Lightening the stock flywheel... - The Saab Link Forums

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Performance Modifications for the NG900 / Old 9-3 This forum contains PERFORMANCE related Q&A's for the NG900 and 9-3. This may also include suspension.

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Old 06-18-2008, 10:22 AM   #1
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Lightening the stock flywheel...

Is so worth it! $50 to resurface the flywheel, $80 to lighten it.

This weekend my buddy and I spent some quality time on the '99.

He has a lift, tranny jack, and a whole host of air tools. We got the gearbox out in about 2 hours. back in took another 2 or so.

New slave/throwout
New Vig clutch/PP
Nahum's old flywheel, lightened 3 lbs

Bleeding the clutch SUCKS! 3+ hrs of pressure bleeding, reverse bleeding, pumping the pedal. Finally she feels good.

Things I discovered while we tore the car apart?

RH Inner CV boot must have a tear....tons of grease on the subframe. New boot to go on tomorrow

RH Tie Rod fcuked. Two new tire rods to be installed tomorrow (thanks eEuro!)

RH Koni spring installed upside (that was my fuckup), flipped it and threw in a new strut bearing....all good.

Vacuum line flopping around on the intake manifold, this is the line that goes to the end of the fuel rail. I have no idea how this car was even running.

Anyway, she's running great now. Damn just a few pounds off the flywheel and she really rips!

Coming soon:
Viggen IC install (anyone have some hoses to sell cheap?)
Viggen brakes (just need to find some good rotors)
SS brake lines
T5Suite Tune (w/my homemade BDM)

Oh, and my DP is now held on with 2 out of 3 bolts....one was so frozen we had to cut it with a cutoff wheel. I couldn't get the stud out of the turbo housing either (I had new studs to put in.)

Guess this means I'll have to get a TD04 for next season.
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Old 06-18-2008, 01:13 PM   #2
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Sounds awesome! Lightening the flywheel is something I want to do sooner or later. How did you arrive at a 3-lb figure?

How heavy is the flywheel stock? I suspect it is pretty hefty. I came to my '01 9-3 SE from a '91 Nissan Sentra SE-R, which had a pretty light stock unit; I had to make a big adjustment as to how soon I clutched in on upshifts.

I had to clutch in later after easing up on the gas on the 9-3 since RPMs stayed up longer during shifting. Makes for smoother shifts during easy driving, but throttle blipping is adversely affected.
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Old 06-18-2008, 01:21 PM   #3
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Stock flywheel is 15.4 lbs IIRC. Usually most places will tell you that 20% is about the max they can safely lighten.

This shop removed 2.9 lbs, which is 18.8% lighter.

Definitely noticeable on the revs and on heel/toe shifts. Idle is perfect. Requires just a hair more gas to get going in first.

For comparison, the GenuineSaab Fidanza aluminum fly wheel is 7.4 lbs, mine is now 12.5lbs. It really feels perfect for the street/autocross use. And it's a fraction of the cost.
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Old 06-18-2008, 01:36 PM   #4
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Where did you have it done?
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Old 06-18-2008, 01:37 PM   #5
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Nice. Nick's flywheel is on my list of purchases to go with the LSD and trans rebuild coming over the next few months.
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Old 06-18-2008, 01:41 PM   #6
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I find with pressure bleeding that it can take a lot of pumping during the bleed to get it feeling right.

The longest it has taken me was maybe 20 minutes, and that was with very drained out clutch line and master cyl. I was beginning to worry at that point, because it had never taken me so long, but eventially I got the stubborn air out and it worked out fine.
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Old 06-18-2008, 02:26 PM   #7
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Nicks flywheel is from spec and is 7 lbs and oh so nice.



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Old 06-18-2008, 05:11 PM   #8
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I had it done by AC Performance, in Colchester (I can walk to their shop from work). They do mostly 'Murican Iron, but it's a nice shop. Very friendly guys.

I would love a LSD, but it's out of the question for the time being. I'm getting a little tired of spending money on the Saab. My goal will be to get as much power/handling/braking for autocrossing and trackdays for as little coin as possible.

I'd rather start dumping the money into my MGBGT which I'm planning an Ecotec swap into.

I think my main problem with bleeding the 9-3 clutch is I didn't bench bleed it prior to install, and my hose fitting on the bleed nipple was a little large, so I was probably leaking some air back in there....finally I got it all out though. Way harder than a C900 slave bleed though.

I thought GS's flywheel was Fidanza, I stand corrected....it looks way sweet, just more than I wanted to spend.
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Old 06-19-2008, 07:31 AM   #9
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off the front or off the back?
Machine shop wants to know, is it stepped on the back? How many thousands off the front?

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Old 06-19-2008, 08:14 AM   #10
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Quote:
Originally Posted by BlackDog View Post
off the front or off the back?
Machine shop wants to know, is it stepped on the back? How many thousands off the front?

They began by soaking the flywheel in a hot tank. Then they weighed it. Then, they did a standard resurfacing to the front face ( think they took off a few thou on the front, maybe ten thou tops). They weighed it again.
Then they flipped the flywheel and started carving out the rear. I don't know how many thou they took off, it was pretty noticeable though.

IIRC,They went within a 1/2" or so of the ring gear at the outer diameter, and within 2" of the crank bolt spider. Most of the meat was taken out of the middle-outer diameter (where it has the most effect anyway). It was stepped and radiused.

Then they weighed it again, it was 2.9lbs lighter than the pre-resurfacing weight. They decided to call it quits then. (I asked for approximately 3 lbs).

They charged me for 1.5hrs of shop time for the lightening, and 1 hour for the hot tank and resurfacing. Total was $130.
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Old 06-19-2008, 08:29 AM   #11
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cool, thats what he figgered. off the back, just wasn't sure if it was set up that way.. gonna pull and drop off a JunkYard flywheel today....
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Old 06-19-2008, 09:08 AM   #12
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I cut a bunch of stock flywheels down on our cars. Problem is you really can't get light enough by cutting on factory. This is why I went for an ALU custom made. So your "big difference" was less than half the change on the spec.
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2.0 GOOSE 500whp + 8500rpm = 11.06 @125 E85
Viggen 439whp / 447tq 12.43 @114 on Gt2871.64, (Now 511whp Gt3076)
Nordic E85 9-3 SS Aero 320hp / 350ftlbs
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Old 06-19-2008, 09:33 AM   #13
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20% lighter is still 20% lighter. It's noticeable. Certainly enough to knock off a tenth or two on the in-gear accelerations.

Believe me, a Spec flywheel would have been nice. But it's not cheap. My route was almost a third the cost and I got some benefit.

My goal isn't to build a monster. I want to have a AutoX/occasional trackday car that won't be running in an uncompetitive class. In my local sports car club, lightening a stock flywheel is penalized 2 points, swapping to a alloy one is penalized 5 points (every 14 points you jump a class, and I'm right on the edge of jumping into a class where I don't think I can be competitive) therefore the cost-benefit wasn't enough for me.
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