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Discussion Starter #1
Does anyone have a clue on how much weight affects speed and HP. For example. I love my music in my car. I have 2 12's in a big speaker box. Acutally i have about 4 inches of room in my truck. The box must weight 150lbs or more with the speakers in it. How much does that affect my car's perfomance? I got a 3.5 2k4 Auto.
 

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a lot, I believe for every extra 7 pounds you have in your car, thats 1 hp less you have. So lets see 150lbs for the boc, 50lbs for both speakers, 10lbs for a amp I am assuming you have. Thats 210lbs divided by 7, is well 30 less hp that you have. Its like having a fat ass in the passenger seat, and yes it makes a difference.
 

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Heard somewhere that every 100 pounds you add is like knocking 10hp off of the bottom line.

Or inversely, every 100 pounds you lose is like gaining 10hp.

Of course this is just a rule of thumb.
 

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i would say its different for every car...depends on where they make most of there power and all that type of stuff...basically, the heavier you are, the slower...doesnt necessarily mean a heavy car is slow...but if you add weight to ur car, it'll be slower...
 

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that system should knock your 1/4 time anywhere from .1 to .25
 

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Discussion Starter #7
yea i guess i am losing HP for sound and style. I have the whole works DVD player, 2 12's, amp, CD changer, capasitor, etc... so i guess i just have to kick up the mods to get it back to before. I was looking to see how big of a difference the weight made. I noticed it alot when the car was bone stock i could peel out from standing still. Now i can only peel out by taking a corner doing 40 mph.
 

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Discussion Starter #9
Hmmm... i don't do it all the time. I would say once and a blue moon. But if it does that much damage ok then good point last thing i need is to replace the trans on a 2004 car for jerking around.
 

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I see a silver lining in your case. Yes, straightline performance is hindered obviously. But w/ the extra weight in the back, you're closer to a 50/50 weight distribution. And that obviously affects how the car feels and behaves in the turns.
 

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yea^^^ thats my excuse why I need 3 12"s in my trunk... for the weight balance.... :lol:

theres no cardinal rule for weight because on a 2000lb car an extra 150lbs hurts alot but on a 3500lb car a extra 150 doesnt hurt nearly as bad. It depends on how much it affects your powr to weight ratio... but on a v6 alty 150lbs would hurt a little but not massively... now if u race another alty with the same mods u are at a obvious disadvantage because of the weight but it will not slow u down .5 or anything in the quarter..
 

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masonaltima said:
a lot, I believe for every extra 7 pounds you have in your car, thats 1 hp less you have. So lets see 150lbs for the boc, 50lbs for both speakers, 10lbs for a amp I am assuming you have. Thats 210lbs divided by 7, is well 30 less hp that you have. Its like having a fat ass in the passenger seat, and yes it makes a difference.
what box weighs 150 lbs? what 12 inch subs weigh 50 pounds? 2 12 inch subs would weigh no more than 25 lbs...just correcting you. but on another note if you get lightweight rims compared to your stock rims or heavy chrome rims you will notice a difference in acceleration.
 

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hahaha this weight vs hp difference messed me over yesterday and the day b4 while i was driving to palm springs. i caught 2 races and lost both. i had 5 full sized ppl in my car and a totally FULL trunk full of heavy shit like 30 packs of beer, sodas, clothes, etc. we guessed we put on 865lbs of person weight and about another 200 for cargo. my car looked as if it was dropped/slammed in the back.

well anyways, my first race i dont think i would have won if i was alone in the car, but i would have came very close to matching its speed considering how i did with like 1000lbs of extra weight. it was a race with a red srt-4 on the high way at speeds of 70+. he pulled away from me even if i floored it first, the driver was very cool, after we raced he pulled up to us smiled and we yelled a few complements back and forth while driving. haha b4 he left he put his hand up and raised 4 of his fingers (for 4 cylinders) and boned out.

my second race i know for sure that i would have won if i was alone. an older s500 got on my right and with the intention to try to pass me when the light turned. this dude was like 70 and had a handicap plaque haha. oh ya there was a hot chick in a civic who also decided to race on my left but she got dusted so fast that i dont remember much of her. light turned green, i pressed the gas slowly as to get traction then floored it. he also floored it, his car walked away from me very very SLOWLY. by 40 he was 3/4 a car ahead. i know that if i didnt have my A/C on and i didnt have 1000+lbs in my car i would have smoked the grandpa like no other. i was just pissed to lose to something i could have taken easily.
 

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when you get right down to it power to weight ratio is the ONLY thing that matters. A VW bug with 110 hp that weights 1200lbs will smoke 99% of the cars on this forum.

As for how much difference weight makes... take a 2nd gen alty for example. 150hp / 3000lbs (approximentally) = power to weight of .05

Now drop 300 lbs. Thats 150 / 2700 = .055
To get that same ration by adding power you would take .055 * 3000 and you get 166hp. So in this case dropping 300lbs is like adding 16hp.

The problem is you cant really make an accurate "rule of thumb" on this, because its a ratio, so the starting points of both weight and power effect how much changing each will effect the output.
 

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Discussion Starter #16
Damn that was all technical. I had to pull out a calculator and everything. Thanks i actually learned something.
 

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I had 3 10's in my car before and the box/amp weighed 125lbs. My 1/4 times would be about 2 tenths slower and I would lose about 1.5mph.
 
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