rule of thumb

fordkid68 · 02-24-2002, 12:29 AM

first of all sorry that this doesn't have any thing to do with classic mustangs. but this questiong also isn't realated to A show or A type of engine so I thought I would post it here.

ok I thought I could remember there being some sort of hot rodders rule of thumb like so many pounds of wheight to hp would get you around 10 seconds. now I am sure that it couldn't be exact cause of other things that add performance without adding hores power. but is there some kind of rule like this.

thanks
ford kid

mean81GT · 02-24-2002, 08:58 PM

the rule that i remember goes like this : for every 100 lbs of weight you drop from the car, you gain .1 of a second in the quarter. I don't know of any rule relating to hp and weight, because there are too many variables. two identical cars will go two different speeds with two different drivers, two identical cars will go two different speeds with different gear ratios, tires, tire pressure, clutch setups, and so on. every variable from one car to another is going to change each car slightly, so you can't really compare the two.

fordkid68 · 02-25-2002, 02:04 PM

yea I new it wouldn't be exact but o well. thanks for letting me know that for every hundred pounds you drop takes .1 second off. thats big difference between the two cars going 100+ mph.

thanks
ford kid

Rev · 02-25-2002, 08:37 PM

OK, for my car @ 3000 lbs and 300 HP, then 100 lbs=10 HP. This is just a general rule of thumb and may be right for +/- 10%, but is good for a general rule, IMHO.

Rev

fordkid68 · 02-25-2002, 08:56 PM

kool thanks

thanks
ford kid

mean81GT · 02-25-2002, 10:00 PM

rev, i didn't understand the rule. what, for every hundred pounds, you have 10 hp? my cavalier weighs three thousand pounds< and has one hundred and thrity horsepower> so in that case that rule doesn"t work> please elaborate on the rule>

PKRWUD · 02-26-2002, 02:00 AM

Unrelated, but another rule of thumb none the less:

Once you reach 12 seconds in the quarter, plan on spending $1000 per tenth of a second you wish to reduce your time by.

Take care,
-Chris

mustangman65_79 · 02-26-2002, 10:40 AM

Too many rules, what, are we in road school now?

mean81GT · 02-26-2002, 01:37 PM

OK, new rule. How bout we forget the rules, drive the s out of our cars, and enjoy every minute?

Rev · 03-01-2002, 04:29 PM

Actually it's very simple. So much percetage of weight loss equals the same percentage of HP gain. There is some slight amount of descrepancy, but not much.

A 3000 lb. Cavaleier with 130 HP losing 100 lbs. would have lost 3.33% weight. That would be (more or less) a 3.33% gain in HP or about 4.3 HP.

Those that think these things are of no importance probably will always be as slow as they are now.

Rev

fordkid68 · 03-02-2002, 02:22 AM

hey thanks. that helps out alot. and yup every single hp counts.

thanks
ford kid

02-24-2002, 12:29 AM	#1
fordkid68 Registered Member Join Date: Jan 2002 Location: fremont Posts: 306	rule of thumb first of all sorry that this doesn't have any thing to do with classic mustangs. but this questiong also isn't realated to A show or A type of engine so I thought I would post it here. ok I thought I could remember there being some sort of hot rodders rule of thumb like so many pounds of wheight to hp would get you around 10 seconds. now I am sure that it couldn't be exact cause of other things that add performance without adding hores power. but is there some kind of rule like this. thanks ford kid

02-24-2002, 08:58 PM	#2
mean81GT Registered Member Join Date: Nov 2001 Location: NY Posts: 299	the rule that i remember goes like this : for every 100 lbs of weight you drop from the car, you gain .1 of a second in the quarter. I don't know of any rule relating to hp and weight, because there are too many variables. two identical cars will go two different speeds with two different drivers, two identical cars will go two different speeds with different gear ratios, tires, tire pressure, clutch setups, and so on. every variable from one car to another is going to change each car slightly, so you can't really compare the two. __________________ I'm a glutton for punishment.

02-25-2002, 08:37 PM	#4
Rev Registered Member Join Date: Nov 1998 Location: Houston, Tx. Posts: 3,887	OK, for my car @ 3000 lbs and 300 HP, then 100 lbs=10 HP. This is just a general rule of thumb and may be right for +/- 10%, but is good for a general rule, IMHO. Rev __________________ '66 Coupe, 306, 350-375 HP, C-4, 13.07 e.t., 104.8 mph, 1/4 mi. O.B.C. #2 '66 coupe

02-25-2002, 10:00 PM	#6
mean81GT Registered Member Join Date: Nov 2001 Location: NY Posts: 299	rev, i didn't understand the rule. what, for every hundred pounds, you have 10 hp? my cavalier weighs three thousand pounds< and has one hundred and thrity horsepower> so in that case that rule doesn"t work> please elaborate on the rule> __________________ I'm a glutton for punishment.

02-26-2002, 02:00 AM	#7
PKRWUD Junior Member Join Date: Mar 1999 Location: Ventura, California Posts: 8,981	Unrelated, but another rule of thumb none the less: Once you reach 12 seconds in the quarter, plan on spending $1000 per tenth of a second you wish to reduce your time by. Take care, -Chris __________________ Webmaster: Rice Haters Club Jim Porter Racing Peckerwoods Pit Stop Support Your Local RED & WHITE!

02-25-2002, 02:04 PM	#3
fordkid68 Registered Member Join Date: Jan 2002 Location: fremont Posts: 306	yea I new it wouldn't be exact but o well. thanks for letting me know that for every hundred pounds you drop takes .1 second off. thats big difference between the two cars going 100+ mph. thanks ford kid

02-25-2002, 08:56 PM	#5
fordkid68 Registered Member Join Date: Jan 2002 Location: fremont Posts: 306	kool thanks thanks ford kid

02-26-2002, 10:40 AM	#8
mustangman65_79 My poor 79 RIP Join Date: Oct 2001 Location: Suisun City, Posts: 2,320	Too many rules, what, are we in road school now? __________________ '84 mustang GT turbo '85 LTD '89 Camaro Irocz z28 '94 Lightning '96 Trans am

02-26-2002, 01:37 PM	#9
mean81GT Registered Member Join Date: Nov 2001 Location: NY Posts: 299	OK, new rule. How bout we forget the rules, drive the s out of our cars, and enjoy every minute? __________________ I'm a glutton for punishment.

03-01-2002, 04:29 PM	#10
Rev Registered Member Join Date: Nov 1998 Location: Houston, Tx. Posts: 3,887	Actually it's very simple. So much percetage of weight loss equals the same percentage of HP gain. There is some slight amount of descrepancy, but not much. A 3000 lb. Cavaleier with 130 HP losing 100 lbs. would have lost 3.33% weight. That would be (more or less) a 3.33% gain in HP or about 4.3 HP. Those that think these things are of no importance probably will always be as slow as they are now. Rev __________________ '66 Coupe, 306, 350-375 HP, C-4, 13.07 e.t., 104.8 mph, 1/4 mi. O.B.C. #2 '66 coupe

03-02-2002, 02:22 AM	#11
fordkid68 Registered Member Join Date: Jan 2002 Location: fremont Posts: 306	hey thanks. that helps out alot. and yup every single hp counts. thanks ford kid

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