power to weight

[Qmobile]

what's the power to weight ratio? I'm just wonderin what lb/hp would be for my car. I'm just curious

[Tamago]

how much does your car weigh?

and typical stock yarii dyno now at what, 93whp?

[Morgan]

your car's curb weight divided by your car's horsepower

Each car is slightly different to get a rough calculation, you can use stock numbers

[talnlnky]

how did you get 10.5?
I got 21.7:1

2300/106 = 21.7


I remember playing GT3 on PS2 and getting some of those cars to like 1:1.1 Thinking the Mazda 787B was one of the best.

[Loren]

Originally Posted by talnlnky

how did you get 10.5?
I got 21.7:1

2300/106 = 21.7


I remember playing GT3 on PS2 and getting some of those cars to like 1:1.1 Thinking the Mazda 787B was one of the best.

You didn't account for your 200 pounds of stereo equipment and your own weight, unfortunately.

(and the car weighs closer to 2400 in stock trim)

[talnlnky]

Originally Posted by Loren

You didn't account for your 200 pounds of stereo equipment and your own weight, unfortunately.

(and the car weighs closer to 2400 in stock trim)

haha... fair enough... tho i'm all into the relatively lightweight stereo setups... The subs in my avatar are only in there until I get access to the tools I need to do my install... total stereo weight will only be around 20-30lbs... plus another 50 for sound deadening.

[eric81]

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.

[dallas]

For revolving mass like flywheel. pulley, rims etc, the basic rule is :
each 1 lb is like 7 lbs of dead weight.

Example : If you save 2 lbs for your wheel and tire combo X 4 of them it = 8 lbs is like removing 56 lbs from the car.



is

Originally Posted by eric81

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.

[scape]

For revolving mass like flywheel. pulley, rims etc, the basic rule is :
each 1 lb is like 7 lbs of dead weight.

Example : If you save 2 lbs for your wheel and tire combo X 4 of them it = 8 lbs is like removing 56 lbs from the car.

it also depends where the weight is displaced on the wheels and tires. a 14 lbs wheel with weight mostly in the center and a 22lbs tire might take longer to spin up than a 18lbs wheel with weight in the center along with a lighter 18lbs tire...adversely a 14lbs wheel with weight at the lip, and a 22lbs tire might take the longest...
the farther the weight is from the spinning center, the more inertia you have to overcome...the smaller the diameter, the closer the weight is to the center

b/c all tires and wheels are different, I don't think there is a great rule of thumb, but there is a method for determining the actual values by spinning the wheel/tire and determining the moment of inertia, but I do not actually know how-- something to do with tieing a weight with a string and watching the weight fall (spinning the wheel with it)...
http://dev.physicslab.org/Document.a...ertiaWheel.xml

here's another method, using a pendulum and torsion bar: http://www.velonews.com/article/79893

I'm also not sure having a lighter flywheel necessarily means your car will be faster, it just means the engine can rev with a quicker response, both up and down-- you still have to push the same car around.
now having lighter but strong pushrods, cylinders, camshafts, etc., would be interesting for a higher redline; in which case that lighter flywheel would be pretty handy I bet

[cali yaris]

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

I think .1 second per hundred pounds is closer for a general rule, right?

[CDavis7M]

Originally Posted by cali yaris

I think .1 second per hundred pounds is closer for a general rule, right?

+1. This applies to sprung mass, with unsprung or rotating mass giving a much greater benefit.

[MadMax]

I have a 396 lb (dry weight) motorcycle with 150 HP, if I want to feel unadulterated acceleration, I take the bike out...even with a full tank of gas (less than five gallons), oil and my 215 lb fat ass on it, it'll pull like there is no tomorrow...

I don't worry about the power-to-weight ratio in the Yaris, that's not what I ever expected out of--or intended to do with--the car...

[scape]

http://yarisworld.com/forums/showthr...ight+reduction

the bottom of that first post is a power to weight calculation

[eric81]

yeah, it is closer to 100 lbs per .1, but probably not quite that much. That calculator is better, but it still does not account for everything, such as how high the car sits for drag ratio and wind resistance. Or how tall and wide the tires are. Taller tires will spin slightly faster, while wider tires have more resistance, but get better grip at the beginning and in turns. That is why you pay the insane amounts of money for cars that are calculated and engineered to perfection, like Porsche, and Lambourghini (sp?), and Ferrari, and Lotus, and stuff like that. Still, taking dead weight out of a car is a great way to make it turn better.

[scape]

Originally Posted by eric81

yeah, it is closer to 100 lbs per .1, but probably not quite that much. That calculator is better, but it still does not account for everything, such as how high the car sits for drag ratio and wind resistance. Or how tall and wide the tires are. Taller tires will spin slightly faster, while wider tires have more resistance, but get better grip at the beginning and in turns. That is why you pay the insane amounts of money for cars that are calculated and engineered to perfection, like Porsche, and Lambourghini (sp?), and Ferrari, and Lotus, and stuff like that. Still, taking dead weight out of a car is a great way to make it turn better.

well for sure power to weight calculation of dead-weight is dead on, but I'm guessing you're referencing the rotational weight reduction; I totally agree there is no single method to determine that, and I'm def. no engineer :D

[eric81]

Yeah, any way you look at it, rotational weight is the place to do the reductions, unless cost is the main issue, then rock on with your bad self. I am not an engineer either, just like to research stuff like that. That's why lighter oils help improve power (even if it's just 1 to 3 hp), because the less resistance there is for the engine to work, the more it can put to the ground. That is why air intakes and headers and mufflers work so well. The engine works less to get air in and out, the more it can put towards the ground. Try sucking through a straw sometime, maybe 1/16" or so. Then try sucking through a straw that is 2/16" (or 1/8" for those who suck at math) and see how much easier it is. Same goes for your car. Slowly sucking is about the same, but suck something in really fast, and see how much difference there is. And it just occured to me how dirty this all sounds, but trust me, the idea is sound, and it has been proven by a LOT of companies.

[Tamago]

Originally Posted by eric81

Yeah, any way you look at it, rotational weight is the place to do the reductions, unless cost is the main issue, then rock on with your bad self. I am not an engineer either, just like to research stuff like that. That's why lighter oils help improve power (even if it's just 1 to 3 hp), because the less resistance there is for the engine to work, the more it can put to the ground. That is why air intakes and headers and mufflers work so well. The engine works less to get air in and out, the more it can put towards the ground. Try sucking through a straw sometime, maybe 1/16" or so. Then try sucking through a straw that is 2/16" (or 1/8" for those who suck at math) and see how much easier it is. Same goes for your car. Slowly sucking is about the same, but suck something in really fast, and see how much difference there is. And it just occured to me how dirty this all sounds, but trust me, the idea is sound, and it has been proven by a LOT of companies.

[scape]

Originally Posted by eric81

Yeah, any way you look at it, rotational weight is the place to do the reductions, unless cost is the main issue, then rock on with your bad self. I am not an engineer either, just like to research stuff like that. That's why lighter oils help improve power (even if it's just 1 to 3 hp), because the less resistance there is for the engine to work, the more it can put to the ground. That is why air intakes and headers and mufflers work so well. The engine works less to get air in and out, the more it can put towards the ground. Try sucking through a straw sometime, maybe 1/16" or so. Then try sucking through a straw that is 2/16" (or 1/8" for those who suck at math) and see how much easier it is. Same goes for your car. Slowly sucking is about the same, but suck something in really fast, and see how much difference there is. And it just occured to me how dirty this all sounds, but trust me, the idea is sound, and it has been proven by a LOT of companies.

lol, and I believe you that there are priorities in tuning a car for performance...
either way I was just pointing out something to the OP. but we can talk about engines too ;)

I think if you're looking to put the most power to the ground, your best bet is removing the entire transmission/driveline altogether and using generators and high KW AC motors-- then you will have the most efficient engine to ground power transfer possible-- and also an unbelievably expensive car. but perhaps this is all for a different thread