Alum. vs. Steel Flywheel

The difference in Aluminum and steel isn't too complicated. I'll try to explain below:

Take two identically sized objects with different masses (I.E. a light Flywheel vs. a heavy Flywheel.) The Heavier of the two will carry more rotational inertia (Energy) once it's turning. But will be harder to accelerate (requires more Energy to change it's speed.) The lighter of the two will carry less rotational inertia at a given speed than the heavier version, but will not require as much energy to accelerate.

Laymens terms: The steel wheel will help you develop more torque for driving around on the street. The motor will REV like it always has because of the mass of the wheel.

The Aluminum wheel will make the motor REV a bit faster. But you will lose some of the torque that a steel wheel helps to develop.

Your car probably has enough torque that losing a few Ft-Lbs. probably won't be noticable or enough to effect your streetability. The accelerated speed at which your motor will REV will probably be slightly noticable.

unless the car is light or you are running a tall gear, I would get a billet steel. the light weight flywheel will alow the engine to rev quick but the heavy steel with build inertia at the launch, if the flywheel is to light and the car isnt geared correct it would be a turd out of the hole. My old carbed N/A 306 went 11.80 with steel flywheel and 4.56's

I am fan of the billet steel flywheel.

An AFW has some quirks to it that I don't particularly care for: stalls easier, lowend loss, and the replacement plates are about $90 bucks I think. Steel takes heat better as well...

Also worth considering is idle quality.

I have been told that the lighter flywheel will not dampen the uneven pulsations from the crankshaft as well. This is probably more of an issue the fewer the number of cylinders.

Anyone know how much power/et can be gained with an Al flywheel?

Good points. Jason's is one that would concern me. It can affect clutch take-up as well.

Fishhawk said:

One more thing: He also mentioned that the Ford Racing stock replacement flywheel ($99 from Sumit) is Chinese made. Looks like I'm making a trip to my local Ford dealship for the flywheel, or maybe a junkyard for a used one to be resurfaced.

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Sounds like the stock unit is the best bet for a street-ish car.

You would be suprised at how much of a Boeing Commercial jet is built oversees. My point is that imported products are not necessarily inferior. Then again I have bought some trash from Summit before.

Has anyone used the Summit flywheel?
I would like to hear some comments as well since I will need a flywheel soon.

jason

Fishhawk said:

While I was at the clutch shop the owner took me back to the machine that resurfaces flywheels and showed me the difference between a US flywheel and a Chinese flywheel. The flywheel made with US steel shaved evenly. The Chinese flywheel chunked metal off. Almost impossible to resurface. Also he showed me the difference between a Chinese and Korean aftermarket preassure plate and and a Valeo heavy duty OEM preassure plate (made in USA). Like night and day. The scary thing was he pulled out a preassure plate from a Ford Racing King Cobra clutch kit (right out of the box unopened). The same one that Summit sells for $189. It is the EXACT same clutch and preassure plate as the Chinese knock-off. The same stamped part number. Same springs, same case. Just different paint. The Valeo heavy duty OEM has a different part number stamped on the preasure plate and is a lot beefier. Looks like a huge scam.

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Wow!
I greatly appreciate you sharing that with us.
I will be keeping this thread in mind while I do my shopping.

Not to bash on Summit more, but they seem to have sketchy quality. I purchased a leak down tester there a few months ago. Used it 3-4 times. Now one of the gauges is toast. No reading, at all. Total crap. Then again I purchased a brake prop. valve from them, that had actually been produced by one of the major brake companies (can't remember which one right now). Guess there is no way of knowing.

Good luck with the flywheel endeavor.

I run an aluminum flywheel in my street car. I will tell you this from my experience, it drives NO different than the stock heavy iron flywheel I had on the 302. Take off's from a stop are no different, driveability is the same too. Put it this way, I got stuck tonight and last weekend in new york city rush hour traffic. That was all stop n go first gear, neutral, first gear, neutral, you get the idea. The car was fine.

For a drag car, i've seen a few guys in my online searches go around 2mph quicker. One dude in a 363" stroker switched from a billet steel to a alum and went almost 2mph quicker no other changes!

Another benefit that i love besides revving up faster is the fact that its less wear/tear on the rotating assembly since its less weight the crank has to turn!

Looks like i'm the only one in this thread with EXPERIENCE with an aluminum flywheel in my street car. So, just remember to take advice from those who've been there/done that

Oh by the way, 03 cobra's come stock with aluminum flywheels among many factory cars.

good point, Mike!

Fishhawk said:

conclusion was that for a mildly modified car like mine that is driven on the street 85% of the time, stock cast iron is the way to go. One more thing: He also mentioned that the Ford Racing stock replacement flywheel ($99 from Sumit) is Chinese made. Looks like I'm making a trip to my local Ford dealship for the flywheel, or maybe a junkyard for a used one to be resurfaced.

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And i have 2 stock stang flywheels sitting in my room...

If the idle/drivablility problems associated with the aluminum flywheel actually exist, you would think that the pressure plate would help or make a difference.

Grn92lx also installed a 347 with his AFW...that will effect the differences he feels greatly with a broader torque curve in the lower rpms in stop and go traffic.

Also the 03/04 Cobra has a bigger clutch so it requires a bigger flywheel, whether aluminum or not it still is bigger and "weighs" more compared to our flywheels in the same configuration. There is a lot more factors to compare how a car acts than whether it has an aluminum flywheel or not.


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

Let me copy a couple post from other discussion 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.

Now let me say I run the stock "$99" dollar flywheel from summit and have no problems with it. Looked just like the stocker it replaced and feels the same.

i used to drive the 95 cobra on the street all the time.. it had a alum flywheel, and a very small mc leod 8.5" triple disc clutch.. now maybe it is just me.. but it drove fine on the street.. drove just like a normal big cammed mustang.. with a stiff clutch..

but as said for the chinese and usa made parts.. yes it is funny to see the difference in quality between the two.. then again i have seen alot of american made junk too.... like gm's f-bodies. crapola .. stupid pos rattle themselves apart.. sorry for my rant.. customers car.. ugh

Fishhawk said:

Thanks for that info. It kind of reinforces what I've been thinking. The car is a street car and I don't want to have to change my driving habits. The more I read about it the more I think I will just find a stock flywheel and call it a day. The $300 I save on the flywheel is my clutch and a new quadrant cost.

Click to expand...

That is the only downfall I saw with putting an aluminum flywheel on my street car, the cost. I needed a 28oz flywheel so alum was the only logical choice. I talked to my engine builder, Rick 91GT, and he said aluminum was a good choice and he set me up with one.

I highly suggest you do some homework and you'll see plenty of street cars with an alum flywheel. One example I listed earlier, that guy did slightly hurt his 60' time but then laucnhed a little higher and got the 60' back where it was with the heavier flywheel. He gained close to 2mph with the swap. Not too shabby. Theres another guy on here I recommended go aluminum and he took my advice and went against what the guys who never ran an alum flywheel said and he is VERY happy. His name on here is 1990LXDroptop I think? I also like less wear/tear on my $1,200 rotating assembly

If you don't feel happy after putting down $300 bucks on a flywheel...I would think something is wrong with you. It's all mental. There was a thread a few days ago about this and those with the AFW said they liked their flywheel but gave what they noticed, which was different driving characteristics.

The balance of a flywheel is even around. It isn't going to extend the life of your engine if you get a lighter one. They do it both equally. They are imbalanced on either side. Don't forget that thing called a harmonic balancer

You can't fight physics...and track times differ easily because of different factors.

Their is a difference between a street car and daily driver.