power to weight - Toyota Yaris Forums

eric81 · 06-22-2009, 12:41 AM

My car weighes 2,380 with me in it, and spare tire and all. I am about 200 with clothes, tire is almost 10, jack and spare parts about 40 or so, and then I took off heat shield, put in aftermarket battery, (slightly less weight, maybe 3 or 4 pounds) and I have NOT added any stereo equipment. Now, I drive a 5 gear manual, so it is a little lighter than an auto, but all in all the same. I figure my car is pushing close to 110 hp, all parts and improvements in place, so the car is about 2100:110, or we could just say about 19:1. Not bad all said and done, but then there is the difference between dead weight and rotational weight, which I explained before, but will gladly do again.

First off, dead weight is the frame, body, battery, engine block, seats, windows, and anything else not rotating with the engine to make the car go. Then you have rotational weight, which is cams, pistons, crank shaft, pulleys, tranny, rims, tires, axels, a/c, alternator, and fun stuff like that.

If you take 5 lbs of dead weight off the car, like the spare tire, for instance (it is more than 5, but just follow me here), then your car might possibly get about .1 seconds faster on the 1/4 mile time, and maybe .5 mph faster. Now, take the same weight off of your pulleys (NST kit, for example, for just $240 or close to that), and you will get about .5 seconds or better, and easily achieve 2 or 3 miles faster on the 1/4 mile end.

How is this so? Well, it takes more energy to rotate something than it does to simply push/ pull it. There is this new thing (at least, it's new to me) called "knifing", which simply means "smoothing the edges on the crank shaft so they form a smooth edge, so the crack shaft can flow through the oil faster and with less resistance and weight" It costs a lot to have it done because the crank shaft has to be rebalanced, but the results in top end horse power, and the time it takes to rev the engine from idle to max, are incredible. If I ever get enough money to play with, that is one of the main things I would like to do to my car.

So, weight to power is not everything, just to be clear.

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06-22-2009, 12:41 AM	#7
eric81 View User's Garage Drives: Toyota Salesman Join Date: Nov 2008 Location: Clarksville, IN Posts: 297	My car weighes 2,380 with me in it, and spare tire and all. I am about 200 with clothes, tire is almost 10, jack and spare parts about 40 or so, and then I took off heat shield, put in aftermarket battery, (slightly less weight, maybe 3 or 4 pounds) and I have NOT added any stereo equipment. Now, I drive a 5 gear manual, so it is a little lighter than an auto, but all in all the same. I figure my car is pushing close to 110 hp, all parts and improvements in place, so the car is about 2100:110, or we could just say about 19:1. Not bad all said and done, but then there is the difference between dead weight and rotational weight, which I explained before, but will gladly do again. First off, dead weight is the frame, body, battery, engine block, seats, windows, and anything else not rotating with the engine to make the car go. Then you have rotational weight, which is cams, pistons, crank shaft, pulleys, tranny, rims, tires, axels, a/c, alternator, and fun stuff like that. If you take 5 lbs of dead weight off the car, like the spare tire, for instance (it is more than 5, but just follow me here), then your car might possibly get about .1 seconds faster on the 1/4 mile time, and maybe .5 mph faster. Now, take the same weight off of your pulleys (NST kit, for example, for just $240 or close to that), and you will get about .5 seconds or better, and easily achieve 2 or 3 miles faster on the 1/4 mile end. How is this so? Well, it takes more energy to rotate something than it does to simply push/ pull it. There is this new thing (at least, it's new to me) called "knifing", which simply means "smoothing the edges on the crank shaft so they form a smooth edge, so the crack shaft can flow through the oil faster and with less resistance and weight" It costs a lot to have it done because the crank shaft has to be rebalanced, but the results in top end horse power, and the time it takes to rev the engine from idle to max, are incredible. If I ever get enough money to play with, that is one of the main things I would like to do to my car. So, weight to power is not everything, just to be clear.