Lightened Flywheel

[4AL2NV]

Hi i was just wondering what the advantages and disadvantages are of putting a lightened flywheel in my r33 gtst. Does it wear the clutch out quicker? Does it affect performance in a big way and in which ways?

Edited September 3, 2006 by 4AL2NV

[TokyoTaxi]

From my experience, a lightened flywheel makes for easier gear changes when you're really up it but for normal street duties it's more of a pain since it can promote stalling and make it a bit harder to drive off from a standing position in traffic. ( This was on an RB20DET but it might be different on an RB25DET or larger engine and might differ depending on how light you go ).

[insu]

Try running some searches, there have been a fair few threads on this topic.

http://www.skylinesaustralia.com/forums/in...=102395&hl=

[shanef]

Drag racing - use standard flywheel, reasons is it wont drop off boost during shifts (as much as a light weight one), it will hold up better than a ligthweight one i.e wont bend/warp as much/quickly

Circuit racing - Lightweight flywheel, reasons is better throttle control during cornering, revs quicker, less rotating mass on engine

[Cubes]

Drag racing - use standard flywheel, reasons is it wont drop off boost during shifts (as much as a light weight one), it will hold up better than a ligthweight one i.e wont bend/warp as much/quickly

Unfortunately both of these statements are false.

Dropping off boost during shifts.... No matter what flywheel its going to drop boost between gear shifts as you shut the throttle slightly. If anything a light flywheel will help get the car accelerating again as there is less flywheel inertia to overcome.

The bend/warp statement is also strange; flywheels don't bend and warp, they simply chew out.

Aftermarket items such as molly have a greater resistance to being chewed out compared to the std item.

I ran an aftermarket lightened molly flywheel on my old mild rb20det some years ago.

Personally... There were no negatives and all positives.

Off idle acceleration in low gears was noticably brisker, no increase in stallability, if anything it felt freeier accelerating from idle rpm.

Gear changes were considerably easier at high rpm

Rev's would drop quicker making it sounder crisper when coming off a hard second gear boot.

Boost felt like it snapped on just that little bit harder.

Fuel economy didn't change

No noticable change in constant cruise feel when you hit a slight incline

Simply.. the car did feel slightly quicker/brisker in the lower gears; high gears, it felt the same.

The ONLY noticable difference is the car required a few more launch rev's. It actually made the car easier to get off the line even though the car now required a higher rpm launch (4000rpm vs ~3800rpm)

Definitely worth while.

I've since gone back to a std flywheel due to different motor and upon the next clutch change I WILL be dropping in a lightened flywheel.

[4AL2NV]

Unfortunately both of these statements are false.

Dropping off boost during shifts.... No matter what flywheel its going to drop boost between gear shifts as you shut the throttle slightly. If anything a light flywheel will help get the car accelerating again as there is less flywheel inertia to overcome.

The bend/warp statement is also strange; flywheels don't bend and warp, they simply chew out.

Aftermarket items such as molly have a greater resistance to being chewed out compared to the std item.

I ran an aftermarket lightened molly flywheel on my old mild rb20det some years ago.

Personally... There were no negatives and all positives.

Off idle acceleration in low gears was noticably brisker, no increase in stallability, if anything it felt freeier accelerating from idle rpm.

Gear changes were considerably easier at high rpm

Rev's would drop quicker making it sounder crisper when coming off a hard second gear boot.

Boost felt like it snapped on just that little bit harder.

Fuel economy didn't change

No noticable change in constant cruise feel when you hit a slight incline

Simply.. the car did feel slightly quicker/brisker in the lower gears; high gears, it felt the same.

The ONLY noticable difference is the car required a few more launch rev's. It actually made the car easier to get off the line even though the car now required a higher rpm launch (4000rpm vs ~3800rpm)

Definitely worth while.

I've since gone back to a std flywheel due to different motor and upon the next clutch change I WILL be dropping in a lightened flywheel.

Hi i just wanted to know which flywheel you used as this one you had seemed to be very good. Thank you.

[jantolis]

I sorta hate my lightened flywheel a bit because take off on the street are annoying. My girlfriend always complains about it and i don't wanna ride the clutch a bit to make it smoother because the os giken twins hate that alot.

[predator]

I ran an aftermarket lightened molly flywheel on my old mild rb20det some years ago.

I think this is the one now in my car yours wasn't really that 'light' 7kg as opposed to 9kg I weighed it in at There would be a fair difference between a 7kg one and the more expensive 4.5kg ones I would say.

[shanef]

Unfortunately both of these statements are false.

Dropping off boost during shifts.... No matter what flywheel its going to drop boost between gear shifts as you shut the throttle slightly. If anything a light flywheel will help get the car accelerating again as there is less flywheel inertia to overcome.

The bend/warp statement is also strange; flywheels don't bend and warp, they simply chew out.

Aftermarket items such as molly have a greater resistance to being chewed out compared to the std item.

I ran an aftermarket lightened molly flywheel on my old mild rb20det some years ago.

Personally... There were no negatives and all positives.

Off idle acceleration in low gears was noticably brisker, no increase in stallability, if anything it felt freeier accelerating from idle rpm.

Gear changes were considerably easier at high rpm

Rev's would drop quicker making it sounder crisper when coming off a hard second gear boot.

Boost felt like it snapped on just that little bit harder.

Fuel economy didn't change

No noticable change in constant cruise feel when you hit a slight incline

Simply.. the car did feel slightly quicker/brisker in the lower gears; high gears, it felt the same.

The ONLY noticable difference is the car required a few more launch rev's. It actually made the car easier to get off the line even though the car now required a higher rpm launch (4000rpm vs ~3800rpm)

Definitely worth while.

I've since gone back to a std flywheel due to different motor and upon the next clutch change I WILL be dropping in a lightened flywheel.

So then how do you explain the fact that the bresciani wrx couldnt run the times it could with a lightened flywheel that it did when they swapped to a standard one?

What i said above is what i have been told by a certain clutch builder, and im pretty sure you can guess who that is

[benm]

The bend/warp statement is also strange; flywheels don't bend and warp, they simply chew out.

Or shatter into 100 pieces

[Cubes]

Or shatter into 100 pieces

What brand was that?

As with anything you get what you pay for.

Or if its a manufacturing fault... Nothing can be done about that.

[Cubes]

So then how do you explain the fact that the bresciani wrx couldnt run the times it could with a lightened flywheel that it did when they swapped to a standard one?

What i said above is what i have been told by a certain clutch builder, and im pretty sure you can guess who that is

Since when are we talking about WRX's. They are well known for being cops off idle when running a lightened flywheel, RB's are not.

[Cubes]

I think this is the one now in my car yours wasn't really that 'light' 7kg as opposed to 9kg I weighed it in at There would be a fair difference between a 7kg one and the more expensive 4.5kg ones I would say.

I remember I weighed it in as I believe 6-6.5kg's without clutch. But either way, go too light and you loose go nicely weighted and there's gains.

This is the one I bought.

http://www.horsepowerinabox.com/HPIAB2/category16_1.htm

Right down the bottom, the pic does look a little different as it now runs holes in the center but none the less its essentially the same.

I personally don't think I would feel comfortable running anything lighter than 5.5kg's.

[Bl4cK32]

I agree with cubes. Ive gone from the std item to a os twin with its lightened flywheel, nothing but ++'s

[T04GTR]

Drag racing - use standard flywheel, reasons is it wont drop off boost during shifts (as much as a light weight one), it will hold up better than a ligthweight one i.e wont bend/warp as much/quickly

Circuit racing - Lightweight flywheel, reasons is better throttle control during cornering, revs quicker, less rotating mass on engine

WERD

[T04GTR]

well kinda

[T04GTR]

but...

circut use use a light one. better rev up when going up and down gears.

drags use a stock weight one. it gives more torque and better harmonics control. (ie.. dont bust that oil pump)

both statments are from my knowedge commonly accepted as a general rule of thumb. and if you dont agree cool. its your motor not mine lol

[T04GTR]

and a stock weight one is easier to use in traffic given the same clutch combo

[T04GTR]

but. the whole weight of a multiplate clutch is not far of the stockr anyway

[Cubes]

Reducing inertia (lightened flywheel) improves lower gear acceleration. How can this not be a benefit for street use?

The negatives..

Decreased stored kinetic energy thats used when launching. As a result you may need a few more hundred rpm on board when popping that clutch. Possibly a problem for 4wd's, not likely in rwd's.

And as you say the flywheel is also there to absorb firing pulses, reduce vibration harmonics, and torsional twist. Reducing this mass can reduce reliability and how smooth the engine feels.

I'm all for a slightly lighter stronger molly flywheel that I HAVE noticed a seat of the pants improvement with the gutless rb20 in the lower gears. If I ran a 4.5kg flywheel it may have been a different story. My little old rb20 covered around ~110,000km's with a lightened flywheel giving a total of 178,000km's total. The motor was still in excellent condition when it came out.

Too light yes its not good; slightly lighter I've noticed gains with no reliability issues.

I am currently running a ceramic puk clutch on the stock flywheel. Ceramic puk clutch + std flywheel is not a good combination.

The std flywheel material is too soft and chews out too quickly.

I'll have no issues dropping a few kg's from the weight of a stock flywheel for a stronger molly item. The last motor held together perfectly fine and was often reved in the lower gears to ~7300rpm.