Benefits of 7A/NM flywheel?

[Nik0las]

What are the benefits of such flywheel? And how hard is to install one?

[S2central.net]

It is lighter (reduced rotating mass means reduced parasitic losses in the engine ==> more power at the wheels) and the engine revs more freely as a result. There are some drawbacks though...

1 - Engine out job to change of course
2 - Flywheel should be dynamically balanced with crank etc by a professional who knows 5-cyl engines
3 - Some more drivetrain vibration and harshness comes with this type of single mass flywheel

The dual-mass flywheel used on more recent Audi engines is there to provide a more smooth character to the engine... but it removes some 'sporty' character of the engine as a result.

[Rusty]

Same installation as the 3B FW, check out the stickys in the transmission section by msyelf and others. Well worth doing for a more focussed car, not so worth doing for an everyday car...

[AndersS2]

It is lighter (reduced rotating mass means reduced parasitic losses in the engine ==> more power at the wheels) and the engine revs more freely as a result. There are some drawbacks though...

2 - Flywheel should be dynamically balanced with crank etc by a professional who knows 5-cyl engines

Paul,
I spoke with the guy balancing my bottom end, and he stated that they used heavier FW's on rallycross cars and street/race cars with turbo engines, as the turbo need more load in order to work better/more efficient. Adding weights on FW's on turboed engines was a common thing apparently. So he did not understand why everyone with turboed engines got ultra light FW's as they did not perform as well with the added weight/mass.

Im no expert on the area, but I think its worth the extra thought.
Based on that I kept my 7a FW standard.
I will read around some more to confirm this

as you say paul, balance the whole bottom end at a tuner familiar with the I5 crank. BTDT..

Nik0las: Its not so hard to do, but I recomend you have all new parts balanced for optimum harmony (harmonic damper, crankwheel, crank, pistons, rods, fw, clutch and all bolts holding it together). Just make sure you got all info needed on the swap.

1. Separate engine from gearbox (duh)
2. removed old FW/clutch package (document, write up where all parts are just in case)
3. Clean new FW friction area thuroughly. Clean gearbox axel free of old clutch dust, and rub off heatmarks. apply with a fingertouch of oil to lubricate the spline ONLY. Once there put in a new bearing in the new FW.
4. ALWAYS use new FW bolts w/loctite (short ones for 7a fw, long ones for dualmass FW)
5. FW bolts are tighten in a star shape, to 110NM.
6. apply the disk and clutch and make sure the disk is in centre of the clutch/pressure plate (important or it will wobble if not centerd). Can use special tool # xxx here, or use a accurate measuring device to check clearance all round the FW edge to disk.
7. put back together in reverse order.
8. bleed clutch pedal
9. Happy driving

The other stickys are probably better descirbed how you do it.

Benefits? Is there any? -But use these SM FW (Single Mass Fly Wheel) when building a new bottom end for full balancing, as the DM FW wont allow for correction/balancing.

[Nik0las]

thanks for the comprehensive answer