power to weight - Toyota Yaris Forums

Qmobile · 06-21-2009, 12:45 AM

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

Tamago · 06-21-2009, 12:49 AM

how much does your car weigh?

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

Morgan · 06-21-2009, 12:49 AM

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 · 06-21-2009, 12:19 PM

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 · 06-21-2009, 12:21 PM

Quote:

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)

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.

cali yaris · 06-22-2009, 03:43 AM

Quote:

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 · 06-22-2009, 04:53 AM

Quote:

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 · 06-22-2009, 10:38 AM

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 · 06-22-2009, 11:20 AM

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

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

eric81 · 06-22-2009, 02:40 PM

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 · 06-22-2009, 02:49 PM

Quote:

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 · 06-22-2009, 03:01 PM

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 · 06-22-2009, 03:15 PM

Quote:

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 · 06-22-2009, 03:38 PM

Quote:

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

Tamago · 06-22-2009, 03:45 PM

my car used to be 13.54lb/hp :(

gokartride · 06-22-2009, 03:47 PM

I have a friend who was into tuning Volkwagons and Porches and Triumphs back in the day....he says there is something "just right" about 100 hp in a 2,000 lb car. "Just right" is fine as the whole "need more hp" thing is totally lost on me. I've always said "if a car isn't fun while driving the speed limit, it's just not good enough"...but then I come from Sprites, Midgets, and Spitfires. The Yaris' delightfully twitchy and snappy turning radius are the fun part of this car for me, and I can use that every day jsut driving around town. The car plenty of power, imo.

scape · 06-22-2009, 03:56 PM

Quote:

Originally Posted by Tamago

my car used to be 13.54lb/hp :(

what car was this? that's a good ratio! probably could spank a stock evo with that, haha

06-21-2009, 12:45 AM	#1
Qmobile that's right I went there View User's Garage Drives: '08 Blazin' Blue,'10 Dark Red Join Date: Oct 2008 Location: Hoytville, ohio Posts: 800	power to weight what's the power to weight ratio? I'm just wonderin what lb/hp would be for my car. I'm just curious __________________ Mods: 15" SSC rims, TRD Exhaust, TRD Sway bar, TRD oil filler, TRD rad. cap, TYC tails, Debadged, Painted engine cover, Stock spoiler, Stock mud gaurds, OBX pedals. suggestions always welcome

06-21-2009, 12:49 AM	#3
Morgan View User's Garage Drives: 07 MM LB Join Date: Oct 2008 Location: PCB, FL Posts: 504	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 __________________ Last edited by Morgan; 06-21-2009 at 01:18 PM.

06-21-2009, 12:19 PM	#4
talnlnky Audio Junky Drives: 08 liftback Join Date: Oct 2008 Location: Spokane, Wa Posts: 1,412	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. __________________

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06-22-2009, 12:41 AM	#6
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.

06-22-2009, 10:38 AM	#9
MadMax Drives: 2008 Yaris Liftback (Sprocket) Join Date: Oct 2008 Location: San Antonio, Texas! Posts: 2,799	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...

06-22-2009, 11:20 AM	#10
scape View User's Garage Drives: 2007 Yaris Hatchback Join Date: Jul 2007 Location: Beaufort, South Carolina Posts: 388	http://yarisworld.com/forums/showthr...ight+reduction the bottom of that first post is a power to weight calculation

06-22-2009, 02:40 PM	#11
eric81 View User's Garage Drives: Toyota Salesman Join Date: Nov 2008 Location: Clarksville, IN Posts: 297	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.

06-22-2009, 03:01 PM	#13
eric81 View User's Garage Drives: Toyota Salesman Join Date: Nov 2008 Location: Clarksville, IN Posts: 297	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.

06-22-2009, 03:47 PM	#17
gokartride Drives: 2009 Yaris 3-Door Liftback Join Date: Jun 2009 Location: Texas Posts: 213	I have a friend who was into tuning Volkwagons and Porches and Triumphs back in the day....he says there is something "just right" about 100 hp in a 2,000 lb car. "Just right" is fine as the whole "need more hp" thing is totally lost on me. I've always said "if a car isn't fun while driving the speed limit, it's just not good enough"...but then I come from Sprites, Midgets, and Spitfires. The Yaris' delightfully twitchy and snappy turning radius are the fun part of this car for me, and I can use that every day jsut driving around town. The car plenty of power, imo.