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There are four basic types of flywheels used on Subaru engines from 1990 to now. There are then multiple different interchangeable flywheels within some of the three types. Fortunately they are all interchangeable, in terms of bolting to the same design of crank flange, whether naturally aspirated or turbo, four or six cylinder, manual or automatic transmission.
All standard Subaru flywheels are cast iron, with a shrink fitted steel ring gear. Steel and steel faced aluminium flywheels are available from aftermarket specialists.
Naturally Aspirated Flywheels
Most naturally aspirated Subaru’s have a conventional single mass flywheel. The exception is the MY00 - MY01 models which have dual mass flywheels (see below).
The single mass naturally aspirated flywheels are basically the same design as the ‘flat faced’ turbo flywheels, except for the 268mm clutch pressure plate bolt / dowel PCD. There are at least two variations on the single mass naturally aspirated flywheel design. The MY90 - MY92 Legacy version is considerably lighter, at 7.5 kg, then the later versions, and is probably better suited for use on lighter weight VW’s. The MY 93 --> version, as fitted to all models using the EJ series engine, weigh about 10 kg, and their design changed very little until at least MY02. The flywheels are the same for all naturally aspirated (push to release)clutch sizes (215 and 225mm).
All single mass naturally aspirated Subaru flywheels are suitable for use in VW conversions using RJES components.
It is also worth noting that the MY90 - MY92 Legacy flywheel is lighter than some aftermarket light weight flywheels.
Dual Mass Flywheels
The dual mass flywheels can be used in VW conversions, but require a custom made clutch disc with no torsional vibration damping springs in the centre (i.e. a solid hub). All clutch components except the release bearing are unique to the dual mass flywheels. The flywheel and clutch pressure plate and disc are made by Valeo.
Unfortunately, dual mass flywheels are not really suitable for performance use, so if you intend to give the clutch a hard time in your conversion. replace the dual mass unit with a single mass one. Performance use of dual mass flywheels is limited as the iron flywheel on which the clutch disc runs is very thin. This both limits it’s ability to absorb heat, so making them more prone to warping, and makes them less stiff in the first place, so more likely to warp. Therefore engaging the clutch at high revs, such as drag racing starts, will almost certainly kill a dual mass flywheel very quickly.
See this link for a good explanation of how dual mass flywheels work, from clutch manufacturer, LUK
5 Speed Turbo Flywheels
The flywheel used in all five speed Subaru turbo’s is basically the same flat faced design as the naturally aspirated flywheel, apart from the 254mm clutch pressure plate bolt / dowel PCD. There are at least two variations on the single mass turbo flywheel design. Both have a similar mass of around 10 kg, but one is a true single mass design, as used up to about MY99, and the other has a torsional vibration damper built in, as used from about MY00 -->.. Don’t confuse the damped turbo flywheel with a dual mass flywheel though. True dual mass flywheels were only used on certain naturally aspirated models. These flywheels are suitable for both the 225 and 230mm turbo (pull to release) clutches.
All single mass turbo Subaru flywheels are suitable for use in VW conversions using RJES components.
6 Speed Turbo Flywheels
From MY02 --> the six speed gearbox became available in STi models. These use a unique 240mm flywheel and clutch design. The 240mm six speed Subaru flywheel is not a flat faced design. The clutch bolts on to raised pads which protrude from the clutch surface. All other clutch components except the release bearing are unique to the six speed 240mm clutch.
The six speed 240mm flywheel can be used in VW conversions uding RJES components.
Identifying Flywheel Types
This flow chart will help to identify a Subaru flywheel. Click the image to view it as a pdf:
The pictures below show some of the different flywheel types:
Single mass flywheels are fairly readily available second hand, as there are plenty of people who fitted light weight flywheels to Impreza’s. Most of the standard flywheels that you find for sale will be from turbo cars, with the 254 mm PCD.
Here the difference in the two PCD’s can be seen - nor the difference in distance between the clutch mounting holes and the edge of the flywheel. There is enough difference between the two PCD’s to make it easy to measure the PCD between two opposite hole centres. Alternatively, measure between the centres of the two clutch alignment dowels:
Clutch mounting Distance between
bolt PCD dowels:
Flat face 1990-1992 EJ18 carburettored flywheel, 7.5 kg 268mm 232.1mm
All other flat faced flywheels (turbo and N/A), 10 kg 254mm 220.0mm
The following pictures show the dual mass flywheel, and various aftermarket light weight flywheels:
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