Turbo vs. Lightweight Flywheel

[speedminded]

When is a lightened flywheel too light for turbo applications?

A common upgrade on 996 turbos is a 50% lighter flywheel than stock, or around 13lbs. That's a 3.6L. I have a 2.8L. I want lighter...I think.

It seems like it would be difficult to get any data other than the difference in torque, if any, on a dyno...but what about spooling between shifts? Can't exactly test that on a dyno since you aren't snatching gears...or can you? What's the chances someone has data logged it, swapped flywheels, then gone out and data logged all the data to compare? lol.

[Axix23]

what i hear is on turbo cars, a ligten flywheel will cause your revs to drop too fast in between shifts and make you drop out of boost while shifting... Resurfaced stock flywheel is better..

[Drummerboy]

I have a lightened flywheel. 2.2L T3T4.

I do tend to drop out of boost quick unless I'm haulin' balls and just poppin' the clutch.

I have no logged Data, but i would think you would be fine with a 12lbs flywheel.

[WhiteAccord]

Off topic.... Speedminded... Clear your PM's...

[speedminded]

I have a lightened flywheel. 2.2L T3T4.

I do tend to drop out of boost quick unless I'm haulin' balls and just poppin' the clutch.

I have no logged Data, but i would think you would be fine with a 12lbs flywheel.

The lightened flywheel would allow the engine to rev quicker and the turbo to spool faster...the only downside that I can see is the revs drop faster when off the throttle between shifts, which means boost significantly drops, possible lag, etc...with that only really being an issue if you aren't getting on it? Couldn't that be easily fixed with a little spray if was really an issue?

Then there could potentially be a slight loss in torque at the top end. Let's say I have a 7k RPM 2.8L with a GT30R making around 360whp & 400 to 420 lbs-ft torque @ 10-12psi with full boost reached under 2,800 RPM's. With a 0.140" head gasket and ARP studs the engine will hold up to 25psi...think I can afford to give up some "torques" for an insane throttle response?

I'm looking at a 8.5lb flywheel with a sprung "cerametallic" M5 clutch kit.
http://www.uucmotorwerks.com/flywheel/LFWLE36SH.htm

[Psycho]

Here's the dealio, if you go too light of a flywheel on most cars, you start throwing check engine lights. Something about the crank position sensor getting tricked. Also, the lighter you go, the harder it is to drive your car around when coming from a complete stop (going over speed bumps, or re-parking in a parking spot).

What ever flywheel you decide to go with, you need to choose the correct clutch to go with it. If you get and un-dampened flywheel (solid metal) you need a sprung hub clutch, if you go with a dampened flywheel like a fidanza (has a replaceable insert on the face of the flywheel) you need an un-sprung hub clutch.

If you get an un-dampened flywheel and a un-sprung hub clutch, you'll put a lot of shock into your drive train on launches and possibly start breaking stuff. If you Mate a dampened flywheel to a sprung hub clutch, you'll have too much dampening and you'll wear your clutch out really fast.

[Bridged]

My ACT 2600 and 8lb Flywheel work just fine.

[IDCoconut]

I don't think you'll have a problem. You'll like the response more than anything. As far as dropping revs too quick and losing boost, shift faster .

My 993T has a light flywheel and I love it.

[Axix23]

Why the fk would you want to rev faster when your throwing a turbo on a fwd car, your revs will be hella fast when you lose traction... LOL

[Big Baller]

You aren't giving up anything unless you drag race.

Its easier to launch a car with a heavier flywheel because it maintains its momentum better. When the clutch clamps down it still has some balls behind it.

[SleepingTalon]

The weight that is kept on the crank to keep the boost up is negligible and entirely based on what you're doing/size of the turbo. Like Baller said, drag racing seems to be the most obvious situation, but with the way some of these "street" cars have gone lately, I can see where you might want a flywheel with some ass on it. A simple example would be if you're running a 2 liter with a 35r, the LW flywhel would be just fine. Conversely, a 88mm turbo on a Supra would suffer with a LW flywheel. It's all in the setup/turbo size/utility of the car.

[speedminded]

Here's the dealio, if you go too light of a flywheel on most cars, you start throwing check engine lights. Something about the crank position sensor getting tricked. Also, the lighter you go, the harder it is to drive your car around when coming from a complete stop (going over speed bumps, or re-parking in a parking spot).

What ever flywheel you decide to go with, you need to choose the correct clutch to go with it. If you get and un-dampened flywheel (solid metal) you need a sprung hub clutch, if you go with a dampened flywheel like a fidanza (has a replaceable insert on the face of the flywheel) you need an un-sprung hub clutch.

If you get an un-dampened flywheel and a un-sprung hub clutch, you'll put a lot of shock into your drive train on launches and possibly start breaking stuff. If you Mate a dampened flywheel to a sprung hub clutch, you'll have too much dampening and you'll wear your clutch out really fast.

Running a 8.5lb Cusco on my ITR, no check engine light and no other issues. I'm all for a light flywheel, single best mod I think you can do really if you're truly a driver...just not entirely sure how light with a turbo.

The check engine light wouldn't matter on this car because I'll be running a full standalone anyways. Doubling the HP with the engine swap from a different BMW then doubling that power with the turbo at low boost.

I could care less how difficult it is to drive, you learn to deal with it! The clutch flywheel combo I'm looking at is very streetable though...uses an OEM BMW pressure plate with a resurfaced sprung OEM clutch disc. Granted the flywheel is practically 25lbs lighter than the original dual mass mess there is still virtually no chatter or transmission noise with the way it was designed. I just have not met anyone with a turbo running it. Click the link I originally posted, that combo setup has been out for 5 years and still selling.

Why the fk would you want to rev faster when your throwing a turbo on a fwd car, your revs will be hella fast when you lose traction... LOL

quit talking, lol. FWD and turbo's only have one purpose in life: that's 10" slicks and driven in a straight line....that's not for me, sorry!

You aren't giving up anything unless you drag race.

Its easier to launch a car with a heavier flywheel because it maintains its momentum better. When the clutch clamps down it still has some balls behind it.

ahh, just who I wanted to hear from! The old Group B rally cars and turbo Formulas all seemed to have ultra lightweight flywheels...so it always made me curious why its normally not encouraged. I tend to believe what is race proven and from people who know first hand before anything else

[Axix23]

you never did mention what kinda car this lighten flywheel is for anyways, so I assumed its for your teg..

[speedminded]

you never did mention what kinda car this lighten flywheel is for anyways, so I assumed its for your teg..

2.8L Integra?

...with more torque than hp?

[§treet_§peed]

lol

[Stormhammer]

Personally, I would lighten your flywheel up to say - 17lbs or so. Keep about 60-75% of its weight.

[Stormhammer]

Psycho - also what you mentioned about the clutch vs flywheel stuff - it doesn't apply to all cars for the record

And a Fidanza isn't a dampened flywheel....