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I agree with the physics... but here is the problem. How much do we weigh factors? A lot of times, that is just pure assumption and something we thought would be a big deal, doesn't turn out to weigh in greatly at all.

Look at my bike for example.

124hp and 89ftlbs of torque at the wheel... but it weighs around 750lbs with driver on board and consequently puts out mid-high 10 second 1/4 mile times. A Viper needs at least 4X that much power to get a MUCH slower 1/4 mile speed (2 seconds or so behind).


Motorcycles are an aerodynamic nightmare with a very funky turbulant shape, but the light weight still works wonders up to 100mph before wind resistance gets particularly heavy. 1/4 mile speeds don't exceed 100mph very much, and neither will you on the street. Consequently, you WILL feel weight reduction.

So even in this instance with a really unaerodynamic shape, but ultra-lightweight it works wonders. Now if I were to race the Viper on the salt flats from 100mph to 150mph, the Viper would probably pull on me.
 

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so, if I quit working out, and dropped from 200 to 160 or some other normal weight I should be around 4hp faster, pretty cool
but if I wanted to go that far, I'd strip the car down first


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<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>For all of us drag racers lets weigh the cars with driver & post the ET. Lets prove this theory.<HR></BLOCKQUOTE>
You can't prove theories if you change more than one variable at a time. If you want to prove it... do this.

Run a restrictor plate on your intake and figure out on a dyno how much each restrictor plate lowers power. Then get a lot of sand bags and try to distribute them evenly front/rear. Then all you have to see is to run with a restrictor plate that lowers power say 30hp, and then compare that to running 300 extra lbs of weight. Do two more with different numbers and you can get a good approximation.


THAT would be reasonably conclusive provided you have a consistent driver.
 

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Discussion Starter · #26 ·
i just read 2001 zts post:

Yes, loosing 1000 pounds is like adding 100hp to your car. Think about it. Ok, the AC turbo focus with about 230hp at the crank is about 100hp over stock correct? It is good for low 14second passes. Lets say 14 flat.

Now take a car that weighs 1600lb instead of 2600lb. My friend has a honda crx, the lightest one with a b16 swap out of an si. It is completely stock, so 160hp at crank. His car runs mid 13's. Hows that possible? Hmmm.... Lets even loose 2000lb, still the same, if not even more. a 600lb bike with only 130hp, like our car, will run 10's in the 1/4mile. So it is just the same with more weight loss, IF NOT BETTER. Now it would be impossible to go too much under 2200lb with our car, so thats where you would be right, in the fact that we cant go too far. Hell, look at Focussport car, they stripped it to 2300lb, and are only running bolt ons and ran a 14.3!!!!!!!!!!!!!!!! Thats what an Aerocharger stage 3 with 200WHP runs. So how is my math possibly incorrect?
BANDIT: Are you serious about the hotrod thing? You cant possibly say that you dont agree with me
 

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Naz, believe me I,ve been drag racing for a long time. I alwas believed a 100lbs = 1/10 up to a point. Thats what the magazine said. This article was written a few months ago now I have to go look for the damn article. Just goes to show you, you can't always believe what you read!
 

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So would this work the opposite way too? If I add about 100lbs of stereo equipment will I lose about 10 hp?

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Its not a mather of adding more power. What nazthug means is that your engine will have to work less since the car is lighter. For example.. Put 1 person on a horse... then put a full plate armor to your horse and to yourself and see if the same horse performs just as good. The horse isn't more powerful, its just easier to pull/hold that weight. The horse still has the same power/strength, but hes got more weight to carry.. so no wonder he'll be slow

As for the 10th of a second, its just to show that the car is faster, but it is equal to what 10 more HP would do to a car
 

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Discussion Starter · #31 ·
i cant believe some of you guys dont know this, YES your car will act as if it has 10hp less if you still tons of audio in it. You can totaly tell, when i had my system in my car, about 180lb of it, the car felt way slower. Im not saying if you roll up to a dyno with a system, youre gonna dyno less, im saying thats what the car will act like, im just using the HP as an example so people understand. What do you think would happen if you stuck our engine into a go cart???? Why do you think the race course classes with those indy car looking cars only have a neon engine in a 1400lb chassis, outruning cobras, ferraris, and vipers....

Hell, how fast do you think a car will be while its hooked up to a trailer towing a 15' boat. Comeon guys, use your heads

Im saying if your focus is towing a 500lb bike on a trailer, your focus will be as slow as a focus with lets say 90hp or so. Its as simple as that
 

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Discussion Starter · #32 ·
I also exhale right before i launch

I also thought about taking my engine out, thats about 200lb

Once i even got out of the car to lose the extra weight, it ran pretty fast....i never saw it again
 

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question? In theory would it be safe to say...if you have 180HP at the crank and lost 200lbs from the car you have a 200HP Focus? In theroy yes?
Just wandering
 

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i tell you what Naz and people. just hae a turbo Zetec, then have only the front wheels. then on top of that just put wheelie bars in the back so you do tip over. and then strap yourself to the motor. you should have 2 second quater miles and in thereoy 40000000000000WHP. haha
 

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I've heard its about 7 or 8 eight horsepower per 100 lbs. i've never really thought this out , i mean i want my car to be faster but i also want it to look like a street car !! the only way for me is to add more horses
just my 02. cents
 

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<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by Daniel:
Hmm.. The power-to-weight ratio improves... Yup.

<hr></blockquote>

I read in SCC that for every pound lighter your rims are it is actually the equivalent of 6-7 pounds lighter because of rotational mass. think about it, that is why a lighter flywheel makes your car "feel" 200 pounds lighter in 1st gear. so if you get rims that are 5 pounds lighter you are making your car seem 140 pounds lighter.
 

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<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by 2001 ZTS:
The weight loss=HP gain is true to a point and I won't question anyones figures but "the law of diminishing returns" kicks in at some point. Loosing the first 100 lbs of weight may gain the equivalent 10HP, and maybe even dropping 200 lbs may gain you twenty but if you half the weight of the car (say 1300 lbs) you aren't going to gain the equivalent of 130 HP. This is because other things start to kick in like drag co-efficient, rolling resistance etc. Same idea if you put two 130HP Zetec engines in your car, it wont go twice as fast.<hr></blockquote>

this is wrong. drag coeffients and rolling resistance are functions of speed NOT horsepower. you are assuming that the car will be going faster because it is lighter which doesn't factor into this equation. this "law of diminishing returns" you speak of may apply in the economics class you took but not here

 

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I don't agree with the 100 lbs = 10 HP approximation. If a stock Focus weighs say 2,800 pounds with the driver and has 115 WHP that would give a power to weight ratio of about 24 pounds per HP (!). At this PW ratio, 10 HP equivelance should require losing about 240 pounds, not 100 pounds.
 

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<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by Welding Rod:
I don't agree with the 100 lbs = 10 HP approximation. If a stock Focus weighs say 2,800 pounds with the driver and has 115 WHP that would give a power to weight ratio of about 24 pounds per HP (!). At this PW ratio, 10 HP equivelance should require losing about 240 pounds, not 100 pounds.<hr></blockquote>

Not so. If you take a 100 hp car which weighs 2000 pounds and reduce its weight to 1000 pounds then the effective horsepower equivalent is 400 hp. The relationship between weight and power is not linear, it is exponential. If you double the weight of a car you need to quadrupal the power in order to achieve the same performance. Likewise, if you half the weight of a car then you've effectively quadrupaled the performance (minus the drag and wheel friction another poster noted, since we are considering performance or speed not simply the relationship to horsepower).
 
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