To give some background, this wasn't a mod that I wasn't actually planning on doing......but thanks some bad influences on here it was one that I just couldn't resist taking on :twisted:
Before I start, this mod isn't exclusive to the M52 :P ! It can be done on a number of E36 BMW's. I did quite a bit of reading up before taking on this mod and in doing so found an excellent write-up that I would highly recommend:
Black Forest Industries - M42 M20 flywheel install
Back to the M52
:
Here's why you'd do it:
- Stock 328 M52 flywheel (dual mass) = 11 KG (just the flywheel)
- M20 flywheel (single mass) = 7 KG (just the flywheel)
- no increase in gear noise (most after market kits are affected by this)
- easy to source second hand parts
- clutches kits are VERY cheap compared to M52 kits (pressure plate, clutch etc)
The clutches are also different weight wise between the two but didn't weigh them so can't give figures - needless to say that the M20 item at 228mm as compared to 240mm for the M52 jobbie is lighter :wink:
Here's why you wouldn't:
The install is a royal pain the in the backside, equalled only my my recent fitment of M3 3.0 exhaust manifolds!!! In my case the install required:
- the engine to be lifted to gain access to the top bolts of the bell housing
- about a million extensions / knuckles to actually get onto the gearbox bolts
- fitment of an M20 starter (I cannot convey just how hard this job in itself is on the M52!!)
It doesn't sound like the above should be too much hassle, but trust me on this, this job is not to be taken lightly. If you do fancy it give yourself at least 2 full days to get it done (8 hour days).
What you need to do it (on an M52 anyway):
- M20 flywheel (must be from an 89 - 91 E30 325i)
- M20 starter motor (the M52 starter will not mesh with an M20 flywheel)
- M20 clutch kit (clutch + pressure plate)
- E21 323i release bearing (30mm height)
- M20 flywheel bolts as the M52 items are too long (I'd recommend new pressure plate bolts too)
NOTE: You MUST get the M20 flywheel machined to fit the M52. This involves removing a minimum of 4mm (from what I've read elsewhere) but I chose to remove 6.5mm to be doubly safe given the mammoth effort involved to get this job done!
To give you a rought idea of costs, I did the whole job for approximately £300 - that includes the cost of having the flywheel professionally machined and checked for re-balancing at a motor sport machine shop (£40).
The install
As hinted at above this job is a hassle on the M52.
One of the hardest battle you'll have is swapping out the starter motor. As anyone with an M52 will know the starter lives under the intake manifold :evil: ! It's actually secured by two bolts coming through from the back of the gearbox into the engine bay and into a couple of threaded bolt holes (on the starter housing). So, if you ever need to swap the starter out you need to get to the upper most face of the garbox!!
I chose to fit a brand new starter rather than risk a second hand one - I do not want to have to replace the starter in a hurry
: !
The other major drawback with this mod is the lack of access to the gearbox bolts from underneath the car. The transmission itself takes up a large amount of space and without tilting the engine / gearbox down I'm not sure this job is possible.....we ended up loosening the engine mounts and using one of these to gain some angle:
Once you've got the gearbox tilted down it get easier....but this is a
relative term
: ! Access to the Torx bolts that bolt the gearbox to the engine is still difficult and will require two people - one to guide the bit onto the bolts, the other to actually feed in the several feet of extensions and knuckles required to get onto the bolts :P .
Once the gearbox is out the job of swapping the flywheel bits out and fitting the new ones is easy.
Re-assembly is easier than disassembly as by this time you've got an idea of what angles / tools work best to gain access to the gearbox bolts.
Driving Impressions
- clutch pedal action changes
The actual engagement is much lighter than with the stock 328 bits. This was strange at first as I was certainly used to having to exert a certain amount of force and with less force now being required I tended to almost stamp on the clutch pedal initially. After 300+ miles I've now adjusted and it's great 8) .
- a nice improvement in acceleration in pretty much any gear (more noticeable lower down the ratios)
Acceleration from a standing start it quite different. The first 3 gears are noticeably "sharper" but in a good way. The engine gets into its stride more easily and gear changes seem to require less effort somehow.
- motorway cruising is great :twisted:
I was expecting hills and steep inclines to be more of a problem thanks to the reduced mass of the flywheel. In reality the different isn't noticeable. If anything I find it easier to accelerate up hill now than I did before. The 230 mile journey home from my parents place was once of the most relaxing I've done in a long time. Obviously much of this was due to lack of traffic but the car seemed to be wafting me along more easily somehow.
- gear rattle @ idle
This was probably my biggest concern about doing this mod. I've read countless threads one other forums from people that have used the likes if UUC and Rogue lightweight flywheel kits only to be greeted with big increases in gear "rattle" at idle
.
I'm pleased to report that so far I have noticed no increase in noise at idle :P !
Conclusion
This is another great mod for the M52 :mrgreen: ! The results are worth the effort but this is not a job to be underestimated in terms of the effort required to get it done.
The really nice thing about this mod for me is that I've managed to stick with all BMW parts 8) . It's a choice I've stuck to all the way through with my car and again it has served me well i.e. US S50 cams, custom M3 3.0 diff, M50 manifold, UK S50 exhaust manifolds etc.
Overall I'm delighted with the mod :thumb:
As always I have to thank plenty of people, without whom this mod would not have happened:
Jon_M3
James @ Beemer Redeemer
DTMDan
Turbo-Brown
Finally, here's some of the piccies I managed to take during the install:
M52 clutch / pressure plate / flywheel (fitted):
M20 clutch / pressure plate / flywheel (fitted):
M20 flyhweel (fitted):
M20 flyhweel (on right) vs. M52 flywheel :
M20 flyhweel (on right) vs. M52 flywheel :
M20 flyhweel (on right) vs. M52 flywheel :
M20 starter fitment:
M52 starter fitment:
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