Welcome to Club Hot Rod!  The premier site for everything to do with Hot Rod, Customs, Low Riders, Rat Rods, and more. 

  •  » Members from all over the US and the world!
  •  » Help from all over the world for your questions
  •  » Build logs for you and all members
  •  » Blogs
  •  » Image Gallery
  •  » Many thousands of members and hundreds of thousands of posts! 

YES! I want to register an account for free right now!  p.s.: For registered members this ad will NOT show

 

Thread: Effect of weight on 1/4 mile times
          
   
   

Reply To Thread
Page 1 of 2 1 2 LastLast
Results 1 to 15 of 22
  1. #1
    hhaywoodjr is offline CHR Member Visit my Photo Gallery
    Join Date
    Nov 2009
    Location
    huntingtown
    Posts
    3

    Effect of weight on 1/4 mile times

     



    If two cars were to race, both with 7.6 lb/hp ,one weighing 3300 lbs with 425 flywheel hp and the other 4300 lbs and 565 flywheel hp. What would be the effect of moving the extra 1000lbs even though they're putting the same power to the ground.

  2. #2
    Itoldyouso's Avatar
    Itoldyouso is offline CHR Member Visit my Photo Gallery
    Join Date
    Jan 2006
    Location
    fort myers
    Car Year, Make, Model: '27 ford/'39 dodge/ '23 t
    Posts
    11,033

    Not that simple. A lot depends on how the two cars hook and launch, and the torque put out by the two different engines. HP is what we all talk about, but torque is what wins races.

    The old rule of thumb was, for every 100 lbs you remove from a car you pick up one tenth second et, so 1000 lbs less equals 1 second faster time. Beyond that, my mathmatical skills run out.

    Don

  3. #3
    HOTRODPAINT's Avatar
    HOTRODPAINT is offline CHR Member Visit my Photo Gallery
    Join Date
    May 2005
    Location
    tucson
    Posts
    3,043

    I'm not a pro drag racer, but have been around it all of my life.

    Another thought that occurs to me... besides simply increasing power... is that the tires are gripping the asphalt, trying to accelerate the car's mass. But as weight increases, you may approach or surpass the limit of the tires "gripping" ability.

    ...of course there may be the option of bigger tires... :-)

    Other advantages to light weight are the decreased stress on the drivetrain, and the potential to go even faster, when the power is increased... as you did in the heavier example.

  4. #4
    dlotraf33's Avatar
    dlotraf33 is offline CHR Member Visit my Photo Gallery
    Join Date
    Sep 2009
    Location
    Georgetown
    Car Year, Make, Model: 48 Ford Truck
    Posts
    471

    If you are talking moving weight..... The more weight of the car, highest percentage, you can put on the rear the better. Better weight transfer, in theory, the better the car will hook up. Of course there are so many varriables it's hard to say. Like don said torque, torque, and you got to get it to the ground. You could have a 7hp per lb advantage over another car and if you blow the tires off......well guess who will come out ahead. Of course that's a drastic exageration, but you get the point. With any race car the lighter the better. Then if you have a weight minium you put it where you want it. And with a very light car, and no weight minium, you may find that adding weight to the rear, will make car hook up better and better et's.

  5. #5
    Big Tracks's Avatar
    Big Tracks is offline CHR Member Visit my Photo Gallery
    Join Date
    Aug 2005
    Location
    Keller
    Car Year, Make, Model: '79 Dodge Diplomat Coupe
    Posts
    832

    Quote Originally Posted by HOTRODPAINT View Post
    Another thought that occurs to me... besides simply increasing power... is that the tires are gripping the asphalt, trying to accelerate the car's mass. But as weight increases, you may approach or surpass the limit of the tires "gripping" ability.
    There was a time when a "small amount" of wheel spin was to be expected .........

    Procedures do change!

    Why did this work as well as it did?

    Jim
    Attached Images

  6. #6
    joe_and_jeep is offline CHR Member Visit my Photo Gallery
    Join Date
    Oct 2006
    Location
    Pittsburgh
    Car Year, Make, Model: 47 Dodge Pickup, 68 Chevy C10
    Posts
    32

    I have a Suzuki Samurai and a Jeep. The Jeep is 180hp 4k lbs and the Sanurai is 60hp 2300lbs. The Jeep runs a 33x15.50 and the Samurai runs a 31x11.50. Both are the same brand of tire, Super Swamper TSL. Now this aint drag racing but the Samurai will definately climb a muddy hill (level, no ruts just slick greasy) the Jeep will spin the tires more and will definately accelerate better. But the little light weight Samurai will climb better, hold a line better and not slide in off camber situtions. Weight plays a huge factor in how a car performs. I think in a weight distributing, traction perfect world, a 2300lb 7.9hp per lb car won't accelerate like a 400lb 7.9hp per lb. I have no scientific or mathmatical evidence but I would assume that the hp per lb would have to increase slightly. Maybe a small percent, like 7.9 to 8.1.

  7. #7
    robot's Avatar
    robot is offline CHR Member Visit my Photo Gallery
    Join Date
    Feb 2004
    Location
    Tucson
    Car Year, Make, Model: 39 Ford Coupe, 32 Ford Roadster
    Posts
    2,334

    Dont forget the other factor....age.

    Since I got old and fat, I cant run 1/4 mile without having
    a heart attack!

    mike in tucson

  8. #8
    Geezer2's Avatar
    Geezer2 is offline CHR Member Visit my Photo Gallery
    Join Date
    Aug 2007
    Location
    Dunedin
    Car Year, Make, Model: 1976 Cadillac Seville with 454 Chevy
    Posts
    421

    The 100 Lbs 10th of a second rule applies only if bothcars are making the same HP.

    If both cars hook well and launch hard (within .002 @ 60 ft) they should theoretically run the same ET although the MPH may be different.

    Why not just run them and find out?

    Buying parts I don't need, with money I don't have, to impress people I don't like

  9. #9
    pat mccarthy's Avatar
    pat mccarthy is offline CHR Member/Contributor Visit my Photo Gallery
    Join Date
    Apr 2005
    Location
    bay city
    Posts
    10,546

    Quote Originally Posted by joe_and_jeep View Post
    I have a Suzuki Samurai and a Jeep. The Jeep is 180hp 4k lbs and the Sanurai is 60hp 2300lbs. The Jeep runs a 33x15.50 and the Samurai runs a 31x11.50. Both are the same brand of tire, Super Swamper TSL. Now this aint drag racing but the Samurai will definately climb a muddy hill (level, no ruts just slick greasy) the Jeep will spin the tires more and will definately accelerate better. But the little light weight Samurai will climb better, hold a line better and not slide in off camber situtions. Weight plays a huge factor in how a car performs. I think in a weight distributing, traction perfect world, a 2300lb 7.9hp per lb car won't accelerate like a 400lb 7.9hp per lb. I have no scientific or mathmatical evidence but I would assume that the hp per lb would have to increase slightly. Maybe a small percent, like 7.9 to 8.1.
    i sold my old bbc 572 to some guys that ran it in a samurai they ran it in a mud pit with alot of Nos i would hate to see that run down the track
    Irish Diplomacy ..the ability to tell someone to go to Hell ,,So that they will look forward to to the trip

  10. #10
    joe_and_jeep is offline CHR Member Visit my Photo Gallery
    Join Date
    Oct 2006
    Location
    Pittsburgh
    Car Year, Make, Model: 47 Dodge Pickup, 68 Chevy C10
    Posts
    32

    Quote Originally Posted by pat mccarthy View Post
    i sold my old bbc 572 to some guys that ran it in a samurai they ran it in a mud pit with alot of Nos i would hate to see that run down the track
    I have mine geared way down for RockCrawling, I'd like to put a ported rotary in it but the complete lack of lowend torque would suck in a crawling situation. Or a turbo EcoTec... But my 1.3L motors are dirt cheap

  11. #11
    HOSS429's Avatar
    HOSS429 is offline CHR Member Visit my Photo Gallery
    Join Date
    Jun 2007
    Location
    New Market
    Posts
    2,590

    so .. would an elephant pulling a deisel truck out run a man pulling a pickup truck ?
    iv`e used up all my sick days at work .. can i call in dead ?

  12. #12
    pat mccarthy's Avatar
    pat mccarthy is offline CHR Member/Contributor Visit my Photo Gallery
    Join Date
    Apr 2005
    Location
    bay city
    Posts
    10,546

    Quote Originally Posted by joe_and_jeep View Post
    I have mine geared way down for RockCrawling, I'd like to put a ported rotary in it but the complete lack of lowend torque would suck in a crawling situation. Or a turbo EcoTec... But my 1.3L motors are dirt cheap
    yep i did a eco tec were he lean abit to much on it with a blower blocks need a up grade on sleeves but rods and crank look good
    Irish Diplomacy ..the ability to tell someone to go to Hell ,,So that they will look forward to to the trip

  13. #13
    1gary is offline Banned Visit my Photo Gallery
    Join Date
    Feb 2010
    Location
    Roch
    Car Year, Make, Model: 1985 high top Astro van
    Posts
    2,520

    We always thought losing 100lbs was equal to 10hp.And that to lose 100lbs was a whole lot cheaper than to build 10hp.
    Good Bye

  14. #14
    Big Tracks's Avatar
    Big Tracks is offline CHR Member Visit my Photo Gallery
    Join Date
    Aug 2005
    Location
    Keller
    Car Year, Make, Model: '79 Dodge Diplomat Coupe
    Posts
    832

    The B/Modified roadster that my partners, John and Shirley Ryan, and I raced in the late fifties and early sixties was heavy for its class.

    You can tell that by lookin'.

    The frame was water pipe (heavy) and the engine a 354" Chrysler (read that heavy, too).

    That (along with a degree of driver ineptitude) didn't exactly give us an advantage over our competition, most of which consisted of light tube chassis running 265 and 283 Chevys.

    We all had the same cubic inches to weight ratio but when the flag dropped, we had a lot more inertia to overcome than they did. By the time the Chrysler figured out what it was there for, it was usually too late.

    We had some very good top speed numbers. That's okay, but the object is to win the race.

    We just had more to get moving.

    Say you got two cars on the line, identical in every way, and both set up and tuned by the same person. One has a driver that weighs three hundred pounds and the other has a driver that weighs one hundred pounds. I'll put my money on the skinny guy.

    Anything wrong with that thinking?

    Jim
    Attached Images

  15. #15
    1gary is offline Banned Visit my Photo Gallery
    Join Date
    Feb 2010
    Location
    Roch
    Car Year, Make, Model: 1985 high top Astro van
    Posts
    2,520

    Quote Originally Posted by Big Tracks View Post
    The B/Modified roadster that my partners, John and Shirley Ryan, and I raced in the late fifties and early sixties was heavy for its class.

    You can tell that by lookin'.

    The frame was water pipe (heavy) and the engine a 354" Chrysler (read that heavy, too).

    That (along with a degree of driver ineptitude) didn't exactly give us an advantage over our competition, most of which consisted of light tube chassis running 265 and 283 Chevys.

    We all had the same cubic inches to weight ratio but when the flag dropped, we had a lot more inertia to overcome than they did. By the time the Chrysler figured out what it was there for, it was usually too late.

    We had some very good top speed numbers. That's okay, but the object is to win the race.

    We just had more to get moving.

    Say you got two cars on the line, identical in every way, and both set up and tuned by the same person. One has a driver that weighs three hundred pounds and the other has a driver that weighs one hundred pounds. I'll put my money on the skinny guy.

    Anything wrong with that thinking?

    Jim
    So your saying fat drivers should be on the Tv show "The Biggest Loser"???.
    Good Bye

Reply To Thread
Page 1 of 2 1 2 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
Links monetized by VigLink