# How much does less weight matter?



## Guest (May 2, 2003)

In the trunk of my car I just put in a new cut out of wood to cover up the spare tire well (3/4 in plywood). I also have a 12" eclipse sub and an amp, which probably weighs 30 or 35 lbs altogether. Will this extra weight ultimately slow me down? If it has, I might not have noticed because I have been adding it gradually. I would love to hear what you guys think.


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## zeno (Sep 17, 2002)

It is all about power to weight ratio. Weight is the bane of racers, a good rule of thumb is you are losing 5hp for every extra 100lbs.


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## Nissan200sxSER (Dec 20, 2002)

Or every 50 lbs. is .1 second in the 1/4 mile.


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## akapaul (May 25, 2002)

Check it out for yourself. Go to www.sr20.us and watch SDF's videos. Roughly around 2000 lbs running 14.0 with just i/h/e.


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## johnnykomac (Jan 30, 2003)

check out the article in the latest Grassroots motorsports.....great article!

although its really not about weight, its more about inertia.
if you really want to save it, lightening your flywheel is like killing over 300lbs off the cars body weight. Crazy physics!


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## zeno (Sep 17, 2002)

> Roughly around 2000 lbs running 14.0 with just i/h/e.


Damn! If only I could strip my car 

Other than getting rid of the spare tire and jack, what are some other cheap ways of getting rid of weight?


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## akapaul (May 25, 2002)

zeno said:


> *Damn! If only I could strip my car
> 
> Other than getting rid of the spare tire and jack, what are some other cheap ways of getting rid of weight? *


http://www.sr20deforum.com/showthread.php?s=&threadid=42824


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## sno (Oct 4, 2002)

^^i can't believe what some of them did to their cars. but i guess if it's just a track car...


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## akapaul (May 25, 2002)

sno said:


> *^^i can't believe what some of them did to their cars. but i guess if it's just a track car... *


what can't you belive? lol
if you want to go fast...

i know some people that want to get into the weight reduction thing but won't take out their 2 12" subs  

or even get some heavy 17" rims and a c/f hood.


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## ForsakenRX7 (Mar 14, 2003)

Less weight is just as good as horsepower. The better the power to weight ratio the faster the car. Its like a caprice with a 350 pushing 300 horses. Thats a heavy car. But you take a 240sx with 300 horses and that a differant beast entirely.


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## anthony jackson (Jul 16, 2002)

yeah, and you take a pinto and .......well never mind......


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## XsjadoTwin11 (Dec 31, 2003)

an old drag strip trick my dad taught me from his days at the track... For ever 100lbs = 10hp (which translates to (10lbs = 1hp) if it helps, then it helps right? right. RIGHT! ok ok i get it


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## Harris (Nov 11, 2002)

I don't know about that. You're not gaining power by losing weight. You have the same power carrying less weight, which translates to less momentum needed to move the car, thus increasing its rate of initial acceleration than when the car was heavier.


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## ccj_drivinaround (Sep 12, 2003)

Losing weight not only helps acceleration, but handling and braking too. And its free.


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## djmamayek (Aug 26, 2003)

Harris said:


> I don't know about that. You're not gaining power by losing weight. You have the same power carrying less weight, which translates to less momentum needed to move the car, thus increasing its rate of initial acceleration than when the car was heavier.



You don't need momentum to move the car, the car has momentum once it is moving, however you need to overcome the car's moment of inertia to get it moving.

Weight is precisely 50% your power/weight ratio.

This is why a 2400lb Classic se-r with 140hp is faster than a 2900lb civic si with 160hp... (excluding variables such as limited slip differentials, and whatnot)

Losing weight does not give you more power, however it provides less mass for that power to act on, it betters your braking because a lighter car has less momentum, and therefore less energy needs to be removed to slow it down. This will also save on the life of your brakes, clutch, and tires, not to mention you will get better gas milage.

My advice, if you want a fast car, lose the subwoofers. If you want creature comforts, then leave everything intact.

My SE-R has had a battery relocation, EGR removal, A/C removal, along with the power gains that are lost from hot exhaust being huffed into your intake and paracitic losses of having another pulley turned by the crank I lost about 35lbs right there. 

My 95 Talon Tsi AWD is completely stripped. At 3200lbs stock I thought the car was too porky, now it weighs in around 2800lbs and I am still looking for weight to lose.


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## Harris (Nov 11, 2002)

My terminology was incorrect. Thank you for correcting me. I will rephrase it to say that the force used to move a lighter car will have "quicker" results than a heavier one. 

Its like flicking a pebble versus flicking a rock. Using the same force, the pebble will move quicker/faster than the rock. Because the weight of the pebble is lighter, it has the natural advantage of requiring less force to move it than the rock.

That should get things right. Let me know if I still need to be corrected.


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## djmamayek (Aug 26, 2003)

Harris said:


> My terminology was incorrect. Thank you for correcting me. I will rephrase it to say that the force used to move a lighter car will have "quicker" results than a heavier one.
> 
> Its like flicking a pebble versus flicking a rock. Using the same force, the pebble will move quicker/faster than the rock. Because the weight of the pebble is lighter, it has the natural advantage of requiring less force to move it than the rock.
> 
> That should get things right. Let me know if I still need to be corrected.


  :thumbup:


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