The Power Puzzle: Why the Jaguar XJS Lacks High Horsepower Despite a Massive V12 Engine
Have you ever wondered why the Jaguar XJS, powered by a massive 6.0L V12 engine, seemingly lacks the horsepower that one would expect from such a powerful motor? This question has puzzled many automotive enthusiasts and car historians; after all, why does a car with a big engine not perform to its full potential? In this article, we will explore the reasons behind this unique design and why the Jaguar XJS is not a high horsepower machine, but rather a grand tourer built for comfort and smoothness.
The Influence of Transmission Design
Why Does the Jaguar XJS Have So Little Horsepower?
The craptacular automatic transmission plays a significant role in the XJS's power performance. Jaguar prioritized drivability and a high top speed, so they opted for a three-speed automatic transmission. This decision required the engine to produce a broad, flat torque curve, pulling from lower RPMs. Unfortunately, this design choice meant that the engine would struggle with the performance that contemporaries like Ferrari were achieving with their six-speed manual transmissions. For instance, a 6-liter, 300 horsepower grand tourer from Jaguar would have been a match for a 5.5-liter Ferrari equipped with a six-speed manual. In essence, the three-speed automatic transmission severely limited the potential of the V12 engine.
Engine Design and Purpose
The V12 Engine's Design Philosophy
The Jaguar V12 engine was designed with a focus on smoothness and torque, not high horsepower output. It features a single camshaft per cylinder bank and two valves per cylinder, traits that favor a smooth and reliable performance. Jaguar experimented with twin-cam versions in the past, which produced well over 500 bhp, but these were too complicated and expensive to be produced in mass quantities. Consequently, the V12 engine prioritized these over the sheer power that enthusiasts might desire.
Role of the Jaguar XJS as a Grand Tourer
A Luxury Sedan Built for Comfort and Speed
The Jaguar XJS is intended to be a luxury sedan, a car that needs to be large and heavy yet capable of achieving high speeds. Despite being equipped with a massive engine, the XJS is not designed to be a high-performance car but rather a grand tourer that emphasizes smoothness, comfort, and drivability. The 305 bhp output, while more than sufficient for the UK roads at the time, also contributes to its reputation for power and torque without being a high-horsepower machine.
Why People Bought the Jaguar XJS Anyway
The XJS's Distinctive Attractions
People purchased the Jaguar XJS not just for its power, but for its smooth ride and incredible drivability. The XJS is a car that should be driven, and when driven, it offers an exceptional experience. Despite lacking the peak horsepower that many might expect, the car's broad torque curve and smoothness made it an attraction in its own right. A person who buys a Jaguar XJS understands that they are getting a car that is exceptional in its own way, not just in raw power metrics.
It is fascinating to consider that while the V12 engine of the Jaguar XJS might not reach the stratosphere in terms of horsepower, it still delivers the experience that buyers expected and enjoyed. The key lies in the careful balance of performance, luxury, and drivability that made the XJS a beloved car for its time.