Aluminum flywheels - what you need to know
09-12-2002, 07:38 AM
#1
FormerVendor
Thread Starter
Join Date: Nov 2001
Location: columbia, sc
Posts: 366
Likes: 0
Received 0 Likes
on
0 Posts
Aluminum flywheels - what you need to know I constantly see questions posted here regarding aluminum flywheels. Here's a few facts I use for my salespeople that everyone should know if you are considering this mod.
WHAT DOES A FLYWHEEL REALLY DO?
INERTIA - THE FLYWHEEL'S JOB
The job of a flywheel is to provide inertia to get a vehicle moving. The heavier the flywheel, the easier it is to pull off with minimal clutch slippage. On the other hand, light flywheels do not create as much inertia, and thus the clutch must be slipped harder on takeoff to achieve a smooth transition. This will also effect clutch life, since the slip time is greater. Thus, street applications will benefit more from a steel than aluminum flywheel.
LIGHTER IS BETTER FOR RACING... SOMETIMES
In a race vehicle, a light flywheel may reduce inertia on launch and keep the vehicle from spinning the tires excessively, and allow the vehicle to accelerate quicker. The most important factor here is gearing. Too little of rear gear (lower numerically) may cause the engine to nose over or 'bog' on launch. So in order to use an aluminum flywheel effectively, some changes in rear or even transmission gearing may be necessary.
ALUMINUM FLYWHEELS DO NOT INCREASE HORSEPOWER
While some may try to have you believe this, there is no real horsepower gain by using an aluminum flywheel. Lighter flywheels will allow the engine to rev faster, giving the illusion of power increase. However, use an aluminum flywheel in a street vehicle will cause a decrease in driveability.
GRINDING AWAY?
Some manufacturers will have you believe that flywheel inserts do not need to be surface ground. This is false!!! The clutch disc needs a parallel ground friction surface in order provide an adequate mating surface for the clutch disc. This assures minimum runout and maximum clutch life. Flywheels that are not surface ground also cause a decrease in driveability.
BALANCING ACT
Proper balance of the flywheel, whether steel or aluminum, is critical. Make sure the flywheel you use is properly balanced from the factory... some may not be spin balanced at all!
I know this is long but it tells the story! <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />
WHAT DOES A FLYWHEEL REALLY DO?
INERTIA - THE FLYWHEEL'S JOB
The job of a flywheel is to provide inertia to get a vehicle moving. The heavier the flywheel, the easier it is to pull off with minimal clutch slippage. On the other hand, light flywheels do not create as much inertia, and thus the clutch must be slipped harder on takeoff to achieve a smooth transition. This will also effect clutch life, since the slip time is greater. Thus, street applications will benefit more from a steel than aluminum flywheel.
LIGHTER IS BETTER FOR RACING... SOMETIMES
In a race vehicle, a light flywheel may reduce inertia on launch and keep the vehicle from spinning the tires excessively, and allow the vehicle to accelerate quicker. The most important factor here is gearing. Too little of rear gear (lower numerically) may cause the engine to nose over or 'bog' on launch. So in order to use an aluminum flywheel effectively, some changes in rear or even transmission gearing may be necessary.
ALUMINUM FLYWHEELS DO NOT INCREASE HORSEPOWER
While some may try to have you believe this, there is no real horsepower gain by using an aluminum flywheel. Lighter flywheels will allow the engine to rev faster, giving the illusion of power increase. However, use an aluminum flywheel in a street vehicle will cause a decrease in driveability.
GRINDING AWAY?
Some manufacturers will have you believe that flywheel inserts do not need to be surface ground. This is false!!! The clutch disc needs a parallel ground friction surface in order provide an adequate mating surface for the clutch disc. This assures minimum runout and maximum clutch life. Flywheels that are not surface ground also cause a decrease in driveability.
BALANCING ACT
Proper balance of the flywheel, whether steel or aluminum, is critical. Make sure the flywheel you use is properly balanced from the factory... some may not be spin balanced at all!
I know this is long but it tells the story! <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />
09-16-2002, 07:18 PM
#3
TECH Addict
Re: Aluminum flywheels - what you need to know So even though there wouldn't be an increase in hp with an aluminum flywheel, there would be an increase in rate of acceleration right ? Especially in the lower gears. Of course that means that the chance of blowing off the tires would also increase .
09-17-2002, 02:33 AM
#4
Staging Lane
Join Date: Apr 2002
Location: san jose
Posts: 54
Likes: 0
Received 0 Likes
on
0 Posts
Re: Aluminum flywheels - what you need to know well thank you again for reminding me what the flywheel does. i think i am just now going to stick with a stocker since most people who like to launch say it does bog your motor. cause that weight is there for a reason, to get those pistons turning!!!
09-17-2002, 07:08 AM
#5
FormerVendor
Thread Starter
Join Date: Nov 2001
Location: columbia, sc
Posts: 366
Likes: 0
Received 0 Likes
on
0 Posts
Re: Aluminum flywheels - what you need to know Not exactly, Racehead. Even though the engine is accelerating faster, the inertia the flywheel creates is lower. Sometimes if tirespin is an issue, you can use aluminum to decrease the inertia, which can reduce the tirespin. This is really just a band aid for better gearing, which is sometimes necessary with transmissions such as ours that do not lend themselves to easy gear ratio changes.
It seems that in LS1 apps its is more of a hinderance than a help at the track. Now on the flip side, our fine pony friends this often helps alot.
It seems that in LS1 apps its is more of a hinderance than a help at the track. Now on the flip side, our fine pony friends this often helps alot.
10-09-2002, 07:56 PM
#6
Re: Aluminum flywheels - what you need to know So here's my problem....I have no whelspin off the line with my street tires (I intentionally bog the motor for traction) until I reach about the 100' mark and then the tires start spinning at about 4500 RPM on up. When I shift to 2nd gear, all of that momentum is still there and the tires just continue to incinerate. Will this help out in this situation with my M6 and 4.10's?
<small>[ October 10, 2002, 02:03 PM: Message edited by: John B ]</small>
<small>[ October 10, 2002, 02:03 PM: Message edited by: John B ]</small>
Trending Topics
10-10-2002, 06:51 AM
#9
FormerVendor
Thread Starter
Join Date: Nov 2001
Location: columbia, sc
Posts: 366
Likes: 0
Received 0 Likes
on
0 Posts
Re: Aluminum flywheels - what you need to know You guys are getting the picture now! <img border="0" alt="[Burnout]" title="" src="graemlins/burnout.gif" />
10-10-2002, 04:33 PM
#10
TECH Enthusiast
Join Date: Apr 2002
Location: Chesterton, IN
Posts: 588
Likes: 0
Received 0 Likes
on
0 Posts
Re: Aluminum flywheels - what you need to know Just to pick the nit, a fly wheel does not, and can not "CREATE inertia" or "GET the pistons moving." The explosion of fuel and oxygen gets the pistons moving. Kinetic energy is transfered to the flywheel via the crankshaft. Once the flywheel is moving, it has inertia. The inertia of the flywheel then keeps the pistons moving between explosions.
Not that anyone cares.
Not that anyone cares.
10-10-2002, 04:36 PM
#11
TECH Enthusiast
Join Date: Apr 2002
Location: Chesterton, IN
Posts: 588
Likes: 0
Received 0 Likes
on
0 Posts
Re: Aluminum flywheels - what you need to know Okay, before I get my own nits picked at, I know that the flywheel has inertia even when it's not moving. <img border="0" title="" alt="[Roll Eyes]" src="images/icons/rolleyes.gif" />
I guess the correct way to phrase those last two sentances would be:
Once the flywheel is moving, its inertia then keeps the pistons moving between explosions.
I guess the correct way to phrase those last two sentances would be:
Once the flywheel is moving, its inertia then keeps the pistons moving between explosions.
01-03-2003, 01:22 AM
#17
TECH Enthusiast
Join Date: Jul 2002
Location: Pensacola, FL
Posts: 618
Likes: 0
Received 0 Likes
on
0 Posts
Re: Aluminum flywheels - what you need to know Okay, you gave us a bunch of cons on the aluminum flywheel. What happened to the pros?
I cannot accept what you say as unbiased for some reason or another unless you give us pros. I know there are some, otherwise aluminum flywheels would not have been around as long as they have and would not be increasing in popularity over the last few years.
You are correct that light weight flywheels don't make hp, that would be ludicrous to believe, but they do allow more power to reach the ground. Any weight on a car that is reciprocating or turning is much more detrimental to performance than fixed weight. That is why you benefit more from lightening things like brakes and rims than things like body panels. GMHTP has a clutch and flywheel article in the new issue that praises the use of a lightweight flywheel on LS1 cars, touting it as a must do sort of mod.
The only thing I have heard first hand about a light flywheel that is an unwanted side effect is that your engine loses it's 'braking' ability when downshifting.
So let's talk some more.
Dave
I cannot accept what you say as unbiased for some reason or another unless you give us pros. I know there are some, otherwise aluminum flywheels would not have been around as long as they have and would not be increasing in popularity over the last few years.
You are correct that light weight flywheels don't make hp, that would be ludicrous to believe, but they do allow more power to reach the ground. Any weight on a car that is reciprocating or turning is much more detrimental to performance than fixed weight. That is why you benefit more from lightening things like brakes and rims than things like body panels. GMHTP has a clutch and flywheel article in the new issue that praises the use of a lightweight flywheel on LS1 cars, touting it as a must do sort of mod.
The only thing I have heard first hand about a light flywheel that is an unwanted side effect is that your engine loses it's 'braking' ability when downshifting.
So let's talk some more.
Dave
01-03-2003, 02:12 AM
#18
TECH Resident
Join Date: Aug 2002
Location: TN
Posts: 920
Likes: 0
Received 0 Likes
on
0 Posts
Re: Aluminum flywheels - what you need to know I got to do some launches on christmas day in a parking lot. From what i noticed is that the car is very easy to launch, but it does require more feathering. I love my flywheel it makes shifting better. Not to mention if you heal/toe downshift then you will love it. Since i did other mods i never noticed a difference in hp from this alone. Soon i will have mustang dyno numbers to compare after my tuning. I am waiting on autotap. It sounds cool as hell to. i like how you don't break the tires as easy.
01-03-2003, 10:10 AM
#19
6600 rpm clutch dump of death Administrator
Re: Aluminum flywheels - what you need to know Aluminum is great for dyno queens, and for road racing.
I know this is an oversimplification. It takes X ammount of energy to move your vehicle down the 1/4 mile. Now, any energy that is stored in the flywheel before you trip the beams is energy your motor doesn't have to be produced during the run. The flywheel has sored potential energy related to its mass. The more mass you accelerate initiall the more power you transfer at launch.
Let me give you my example. I drag race my 2002 Z06. It is stock. On ET Streets @ 12psi the car will dead hook and bog the car launching at 6600 rpms. Now, jack the tire pressure up to 18-20 psi and I can spin the tires about 20 ft. That results in my times being .2 quicker.
Putting an aluminum flywheel in my car would only make it worse. Putting a heavier flywheel would actually help my car.
On the dyno it would hurt my RWHP numbers since the car would accelerate slower. Remeber HP is a measure of the speed of acceleration.
If you want to roadrace go aluminum.
If you want to drag race go steel. Go to any NHRA event and look at the cars in the stock class. Many of them have 80lbs flywheels in them and superdeep 6.xx gears. It takes forever for them to get rev'd up. When they lift off the throttle the engine takes forever to decelerate.
If you want sick dyno numbers, go put an aluminum driveshaft, an aluminum flywheel, emergency spares on the back of your car, and put 2.73s in your car. You'll have a pretty dyno sheet, but that is about all....
I know this is an oversimplification. It takes X ammount of energy to move your vehicle down the 1/4 mile. Now, any energy that is stored in the flywheel before you trip the beams is energy your motor doesn't have to be produced during the run. The flywheel has sored potential energy related to its mass. The more mass you accelerate initiall the more power you transfer at launch.
Let me give you my example. I drag race my 2002 Z06. It is stock. On ET Streets @ 12psi the car will dead hook and bog the car launching at 6600 rpms. Now, jack the tire pressure up to 18-20 psi and I can spin the tires about 20 ft. That results in my times being .2 quicker.
Putting an aluminum flywheel in my car would only make it worse. Putting a heavier flywheel would actually help my car.
On the dyno it would hurt my RWHP numbers since the car would accelerate slower. Remeber HP is a measure of the speed of acceleration.
If you want to roadrace go aluminum.
If you want to drag race go steel. Go to any NHRA event and look at the cars in the stock class. Many of them have 80lbs flywheels in them and superdeep 6.xx gears. It takes forever for them to get rev'd up. When they lift off the throttle the engine takes forever to decelerate.
If you want sick dyno numbers, go put an aluminum driveshaft, an aluminum flywheel, emergency spares on the back of your car, and put 2.73s in your car. You'll have a pretty dyno sheet, but that is about all....
01-03-2003, 03:01 PM
#20
FormerVendor
Thread Starter
Join Date: Nov 2001
Location: columbia, sc
Posts: 366
Likes: 0
Received 0 Likes
on
0 Posts
Re: Aluminum flywheels - what you need to know The reason you don't see many pro's for running aluminum in these cars is that there are not that many. As stated above, they are excellent for road racing where you want to use the engine as a brake, or get a little quicker response out of the turn. On the street, you will feel a little quicker acceleration once the clutch is engaged, but the extra slip required to engage the clutch smoothly will probably offset this in terms of overall wear.