Apr 11, 2011

Forget Horsepower


Winning the power race is about as easy (and expensive) as keeping your wife in her mid 20s.  But if you chose wisely, you'll be happy.

Forget horsepower. Blasphemy, I know, but after just discovering that my SUV has more horsepower, and is actually faster than my '98 Carrera I thought I may need to give myself a pep talk. I'm not trying to define what makes a sports car here, but rather simply suggesting a few alternatives to measuring horsepower.  So here goes. 


2007 SRT8
over 400hp
0-60 just under 5 sec
 1/4 mi 12.7 @ 110.7
1998 Carrera S
under 300hp
0-60 just over 5 sec
1/4 mi 13.5 @ 102
(Still the one I want to drive)

Horsepower (or torque for that matter) alone cannot explain the experience of one car vs. another. How long and how hard a car pushes our body into the seat is basically what we're trying to measure there.  But there is more to it than simply counting the ponies. Dynamically, much more is going on than mere engine output. Even when discussing relatively similar cars like the Corvette ZR1 and ZO6, horsepower alone just doesn't define the experience well. Regardless, we mourn when a car bests ours in the horsepower department. If you are going to find a car to enjoy until the end of time, it's going to have to be about more than hp. 

Horsepower is great if you're comparing the same car before and after modifications.
 Heck, who doesn't love spending the day lashed down to a chassis dyno. 

Power to weight ratio defines an experience much more tactile than horsepower alone. I'm not going to turn this into Wikipedia, but basically a light, powerful car is faster than a heavy car with the same power. Most  fun things in a car happen faster when a car is lighter. Why do you think race cars have no cup holders? Because that Big Gulp is heavy and robs power.

The common consensus is for every 10lb you can lose in a car, you've effectively created 1 additional hp. A perfect ratio is about more than just light cars and powerful motors, but that's a good start. With modern materials and techniques emerging all the time ten, but a good ratio is hard to beat and will satisfy your soul. Clearly, understanding your power to weight ratio beats sitting on your couch Googling up a hp rating.


4 cylinder Turbo Esprit. Not excessively powerful, but it's regarded as a very fast machine.
Later models offered a heavy V8 which may or may not have helped lead to its demise.
 I've seen 4 cylinder models for as little as $16K. You just need to be 5'8" or shorter
 to enjoy one.

The nature of a sports car's power curve defines your acceleration experience. By power curve I mean the linear progression of hp vs. rpm on any dyno sheet. Most people can't look at a curve and tell you what will feel exciting, which is too bad. Often a curve that escalates steeply as the rpms climb can feel quit exhilarating, providing the rpms climb at a satisfactory rate of speed. "Yahoo" is often yelled out when a car climbs in rpm and power at the perfect rate. Flattening this curve, so more power comes on early in the rpm range, is the goal of any complicated intake system. This does not necessarily mean a car will feel more fun, but does mean it will be faster. Good examples of exhilarating climbs up the power curve would be early turbo cars and sport bikes.


Gone, but should not be forgotten. The RX7 rotary motor definitely built power rapidly
 as rpm climbed. Throw in a turbo, and you've got some legendary fun. Being the last
 of its kind, (unless you count the hideous RX8) you have a pretty unique machine.

Up next is power delivery. How power is translated into motion is a huge factor in car satisfaction. Transmissions can soak up power and turn it into boredom or bliss. Clutch design, shifting, gear ratios and torque converters can make or break a sports car experience.  Suspension then delivers that power onto the asphalt in a satisfying or unsatisfying way. Modern electronics can manage some of the shortcomings of a poor suspension design, but I think we would like to think our dream car is truly a masterpiece in both engineering and programming, right?

All excessively powerful rear wheel drive cars. Each car is an indisputably different experience.
One may be over our $50K budget, but analyzing extreme cases helps make my point that these
 cars are different even if they all have similar power output.

Horsepower is a factor, but it is not the factor in evaluating a sports car. Regardless of the different driving dynamics in a car, getting a higher horsepower number may not mean as much as you think.  Hp ratings measured from near the red line may not have an impact on your perception of performance in a street driven car.  Peak power is what everyone reports, but you may find the actual torque curve unimpressive until at high rpm. Heck, many camshaft and intake modifications actually lose power in the rpm range you spend the most time using.  Next time your see a big comparison article don't be like me and just look at the pictures and performance statistics,  read it too.

Look deep into the oil pan that is your soul.  Define what good sports car performance is to you.  Find a minimum horsepower or performance standard if you must, but then move on to the rest.  A sports car is much much more than it's position on a power comparison chart.  Besides, the horsepower race is one you cannot win for long.

Do you think he cares that his car isn't as fast as the Enzo?
Judging from the smile, I'd say no.

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