Horsepower And Torque Ratings For All Nissan 240sx Factory Engine Variants

The Nissan 240SX, a beloved sports coupe, enjoys a legendary status among car enthusiasts for its rear-wheel-drive layout, balanced handling, and readily tunable engine. At the heart of each 240SX model lies an engine, and understanding the horsepower and torque figures of each factory engine variant is crucial for anyone looking to buy, modify, or simply appreciate this iconic vehicle. This article provides an in-depth look at the horsepower and torque ratings for each engine that powered the 240SX, exploring the underlying engineering that contributed to these figures.

KA24E: The Single Overhead Cam Workhorse (1989-1990)

The first generation (S13) 240SX, produced from 1989 to 1990, was equipped with the KA24E engine. This 2.4-liter inline-four cylinder engine features a single overhead cam (SOHC) and twelve valves (three per cylinder). Its design prioritized reliability and low-end torque, making it a practical choice for everyday driving. However, compared to its more advanced successor, its power output was relatively modest.

Engine Specifications and Output

• Engine Code: KA24E
• Configuration: 2.4L Inline-4, SOHC, 12-valve
• Bore x Stroke: 89.0 mm x 96.0 mm
• Compression Ratio: 9.1:1
• Fuel Delivery: Electronic Fuel Injection (EFI)
• Horsepower: 140 hp (104 kW) @ 5600 rpm
• Torque: 152 lb-ft (206 Nm) @ 4400 rpm

The KA24E's 140 horsepower and 152 lb-ft of torque were competitive for its time and market segment. The relatively long stroke (96.0 mm) compared to the bore (89.0 mm) contributes to its strong low-end torque characteristics. This design, often referred to as an "undersquare" engine, prioritizes pulling power at lower engine speeds, making the car feel responsive in city driving. However, the single overhead cam design and twelve-valve configuration limited its ability to breathe efficiently at higher engine speeds, resulting in a power curve that plateaued relatively early.

The 9.1:1 compression ratio is relatively conservative, allowing the engine to run on regular unleaded fuel without issues. The EFI system ensured precise fuel delivery, contributing to smooth operation and decent fuel economy for the period.

KA24DE: The Dual Overhead Cam Evolution (1991-1998)

In 1991, Nissan significantly upgraded the 240SX engine with the introduction of the KA24DE. This engine, also a 2.4-liter inline-four, featured a dual overhead cam (DOHC) and sixteen valves (four per cylinder). This improved design allowed for better airflow and breathing, resulting in increased horsepower and a more refined power delivery.

Engine Specifications and Output

• Engine Code: KA24DE
• Configuration: 2.4L Inline-4, DOHC, 16-valve
• Bore x Stroke: 89.0 mm x 96.0 mm
• Compression Ratio: 9.5:1 (early models), 9.0:1 (later models)
• Fuel Delivery: Electronic Fuel Injection (EFI)
• Horsepower: 155 hp (116 kW) @ 5600 rpm (1991-1993), 142 hp (106 kW) @ 5600 rpm (1994-1998)
• Torque: 160 lb-ft (217 Nm) @ 4400 rpm (1991-1993), 155 lb-ft (210 Nm) @ 4400 rpm (1994-1998)

The KA24DE's transition to a DOHC, 16-valve configuration was a significant improvement. Having two camshafts allowed for more precise control over valve timing and lift, resulting in better cylinder filling and exhaust scavenging. This, in turn, led to a noticeable increase in horsepower and torque compared to the KA24E.

Interestingly, the KA24DE experienced a slight power reduction in later models (1994-1998). The reason for this decrease is primarily attributed to changes implemented to meet stricter emissions regulations. These changes included modifications to the ECU (Engine Control Unit) mapping, exhaust system, and catalytic converter.

Despite the power reduction, the later KA24DE engines remained a popular choice due to their increased reliability and durability. Nissan addressed some of the issues that plagued earlier KA24DE engines, such as timing chain issues, making them more robust and long-lasting.

The compression ratio also saw a slight change. Early models (1991-1993) featured a 9.5:1 compression ratio, while later models (1994-1998) had a slightly lower 9.0:1 compression ratio. This adjustment was also likely influenced by emissions regulations and the desire to improve engine longevity.

Comparison of KA24E and KA24DE

The KA24DE represents a significant technological leap over the KA24E. While both engines share the same displacement and basic architecture, the DOHC configuration of the KA24DE allowed for much greater power potential and refinement. The following table summarizes the key differences:

Understanding Horsepower and Torque

It's essential to understand the difference between horsepower and torque to fully appreciate the characteristics of each engine. Torque is a measure of rotational force, representing the engine's ability to do work. A high torque engine can accelerate quickly from a standstill and pull heavy loads with ease. Horsepower, on the other hand, is a measure of the rate at which work is done. It is directly related to torque and engine speed (RPM). The higher the horsepower, the faster the engine can perform a given amount of work. Here's the fundamental relationship:

Horsepower = (Torque x RPM) / 5252

The KA24E, with its longer stroke, produced more torque at lower RPMs, making it feel responsive in city driving. The KA24DE, with its DOHC configuration, was able to maintain its torque output at higher RPMs, resulting in a higher horsepower rating. The slight decrease in horsepower in later KA24DE models was achieved by sacrificing some top-end power in favor of improved emissions and fuel economy.

Tuning Potential

Both the KA24E and KA24DE engines have considerable potential for performance modifications. The KA24DE, with its more advanced cylinder head design, generally responds better to performance upgrades such as aftermarket camshafts, headers, and engine management systems. Swapping to a standalone ECU, for example, allows tuners to optimize fuel and ignition timing for maximum power output. Forced induction (turbocharging or supercharging) is also a popular modification for both engines, capable of yielding significant horsepower gains.

However, it's important to remember that increasing horsepower and torque also puts greater stress on engine components. Strengthening the bottom end with forged pistons and connecting rods is often necessary for high-horsepower builds to ensure reliability.

Conclusion

The Nissan 240SX was offered with two distinct engine variants: the KA24E and the KA24DE. The KA24E provided reliable and torquey performance, while the KA24DE offered improved power and refinement thanks to its DOHC configuration. Understanding the horsepower and torque ratings, as well as the engineering differences between these engines, is crucial for anyone interested in the 240SX. Whether you're a prospective buyer, a weekend mechanic, or simply a car enthusiast, this knowledge allows you to appreciate the unique characteristics of each engine and make informed decisions about modifications and maintenance.