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Thread: Write-up: How to determine approx. HP gains from removing weight! Reply to Thread
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Topic Review (Newest First)
12-07-2005 09:33 AM
Carrera26 ^^^Just a tick off of a C6. Good Job! There's always the question of gearing, traction, and how you're accesing the power curve, but I have always thought that this is the best "from the hip" estimate.

I think it's pretty fun to look up too, so here's 3 race cars

2005 Dodge Magnum NASCAR - (3400lbs / 850bhp) = 4.00 lb/bhp
1973 Porsche 917/30 - (1872lbs / 1100bhp) = 1.70 lb/bhp
2005 Ferrari F2005 F1 car - (1333lbs / 1000bhp) = 1.33bhp

It just cracks me up that a street-legal, $40K, 4-cylinder, Honda engined car (Atom) has a noticeably better power to wieght ratio than a full-on Nextel Cup car...
12-07-2005 08:50 AM
b16sir1991 I just figured mine (keep in mind this is a approximation because im going off of what Wayne dynoed one at already) and it should be appx. 8.57hp/lb. Not bad, never thought about it till i saw this thread.
12-07-2005 08:34 AM
Blurry Can't wait till spring...bought a set of SSR GT1s that weigh 15lbs. so that's about 7 lbs. a wheel lighter then the stock SVTF rims...new tires that weigh 1.5 lbs. less each then the stock Contis and so far I've lost 35lbs. with some more to loose...My SVTF should really feel much quicker by spring.
10-17-2005 05:21 PM
Carrera26 If anybody wants to use power to weight, here are some decent baselines.

Weight / BHP = Power to weight ratio = Pounds each BHP has to push around.

Remember to apply the ratio for type of weight loss as well

Sprung 1:1
Unsprung Rotational 1:3 (Wheels, tires)
Driveline 1:15 (Flywheel, clutch, pistons, Rotating driveline mass)

There is also the element of torque to weight, which will make a real difference, especially with FI cars. But as this also involves the area under the torque curve, it is much more complex, so let's keep it simple. That is, unless somebody really feels like diving into it.

(Rounded to the hundreth)

ZX3 Zetec - 20.53
ZX3 ST - 18.13
SVTF - 16.18
RS - 13.08

2005 Mustang V6 - 15.71
2005 Mustang GT - 11.5

Cobalt (LS Coupe) - 20.62
Cobalt SS Supercharged - 14.59 <@ 205 BHP, this has been argued as low, 13.29 @ 225BHP>

Corvette C6 (coupe) - 8.1

WRX STI (2005) - 11.02

Ferrari Enzo - 4.41
Ariel Atom - 3.38
TVR Speed 12 - 2.358

Suzuki GSXR 1000 - 2.33


Here is a good site to look cars up.
10-17-2005 02:39 PM
Taiden
Quote:
Originally posted by Carrera26
Maybe just going for power/weight ratio from the beginning would have been easier...
Maybe not making this post in the beginning would have been easier. ;P


To everyone else:

Know that the concepts discussed in this thread are not false in any way, and are reasonably accurate. This is not the end all be all mathematics for determining HP/LB equivalents, if we wanted that, it would involve calculus.

These are meant to be used to give someone an idea, or an estimate of how much weight they could lose to get the same performance out of a given upgrade.

Example:

Since my car wieghs W pounds, and I want the performance of Y hp, I could either spend money on upgrade X to get Y hp, or I could remove Z lbs from my car.
10-17-2005 10:42 AM
Carrera26 Maybe just going for power/weight ratio from the beginning would have been easier...
10-15-2005 12:23 PM
Taiden
Quote:
Originally posted by remyx
I only read two pages in the thread so far, but your (original poster) equation is just wrong, yet alone doesn't make any sense.

Think of it this way, if you take a 350 HP Hemi (just an example) and put it into a Focus, it's still going to be a 350 HP Hemi. Of course your performance will increase but your calculations are just ridiculous. Nice try though.
To those who say I am wrong, please read the original article fully before making yourself look stupid. This is HORSEPOWER EQUIVALENTS. There is no way in hell that removing weight would increase horsepower at the crank or the wheels. What I am doing is converting "weight loss" into a more palpable form like "horsepower." Of course, this weight "horsepower" only effects acceleration. It has a greater effect on handling, but not one that can be measured in theoretical "horsepower."

There are two ways to make your car accelerate faster.

1) Increase horsepower.
2) Decrease weight.

At some point, removing a certain amount of weight will be just as effective as increasing your housepower by a given amount. This allows you to find out just when that is.

Once again, before flaming, read and UNDERSTAND what I have written. This is not meant to be 100% accurate, but to give a ballpark estimate.
10-14-2005 05:24 PM
remyx I only read two pages in the thread so far, but your (original poster) equation is just wrong, yet alone doesn't make any sense.

Think of it this way, if you take a 350 HP Hemi (just an example) and put it into a Focus, it's still going to be a 350 HP Hemi. Of course your performance will increase but your calculations are just ridiculous. Nice try though.
10-13-2005 07:02 PM
wayne newton if the driver looses 20lbs, i guess that also counts... god i gotta start running more.
10-03-2005 05:46 PM
ILLchyld You are correct, but I digress. Weight-et is a more accurate method of measurement compared to weight-hp. The effects of lighter weight are immeasureable in a road course or autocross enivronment, better traction, braking, lower center of gravity, acceleration. Only one of which is related to horsepower.
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