langg

I am curious as to the merit of an aluminum flywheel from an inertia point of view. The mass moment of inertia of an aluminum flywheel is about 1/3 of a steel flywheel of the same dimensions. So how does this compare to the "effective" mass moment of the system for our corvettes? Will there be a measurable difference in the 1/4 mile time, or is it an urban myth?

One thing an aluminum flywheel does seem to do is to help exaggerate a rough idle.

Comments and opinions welcome.

langg

pauldana

First off, i am running a light weight billet steel flywheel. 22lbs i think... when i changed from my heavy stock flywheel it was amazing! i do road race, thus dropping the clutch is not my thing as it destroys the drive train. Now..on the freeway, when you just hit the gas, it is a noticeable difference in the instant pull of the lightweight FW... love it!!! and on my new engine, i went to a light weight clutch as well... the heavy flywheel is good for low tq motors that need the stored inertia to get moving without revving the engine at every light. in my case i do not need this stored power. a stock L48 may be a different issue.

cv67

i run a little heavier billet FW and love it.
Good recovery on shifts, can idle it into gear (not that I do) just makes it easier and more pleasant to drive. They both have pluses and minuses at the end of the day it doesnt matter long as it doesnt explode on you. I will never run an iron FW period

terrys6t8roadster

in my case, I installed a Fidanza billet alumiun flywheel on a stock block 327, new roller cam & dart heads. the engine revved faster than the tach . I was concerned about holding constant speeds with an 11#flywheel on the street, but no problem. Terry

Gordonm

I ran a 30 poundsteel wheel for years. I switched to an aluminum 14 pounder and would not go back. It revs much faster and is just overall a much better wheel for the street. Our motors make plenty of torque for getting the car moving so the inertia thing is not a problem. If you drove a 90 HP 4 cylinder in a heavy car maybe you could use a heavy wheel.

Driving on the autX it was a much improved feeling. It came out of the corners much quicker. My new LS3 has an aluminum wheel in it also.

MSGT-R

It was a Turbo Toyota 22R motor with a Kevlar clutch, but the lighter weight flywheel was an immediate difference, even on such a small motor compared to Vettes. I had a 15 pound steel wheel vs. a 40-something pound cast iron that came off of it.

If you have a radical "rumpity-rump" cam, its not going to want to idle smoothly.

TheSkunkWorks

Lower rotating inertia will improve throttle response, which can significanlty reduce the time it takes to sync revs when shifting, especially downshifting. And, don't listen to anyone who tells you this doesn't matter because the clutch is supposed to be disengaged when selecting a different gear anyway, as they obviously don't have a clue about driving "in anger". The only reason I'd change from my 15# SFI flywheel would be for even less rotating inertia. My $.02

Solid LT1

The 67-9 L-88 flywheel is a 14.8LB Nodular iron flywheel, I have run these since the 1970's in varoius Chevys without problems. The flywheel of a C4 Vette is same casting as L-88 10.5" clutch flywheel and performs well.

69427

Been running these flywheels in my C3 and C4 for years. Great throttle response and durability.

PeteZO6

I had a Weber aluminum f/w on a Ford 289 K code engine in a Mustang 2+2. Small block, short stroke, solid lifter engine that revved like crazy. Not a torquey engine but the lightweight f/w was a good match. The car was quicker to 100 mph than my base engine '69 Corvette.
I can't imagine that a SBC wouldn't benefit from an aluminum f/w.

Pete

iokepakai

When I did my 6spd trans swap went to a lighter billet steel flywheel.Revved quicker for sure.Don't think I'd use aluminum for a street cruiser.

Danish Shark

How does it affect the idle quality?

gkull

Weight of the fly wheel is only part of the story. It is the total weight of the rotating assembly. From the damper pulley to the Pressure plate fingers.

So lets say that we have two identical power and TQ 383 stroker motors build.

Motor "A" has a 400 journal internally balanced cast crank. the damper weighs 11 pounds, the crank 58 pounds and they installed a 15 pound super light weight aluminum flywheel. total of these parts is 84 pounds

Motor "B" has a 4340 small journal, hollow drilled, internally balanced. The fluid damper is small diameter 6 pounds, the crank is 42 pounds, and they install a 30 pound steel flywheel for a total of 78 pounds.


So if somebody tells you that they bought this 15 pound aluminum flywheel. I would say great, but it is still not as light as my setup with a heavier fly wheel.

Actually in my case I have a 22 pound steel with the 42 pound crank tiny 6.125 damper with a aluminum damper pulley. So I have about 70 pounds of rotating weight. compared to the more common people that end up with 80+ even with their 15 pound aluminum flywheel.

MSGT-R

Why not? the steel facing for the friction surface will sufficiently heat-sinc into the aluminum without any damage. The ring gear is pressed on the same as other flywheels.

lionelhutz

But it's inertia that effects the acceleration rate, not just weight.

Inertia is mass x distance squared, so a change in the distance the mass is from the center line of the shaft has a bigger effect then just a change in the mass.

Lowering the weight by 10% with the same weight distribution would lower the inertia to 90%.

Lowering the diameter of the weight distribution by 10% would lower the inertia to 81%.

That is one reason why a small diameter multiple plate clutch or a small diameter torque converter gives such a big performance advantage.

gkull

Yes, run an equal weight 153 tooth fly wheel has advantages compared to running a 168 tooth larger diameter fly wheel.

langg

I understand that the engine will rev faster (with the clutch released) using an aluminum flywheel. But once the clutch is engaged, and you are winding up all the pieces like pressure plate, transmission gears, rear end gears and wheels and tires, is the difference in flywheel inertia significant? What percentage of the total system inertia is the flywheel? And, as long as the tires don't slip, can you accelerate the system fast enough to realize the benefit of the change in inertia from the flywheel.

langg

iokepakai

If your set on using an aluminum flywheel,install a blow proof bell housing at the same time.Protect those toes!! Here's a post from a forum member about his issues with an aluminum flywheel on the street.Read several posts that were similar .Build your car for how you intend to use it.For street use I'll stick with a billet steel flywheel.Good luck..


I put an aluminum flywheel on my 92 Rustang GT. It was a mistake!!! The clutch and flywheel only lasted for around 15,000 miles. The heat that is generated with daily driving will warp the aluminum discs on the flywheel and chew up the clutch. I also lost some low end in doing the change. Lighter is better when you are at high RPM's, but not street driving. There, you need the weight. You also need a flywheel that can take the heat transfer of all the additional shifting you do on the street, compared to drag racing. I talk from experience here...unless you are only driving the car to and from the drag strip and intend on only racing it, I would NOT put the aluminum flywheel on. Unless you enjoy doing all the work again for a new clutch and flywheel in 15,000 miles or so. That is my $0.02. Good luck!

redvetracr

the further (or is it farther?) away from the crankshaft centerline you get the bigger deal moment of inertia becomes, there are two places in your driveline where this is a big deal, the flywheel and next your differential ring gear. I have the 5.5" triple disc clutch with a cover mounted ring gear and reverse mount starter (huge difference over the 7.25" clutch which was a huge difference over a 10.4" standard clutch), there is also a 4.5" clutch and I think for about $4K there is a carbon fiber clutch, thats the ultimate. I was thinking of getting a ring gear EDM lightened but never did it. the 5.5" clutch doesn`t like to be slipped so it`s either in or out and not street friendly, for a while I used a Roltek trans with a gun drilled mainshaft, it worked great but I was always afraid of destroying it. that L-88 flywheel for the street is a great choice, you can probably abuse that more than an aluminum flywheel.

vette427-sbc

ACT makes a 12lb 153T all steel flywheel for cheaper than most lightweight alu ones. A lot of the weight is taken out of the outer ring so it has even less moment of inertia than some other lightweight flywheels.
Have one on my car and love it.


http://www.summitracing.com/parts/acl-600455/