Forget peak horsepower rating: how to buy the best car
There is an old saying that goes ‘horsepower sells cars but torque wins races’, while this statement may or may not be true, most people tend to immediately look at how much power a car produces before focusing on just about any other feature. Auto manufacturers know this and prominently display the peak power outputs of their models on their promotional materials at the expense of every other technical feature. While the amount of power a car makes has a lot of bearing on its performance, we take a look at other important criteria that can at times be even more relevant in the real world.
TORQUE IT
It’s what you really need for everyday driving
Huge, flowing rivers of torque from little above idling speeds used to be the preserve of big capacity engines fitted to luxury and sports cars. With the wholesale adoption of turbocharging, this addictive shove in the back has filtered down to affordable city cars too. This can be a good thing as it is torque, not necessarily power, that you want when overtaking on the motorway or when taking that gap in the traffic. The way it is delivered is important too and brings us to our next point…
WHAT’S UNDER THE BONNET?
Naturally Aspirated Engines
A high performance naturally aspirated engine gives its best at high revs, less stressed large capacity engines make a lot of torque low down which makes them great for typical daily driving duties but of course, there is a fuel consumption penalty to pay. Smaller non-turbo petrol engines need revs to make meaningful forward progress, fine in a small sports car like the Mazda MX-5 but not ideal in your family SUV. Non-turbo engines tend to sound better than their forced-induction counterparts and can still provide serious performance, great examples are the Lamborghini Huracan and Audi R8 which both use a 5.2-litre V10 in different states of tune.
Forced Induction Engines
Turbocharged engines, especially diesels, tend to do their best work at the lower end of the rev range. While turbocharging does add a nice slug of torque if the engine is too small or the turbos are too big, there will generally be a dead-spot low down in the rev range before you get the shove you require. If you are not in the right gear, then it might be a case of ‘too much too late’ as the overtaking opportunity disappears just as you start accelerating rapidly towards a non-existent gap.
Electric Motors
Electric motors offer everything they have straight from the get-go. That is why they feel so keen away from the lights, they also tend to produce massive amounts of torque relative to their power outputs which aids that initial accelerative surge. They do however work with one fixed gear which can hamper acceleration at higher speeds. In general, though, you will need a supercar to keep up with a powerful electric vehicle in-gear, that instant power and torque delivery makes them very rapid indeed. Hybrid cars use both a petrol engine and electric motor to try and offer the best of both worlds. While they aren’t always appreciably more efficient than a conventional petrol-powered alternative, depending on the setup, a hybrid can provide seamless acceleration and partial electric-only operation,
WHAT’S IT WEIGH?
Power (and torque) To Weight Ratios
Weight plays a big role in every aspect of a vehicle’s performance. A car with a low kerb weight such as a Ford Fiesta or Fiat 124 Spider does not need a lot of power to feel peppy but put that same engine in a heavier crossover or large saloon and it will feel underpowered and sluggish. A very powerful engine can make even a heavy SUV feel rapid, remember to look at how much torque per ton a car has too as this will heavily influence how it picks up at lower engine speeds.
HOW DOES IT SHIFT?
Transmission Choices
The wrong gearbox in a car can make a big impact on how it performs. The choice used to be a simple one but modern cars can be had with a variety of transmission options and they each offer their own pros and cons.
Traditional Manuals
Manual gearboxes used to be more efficient and quicker shifting than their automated counterparts. That is not the case anymore and they are now most likely to be found bookending the automotive world, fitted either to budget city hatchbacks or ultra-pricey supercars. The lower cost of a manual gearbox is why they are fitted to cheap cars while driving enthusiasts prefer the more immersive nature of a clutch pedal. If you are stuck in traffic most days, an automatic is going to make a lot more sense.
Single-Clutch Automated Manuals
Early single-clutch sequential manual gearboxes offered quick changes but were rough and uncomfortable in everyday driving. The E60 BMW M5 is a classic example of a great car hampered by a terrible transmission. These days not many cars still come so equipped, one notable exception being the Lamborghini Aventador, its hardcore character makes the vicious gearchanges more acceptable than they would be in your mom’s hatchback.
Dual-Clutch Automatics
The first ever dual-clutch transmission for passenger cars was fitted to the 2004 Golf R32, the ultra-quick gearchanges quickly saw this technology spread throughout the motoring landscape. They are complex and heavy though and most tend to judder a bit at crawling speeds which can be irritating. While there are plenty of dual-clutch transmissions about, some manufacturers like BMW and Mercedes have switched back to more traditional automatics on some of their models in recent years. Dual-clutch systems are still the transmission of choice for high-performance supercars where the fastest shift speeds are very important.
Traditional Torque Converter Automatics
The old slushbox used to be the poor cousin to the rest of the transmission options out there. The power-sapping torque converter and laggy responses of most automatics meant that most were fitted to big powerful cars that could handle the power loss and didn’t need lightning-quick changes between gears. Modern automatics are a different breed altogether, they can be at least as efficient as a dual-clutch setup and shift times have been drastically cut too. They are also smooth at all speeds and can be found in everything from small saloons to powerful SUVs.
Continuously Variable Transmissions (CVT)
CVTs offer very smooth operation and can be the ideal choice for cruising around city streets and can offer good consumption figures too. But there are plenty of downsides too, they cost more to repair than an automatic, cannot handle a lot of horsepower and tend to drone if you want to get a move on. Issues that are not necessarily a big deal if you are buying new and don’t care much about the ‘dynamic’ aspect of the diving experience.
BALANCE IS KEY
The next time you are looking to replace your car and the salesman starts boasting about how the latest model offers 20 more horsepower than your old banger, ask him rather to tell you about what transmission options you can pick from and what the power-to-weight and torque-to-weight figures are. These numbers are often more relevant in daily-driving situations than a peak power figure that can only be accessed at the top of the rev range on an empty stretch of road where speed limits are not a factor.