(042) Power To Weight

In this video I explain power to weight ratios. While you’ve probably heard this term tossed around, I want to make sure you know there are multiple ways to improve your ratios. Your wallet might thank me. 

Power To Weight – Video Transcript

Hey everybody Matt Covert here again from howtobecomearacecardriver.com. In this video we’re going to talk about power to weight ratios. I’m sure you’ve heard of them before. If you’re a fan or Top Gear UK there’s always talking about power to weight ratios. And they always talk about them in horsepower per ton. And here in America we talk about them in horsepower per pounds. So let’s jump into this and see what we can do with it.

Power to weight is a rough estimate of a vehicle’s ability to accelerate. Pretty good indication of how well a vehicle will do in a straight line. And I’m going to go ahead and make the claim that horsepower, by itself, doesn’t matter at all. Let’s say we have a cool little motor that we went and put a little bit of money into and now it makes three hundred horsepower. And that’s pretty cool, that’s a cool motor. But it won’t be that cool of a motor if we put it in a – oh I don’t know – a 1969 Pontiac Safari. If I remember right those weigh more than seven thousand pounds. And all of a sudden that motor is not going to be that great. OK?

But if we go ahead and put that three hundred horse motor in, let’s just say, a little Miata. And that weighs twenty two hundred pounds. Man that’s going to be a fast little car, I’m going to like that. So let’s go ahead and break it down a little bit farther and figure out how we can calculate it and how it’s useful to us as racecar drivers.

Let’s take a theoretical car. Let’s take a theoretical car that weighs twenty five hundred pounds and it makes two hundred horse power. And if we do the math we’ll go ahead and see that we get a power to weight ratio of twelve point five. And we just know this because each horsepower is responsible for moving twelve and a half pounds of weight. So obviously the lower this number is, the faster a car can accelerate. Because each horsepower has to move less weight out of its way. Which is kind of cool.

And there a couple things we can do about this. The first thing we can do is take the same car and add some horsepower to it. Let’s go ahead and add twenty pounds of horsepower to that right off the bat. And if we do the math on that we’ll go ahead and find out that it will make a power to weight ratio of eleven point three six. So by adding a little bit of power we’ve lowered the number and now it will accelerate faster.

Another thing we can do is – we can leave the horsepower the same but we can reduce the car’s overall weight. And when we do the math on that we’ll see that it’s pretty much the same. It’s pretty much the same.

So if you want to lower your power to weight ratio you have a couple options. One, you can add horsepower. or two, reduce weight. Now going to say if you’re on a racing budget this might be the way to go. I contest that you can probably get rid of this much weight just by taking stuff out and not spending any money at all. The result is the same. I can also tell you that adding twenty pounds of horsepower doesn’t come cheap. Probably in the several hundred dollar range. So this is a really viable option and it’s important to understand that.

And I’m just going to go ahead and write this up on the board just so you have it as a reference. We can figure this out by taking the weight, in pounds, and dividing it the horsepower. Not a difficult concept. So when your friends are out there bragging about their horsepower get the whole story. Find out how much their car weighs because that is really what it’s all about. You have to have this set of numbers.

Like I said earlier with the Pontiac Safari, it doesn’t matter if the car weighs a whole bunch, OK? And I think that’s pretty much all I want to say about that.

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