Flywheel Weight Reduction / Lightened Flywheels

manveet · 30th May 2007, 18:50

Quote:

Originally Posted by elf

Sniff. Sniff. Hug. Hug. Kiss. Kiss. Sob. I missed you too. What to do... I was (**ahem**) 'away' & 'unavailable' for a week.

I know about that. I'm happy to see it has done nothing to slow you down.

kkr2k2 · 30th May 2007, 19:15

I guess lot of people are aware of the game known as 'NFS - Porsche 2000 unleashed'. In this game one can modify the cars which you will be racing.

One of the options to increase the acceleration as mentioned in the game is to put in a light fly-wheel. But it is also mentioned that the top speed is decreased.

Though I am a mechanical engineer, i dont have knowledge on this. Any performance tuner here, who actually did such a modification can clarify this thing.

DieselFan · 31st May 2007, 08:36

Reducing weight of the flywheel is not advisable at all for the following reasons -

1. Car manufacturers would have put in an optimal flywheel based on experience and stringent design parameters
2. Reducing the weight will make cruising much more difficult unless you are an expert on the accelerator hence you will have a fluctuating speed/RPM on highways which is not desirable.
3. With lighter flywheel there would be more gear changes when you need to negotiate city traffic.

manveet · 31st May 2007, 10:02

I disagree duee to the following Reasons: -

Quote:

Originally Posted by DieselFan

1. Car manufacturers would have put in an optimal flywheel based on experience and stringent design parameters

Optimal is a very relative Term. The stock flywheel is designed keeping in mind that the same mass produced car would be driven by grandmothers as well as aggressive 20 year olds. Obviously, both would have different expectations from the cars response.

Quote:

Originally Posted by DieselFan

2. Reducing the weight will make cruising much more difficult

How? Any source?

Quote:

Originally Posted by DieselFan

unless you are an expert on the accelerator hence you will have a fluctuating speed/RPM on highways which is not desirable.

If one keeps the throttle steady, why would the RPM fluctuate !!??!!

Quote:

Originally Posted by DieselFan

3. With lighter flywheel there would be more gear changes when you need to negotiate city traffic.

Agreed. There are always two sides to a coin. One needs to weigh the Pro's against the Con's.

manveet · 31st May 2007, 10:35

Quote:

Originally Posted by kkr2k2

I guess lot of people are aware of the game known as 'NFS - Porsche 2000 unleashed'. In this game one can modify the cars which you will be racing. One of the options to increase the acceleration as mentioned in the game is to put in a light fly-wheel.

A VERY good observation Buddy.

Quote:

Originally Posted by kkr2k2

But it is also mentioned that the top speed is decreased.

My logic says that this is incorrect. Arcade games have a tendency to build in artificial trade-offs to any customization. In real life the trade-off would be faster falling/rising RPM's between gearshifts - not something that would be properly appreciated in an arcade game like NFS.

Personally, I would treat GranTurismo as a good reference and not NFS. If you've played the game - I'm sure you'll agree on that count.

But like you rightly said - perhaps someone more knowledgeable can clarify.

elf · 31st May 2007, 12:09

Actually, going by my reasoning, a lightened flywheel may actually reduce the top speed marginally.

A heavier flywheel stores more energy & has greater inertia due to it's relatively higher mass.

FOR EXAMPLE:
Lets say that your 5 speed, non-governed, 130bhp car has a top speed of 200 km/h, with your 5th gear being overdrive. It gets to 190 km/h quite quickly, but the 200 km/h top speed is only attainable on a long stretch in 4th. My guess is the last 10 km/h is achieved due to a combination of the energy stored in the inertia of the heavier stock flywheel & the final production of 'fresh' energy from your engine.

If your flywheel was lightened, it's mass would be reduced & therefore it's capacity for stored energy would also be reduced due to the reduced inertia, thereby only allowing a top speed of say 193 km/h, as the last burst of 'fresh' energy from the engine would be used to attain that speed & not much 'reserve' would be available in the flywheel.

This entire process would only be possible with petrol, diesel, or some sort of fuel.
Cars don't run without fuel.

vipul_singh · 2nd June 2007, 00:21

As some of the bhpians have correctly identified, one of the basic purposes of the flywheel is to store energy while the pistons go through the combustion cycle (4 stroke in most cars). The lesser the number of cylinders, the more crucial the flywheel becomes to the smooth running of the engine. For example, in a single cylinder engine, when the piston is at the bottom dead center, it is the inertia offered by the flywheel that forces the piston to the top again. Without the flywheel, the piston may stall at the BDC. At the very least, this would lead to a very jerky engine.

So, lightening the flywheel is very likely to reduce the balance of the engine, and increase vibrations (unless of course, you have a V16 like a Cizeta Moroder). From whatever I have read, reduction in vibration was the reason the flywheel was added to the piston engine in the first place.

speed0mania · 2nd June 2007, 03:20

well ive done my research on flywheels actually made a project on it!
im going to leave out the technical terms and try and explain the concept to those who still have some doubts.

the flywheel basically smoothens out the power transmission, the power from the engine comes in the form of thrusts which are smoothened out by using a flywheel of calculated weight and diameter.
any reduction in weight would cause this delivery of power from the engine to wheels become jerky ! and as rightly explained by others it would lead to faster drop in rpm!!
as per top speed the heavier flywheel helps the car gain momentum in the form of inertial energy stored in the flywheel hence it should lead to a reduction in top speed but i think it would be marginal!
the bigger disadvantage being the uneven power transmission!!

@manveet, steady throttle does not translate to constant rpm! if there were no external forces acting on the car constant throtle would lead to constant acceleration (increase in rpm) but since there are lots of external forces acting on the car this does not hold true! the flywheel also reduces this acceleration and hence at constant throttle the rpm increases quite slowly!!

paras211 · 2nd February 2008, 15:07

hey this is nicked from newcelica.org by FITGT

I used Excel and a BMW website that explained the math behind finding how much a lightweight flywheel helps you. I just redid for the celica info, and I have a rapidshare link. The numbers in red are the ones you can change. Enjoy

RapidShare: 1-Click Webhosting

Here is the BMW link.

http://www.uucmotorwerks.com/flywhe...wheel_works.htm

EDIT: FYI The gear ratios are for a GT, you can find the GTS from searching.

I didnt know a light weight flywheel can freeup so much hp.

30th May 2007, 19:15	#32
kkr2k2 Senior - BHPian Join Date: Sep 2006 Location: Melbourne, Hyd Posts: 1,294 Thanked: 66 Times View My Garage	I guess lot of people are aware of the game known as 'NFS - Porsche 2000 unleashed'. In this game one can modify the cars which you will be racing. One of the options to increase the acceleration as mentioned in the game is to put in a light fly-wheel. But it is also mentioned that the top speed is decreased. Though I am a mechanical engineer, i dont have knowledge on this. Any performance tuner here, who actually did such a modification can clarify this thing.
	() Thanks

31st May 2007, 08:36	#33
DieselFan Senior - BHPian Join Date: Mar 2007 Location: Bangalore Posts: 1,584 Thanked: 259 Times	Reducing weight of the flywheel is not advisable at all for the following reasons - 1. Car manufacturers would have put in an optimal flywheel based on experience and stringent design parameters 2. Reducing the weight will make cruising much more difficult unless you are an expert on the accelerator hence you will have a fluctuating speed/RPM on highways which is not desirable. 3. With lighter flywheel there would be more gear changes when you need to negotiate city traffic.
	() Thanks

31st May 2007, 12:09	#36
elf BANNED Join Date: Jan 2005 Location: Bombay Posts: 1,039 Thanked: 13 Times View My Garage	Flywheels & Top Speeds 101... by elf. Actually, going by my reasoning, a lightened flywheel may actually reduce the top speed marginally. A heavier flywheel stores more energy & has greater inertia due to it's relatively higher mass. FOR EXAMPLE: Lets say that your 5 speed, non-governed, 130bhp car has a top speed of 200 km/h, with your 5th gear being overdrive. It gets to 190 km/h quite quickly, but the 200 km/h top speed is only attainable on a long stretch in 4th. My guess is the last 10 km/h is achieved due to a combination of the energy stored in the inertia of the heavier stock flywheel & the final production of 'fresh' energy from your engine. If your flywheel was lightened, it's mass would be reduced & therefore it's capacity for stored energy would also be reduced due to the reduced inertia, thereby only allowing a top speed of say 193 km/h, as the last burst of 'fresh' energy from the engine would be used to attain that speed & not much 'reserve' would be available in the flywheel. This entire process would only be possible with petrol, diesel, or some sort of fuel. Cars don't run without fuel.
	() Thanks

2nd June 2007, 00:21	#37
vipul_singh BHPian Join Date: Sep 2005 Location: BLR / Lucknow Posts: 595 Thanked: 833 Times View My Garage	As some of the bhpians have correctly identified, one of the basic purposes of the flywheel is to store energy while the pistons go through the combustion cycle (4 stroke in most cars). The lesser the number of cylinders, the more crucial the flywheel becomes to the smooth running of the engine. For example, in a single cylinder engine, when the piston is at the bottom dead center, it is the inertia offered by the flywheel that forces the piston to the top again. Without the flywheel, the piston may stall at the BDC. At the very least, this would lead to a very jerky engine. So, lightening the flywheel is very likely to reduce the balance of the engine, and increase vibrations (unless of course, you have a V16 like a Cizeta Moroder). From whatever I have read, reduction in vibration was the reason the flywheel was added to the piston engine in the first place.
	() Thanks

2nd June 2007, 03:20	#38
speed0mania BHPian Join Date: Jun 2005 Location: new delhi Posts: 463 Thanked: 7 Times View My Garage	well ive done my research on flywheels actually made a project on it! im going to leave out the technical terms and try and explain the concept to those who still have some doubts. the flywheel basically smoothens out the power transmission, the power from the engine comes in the form of thrusts which are smoothened out by using a flywheel of calculated weight and diameter. any reduction in weight would cause this delivery of power from the engine to wheels become jerky ! and as rightly explained by others it would lead to faster drop in rpm!! as per top speed the heavier flywheel helps the car gain momentum in the form of inertial energy stored in the flywheel hence it should lead to a reduction in top speed but i think it would be marginal! the bigger disadvantage being the uneven power transmission!! @manveet, steady throttle does not translate to constant rpm! if there were no external forces acting on the car constant throtle would lead to constant acceleration (increase in rpm) but since there are lots of external forces acting on the car this does not hold true! the flywheel also reduces this acceleration and hence at constant throttle the rpm increases quite slowly!!
	() Thanks

2nd February 2008, 15:07	#39
paras211 BHPian Join Date: Nov 2006 Location: mumbai Posts: 646 Thanked: 108 Times View My Garage	lightweight flywheel. hey this is nicked from newcelica.org by FITGT I used Excel and a BMW website that explained the math behind finding how much a lightweight flywheel helps you. I just redid for the celica info, and I have a rapidshare link. The numbers in red are the ones you can change. Enjoy RapidShare: 1-Click Webhosting Here is the BMW link. http://www.uucmotorwerks.com/flywhe...wheel_works.htm EDIT: FYI The gear ratios are for a GT, you can find the GTS from searching. I didnt know a light weight flywheel can freeup so much hp.
	() Thanks