tigertank

isnt there a formula or guestimate on how much HP it takes to make up the weight diff?

like 5 HP for ev 10 lbs of weight?

QUAKEJAKE

My 07 3150 lb stock Z @ 505 hp would figure @ 6.24 lbs/hp. My reasoning would be you for every 6 lbs dropped would that be the equivilent of gaining 1 hp? 60 lbs= 10 hp ? drop 600 lbs = 100 hp equivilent? The result could be: would a 3150 lb Z with an LS7 producing 605 crank hp perform the same as a 2550 lb Z with a stock LS7?

camirocz

The answer is 10 h.p for every 100 lbs.

rattt g

so if i put 500 pounds in my car i only need 50 more hp to run the same number,, i dont think so

Vette5.5

Lower weight alway's rules, as the car will perform better in every way, but very expensive to do. To many factor's in the power/weight ratio for a general rule, as low end engine torque, gearing, traction, ext are all big factor's. Clearly the large displacement LS7 has a good torque advantage here, but moving less weight around is even better. HP number's make for good marketing, but some low torque 5000 lb vehicle's, what does it really mean.

Mopar Jimmy

I have always heard as a general rule of thumb, that for every 100 lbs the car loses it gains approx. .1 tenth in et.

Conversely, every 10 h.p gained is also suppose to shave off approx. .1 tenth in et.

If those rules of thumbs are somewhat accurate, then logically, the above statement may be somewhat accurate, as a general rule of thumb.

WICKEDFRC

Then as a rule of thumb for a Corvette with an iron block and stereo with me in it weighing 3584 race weight, I need another 30+ HP to equal C5s weighing in at 3200+?

If that's all, I am going to order me the Turbonator!!

tigertank

k thx guys i was close

Vito.A

Jimmy is right. In drag racing we use 100# equals .1 second in ET. We do not have a general rule for HP vs ET as it takes a lot more HP for gains in a heavy car than it does for a light car.

You might talk to Jim at Halltech. He has done some major weight reduction on his Z06. He may be able to tell you the decrease in ET.

You can also model the car in software programs like Quarter or Quarter Jr and then experiment with weight reduction.

Painrace

I used to race against a guy named Jerry Dunbar. Jerry was faster than the thunders of hell, but, Jerry weighed more than double what I did. The cars were weighed without driver so the cars had to weigh about the same (2,450# to 2,600# depending on engine displacement and type of transmission). Jerry was a great qualifier but all you had to do was keep up with him and toward the end of the race Jerry's tires would start to give up because of the extra weight. Weight matters a lot in road racing. You don't see many fat pro racers. Take a look at the Corvette guys, Ron fellows, Andy Pilgrim, etc. The more weight you can shed the faster you will go. It is simple physics.

Jim

tigertank

what i was trying to figure out is how much HP is needed to vercome athe weight diff say a car is 300 lbs heaveir than u so if both put out 500 RWHP how much more wud the car that weigh 300 lbs more need to be equal again

so of 10hp for every 100 lbs means the one car wud have to have 530 RWHP to stay even with the lighter car

FNBADAZ06

No way does 50 HP make up for 500 lbs.

Rock36

Fellas just remember your ratios from school. It is a little bit different for each car/hp rating.

Take a stock Z06 assuming 3200lbs.

Power to weight: 3200lbs/505hp = 6.34 lb/hp

If you add 500lbs to the Z06 you need to refigure how much hp you will need to maintain the 6.34 lb/hp so....

3700lbs/ X hp = 6.34 lbs/hp

do a little algebra and you get approx 583.6 hp.

So 500lbs on a 3200lbs Z06 requires about an extra 78 hp.

So every extra 100 lbs on a Z06 requires about 15.6 extra hp to maintain the same power to weight ratio.

Chonger

I would say the answer is all relative to what weight you are starting out with. Or in other words, say 200 lbs. will have a greater impact on one car more than another car depending on what base weight you are talking about.

Car #1 weighs 3,000 lbs. and car #2 weighs 4,000 lbs. They both have the same amount of HP and TQ. If you added 200 lbs. to both cars I would say it would have an overall bigger impact on car #1 more than car #2.

Pretty difficult to apply a simple conversion of X amount of HP per X amount of weight fits all.

LanceFitzgiben

take the vehicle's weight, divide by BHP - and you have the power to weight ratio broken down to lbs per HP. That's the only formula. It is impossible for there to be one figure that's the answer to everything. Every situation is different. At 3150 LBS and 505 BHP, you have each HP carrying around 6.23 LBS. With the same BHP at 2400 LBS each HP would only be carrying 4.7 LBS. To achieve that power to weight ratio while adding HP alone, you would need a 3150 LB car with 670 BHP.

I think. I'm bad at math. But yea, there is no one answer to this question. The "formula" is just weight divided by power.

Rock36

Exactly, and like Lance said it is all about solving for the power to weight ratio. It will be different for every car. Say both cars have 250 hp

Car #1: 3000lbs/ 250hp = 12lb/hp

add 200lbs

3200lbs/ x hp = 12lb/hp

solve for x: x = 266.67 hp. So car 1 needs 16.67 extra hp

Car #2: 4000lbs / 250 hp = 16 lb/hp

add 200 lbs

4200 lbs / x hp = 16 lb/hp

solve for x: x = 262.5 hp So car 1 needs an extra 12.5 hp to maintain its power to weight of 16 lb/hp

FNBADAZ06

While I'll agree with the math, the equation doesn't take into account many other variables. Take that 500 lbs and place it at the wheels (each wheel getting 125 lbs of additional rotating mass) and you'll need WAY more than 78 RWHP to make up the difference.

B505

This will explain it all.

They start with a light car, lose 100 lbs
then lose 500 lbs

they end up gaining more than .1 for every hundred pounds on this particular car. Although its extreme, you can see what weight does. Imagine this gap on a road coarse, turn after turn, and you'll see why lighter is better!

http://www.hulu.com/watch/228074/car...pped-for-speed

Chonger

Math and real world results are not the same. A 3,150 pound Z-06 with 505 HP equals a 6.24 ratio. To get a 6.24 ratio on say a GT500 at 3,900 pounds would require 625 HP. That 625 HP equates to about +/- 530 RWHP. A 530 RHWP GT500 would not keep up with a bone stock C6 Z06 from a roll.

So here again 6.24 does not equal 6.24 in the real world.

Vette5.5

Answer: Lighter's better.