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Discussion Starter · #1 ·
Going home last night I was thinking about Newtons F=m/a, and I see alot of products to increase power but hardly anything to decrease the weight of stangs. From what I remember (dont quote me) but stangs have been kind of porky and could use a diet to say the least. By lowering the mass it would have profound effects on performance, handling, braking....etc

Am I missing something here?
 

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Nope, You are correct. Lowering the weigh will increase performace, a rule of thumb is evey 100 pound reduction weight is about .1 in the quarter mile (to a point). There are quite a few products that can help the "Portly Pony" shed some pounds; aluminum heads and blocks, lighter fly wheels, racing seats, rims, carbon fiber/fiberglass hoods and fenders etc... and the usual removal of unwanted sound deadening material ac equipment etc.

Dart
 

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Discussion Starter · #3 ·
Dart-

I think that rule of thumb applies to a 3000# car, it even gets more increasing noticable the more you loose weight. On the extreme end to show an example, take an 04 R1 like I have, makes 180 stock hp, weighing I think roughly barely over 400# wet. If I took a 100 pounds off of that bike, I wouldn't be able to hang on it. I am going to crunch some numbers and then cross convert the differences into horsepower now that I am curious.

Hopefully in the end I can come up with a simple equation to plug in your cars weight, proposed weight loss, and how much "hp" that converts too.

Ahhh too much work, but thanks for the thought.
 

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Here is a site http://www.slowgt.com/Calc.htm that has a bunch of calculation stuff you might be interested in, it shows .14 diff when i dropped weigth from 3000lb to 2900lb and again when I dropped to 2600lb @ 300hp. When I upped the horse power to 400, It shows .12 to .13 drop using above weights...and at 1000 horse, got even closer to the .1 drop...so not far off at these weights. Anyway enjoy :)


Dart
 

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Discussion Starter · #5 ·
Nice, thanks, I will check er out.
 

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its simple. the acceleration of your vehicle is related to your power to weight ratio. notice i did not say torque. a 10% increase in your power to weight ratio will yield the same results regardless of how the increase came about (by increasing power or by decreasing weight). of course i am not considering traction. with that said, note that a 10% increase in horsepower will not be as effective as a 10% decrease in weight. also, its obvious that the decrease in weight will also improve handling and braking.
 

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Discussion Starter · #7 ·
Well I created a quick spreadsheet in excel and I did find that it is not a linear function. Meaning it is relative to you current mass and power. What I did was use Newtons F=m*a, got the current settings on my stang, 225 base HP and a wieght of 3498#.

I then in my spreadsheet started dropping the wieght by 50 pounds and recording the increasing acceleration. I took the increasing acceleration and reconverted F=m*a to find out what force (in HP) it would take to make that same increase in acceleration. I then either (and both) added the increasing power to my base and have another column to shown gain in "equivalant" HP.

The numbers it comes up with seem reasonable, by using the numbers above, right now if I lost 50# it would only equate to 3.2628 hp. Since I was bored, and excel is so easy copy and paste this stuff into, I took it all the way to 1498 pounds. At that wieght and a base HP of 225 and then dropped 50 pounds it equates to 69.8758 Hp.

It seems high and i took into no account of rolling or wind resistance. Naturally it will hardly noticably sitting there at the christmas tree since your car is not moving. I suspect thought it would have massive effects on trap speed.

The next thing I am going to do is convert HP to Torq, get a baseline dyno run (graph or any chart) and then plot out a curve with torque and HP in relation to RPM. I get bored at night as you can tell.
 

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Alex,

I see you getting indepth :winks and getting me to recall my physics and engineering classes. :) I am a little rusty, but believe this to be accurate. Now, making some assumptions on how you uses Newton second law, I take it you used F = HP and m = (weight of Car) and
a = ? we will look at "a" later. Using HP and weight your units do not match and the calculations are incorrect. If you have done this, (and are interested) I can make a post explaining why it is incorrect.

Let me know

Dart
 

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Discussion Starter · #9 ·
What I did was took F=ma, and came up with a=f/m and m=a*f. I then took the base wieght of my car along with the base horsepower and converted them to metric. I dont have my fact sheet here with me but I remember it was 1590 kilograms. I also converted the HP (225) to newtons, which was the hardest part.

I then took a=f/m since force and mass where known using my base numbers above to get a acceleration rate. I then used the same formula and started deducting 50 lbs equivelant in kilos and got my accleration gain. I then reversed the forumla using my newly accquired acceleration rates and f=ma. Keeping the mass the same as the base this time, f=ma tells me how much force it would require to move that much mass at the new acceleration rate. I then reconverted the forces to HP.

Am I wrong in something? I got a spreadsheet with it that updates everything by changing either the base wieght or the base power. I would try to insert the file but its on my laptop at home.
 

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Ah..ok..you still need to divide out the gravitational effects from your weight to acheive lbm (m= w/g) which is 9.8m/s(squared) or 32ft/s(squared). I am curious what factors you used to dirieve F.

Dart
 

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Discussion Starter · #11 ·
I didnt take into that account of rolling resitance and wind and such. I was just playing around with some numbers.
 

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Aye..understand..just saying when you use mass for the F=MA formula you need to divide out the gravitational effects, just the way the formula works..to get to the correct units..

Dart
 

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Discussion Starter · #13 ·
I understand, it was just playing around with my laptop. If I was to get serious I would ask one of these Struct Engineers here at work, but they arent gear heads, or wont understand why I would be doing such a thing in the first place.

I remember when Camaro and Stangs were fighting back and forth and the Camaro seemed to always win because of the porkly Stang wieghed more. About the same power, but wieght made the difference.

I was riding to work today and got to thinking. My R1 has 180 hp stock, only 45 less then the stang, but weighs roughly 3000# less. The numbers would be off the charts to match the accelration of that bike and my stang. Boy that would be fun though.............
 
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