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Light vs heavy flywheel

Discussion in 'SVT Shelby GT500' started by Robertt305, Jul 17, 2011.

  1. Robertt305

    Robertt305 Devil Dog Established Member

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    Any opinions for drag racing which would be better?

    I know the inertia factor comes into play but the last thing I need is to hit the tires any harder then it already is after gernading several rearends..

    Quicker revs is a plus but the car bogs already if my launch is a hair off...

    Hopefully this will make a topic for conversation.
     
  2. serickson1

    serickson1 sericksonGT500 Established Member

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    Usually you go heavier for drag racing......lighter for road racing.....but I'm with you, the last thing you want to do is hit the rear tires any harder than you already are. The steel, lightened, SFI flywheel is the way I'm leaning when I replace mine. Interested in what others think as well.
     
  3. Robertt305

    Robertt305 Devil Dog Established Member

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    10-4 I'm looking at the mcloud kit but I can't decide which flywheel to go with cause of the same reason. I
    Tryin to see the pros and cons and make a educated decision which route to go..

    Acceleration and parts safety or launch and blowing $hit apart more then I already am.

    Hopefully some gurus with experience chime in a shed some light on the topic.
     
  4. DMotorsports

    DMotorsports New Member Established Member

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    If you watch vids of lethal's passes, you will see how much their car gets out of shape on the shifts. Despite this, their super-human genetically engineered driver is able to maintain control. To the best of my knowledge they run the heavier flywheel.

    Now, if you watch vids of thebull's passes, his car stays much more composed during shifts, and I'm pretty sure he runs the lighter flywheel.

    Not exactly apples to apples, but a comparison.

    IMO these cars don't need a heavier flywheel. That is more important on naturally aspirated engines or engines a little short on torque. These blown 5.4's make better torque than a lot of n/a big blocks.

    Take that for what it's worth.
     
  5. thebull

    thebull 150 or Bust Established Member

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    Well I'd say Aluminum if you have a big blower car with tons torque...Acceleration is speed...The faster the engine rev the faster you go.

    The heavier the flywheel, clutch, or rotating assembly the slow the engine revs.


    There is a high hp car out there with a steel flywheel in the car and it kills the tires on gears changes....That is coming from Jeremy (UPR) the driver and he has a TON of experience and knowledge with a clutch.

    I'm running the Spec P trim with the aluminum flywheel and love it. Which I believe it's the same weight as stock.
     
  6. Seahorse

    Seahorse Active Member Established Member

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    Just recently installed the McLeod RXT with lightened steel flywheel (middle weight of the three options for the RXT) - the feel is very similar to stock. No bogging on take offs or crazy rpms needed to get rolling, but it still hits the tires hard (315 DR's) breaking them lose on 1/2 and 2/3 if I'm really on it. But again, same as the stock flywheel that was in there. I certainly wouldn't want a heavier flywheel in there hitting them even harder. Just MHO and I'm hardly a track junkie, the car is a daily driven street toy first and foremost. If I had it back now, I'd probably have gone with the aluminum version.
     
  7. rodfarva

    rodfarva New Member Established Member

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    I debated this topic before switching to an auto tranny, making it a non-issue for me. I really think that the aluminum flywheel would be the better choice for these cars, but the only way to know for sure would be to do a head-to-head comparison in the same car in the same weather and track conditions.
     
  8. Robertt305

    Robertt305 Devil Dog Established Member

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    Damn how much lighter do they make the mcloud flywheels from stock?
     
  9. F8L SN8K

    F8L SN8K Active Member Established Member

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    "Light makes right"

    Newtons 3rd law of motion states that any object in uniformed motion stays in that state of motion unless an external force is applied.

    The factory uses a heavy flywheel to provide better NVH and easier drivability when starting from a stop. A heavier flywheel will require less RPM to provide the same kinetic energy of a lighter flywheel. That's pretty much where the advantages stop.

    Now a lighter flywheel(based on the assumption of the lighter flywheel has a corresponding lower moment of inertia) will accelerate faster. Rotational mass reduction is so very important to the drag racers and road racers. Throttle response is much improved. It takes less HP to accelerate the lighter/M.O.I. Flywheel.

    The common misconception is that a heavier flywheel is better for drag racing is a falsehood. The theory is that the heavier flywheel will "hit" harder then a lighter one. If the RPM is remains the same that IS true. HOWEVER, it takes more energy to accelerate the higher mass/M.O.I. Flywheel. And the "advantage" of the heavier flywheel is null and void when you just rev the lighter flywheel just 3-600 rpm higher on launch(and if power shifting the engine will accelerate quicker in-between gear changes causing the RPM to be higher on gear change "rpm flares". It doesnt make a whole lot of sense to hurt the other 99% of the run for a small part of the run that can actually be overcome by just revving the engine a little higher.

    Racers spend a lot of time and money to cut down on weight. Especially rotational mass where rewards are 4-fold. Many have tested and have found that the lighter flywheels to be worth a lot of E.T. and MPH.
     
    Last edited: Jul 18, 2011
  10. F8L SN8K

    F8L SN8K Active Member Established Member

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    So what does a guy who loved his physics, engineering and business management classes takes the biggest intrest in? Drag Racing, what else!


    BTW- Its the lower torque engines that suffer the greatest from a higher weight flywheel. It's harder to recover after being pulled down.
     
    Last edited: Jul 18, 2011
  11. Robertt305

    Robertt305 Devil Dog Established Member

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    Lol very good info on this thread...
     
  12. hydro

    hydro Member Established Member

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    With a light flywheel and these heavy cars daily driveability will suffer.
    You will experience a lot of slipping the clutch and stalling in stop & go driving.
    The heavy flywheel is necessary for "all normal" driving.hydro
     
    Last edited: Jul 18, 2011
  13. Carbd86GT

    Carbd86GT You're Gator Bait Established Member

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    It really depends on what you do with the car. Most of the cars will work very well with the lightened steel flywheel with the McLeod RXT for drag racing and street use. If the car is going to see any street driving, go with the steel. If the car makes over 800 rwtq, and it's strictly a drag car, go aluminum. When we first got the RXT in the car, we were running the heavy steel flywheel, and it would kill the tires. Now, we run an aluminum flywheel, but the car doesn't go on the street anymore.
     
  14. Illtaketwlight

    Illtaketwlight New Member Established Member

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    I run a aluminum flywheel spec clutch, 3.90's and 28 inch tall tire. Never had any problem taking off from a light or the line.
     
  15. F8L SN8K

    F8L SN8K Active Member Established Member

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    There are tons of cars running aluminum flywheels on the street(03-04 Cobra came with one stock). The clutch will be the Biggest determining factor on the street in stop and go traffic as far as drivability. In my street car I run an aluminum flywheel with a McLoed disc and custom pressure plate. The race cars run super light weight flywheels and smaller diameter clutches. The theme in them is to go as light as possible, while keeping as much mass close to the centerline as possible. We try to go has light as we can that doesn't cause an issue with durability.
     
  16. Posi

    Posi Had a blast. Established Member

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    On my 04 I went with a steel flywheel and didn't like it. Daily driving was still perfect but it hit the tires way to hired on the initial hit. I would never do it again.

    Look at your dyno graph and see where your cars make over 500ft lbs of torque. To me it's plenty early and plenty of torque to get the car going. If you get it to where it hooks with a steel flywheel on the initial hit then could it be low enough for the car to have just a little trouble bringing the rpm's back up after the hit?

    Just my opinion.
     
  17. Robertt305

    Robertt305 Devil Dog Established Member

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    Good info... Def made up my mind...

    Light weight will be my pick when doing the clutch.
     

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