Flywheels and IMS Bearing
 

My 2003 Boxster is in need of a clutch replacement. The mechanic I contacted suggested the possibility pf replacing the stock dual-mass flywheel with a slightly less expensive single-mass that also provides a small performance enhancement- so I am wondering about the possible downside of making what appears to be a no-brainer switch.

He also brought up the possibility of replacing the IMS bearing with a retro fit kit from LN Engineering. Seeking opinions from anyone familiar with that.

I would replace the IMS if you have not already done so. It is a wear component and worth replacing if you are going to replace the clutch. I would not do the single mass flywheel unless you know how to drive with one. Single mass flywheels are unforgiving to shifting errors exposing your engine and transmission to extra strain.

Thank you for that insight. My wife, the primary Boxster driver is not the world's greatest manual shift operator so the dual flywheel may be the best in the long run.

As for the IMS bearing...I see that Pelican offers a Renline kit that is about 1/3 the cost of the LN one...any thoughts on that?

You just opened up a can of worms. Haha

First, have you owned the car since it was new? If not, check your engine's serial number. If it has the letters "AT" in it, the engine has been replaced and it MAY be an M97 engine with a non-serviceable IMSB which would make your IMSB question moot.

Second, I think the Rennline bearing is a fine bearing with a service interval of 30K miles. I believe it's Japanese-made. The LN bearing is a ceramic hybrid, has a warranty of 2 years/24K miles, and the website says the service interval is 6 years/75K miles whichever comes first. The choice is yours, but I opted for the Rennline. Unfortunately (or fortunately), I have an "AT" engine with the oversized bearing.

I went through the exact same process on my 2003 Boxster a couple of years ago. You are looking for peace of mind - spend a couple of extra bucks on the LN bearing.

As far as flywheels go, smart guys like Jake Raby say to stay away from single mass flywheels. The M96 engine has no external harmonic dampener - that is what the dual mass flywheel does. You would be putting your crankshaft at risk.

If you do decide to put a single mass, you need to get it balanced as they are out of balance by 8 grams out of the box. You'll need someone with a stock crank and dynamic balancer to spin it along with the clutch and pressure plate.

I would also advise installing a dampening crank pulley and sprung clutch disc.

We always recommend retaining the dual mass flywheel.