs:

KA24E (Single Overhead Cam)

This was the standard engine. Let's break down the specifics:

Displacement: 2389cc (2.4L). Displacement refers to the total volume swept by all the pistons inside the cylinders during one complete stroke.
Bore x Stroke: 89mm x 96mm. The bore is the diameter of the cylinder, and the stroke is the distance the piston travels within the cylinder. The bore to stroke ratio significantly impacts engine characteristics - a longer stroke generally means more torque at lower RPMs.
Compression Ratio: 8.6:1. This is the ratio of the cylinder volume when the piston is at the bottom of its stroke compared to when it's at the top. A higher compression ratio generally results in more power, but also increases the risk of detonation (knocking).
Valve Train: SOHC (Single Overhead Cam), 12 valves (3 valves per cylinder - 2 intake, 1 exhaust). SOHC means there's one camshaft in the cylinder head controlling all the valves. A 12-valve configuration means that each cylinder has two intake valves and one exhaust valve.
Fuel System: Electronic Fuel Injection (EFI). EFI uses sensors and a computer to precisely control the amount of fuel injected into the engine.
Horsepower: 140 hp @ 5600 rpm (SAE Net). Horsepower measures the engine's power output. SAE Net is a standardized testing method that accounts for the power consumed by engine accessories.
Torque: 152 lb-ft @ 4400 rpm (SAE Net). Torque is a measure of the engine's rotational force. It's what gets the car moving.

The KA24E is known for its reliability and decent low-end torque. It's a good engine for daily driving but can be a bit limiting for performance enthusiasts.

KA24DE (Dual Overhead Cam)

This was the optional, more desirable engine. Here's its breakdown:

Displacement: 2389cc (2.4L). Same as the KA24E.
Bore x Stroke: 89mm x 96mm. Also identical to the KA24E.
Compression Ratio: 9.5:1. A slightly higher compression ratio than the KA24E, contributing to increased power.
Valve Train: DOHC (Dual Overhead Cam), 16 valves (4 valves per cylinder - 2 intake, 2 exhaust). DOHC means there are two camshafts in the cylinder head, one for intake valves and one for exhaust valves. This allows for better valve control and higher RPM potential. A 16-valve configuration with four valves per cylinder provides improved breathing, further boosting power.
Fuel System: Electronic Fuel Injection (EFI). Same EFI system as the KA24E.
Horsepower: 155 hp @ 5600 rpm (SAE Net). Noticeably more horsepower compared to the KA24E.
Torque: 160 lb-ft @ 4400 rpm (SAE Net). A slight increase in torque as well.

The KA24DE offers a more responsive and rev-happy driving experience compared to the KA24E. It's often the preferred choice for those looking to modify their 240SX.

Transmission Options

The '91 240SX Hatchback came with two transmission options:

5-Speed Manual Transmission (FS5W71C): This is the most common and desirable transmission. It's a robust unit, though age and abuse can take their toll. Pay attention to synchro wear, especially in 2nd and 3rd gears.
4-Speed Automatic Transmission (RE4R01A): While convenient, the automatic transmission significantly impacts performance. It's less engaging and robs the engine of power.

Suspension & Brakes

The 240SX boasts a well-designed suspension system that contributes to its excellent handling characteristics:

Front Suspension: Independent MacPherson Strut with coil springs and stabilizer bar. MacPherson struts combine the spring and damper into a single unit, simplifying the suspension design. The stabilizer bar (also known as a sway bar) helps reduce body roll during cornering.
Rear Suspension: Independent Multi-link with coil springs and stabilizer bar. A multi-link suspension offers superior handling and ride comfort compared to simpler designs. It allows for more precise control of wheel movement.
Brakes: Power-assisted front disc brakes and rear drum brakes. Some models (typically SE trim) came with optional rear disc brakes. The brake booster uses engine vacuum to assist the driver in applying the brakes.
Anti-lock Braking System (ABS): Optional. ABS prevents the wheels from locking up during hard braking, allowing the driver to maintain steering control.

The suspension geometry of the 240SX is highly tunable, making it a popular platform for drifting and track racing. Many aftermarket suspension components are available.

Steering

Type: Power-assisted rack and pinion steering. Rack and pinion steering provides a direct and responsive feel. The power assist reduces the effort required to turn the steering wheel.

The steering feel of the 240SX is generally regarded as excellent, contributing to its reputation as a driver's car.

Dimensions & Weight

Wheelbase: 97.4 inches (2474 mm). The distance between the front and rear axles.
Length: 176.8 inches (4491 mm).
Width: 66.5 inches (1689 mm).
Height: 50.6 inches (1285 mm).
Curb Weight: Approximately 2700-2800 lbs (1225-1270 kg), depending on options and transmission. Curb weight is the weight of the vehicle with all standard equipment and fluids, but without passengers or cargo.

The relatively light weight of the 240SX contributes to its nimble handling and decent acceleration.

Electrical System

Voltage: 12V DC. The standard voltage for automotive electrical systems.
Battery: Typically a Group 35 battery. Check the CCA (Cold Cranking Amps) rating to ensure it's adequate for your climate.
Alternator: Typically rated around 70-80 amps. The alternator charges the battery and provides power to the vehicle's electrical system while the engine is running.

Maintaining a healthy electrical system is crucial for reliable operation. Pay attention to the condition of the battery terminals and wiring.

Fuel System

Fuel Tank Capacity: 15.9 gallons (60 liters).
Fuel Pump: Electric in-tank fuel pump.
Fuel Injectors: Electronically controlled fuel injectors. The size (flow rate) of the injectors is an important consideration when modifying the engine for more power.

Proper fuel delivery is essential for optimal engine performance. Consider replacing the fuel filter regularly.

Common Issues & Maintenance Considerations

Like any car of this age, the '91 240SX Hatchback has its share of potential issues:

Rust: Rust is a common problem, especially in areas with harsh winters. Pay close attention to the rocker panels, frame rails, and wheel wells.
Worn Suspension Components: Ball joints, tie rod ends, and bushings can wear out over time, leading to sloppy handling.
Leaking Seals: Oil leaks are common, especially from the valve cover gasket, rear main seal, and oil pan gasket.
Timing Chain Tensioner (KA24DE): The timing chain tensioner can wear out, leading to timing chain rattle and potential engine damage. It's a good idea to replace it preventatively.
Ignition System: The distributor, spark plugs, and ignition wires should be regularly inspected and replaced as needed.

Regular maintenance, including oil changes, coolant flushes, and brake inspections, is essential for keeping your 240SX in top condition. The service manual is your best friend for detailed maintenance procedures and torque specifications.

Knowing these technical specifications will give you a solid foundation for understanding, maintaining, and modifying your 1991 Nissan 240SX Hatchback. Happy wrenching!