how weight effects time help please

Discussion in 'PSI Superchargers Tech Questions' started by blown1969camaro, Oct 29, 2011.

  1. blown1969camaro

    blown1969camaro Member

    Joined:
    Apr 18, 2010
    Messages:
    455
    Likes Received:
    2
    ok please awnser only if u have first hand experiance

    we have all heard the roumer 100lbs is a tenth is that true and 1/8mile or 1/4

    my 2900lb car runs 4.20s very consistantly
    if i remove 100 pounds what will it run

    one good sourse says 4.18
    other good sourse says 4.10
    i know this all has to do with setup and chassis but has anyone done the painstaking task of taking 1-200lbs out of their car
     
    #1
    blown1969camaro, Oct 29, 2011
  2. Night Moves

    Night Moves New Member

    Joined:
    Jan 20, 2006
    Messages:
    120
    Likes Received:
    0
    Weight vs. ET

    I don't know the answer to your question....however:

    Is it an option to add 100# to your car and see how much it slows down?

    Mike L.
     
    #2
    Night Moves, Oct 29, 2011
  3. Mike Canter

    Mike Canter Top Dragster
    Staff Member

    Joined:
    Mar 10, 2004
    Messages:
    4,630
    Likes Received:
    189
    Well it is all physics on how much power is needed to move X amount of weight down the track in a set amount of time. The more weight the slower you will go. The standard for quick computation on a 3000 lb car is 100 lb increase will slow you down one tenth of a second in a quarter mile. Also 100 lbs is the same as 20 hp.

    You can find many online computers that you can work the problem out. Try here
    http://www.wallaceracing.com/et-hp-mph.php
     
    #3
    Mike Canter, Oct 29, 2011
  4. Blownalky

    Blownalky Top Sportsman

    Joined:
    May 9, 2005
    Messages:
    826
    Likes Received:
    8
    Mike, only 20HP for 100 LBS? So if you dump 1,000 LBS, you should go one second faster with only 200HP additional? I'd think it would be more than that but maybe it is all relative based on when you measure the current engine HP and current car wieght? Just wondering as I'm not a math expert.

    Tom
     
    #4
    Blownalky, Oct 29, 2011
  5. Mike Canter

    Mike Canter Top Dragster
    Staff Member

    Joined:
    Mar 10, 2004
    Messages:
    4,630
    Likes Received:
    189
    Work it out on the computer and see. If you dump all that weight such as a 1000 lbs then the limiting factor becomes traction. In all those formulas it is asummed that you have 100% traction
     
    #5
    Mike Canter, Oct 30, 2011
  6. moparchris440

    moparchris440 Member

    Joined:
    Jun 8, 2008
    Messages:
    370
    Likes Received:
    0
    Shit 200 hp for 1 second hell even if traction is compromised 20 % and you pick up 1/2 second for 200 hp racing would be pretty easy. That old formula seems to hold true if your running 10's or slower (100 lbs for a tenth) in a 1/4 as you get going faster it gets pretty watered down. start going 6's and its more like 150 ish plus for a tenth.
     
    #6
    moparchris440, Oct 30, 2011
  7. Mike Canter

    Mike Canter Top Dragster
    Staff Member

    Joined:
    Mar 10, 2004
    Messages:
    4,630
    Likes Received:
    189
    Like I said the values I gave for the example was for a 3000 lb car. The formula does not change. As you get faster then the problem becomes traction, clutch slip, convertor slip and other things like that but the formula used in the computation is correct.
     
    #7
    Mike Canter, Oct 30, 2011
  8. moparchris440

    moparchris440 Member

    Joined:
    Jun 8, 2008
    Messages:
    370
    Likes Received:
    0
    I totally disagree sorry! so your saying if I make a 100hp pulley change on my 3200 lbs truck that allready goes 7.02 it will go 6.52 that sure would be nice. You must remember a slower 10 second car must carry that extra 100 lbs for a longer time where a 6 second car doesn't have to carry it as long of a time, therefor the effects of the weight vs Et are different as you go faster.
     
    #8
    Last edited: Oct 31, 2011
    moparchris440, Oct 31, 2011
  9. Mike Canter

    Mike Canter Top Dragster
    Staff Member

    Joined:
    Mar 10, 2004
    Messages:
    4,630
    Likes Received:
    189
    You are argueing with applied physics not me but it does change with the amount of HP and or the amount of weight. So what is the pulley changing that will give you 100 HP? Is it the supercharger drive pulley? If the car runs 7.02 in the 1/8 mile on a standard day (0 ft track elevation, 59*, 0% this is an ultimate condition) then it has 468 hp to push 3200 lbs to that ET of 7.02 at around 95 mph. If you add a true 100 hp so you have 568 hp then it will run .44 seconds faster. The big question is the advertised gain from the pulley really a true 100 hp on your motor?

    If it is a 1/4 mile ET at the same track conditions as above then you have 1821 HP to drive a 3200 lb truck to 7.02 at around 190 mph. If you add a 100 hp then you will go 6.90 at 195 mph
     
    #9
    Last edited: Oct 31, 2011
    Mike Canter, Oct 31, 2011
  10. moparchris440

    moparchris440 Member

    Joined:
    Jun 8, 2008
    Messages:
    370
    Likes Received:
    0
    Now your talking in circles... here you say 100 lbs is the same as 20 hp and you also say 100 lbs is a tenth. but now above you say it takes 100 hp to go 1 tenth faster. Your contradicting yourself.
     
    #10
    moparchris440, Oct 31, 2011
  11. Mike Canter

    Mike Canter Top Dragster
    Staff Member

    Joined:
    Mar 10, 2004
    Messages:
    4,630
    Likes Received:
    189
    My wife tells me the same thing and you and she must be right. About two o'clock this morning I realized I had a memory failure and had stated it in reverse. So let me start over again. 100 HP is equal to 20 lbs and is equal to a tenth of a second on a 3000 lb car. Is that better (lol). Sorry about that.:cool:
     
    #11
    Mike Canter, Nov 1, 2011
  12. Night Moves

    Night Moves New Member

    Joined:
    Jan 20, 2006
    Messages:
    120
    Likes Received:
    0
    Weight vs. ET

    I enjoy using computer programs and math to predict ETs. The laws of physics are fixed, and the calculations are a good tool, however the problem is the varibles (in the real world).

    In practice (as Mike said) traction and track conditions, clutch or converter losses, weight placement, etc. make the real results far more difficult to predict.

    Using the computer programs it seems like my car had a lot of slippage in the converter. Even though it may be a normal condition......it changes the real number from the calculated number quite a bit.

    I think a 3000# car with 600 HP would react as expected to the removal of 100#.....a 2100# car with 1400 hp will not get as good of a result.

    JMHO
    Mike Little
     
    #12
    Night Moves, Nov 1, 2011
  13. iron468

    iron468 Member

    Joined:
    Mar 20, 2009
    Messages:
    93
    Likes Received:
    0
    its rear wheel hp .how you can calcul torque slip ,hp for transmission ,housing,
     
    #13
    iron468, Nov 1, 2011
  14. 560Jim

    560Jim Member

    Joined:
    Aug 11, 2007
    Messages:
    76
    Likes Received:
    0
    Ah, right first time :eek:
     
    #14
    560Jim, Nov 2, 2011

Share This Page





XenPorta 2 PRO © Jason Axelrod from 8WAYRUN.COM