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Summary
Summary
Replace stock flywheel and clutch with high-performance components.
Start Date: July 14, 2012
Odometer: 309,000 km
Total cost: $1003.35
While replacing my transmission recently I decided to try improving my acceleration and shift speed by installing a lightweight flywheel. To replace the flywheel and clutch, the transmission must be removed, so replacing the flywheel and clutch during transmission replacement yields significant labour savings. I chose UUC's "Stage 2" flywheel/clutch kit for E36 engines, which fits my M50 motor and matching Getrag 250 transmission. Note, however, that the E36 kit does not fit M50 engines with E30 318is Getrag 240 transmissions.
Parts
Journal
Journal
I found a used UUC flywheel kit for sale on the maXbimmer forums for $850. It was described as "brand new" but upon arrival it clearly was not. The flywheel was covered in heat spots typically caused by high rev burnouts and "popping" the clutch.
The flywheel had obviously been installed and abused, but seller claimed that it had been used only very lightly for under 500km. Unfortunately, I had the transmission out waiting for the not-so-"brand new" flywheel. I decided to take the risk and install the flywheel anyway. I next discovered that the seller had not included the gall plate (spacer) and reusable crank bolts that originally came with the kit. Shipping the new plate and new bolts overnight express from UUC cost me over $200. Lesson learned: when dealing with clutches and brakes, buy new parts. Used parts from unknown sources aren't worth the hassle.
Here are the bolts and the gall plate. The flywheel-to-engine bolt torque spec is 77 ft lbs (use red loctite on bolts). Clutch-to-flywheel bolt torque spec is 25 ft lbs (no loctite). Note that the flywheel bolts from UUC are reusable, but the BMW original bolts are not.
The used flywheel kit:
The used components were not the only parts with problems. Due to a manufacturing defect, BMW's pilot bearing also did not quite fit on the transmission's input shaft, so I was forced to re-use the used pilot bearing. Another lesson learned: always plan a few buffer days for installation or parts issues.
The Result
The Result
In the end, abused as it may be, I really love the flywheel. The acceleration is noticeably peppier and shifting gears is lightning fast. It's a great upgrade for track use. Matching revs feels more precise and efficient, which makes heel-toe shifting more fluid. But this upgrade is definitely not recommended for street cars. Most daily drivers would not appreciate the rev matching that is required for nearly every shift due to the speed with which the engine's RPM decreases (a drop from 4000 to 600 idle speed takes about a second).
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