Flywheel and clutch
 

Since there's nothing but crickets on lately I figure I'd post about something I've been contemplating recently.

I have do do the clutch soon, and I'm considering an aluminum flywheel which is about 1/2 the weight of the original and putting in a much stronger clutch, probably kevlar as I always liked the kevlar clutch in my 911. I'd obviously have the whole bloody mess balanced properly and I'd likely do all the bearings while I'm at it in the drive line.

Thoughts?

J

That's interesting. If you have half the weight of the original would that diminish initial torque? I have a stage 2 clutch in mine and if I'm not careful, it'll grab and kill the engine.

People have done this. Fidanza is one name. I *think* 034 has something. Typically not all aluminum because you still need a steel ring gear for the starter to engage into and the friction surface needs to be steel as well. One thing that some people had problem with was the manufacturers didn't pay enough attention to size and position of the crank position sensor pin that is on our stock flywheels. Without a good G4 crank position sender signal, the engine will never start.

I have an old TMTek aluminum flywheel with a Sachs 4 puck metallic clutch in my 20vt 90Q and as UrS4boy mentioned, i had some problems with the sensor pin. it ended up being an easy fix(longer 1/4" dowel) but until i figured that out the car would cut out at 3000rpm and go into limp mode.

But the car runs great now but there are definitly some cons to go along with the pros.

Pros:
-The flywheel allows the engine to rev very easily and the race clutch will never slip, its pretty much in or out.
-some people have claimed faster acceleration, but i'm not completely convinced since my urS4 with the steel dual mass FW seems just as fast. Its hard to compare since the 90Q is so much lighter.

Cons:
-its hard to drive, plain and simple. the clutch grabs hard and if i'm not paying attention i will stall the car. once you're past 1st gear you're fine though.
-i get a little gear noise from the tranny. Now i'm not sure that the aluminum flywheel is causing this but people have mentioned similar problems in the past and i don't remember the noise being present before the ALA FW.
-I could be wrong here, but i feel like the car doesn't coast as nicely as the urS4 with the heavy FW. the engine slows quickly when you let off the throttle which would make sense.

overall, i'm not convinced that the Aluminum flywheel is a good upgrade. at the time i just needed an urS4 flywheel/clutch of some sort for the engine swap since the original 3b FW wouldn't work with the 90Q transmission, so i bought it. But there have been many times where i considered just putting a steel Dual mass and urs4 clutch in instead. But again, most of my complaints are probably directed at the clutch more than the flywheel.

I put a SPEC clutch(i think one level above stock?) in the urS4 and with the stage I chip is seems fine and is much more enjoyable to drive than the race clutch in the 90Q.

Yes it sounds like the Fidanza flywheel with a kevlar non-racing clutch would be the best choice.

I'd like to motor to rev just a bit more freely, but I don't want to make the car un-driveable on the street.

So we ended up going with the Southbend Stage 3 daily clutch (good to about 425 ft/lbs of torque) and a single mass 12 lb. Aluminum flywheel with replaceable friction surface from EFI Express (Nice bit of kit and Marc is really great to work with).

The gear noise 60to0 mentioned is likely a result of the vibration not being absorbed by the dual mass flywheel and I would totally expect that.

The car does vibrate a little more at idle but the motor spins up MUCH faster.

Only problem is Southbend shipped the wrong clutch (they shipped the AAN rather than the 7A kit Marc ordered) and we found out only after reassembly (AND very expensive overnight Saturday delivery Fedex so the car would be done Sunday).

Now the whole mess needs to come back out and a new clutch/pressure plate needs to go in.. another 6 hours and the $200+ in FedEx turns out to have been a total waste.

I'll let you know how it drives with the correct parts installed.

FYI: South Bend has recently been having a LOT of problems shipping the correct clutch kit for AANs or modded AANs. Don't know what the issue is. One guy is onto his third clutch kit.

Yes, I had this exact issue.

Carl at EFI was great getting them to ship a new one. But I'm going to make sure Southbend checks the contents of the box before it ships today and I'm going to be having measurements taken before another 6 hours of labor goes down the tube. I'm also going to be talking to them about the labor charge I'm eating. I'm not at all happy with Southbend but at least they are Overnighting the correct one.

Since I have a lightweight single mass flywheel I'm using a 7A clutch for the Coupe Quatro, not the S4 AAN clutch that you'd use with the OEM DM flywheel.

Just as a follow up I'd thought I post and let everyone know how this clutch is since installing it.

There seems to be no issue holding the horsepower of the car. I'm using IE's Stage 3+ ecu upgrade and have done all the normal mods with the exception of the EM which will come soon enough. With the 2.2 WG spring and the updated sensor in the ECU we're making 26 lbs of boost at peak boost and I can't detect any slippage at all.

The engagement is very quick. With a stock clutch and flywheel you have a fair amount of pedal travel to feather the engagement. With the 12 lb flywheel and the new kevlar clutch and stronger pressure plate (to accommodate the increased HP), engagement happens in about 1 cm of pedal travel, so you need to be much more delicate with the pedal or you will stall the car as others have noted. Having spent years on the track with GP bikes and then many, many track days with the Porsche I'm pretty comfortable with this setup. Others who have driven the car note the heavier pedal and more abrupt engagement and have stalled the car more than once. I think this is a matter of driving experience and style. I have adapted to it and having driven another manual car now I found it's clutch soft and mushy by comparison.

The motor absolutely revs faster, especially on the bottom end between 2 and 4500.

In the end, if you're used to a heavier clutch with kevlar friction surfaces, ala the older 993 or earlier Porsche's, then you're going to be fine with this setup. There was a bit of chatter during engagement early on, but after a little more than 1500 miles this has all but disappeared and I hardly miss the dual mass flywheel.

A lighter weight aluminium dual mass flywheel would be a nice upgrade and I wonder if there is a way to get some of the weight out of the pressure plate as well. There's a ton of weight there and I can't help thinking that putting some back into a DM flywheel that's made of lighter materials and then shaving weight off the pressure plate would be a nice upgrade.

Marc at EFI supplied the new flywheel and it went in no problem (remember the new bolts as they are different). The sensor was not an issue with Marc's flywheel.

Hope this helps someone.

J