Aluminum vs Steel Flywheel

Discussion in 'SN95 4.6L Mustang Tech' started by forpit2000gt, Aug 31, 2005.


  1. forpit2000gt

    forpit2000gt Founding Member

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    I started this thread because I didn't want to hijack another.
    I am not diagreeing, I just had some questions.

    This is what was posted.
    Let me copy a couple post from other discussiosn on this:

    "I'm a billet steel fan...

    The aluminum flywheel will help you decelerate quicker and accelerate a tick quicker if you want that little extra addition but some things to think about with the AFW is starting from a stop, particularly on hills, may require more slipping of the clutch to make up for the lower momentum than is stored in the heavier stock flywheel. Some jerking can be occured due to the loss of momentum possibly in between shifts for example as the rpm will drop sooner.

    I would stay away from an aluminum flywheel on a daily driver and plus some of the harder grabbing clutches can tear up the aluminum flywheels...and aren't recommended with a aluminum flywheel.

    Get a stock replacement or a nice billet steel one...(more expensive)...

    This is posted from FastDriver - The answer to your question is that a 15 lbs weight would be easier to catch/stop if it has been thrown at you at the same speed as a 40 lb weight. A pretty obvious answer, but I think you are misinterpretting the results. A drag racing launch has nothing to do with ease of launch. If it did, you wouldn't launch at 6500 rpm, you'd launch right off of idle. Also, my clutch doesn't seem to have any problems grabbing my flywheel at any rpm. My tranny doesn't seem to have any problem managing the shock, and with the right tires and suspension, I will launch this car right off of redline with a single clutch drop.

    The point is that you want as much stored energy to jump into your tires as possible, and you want your suspension/weight distribution/ tire combination set up so that it can handle all of the power and effectively put it to the ground - as opposed to wasting it by blowing away the tires.

    In regard to your posit about stored energy being meaningless, I'll counter that stored evergy has everything to do with the difference between a heavy flywheel and a light one. In fact, stored energy is the only cause of a performance difference between an aluminum and iron flywheel.

    The aluminum flywheel does not store as much energy as rpms increase which gives it an advantage in that the energy that would be stored in the flywheel has instead been exerted into the rotational force in the drivetrain and hence the driving force/power of your car.

    In drag racing, that extra stored energy in the flywheel at a stop is put into your tires as soon as the clutch is dropped causing more force/power driving your car as it leaves the line. As your car moves down the track and rpms increase, the energy is transferred back and forth from the flywheel to the tires as rpms increase and then decrease (as you shift). Finally, when you cross the traps, rpms at the top of their powerband, the stored energy in the flywheel did not get put to good use. So, the advantage after you leave the line is to the lighter aluminum flywheel. Does it make up for the Iron one? Possibly. The longer the track, the more likely. However, will the difference be significant enough to justify the extra expenditure? Not to me."

    "we lost like .20 on our 60 foot times with an alum flywheel. its the initial shock the torque ripping the tires is what was different and in turn they say about every .10 in the 60 foot is about .15 tenths in the quarter. i find this to be a close fact went from 11.50-11.55 to 11.68-11.71 in the quarter i dont remember mph."

    "I have dyno tested several different flywheel and clutch combinations. I was part of the article for MM&FF that Robin mentioned over on HC50. If you can find that, theres alot of good info in there. Since then I have done some prototype testing for another clutch manufacturer. Believe me when I tell you, 9lbs will not make a difference on a chassis dyno doing high gear back to back pulls. If you averaged 5 or 6 pulls, making sure that engine temp, trans fluid temp, rearend oil temp, air intake temps, etc.. were the same, I'd suspect you might see 1 horsepower. Thats doing high gear pulls only. There are other ways of making pulls that will show a greater increase, and give more real world results."

    "I beleive it was Eagle on here (the one that sells the rotating assemblies - Brian?) that said the AFW does react differently under normal conditions. He seems like a pretty credible source on it as well seeing how he does sell the rotating assemblies Ed Curtis and some others (can't remember) where suggesting keeping a steel flywheel in the heavier side of the cars (like 3200lbs and up)...so that is where my lx falls into.

    For autocross cars, I agree...your up in the revs for 99% of the time (almost literally) and your not building up speed (revs) if your autocrossing right so the AFW would be beneficial in that case.

    For the picky daily driver like me...I'm not for the AFW."

    Just a couple...it isn't just "losing weight"...you lose other things as well. Driveability changes. revs drop quicker so your engine will "catch" more in between time when you shift gears...you don't have the rotational weight to help you "idle off"...
    I would keep an AFW for a autocross car...not really a daily driver IMO.


    If you lost .20 in the 60ft, why couldn't you make a suspension change to compensate and possibly pick up a little more?
    #1
  2. Torinalth

    Torinalth Founding Member

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    quick sum up for those that dont like to read - stay billet/iron for a drag racer

    aluminum for a road/autox racer

    there are disagreements as far as which is better for a DD.

    curiously... did you have a question about them? or just reposting pieces of a thread for information.

    Torinalth
    #2
  3. forpit2000gt

    forpit2000gt Founding Member

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    If you lost .20 in the 60ft, why couldn't you make a suspension change to compensate and possibly pick up a little more?


    it was in the first post, just blended in the bottom.

    I guess I will search and see what discussions/ arguments have been made for both sides. What was described above does mostly make sense.
    #3
  4. sonic03snake

    sonic03snake New Member

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    Here is some interesting info from another board, right from Centerforce themselves.

    Originally Posted by Will Baty
    Another thing to think about is that in most cases the steel flyhweel has more heat sink. This typically means longer clutch life, seeing how heat is a big killer for clutches. The steel flywheel has more mass which allows it to absorb and dissipate the heat that is generated from the clutch when the car is put into motion. Both flywheels do have pros & cons, you should look at what some of the other guys with similar or the same set-up as what you have are using. Another thing to look at is what percentage of your driving is around town daily driving? Do you want every ounce of performance out of your car or are will to sacrifice a little performance for more drivable clutch around town? I not saying that the Aluminum flywheel is bad by any means I know allot of guys with the Aluminum flywheel that have no problems what so ever. I am just saying that steel vs aluminum on the street 9 times out of 10 the steel will have the better clutch feel.

    Just my 2 cents.

    Will Baty
    Centerforce Clutches
    #4
  5. forpit2000gt

    forpit2000gt Founding Member

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    I can agree with all of that. I guess I look more at racing in a straight line. Never thought about a flywheel and what it was made of being better or worse for drag or autocross even.
    #5
  6. 5spd GT

    5spd GT "the 5.0 owns all" Founding Member

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    I never really thought of it like that either...but I agree :nice:
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  7. Torinalth

    Torinalth Founding Member

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    the heat issue has been discussed in metalurgy for a long time.... Aluminum will, by nature, absorb heat faster.... although... it will also disapate heat faster then iron.... where Wil makes his point is that iron has a tendance to repel heat fairly well... though once it becomes saturated (road racing, or extreme heat daily driver conditions) the iron will do the same as he is sayin the aluminum will.

    this is the thing with ALL aftermarket things... there is a trade of some sort, period. personaly i'll be getting an aluminum FW with aluminum driveshaft. for less loss on the drive line (however small it might be)

    as far as the question of adjusting the suspension to adjust to the AFW vs the iron the answer is no. in a drag situation, as stated in your own post, the iron is heavier, the inertia (sp) of the heavy FW will try its best to keep it moving, more so then the aluminum which will be a good deal lighter. the benafit of this in drag is the launching, where you will have more force being transfered in a clutch dump.... more rotating mass trying to keep spinning while the clutch tries to stop it... the more mass the more the rotation wins in that contradiction and thus gives more initial hit to the rear wheels.

    then as stated aswell in your post... once you have the driveline started (after launch) you then want as little weight as possible on the driveline making it easier to spin (less weight the easier it is to move) thus making the RPMs climb faster per HP. (increasing efficiancy)..... its just a trade. personaly i will never drag the car except maybe every once and a while on the street.... so i want the lower mass for my daily driver to get better milage, and assist in getting RPMs up faster.

    so, since the FW and driveline in general, has no effect on the launching characteristics, the suspension would have no adjustment to compensate.

    Torinalth
    #7
  8. StangGT96

    StangGT96 New Member

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    ok. I have a question..... i have a billet steel flywheel but i would like to lightened it alittle bit can that be possible? and if its possible what are the limits that i can shave off. thanx
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  9. StangGT96

    StangGT96 New Member

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    I need your guys opinion: I will be getting 4.10 with an aluminum driveshaft, pro-chamber midpipe and flow master exhaust, with PI heads and intake manifold, with probably some laughing gas. whats better billet steel or aluminum flywheel with my set up? i do like to road race once in a while but i prefer 1/4 mile. I was just thinking about keeping the billet steel and shaving a couple of pounds to compisate for the weight?
    #9

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