Clutch/Flywheel Questions

[Silvertop]

I need to know whether my '04 NA Impreza/Outback Sport donor uses the same clutch assembly as a WRX of the same year. I'm going to be separating the transmission from the engine for purposes of installing a Quaife LSD. Although the existing clutch is known to be in good operating condition, it would be smart to change out at least the clutch disc with a new one as long as I have it apart. I'm assuming that I don't need to go to a beefier pressure plate -- unless it is not enough for the higher output of my modified NA build. Note: My engine mods will take Horsepower output from 165 to an estimated 200-210 at the flywheel.

I'm also considering going to a lighter (but still street-worthy, not radically light) flywheel as long as I will have the easy opportunity. However, I have read on some Subaru forum sites that light flywheels sometimes create unwanted CEL's, particularly when lightweight crank pulleys are also employed. A Grimmspeed crank pulley is already in place on my engine. Anybody know anything about this?

I'm looking for input on both of these issues. Feel free to weigh in...........:)

[apexanimal]

you're good with keeping the crank pulley...

the lightened flywheel can and will cause misfire codes when "too" light... but what that point is is widely debated... a 11lb flywheel is likely to give you issues... while a 14lb-ish one might be fine...

you do free up some losses, and revs quicker...

[fateo66]

The Clutches are different. An 04 wrx has a pull clutch and the 04 NA has a push clutch.

[longislandwrx]

I think you'll be fine with a "steetlite" weight flywheel and the pulley. Like apex said, I would shy away from the race one as well. They are very light, tricky to drive on the street, and may throw the CELs

[Ironhydroxide]

for some info:

ALL boosted subarus pre 2005 (legacy GT) or 2006 (impreza chassis) Are a pull style clutch,

ALL STI 6 spd are pull style clutch

ALL NA subarus are Push style clutch

2006+WRX are push style clutch

2005+ Legacy GT are push style clutch.

Unconfirmed if/when the Forester XT went to push style.

[Silvertop]

Some very useful information above. Thanks for that.

Since the original post, I have done a little research. There are two clutches, and two flywheels that I am looking at. I like the Exedy Stage 1 Organic Disc Clutch, since it is basically the same design as the stock clutch, which is also an Exedy, but just a little beefier, with more clamping strength (196 ft/lb of torque at the wheels). Will likely be smoother and less troublesome to release than it's ACT counterpart, the ACT Heavy Duty Performance Street Disc Clutch kit, which is a good deal stronger, rated at 308 ft/lbs. The Exedy is also cheaper, at $370 vs $515 for the ACT. Either will probably be more than adequate for the amount of power I will be developing, particularly since the car is so much lighter than a Subaru sedan. The stock clutch is probably adequate, actually......... But I'm going to make the change, particularly since I'll have the transmission separated from the engine anyways.

I'm looking at the Exedy Lightweight Flywheel (at about 12.7 lbs and $420) vs. the ACT Streetlite (at about 13 1/2 lbs and $260). I actually like the ACT a little better, because it is a little heavier and therefore less likely to throw CEL's, as well as being a little more street-friendly, and at about $260, it is a good deal cheaper.

I'm tempted to mate the Exedy Clutch to the ACT Streetlite flywheel. It would probably give me the level of clutch performance and smoothness that I want and the flywheel weight I would prefer as well, and has the bonus of being the least expensive combination. Saves about $150 over going Exedy/Exedy or ACT/ACT. But basic prudence suggests to me that I might be better off not mixing component brands. Anybody have any thoughts on this?.

Opinions are welcome on all of the above. I'm a Subie Noobie (did I really say that?), so I can use all the help I can get........:rolleyes:

Note: It is possible that the potential CEL issue may have been negated by the Off-The-Shelf Level S-3 tune that Delicious Tuning put on the 02 ECU I will be using. I emailed them today to find out whether this might be so. Although I'll probably be OK anyways, it'd be nice not to have to worry about that.

[bbjones121]

Push or pull, what does it matter how the top of the fork is moved? Shouldn't everything from the pivot point of the shift fork function the exact same way?

[bbjones121]

I run ACT organic heavy duty with the stock wrx flywheel in my Legacy. I would never go lightweight flywheel unless you want some serious chatter. It is an art to make sure I don't make mine chatter. Then again, I was coming from the extremely smooth dual mass stock flywheel, so a major difference was somewhat expected.

[Silvertop]

I run ACT organic heavy duty with the stock wrx flywheel in my Legacy. I would never go lightweight flywheel unless you want some serious chatter. It is an art to make sure I don't make mine chatter. Then again, I was coming from the extremely smooth dual mass stock flywheel, so a major difference was somewhat expected.

Yes, the chatter issue is something to be concerned about. But I'm thinking that in a car as light as the 818, the car will move so readily when the clutch is engaged that chatter will be minimal or maybe even nonexistent. The payback, of course, is a more free-revving engine.

I did find out today in an exchange of emails from the fellow who did the mail-order off-the-shelf tune for my NA ECU that he has just developed an upgrade to his tune that isolates and eliminates the misfire CEL's that some Subie owners experience when using very light flywheels. He's still testing, but the new tune will be available in a couple of months. Promised me a free upgrade. I'm confident that he will make it work as he is a very bright fellow. He once worked for Crawford Performance providing off-the-shelf mail order tunes for NA Subies. But the software involved was something he had developed himself (and owned, apparently), and he took it with him when he left Crawford a year or two back. So I can set that worry aside.

I'm gonna go for it, I think.

[papajon1000]

I had a lightweight flywheel in my Legacy and it didn't chatter. I will however warn you that it is a common occurrence that ACT pressure plates greatly increase pedal effort. I had 2 ACT pressure plates/clutch kits and the clutch pedal was super heavy on both. I then went to a Clutch Masters fx350 and it was great. Definitely overkill for your goals but I was much more pleased with the Clutch Masters over the ACT.

That is my opinion but I thought I would let you know. I also wouldn't shy away from the lightweight flywheel. I went from lightweight when I got the car to a WRX flywheel and I could tell a noticeable difference in engine response. It did have some NVH below 2000 rpms but I have a feeling that you won't be driving your 818 under 2k much.

Cheers
Jon

[Flamshackle]

Silver top I am really looking forward to seeing your hot NA results. Sounds like it will be a sharp little package once it all comes together.

[Silvertop]

Papajon, thanks for that input. After some careful shopping, I found a good price combination on the 13 lb Exedy Flywheel and their Stage 1 organic clutch through Amazon. It's sitting on my dining room table right now! This deal's getting real!

Flamshackle, I'm pretty confident it WILL be a very sweet package when completed, plenty quick but still drivable by ordinary humans:)