Any one have the weight dist for a PWC S197??

Discussion in 'Road Racing Forum' started by Mad Hatter, Apr 16, 2018.

  1. Mad Hatter

    Mad Hatter Gotta go Faster

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    Today I was in a heated (friendly) argument with the shop owner I go to for the harder jobs... Its run by your typical crazy mechanic who back in the 80's and 90's was a successful driver/preparer of stock cars. He is insisting that I add about 50kg of weight above the rear axle for more balance and traction, and I do not want to gain any weight.... Any thoughts? I am currently at F54%/R46%
     
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  2. Drlee50

    Drlee50 TMO Race

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    Thats stupid.
    Why? What ever his answer to that is....a torque arm can probably do.

    Sent from my LG-H932 using Tapatalk
     
  3. Grant 302

    Grant 302 OPM Spent: $665,833 Moderator

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    :eek: Dangit, Hatter! There you go again asking the *hard* questions! ;) :D

    Your mechanic may not be all that crazy...I know the car is better balanced with a 200 lb. passenger. And there are times when I've run the fast lap(s) of the day with one. I also like the way my car feels with all the junk I carry in the trunk.

    Sometimes thinking out of the box pays off...sometimes it just bites you in the ass.

    You still have to see if the squat changes show up in your lap times too.

    Maybe you'd make the weight distribution better by going to a larger, trunk mounted fuel cell and ditching the saddle tanks.
     
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  4. 302BOB

    302BOB TMO Addict

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    Throw the shop owner in the trunk for a few laps to see if there's an improvement in those lap tymes..............If he's right, take him out and buy him dinner.
     
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  5. Mad Hatter

    Mad Hatter Gotta go Faster

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    I think the weight would have to be fixed to have a good affect. With 1.3G's in the corners he would shift quite a bit
     
  6. JDee

    JDee Ancient Racer

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    Put a couple of grab handles in there for him to hang onto. And a drink bottle for longer events. :D
     
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  7. Grant 302

    Grant 302 OPM Spent: $665,833 Moderator

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    Zip ties. C'mon! :rolleyes: ;)
     
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  8. Mad Hatter

    Mad Hatter Gotta go Faster

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    If I did that where would the 4 slicks, tools, chairs etc etc go??!! That means I finally have to get a trailer... Getting the engine rebuilt, ported and polished on our old V8 Discovery for the future tow vehicle...... But lots of spendy items to get still before a trailer.......
     
  9. Mad Hatter

    Mad Hatter Gotta go Faster

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    Grab handles and a head set. So I could ask him to lean into the corners???

    the latest in active weight??
     
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  10. Grant 302

    Grant 302 OPM Spent: $665,833 Moderator

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    One that replaces the spare wheel well area? I dunno. Maybe try a couple of 45 lb. plates in there first...
     
  11. Drlee50

    Drlee50 TMO Race

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  12. Grant 302

    Grant 302 OPM Spent: $665,833 Moderator

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    A torque arm would be counter productive to the squat experiment...
     
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  13. ArizonaBOSS

    ArizonaBOSS Because racecar. Moderator

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    For what it's worth, getting a 50/50 CROSS weight is more important than a 50/50 front-rear balance, at least for S197s.

    My car is 53.5% front with 50/50 cross.
     
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  14. Mad Hatter

    Mad Hatter Gotta go Faster

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    If I remember right my cross is 50.9. But will check

    Sent from my SM-G900M using Tapatalk
     
  15. stuntman

    stuntman TMO Advanced

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    Torque arms don't do anything to alleviate the cornering load on the front tires when cornering in a nose-heavy car.

    Weight distribution ftw.
     
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  16. Drlee50

    Drlee50 TMO Race

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    You are saying the load is not shifted to the rear with a torque arm ? Or just in cornering ?

    If you think about what "cornering" is ....its a deceleration event, usually in a straight line, followed by a transition to neutral weight load front and rear - while adding in steering input, merged with an acceleration event finishing the corner.

    The corner load I "think" you are talking about would be at the end of the braking event with the initiation of the turning event. That would likely be peak load on the front tires, particularly the outside tire.

    That moment is a very small part of the "turn" sequence. How does the torque arm help that?
    It starts with the braking event. The torque arm prevent the weight shift that typically plagues a nose heavy car. The anti squat and anti lift geometry is changed allowing the whole car to hunker straight down rather than nose dive. A car in that position, would have less load on the front tires, and far more rear grip Both for braking and to accelerate out of the turn. You can add greater rear brake bias with a torque arm as well, further reducing nose dive.
    Once neutral , and turn initiated and the transition to acceleration out of the turn, the torque arm additionally adds rear grip while NOT lifting the front end - which keeps the car neutral (front to back) . This increased grip to the rear is to BOTH tires, not just the outside tire, which further acts to "lighten" the front end making the car perform more like a 50 50 weighted vehicle.
    So, if you understand what im saying, the torque arm has significant impact on the front tires cornering load. They are perfect for nose heavy cars.
    A track mustang with xyz parts on it plus 200 lbs in it in the rear or passenger seat with be slower than the same car with xyz parts and a torque arm and while not carrying 200 extra lbs.

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  17. stuntman

    stuntman TMO Advanced

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    In most corners, the first half is a transition from deceleration to peak cornering, while the second half transitions from a peak lateral acceleration to a longitudinal acceleration out of the corner.

    Nose heavy cars tend to be limited by front grip in the first half, and part of the middle of the corner. Adding anti-lift to the rear increases weight transfer to the front, which in a Mustang that most of the braking effort is already done by the front tires (the rear tires don't contribute much to braking), braking performance can be slightly negatively impacted. Remember: body roll and pitch and squat is NOT weight transfer.

    Furthermore, anti-lift from a torque arm would also increase weight transfer to the outside front tire in the first half of the corner (unless you drive like what is taught at HPDE days and you do all your braking in a straight line and then accelerate and transfer weight to the rear at turn-in), which on a mustang is already the limiting factor in your entry and mid-corner speed. (This is why Mustangs generally perform better as you widen the front tire, to spread the load over a wider area). The added load from the increased weight transfer reduces the tractive effort of the tire, thus reducing grip when trail braking and at corner entry. = Slower.

    Moving the weight distribution rearward changes the CG location and how the car transfers weight, improving the tire loading across all 4 tires when braking, reducing load on the outside front tire on entry and mid corner, and then transferring more weight to the rear on corner exit and acceleration. = Faster & better.
     
  18. Drlee50

    Drlee50 TMO Race

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    The one factor that is often over looked with suspension tuning is that you are trying to improve the transfer of load through the control arms and torque arm and frame --the chassis- not the springs. That's where the reduced body roll comes from and thus reduced weight transfer to the front tires. Yes, weight distribution still remains 55/45 but it remains much closer to that through the entire turning procedure. When you add weight to the car to try to make it 50 50, you do nothing to change the geometry and how the weight transfer occurs during braking, turning and accelerating. Upon braking and turning the weight transfer can be 70/30 or more on your 50 50 static based car (depending on the springs and shocks). Often , drivers will try to increase spring rate to compensate because all the forces are going through the springs and shocks and NOT the suspension arms and chassis. The torque arm really helps a car like the nose heavy mustang feel and perform much more like a 50 50 weight car without the sloppy weight transfer that the stock 3 and 4 link setups provide. Now if you have a 50 50 weight car and a torque arm, you are really gonna have a fast car. And maybe that's the point I should be making: which is faster? a 50/50 car with a torque arm and the benefits that it provides to the way the chassis works or the same car without a torque arm? It will be the torque arm car.
    The same results would happen even on a 54/46 distribution car that is 200 lbs lighter as well. It will be faster.

    I enjoy the conversation we are having and please do take anything I am saying as confrontational-- I am here to learn as well as share what I know to this community. I appreciate your comments. keep them coming!
    Thanks!
    Lee
     
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  19. Mad Hatter

    Mad Hatter Gotta go Faster

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    No offense taken!!
     
  20. stuntman

    stuntman TMO Advanced

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    There's a lot of misunderstanding there.

    Reducing body roll, pitch, or dive (via stiffening springs & bars, or raising roll centers and instant centers) DOES NOT reduce weight transfer. That's a common misconception.

    If that were true then we would always run high roll & instant centers, but doing so actually increases weight transfer (which hurts grip), while reducing body movement.

    Torque arms will not improved corner entry front grip. Improving weight distribution will.
     
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