Ed Wright

iTrader: (1)

That depends on your power level. 100 lbs on my car has shown to be .06 to .07 sec. I have a friend that has run several fast NHRA Comp eliminator cars, and changes classes by adding or removing weight, and he says he can figure on .05 sec per 100 lbs. Of course, he makes a couple hundred more hp that I.

I tell guys pounds are the same as hp.

JUICED96Z

Does this make sense?


On a heavier car 100 pounds is not that high of a percentage of weight. Say 100 pounds out of a 4200 pound impy is not that much.

Now 100 pounds out of a 2800 pound car would be a lot more and cut more time because its a higer percentage of weight being pulled?

For example (just throwing out numbers)

10 pounds in a 100 pound go cat is a 10% weight reduction

10 pounds in a 1000 pound car is a 1% weight reduction.

Ed Wright

iTrader: (1)

Not in my experience. Many years ago (late 1960s) I race NHRA Stock Eliminator '56 Chevys. I began with a 9 passenger station wagon with the 225 hp solid lifter 2 X 4 bl carb engine. We were restricted to 7" slicks, and about all there was available were Marsh recaps, so the wagons hooked better and ran a lower class to boot. (Classes are shipping weight divided by hp) Firestone and Goodyear came out with real race tires, so hooking a sedan was easier. The big old wagon was hard on parts, besides ugly. I changed to a 210 series 2 dr sedan, (450lbs) lighter. The wagon ran a best of 14.07, the sedan ran 13.50s right off the bat. Hadn't touched the engine, same drive train. The sedan weighed 3150, my TA weighs 3285 right now. 100lbs was more than 1/10th with that small '56 engine, less than 1/10th with this car I have now. One of the 10.5 Shoot-out cars I help dropped some weight & saw less than .05 from a 100 lb weight loss. He is about 3500 lbs right now, but makes 969 rwhp on my dyno all motor (1175 hp on Reher & Morrison's Super Flow engine dyno 2 days before), I can't measure what it makes on the bottle, I just get a flat line at 1250 hp. The more power you have, evidently the less a 100lb weight loss will get you. I haven't seen where vehicle weight has much to do with it.

Bryan @ Speed Inc.

iTrader: (19)

go kat's sound fun. haha

Demonicbird00

iTrader: (17)

they are, i race them nationaly.

-brandon

JUICED96Z

Hmmm very interesting Ed.

chrs1313

iTrader: (24)

definitely worth it, IMHO

Taubr Unit

iTrader: (32)

To go fast, it all about power/weight ratio. Look at motorcycles, weigh nothing and go 200+ mph with 130ish hp. Make your car weigh 800lbs like a motorcycle and youll hang with John Force, lol.

SLPSS99

iTrader: (7)

I have a lot of weight out of my car yet it still looks stock on the out side, I have not chopped it up you could still DD this car. right now I am at a 3250 race weight and I am 150 pounds. The only missing thing on the interior is the back seat. But will be adding weight as I will be doing a Rollbar. But still need to do a few more costly weight reduction mods.

Dan

CaMaRo67RS355

iTrader: (75)

SLPSS99 what all did you do if you dont mind me asking...

SLPSS99

iTrader: (7)

Where to start,
Bumper Supports!
AC!
Heat!
Radio! and Speaker!
lightweight carpet
light seats
skinnies
15X10s out back
inner fenders!
abs!
PS!
QA1's and Springs
No power Brakes/Brake booster
all susp. is chromoly and tubular
Basically all the free stuff on the weight reduction list

Dan

gforcejunkie

the rule of thumb is 100lbs equals .1 off of your et but there are many factors to consider such as hp, tq and total weight. you dont see as high of an improvement on a high horsepower car because the power to weight ratio isnt changed as much say you have a
1000lb car 100hp your power to weight ratio is 10lbs/1hp
a 2000lb car 100hp = 20lbs/1hp
now say its a 4000lb car and you have 1000hp power to weight would be 4lbs/hp
now say 3900lbs with 1000hp= 3.9lbs/hp
now it should be easy to see how depending on the application what losing weight really does for you.
just for the hell of it something a little closer to our cars.
3500lbs with 300hp = 11.66lbs/hp
3400lbs with 300hp = 11.33lbs/hp
3500lbs with 400hp = 8.75lbs/hp
3400lbs with 400hp = 8.5lbs/hp

chrs1313

iTrader: (24)

wouldn't hp/lbs be better to think about than lbs/hp...that would be like saying cubic inches/hp...much better to have the ratio hp/cubic inch...anyways

Hrod382

In my 2700 pound car 100 pounds doesn't equal a tenth. A 130 pound me ran a 5.997 on a Saturday night in good air then the next morning my 225 pound dad ran it in way worse air and horrible track conditions and still ran a 6.071. Every pass I had .02 better in the '60 and 2 more MPH.

Pays to be skinny.

gforcejunkie

im talking about a 1/4 mile track not a 1/8 mile track i should have specified that. and the reason i put down lbs/hp rather then hp/lbs is it shows a more dramatic difference between the weight change. and to some people its easier to compute whole numbers rather then fractions rather then say the difference like with the 3500 300hp which would be .85hp/lb vs. 3400lbs 300hp .88hp/lb. its easier to see that actually makes a difference to the performance imo

gforcejunkie

see how in the 1/8 its still .074 different thats damn near a 1/10th which it would be in the 1/4.

Hrod382

Well, the DA was a factor in it being as high as .074.

Another run for me the night before was a 6.050 with a 2600 DA with a track temp around 85. My dad was running with 2900 DA on a 130 degree track and still running 6.071's.

Regardless this isn't the greatest comparison given it's different tracks/weather and you are right about me picking up even more in the 1/4 mile because of the lack of weight I was just trying to provide an example.

We might put my dads 548 which has run a 6.06 in a 3150 pound car into my car that will be 2825 with me in it so I am hoping to gain around 2 tenths via less weight then put it on alcohol to gain another one so hopefully some 5.60's.

black_z

iTrader: (4)

Do you know ryan stringfield? He is a good friend of mine that races shifter karts.

Demonicbird00

iTrader: (17)

nah i dont know him, he may race in a different national series, im in the Road Race Enduro Series.

-brandon

XpEdItIoUs

iTrader: (44)

I started with removing my rear seats, Now i went all out removing seat brackets, carpet, and lots of cutting. My car is a daily driver