Dear sirs and madams,

Thought I'd write up what a difference a lightweight flywheel made to my scooby (WRX PPP Sportwagon '03), so others may benefit / make an informed decision.

Long story short, my clutch died, my flywheel was covered in cracks, and no stock weight (10.7kg) flywheels were available that day, so I went for a 6.2kg flywheel from Roger Clarke Motorsport and an Exxedy Pinkbox organic clutch. I was concerned (after reading a thousand threads) that it might be rubbish to drive, but that wasn't the case - here's some mythbusting:

Mythbusting:

• Torque unnoticeably different - I can happily burble along at 25mph in 4th gear at 1,500 rpm no problem, same up hills etc; no noticeable difference. It might be less torquey under data scrutiny but you certainly can't tell whilst driving
• Stalling! In 500 miles, my total number of stalls = 0. Yes you need to be careful when you first take it round the block, but soon acclimatise
• Rev matching - no problem, not even slightly hard to handle; if you're quickly changing down it's easier if anything
• Engine rev speeds were almost exactly the same; launch might be like 200rpm more but you'd have more of a difference jumping into any other car

Benefits:

• Starting the engine is noticeably quicker - 30% less turning the engine over to get it going, which is bound to help when the weather gets cold
• Because it changes revs more responsively, it's generally sharper moving up or down through gears, helpful when you're thrashing it
• General town driving is easier - for example if you're waiting at a junction and someone flashes for you to go, you apply some gas then drop the clutch immediately, rather than *apply the gas* *wait one second for the revs to build* *drop clutch* - very handy in real life situations
• Launch is much quicker overall, due to above
• The clutch is so light! It's way lighter than the previous one, I no longer have to burst my thigh muscle to depress the clutch

Problems:

• The Exxedy pinkbox is pretty grippy - it seriously juddered for the first 300 miles and has settled a bit, but still feels like it has a grippy coating or something because the flutter is hard to control, which is a shame. It may be the combination of RCM flywheel coating vs. pinkbox. The upside to this clutch grip is that under anything more than a slow getaway, it's REALLY smooth - much easier to launch and normal 'fast'-ish pull away is easier.
  
  EDIT: This has now totally settled after about 1600 miles around town. That's a hell of a run-in, but it's smooth now, so no overall problems whatsoever

 

Hi mate,

Did you remove the engine to fit the clutch or did you follow the more traditional route of removing the exhaust, prop shaft, drive shafts and gearbox?

I'm looking at doing a replacement myself very soon and was wondering which would be the best option.

Thanks
Mick

 

I didn't do it myself, but my garage did it via the traditional route. Not sure what the pros & cons are of either - I guess there's much less to unplug/uncouple if you go through the ****, but the downside is you need to support the gearbox when it drops.

 

So overall the lightweight flywheel is a good investment? I have been tempted by one of these... I was told it greatly improves the responsiveness of the car... which you have just backed up

Also I used a pink box clutch in mine and get the same judder, which is calming down now at around 300 miles in. But like you say great with a bit of throttle.

I fitted mine with the engine out, which imo is the easier method. The gearbox removal is more time consuming and messy and just a general pain. Engine out is a piece of cake. Especially if you don't have ramps.

 

Yeah the main benefit is for general town driving - because you don't have to wait a second for the revs to pick up when moving from a standstill, the net gain is noticeable. You do have to be slightly more careful about stalling so I wouldn't go any lighter, but generally I'm glad I moved from 10.7 to 6.2kg.

You did it engine out? Did you follow a tutorial? I found one on this forum (complete with photos of every single stage) but can't find it again as it's such a massive forum!

 

Definitely a investment I would like to make then I think, I just couldn't afford it when I did the clutch and my flywheel was a good condition so couldn't justify.

Yea engine out, its much less faff, its more bolts and generally more awkward stuff to remove the gearbox. Sub frame dropping, steering rack, then supporting the engine afterwards and gear linkage on top of box. Not to mention the box is heavy!! haha.

http://www.iwsti.com/forums/how-inst...emoval-gd.html

I read that first time round.

 

Great news!

Your topic was just in time for me - as I am thinking to get a lightweight flywheel and a new clutch for my Bug sti... Discovered yesterday that my stock clutch slips badly when I shift at ~7000rpm. It's about time as it was never replaced since 2002.. The two previous owners must have been really gentle with it haha

So now that i've read you post I am definitely up for doing it!

How long did it take the guys to do it at your garage? 3-4 hours?

 

Access to ramps it should be done within 5 hours. On my back on my driveway it took a day.

** Thought I should add within 5 hours is 2 guys who have done it before doing the job on ramps.**

 

The garage took 7 hours with one guy doing it. They quoted first though so I paid a flat £350 for the work - so they just took their time. Big job though, either way.

 

engine out way is alot easier , i could do one in 2-3 hours now.

 

£350 ! blimey ! Shouldn't cost more than 4 hours labour or £200 max IMHO 7 hours fpmsl !

 

LWFW is a great upgrade though When I had mine done with pink exedy I had no judder. It all depends on the quality and cleanliness of your facings tbh ... and the care of the technician fitting it

 

Could you explain that a little more, please? About clean/quality facings.. So that i know where to look..


I'm fitting the stuff next week.
Got a quote from local guys who i trust: between £175-200.

£350 is way too much, isn't it?

 

Good write up. The Exedy Pinkbox with lightweight flywheel is one of our most popular sellers.

Has your clutch got 4 springs or 6?

 

Not sure I'd use it again (The clutch - the flywheel's fine), it's still juddering after 1k miles, although it is steadily improving. Just feels like it's a coating or a finish problem with the ablation surface. Garage reckoned any judder was due to 'warped' surfaces', but this is clearly bollocks IMO.

Mine was the 4 spring one...

 

is it fitted correctly I had an exedy and lightweight flywheel from Aztec and been on the car a year and a bit now with zero juddering, its even been on the track and launched down pod a few times.

mine is a six speed version though.

 

No way of knowing really (I didn't watch them do it), but looking at the design of the things, there's very little you can get wrong as long as the points are clean before it's mounted and tightened in order.

The (RCM) flywheel came with fitting instructions, which I made sure the mechanic read before he got started!

 

Fitted the Exedy Pinkbox (4 springs) and lightened flywheel last week - went on a trip to Scotland and back, 1000miles and no juddering at all. 6 speed box. Very contented I am.

 

Is that an Aztec Performance package?

 

Indeed it is

BTW Thanks for quick delivery guys, you did a good job!

 

Thought I'd check back in and say the judder from the 4-spring Pinkbox has now totally gone. It's excellent now, but it took about 1600 miles of urban driving! That's a hell of a run-in.

I'm happy with the Exxedy clutch now, but I took some convincing. Flywheel continues to perform exactly as the first post in the thread says - now the system's settled, we can sit back and enjoy the benefits.

 

What are the benefits (if any) of having a 6 spring clutch or a 4 spring? I imagine the 6 to be stiffer and harder to drive?
Which would you recommend for a car that is mainly used for urban driving/fast road and very minimal (if any!) track time?

 

I think we're talking about the laterally-mounted springs on the clutch plate, rather than springs which apply the pressure of the clutch itself.

The lateral springs smooth rotational chatter - presumably six springs would make the thing slightly steadier and less prone to rotational vibrations?

There's a decent video here which explains it - (from 5 mins in)
<iframe width="560" height="315" src="//www.youtube.com/embed/Td15fzkTfo4?rel=0" frameborder="0" allowfullscreen></iframe>

 

do you get any noise from this set up on the overrun?

 

i did 2500rpm - 2000rpm decelerating only in 4th gear though

 

was it like something rattling?

 

yes and i now think it's the springs chattering. if i press the clutch just enough to leave the car decelerating, it almost stops

 

do we have to learn to live with it or is there a cure?

 

rumour has it (lol) the 6spring plate cures the problem. personally from a engineering point of view, i thing it's harmonics and resonation, why only 4th gear because the harmonics of the engine-gearbox in that gear at 2500-2000 rpm causes the vibration. i have just fitted a 79thousand kilometer gearbox, that was perfect/silent with std clutch/fly so i know it's a clutch problem

 

You're most welcome


Good to hear it bedded in, it's the most popular clutch setup on the Impreza.

The original Exedy Racing Organic was a 6 spring setup but it had very little cushioning in the friction plate. The 4 spring version was introduced to reduce the judder experienced with racing clutches (hence the term anti-judder) and it has been exceptionally reliable.

I would always recommend the 4 spring version for anything used on the road: http://www.superhids.co.uk/clutches-...der-230mm.html