Horsepower vs. Torque

I had a conversation the other day with Charles Hubbard about what people look for in a performance car. Hubbard is with the Lexus College, and one of my favorite resident Lexus-vehicle geniuses.

“You know, a lot of people buy horsepower, when what they really want is torque,” Hubbard told me. “Torque is what gets you to the speed you want quickly; horsepower is what keeps you there.”

The concept of horsepower as a measurement of work was identified in the 1800s by steam engine pioneer James Watt, who ponied up the term based on his observation of horses working in a mill. It’s an arcane concept that has stuck with us to this day.

Torque, on the other hand, is the twisting, rotational force generated by an engine; this force is transferred through the drive system into the wheels. Torque is what pushes you back in the seat when you step on the accelerator.

An engine might have plenty of horsepower, but hardly any torque. Think of a ship’s engine: it has the strength to move thousands of tons of steel, but it takes a loooong time to get up to speed. In other words, very little torque. By contrast, a vehicle can have so much torque that its tires are unable to get a grip, and simply spin. Pointless.

Lexus performance vehicles have exceptional horsepower and torque ratings. A quick look at the online Competitive Comparison, for example, reveals impressive numbers for the Lexus IS F: its horsepower and torque ratings exceed those of the BMW M3 and Audi A4.

THE SWEET SPOT
If you look closely at the comparison, you’ll notice that these peak horsepower and torque ratings are achieved at relatively high rpm. This high-rpm “sweet spot” is where maximum performance is delivered.

This demonstrates why engineering a performance car means far more that just sticking a high-power engine under the hood. The trick for engineers is to optimize the engine management system so that the car gets to this sweet spot quickly and remains there as long as possible. Everything plays a role: valve train, compression rating, transmission gearing, and so on.

Hubbard points out that this can lead to engine management choices that may not seem intuitive to the layman. For example, when the 2013 GS 350 F SPORT made its debut, many journalists asked why it came with a six-speed automatic transmission instead of the eight-speed automatic found in the LS. After all, more is better, right?

Not necessarily. In the case of the GS model, all things considered, the chief engineer felt he wouldn’t get the performance he wanted out of the car using an eight-speed transmission—too much torque for this particular model.

Of course, a great thing about the GS 350 F SPORT is that it offers Drive Mode Select: a dial that allows the driver to choose the level of performance they want: Eco, Normal, Sport, and Sport Plus. This feature lets drivers actually change torque delivery.

“The rotary dial lets me choose an ‘alter ego’ for the car,” says Hubbard. “In Eco mode, I get a real smooth shift; it takes some of the torque curve out of it, and backs off the suspension a little bit for a smooth ride. But if I want an alter ego—a Mr. Hyde to contrast that Dr. Jekyll—I just twist the knob up to Sport Plus. This alters my engine management, my transmission shifts, and my steering and suspension habits to where now I’ve got a real performance car.”

THE QUIET PERFORMERS
Of course, where torque really comes into play is in Lexus hybrid vehicles. Remember when we were talking about how gas engines wind up to a high rpm in order to deliver optimal torque? The same is not true of electric motors.

“The neat thing about our hybrid power trains is that electric motors give you instant torque,” says Hubbard. “As long as I’ve got plenty of juice in the battery, I can get all the power instantly and really make the car cook.”

Put differently, the instant torque provided by electric motors is what gives hybrids their surprising launch.

I guess this means we should set aside arguments about horsepower vs. torque. At the end of the day, it’s the driving experience that matters.

“Bottom line, if I’m going to be looking at a performance car right now, I would look at the GS,” concludes Hubbard. “It could be the GS 350 F SPORT or the GS 450h. Both of them offer Drive Mode Select with the Sport Plus setting, which gives you those alter egos I was talking about. And both are just a kick to drive.”

Courtesy of LexusMagazine