I've been looking at various cars and trying to research online. In doing so I endlessly encountered one of my pet peeves. I'm amazed at how many people, including engineers, say completely silly and ignorant things when it comes to the performance of cars. Accordingly, I thought it might make for an interesting post here. HORSEPOWER DOESN'T MATTER. There I said it. Shocking I know. Before you circle the wagons and send a messenger for the cavalry, please let me explain. Horsepower is a wonderful metric for relative measurement. And by relative, I mean, in comparison to the same engine and powertrain. Note I said, "engine", and, "powertrain", and not vehicle. Again, I've made a provocative statement and have yet to back it up. But hang in there. The first thing you need to know about horsepower (HP) is that it is a derived unit of measure of work. Horsepower is always derived from torque and RPM. In fact, a simple explanation of HP is HP = TxRPM; where T = torque and RPM = RPM of the motor. Its actually slightly more involved than that but that simple formula expresses everything that is important for this discussion. Real formula is TxRPM/5252; but as 5252 is a constant, for ease of comparison we can ignore it. The problem with HP is people all too frequently compare HP between vehicles; all too often vehicles with completely different powertrains and even weights. Its at this jumping off point alone which invalids the irrational obsession people have with HP. But we'll dig deeper yet. You see what really matters is weight to torque ratios and even that is frequently not an apples to apples comparison. I'm sure many are still wondering why and how I came to these conclusions based an incomplete HP formula of HP=TxRPM. In far too many conversations people simply compare HP between two cars and assume the one with the highest rating is the fastest. The truth is, such comparisons are almost always completely meaningless; and therefore useless. Most engines create their HP using one of two philosophies. One, low torque and high RPMs. Two, high torque and low RPMs. This distinction, if we're to generalize, wonderfully categorizes the differences between four cylinders and eight cylinder engines. This is, of course, why they tend to provide wonderfully different performance profiles. So here's an example. Please remember we're using a simplified equation so the numbers won't necessarily seem sane. Engine A makes 300HP with 100ft/lbs of torque and 3RPM. Engine B makes 300HP with 3ft/lbs of torque and 100RPM. So which engine is "better?" The simple answer is, it depends. Both have their uses. For a car, chances are the engine with the highest torque is the superior engine. Notice the measure which held sway was torque. The reasoning is simple. Torque is what pulls you out of the corners and off the line. Torque is what determines how quickly you can generate and build horsepower, and therefore, use that horsepower. The fact HP is directly derived from torque only serves to dilute torque's significance in its contribution to performance. Ultimately, usable HP is all too often a function of time. If it takes you 60-seconds to build to peak HP-RPM, pragmatically, its of no use to us as a daily driver; let alone racer. This is, of course, why hard core motor-heads love long strokes and big displacement; both of which are associated with "torqie" engines. You might think this is the end of the story but I think we can dig deeper yet. You see, that HP rating is typically the rating of the engine at the crank. And chances are, your crank doesn't directly attach to your drive wheels. Chances are, you have a transmission and one or more gear boxes (example, "rear end"") between your engine's output crank and the drive wheels. Moving power from the crank to the drive wheel(s) requires mechanical motion, which in turn requires friction. Not to mention the mere act of transferring power requires movement of other heavy components. This all means the act of transferring power from the crank to the drive wheels loads the engine before it ever turns your wheel. Classically, the amount of power lost between the crank and drive wheel is 10%-15%. What this ultimately means, in most cases, is that the engine which is promoted as, say, 200HP, only has between 170-180HP at the wheel. But frankly, they typically never tell us the efficiency of the transmission and gearbox(s). This difference is normally denoted by the use of WHP vs BHP (or just HP). The WHP means Wheel HorsePower. And yet, this gets even more convoluted. The reason being, when you transfer power through the powertrain, it goes through a number of gears. Each gear, in turn, changes the gear ratio between input and output. What this means is that while the crank may make one rotation, the rear wheels may only spin .5 rotations. This, in turn, directly affects HP and usable torque, not to mention the time required to use our torque to build RPMs which in turn drives usable HP. Made even more confusing, these ratios change with every gear. And while that may not sound like any big deal, the issue is, unless your ratio is 1:1 (one turn input to one turn output), even ignoring transfer losses, the input (from the crank) HP will never equal the output (to the wheels) HP. Which means, when you add it all together, comparing two entirely different vehicles, each having 200HP, its completely impossible to know which one has the advantage without lots of extra details. So when its all said and done, horsepower makes for a incredibly poor basis of non-relative comparison. Which is to say, unless its the same powertrain, comparison on the basis of horsepower alone is completely meaningless. One might even say, horsepower doesn't matter.