Opinions on "RSR" light weight flywheels?

[bigrubberjeep]

What are your coments on doing such a mod on a 3.2 Motronic?

Do you have it in your car?

Pro's and Con's?

[klaucke]

As with any lightweight flywheel, slightly faster acceleration, it will probably feel peppier or snappier, and also, easier to stall, not as smooth on take off from a stop. In theory, more engine braking on deceleration (could be a pro or con).

[randywebb]

"Any flywheel less than 12lbs is likely to cause idling problems and possibly stall the car." - from BMW site, probably re computer sensor issues

This will affect the Porsche DME system also - Andial will warn you if you talk to them - talk to Pete Sanchez.
There will be a wt. that is ok to use with Motronic, whether that wt. is < or is = to stock, I dunno.

Try getting a light PP - tho I hear they sometimes warp.

[bigrubberjeep]

I figure I should ask before the tranny get's mounted to the motor

[Bill Verburg]

It's not like the stock one ois really heavy on the 964/993 stock weighs close to 50#, you can easily save 35#s on them. but only a few on an SC/Carrera. DO replace the clutch w/ a spring loaded version rather than the stock rubber variety.

[geof33]

Go light clutch package... leave the FW alone. There are reports of failure issues with some of the aluminum plates... Performance has stopped selling them, and advises against it, especially in hi perf race motors...

[pjv911]

Here is picture of an authentic RSR lightweight wheel . Notice that its a 6 bolt and not a 9 bolt thats needed for 3.0 and up .


Kurt Williams

[bigrubberjeep]

Originally posted by pjv911
Here is picture of an authentic RSR lightweight wheel . Notice that its a 6 bolt and not a 9 bolt thats needed for 3.0 and up .


Kurt Williams

I would use the 9 bolt version

[pjv911]

Opps . Forgot the picture . Here we go .





Kurt Williams

[Carrera3.5L]

Originally posted by randywebb
"Any flywheel less than 12lbs is likely to cause idling problems and possibly stall the car." - from BMW site, probably re computer sensor issues

Hi Randy,

I'm not sure quoting a different car make would be accurate and apply in every situation. For example, we manufacture 10 lb. billet steel flywheels used for VW 1.8T and VR6 motors combined with a Sachs clutch that removes the heavy dual mass OEM set-ups. There are ZERO stalling issues, most of the stalling problems in late model VW applications that I have seen over the years are the ultra lightweight aluminum flywheels that weigh in the 5-6 lb. range.

To get back on topic: George, I'm not sure I would bother, IMO the money could be better spent elsewhere.

Ralph

[randywebb]

I agree - they both use Motronic tho. But it was the only datum I had to post.

[KTL]

Like Bill V said, there's not much weight to be lost on the flywheel by going with a whole (no material removed from the circular shape) lightweight one. The original flywheel is already relatively light compared to later model 'wheels. The type that Kurt posted is the next step. Obviously any amount of rotating mass is going to make a difference. It's just that there's more savings to be had by going with a lightweight pressure plate/clutch housing. It's good to know that the alum. housings have had some problems. Add that to the brain bank.

Anybody tried Spec clutch kits? They seem to have a pretty good following with other makes, like BMW.

http://www.specclutch.com/specMain.html

[bigrubberjeep]

Thank's to all of you for the imput, I was just thinking back to when someone mentioned the loss of HP at the wheels due to the drivetrain, I've heard up to 15% loss, so I figured if I could minimize that to maybe 10% by using lighter parts it would equal to adding maybe 10hp (the 5% savings from th eweight loss) to the wheels being that I am porbably close to 200hp stock (maybe more, but I wont "QUOTE" it)

Does that not actually hapen in a light fly wheel/lightweight pressure plate/clutch housing COMBO? I was not sure aobut the first but the later was definetly in my plans.

[ChrisBennet]

I'm just guessing here because I've never weighed them but it wouldn't surprise me if the pressure plate is heavier and has a greater rotational enertia than the flywheel . I'd look at a time proven Sachs aluminum pressure plate before I'd look at a "trick" flywheel.
-Chris

[911-32]

Coincidentally, I have just been talking to Patrick MS about the same thing for my G50 3.2. On the G50s the OE flywheel is only 9.5lbs. They offer a lighter flywheel but have not quoted how much lighter. Looking at the picture they sent, it doesn't look like they remove much material. They suggest that if I want lightweight, then they have a 12.5lb Aluminium Pressure Plate for use with the spring centred 930 clutch. This is considered a "race" package in their opinion. For club race/track day they recommend the Centerforce clutch kit which is Sachs components modified for increased clamp load and strength. They have a centre weight system that increases clampload at higher rpm. As Sachs discontinued the aluminium covers they have to use a steel P-P however Patrick advise that it is lighter than the OE P-P and rubber hub style disc arrangement.

I know this is G50 info, but I hope its of some use.

Cheers,
Richard

[KTL]

The only reason I mentioned Spec is because they're one of the few manufacturers that I can recall who's stuff is manufactured for higher clamp loads with matched components. It's not modified stock stuff, pieced together with other brands of components. Not saying there's anything wrong with Patrick MS's setup. Just pointing out that there's complete matched kits that accomplish the same thing for probably less $?

And I wholeheartedly agree that without question, the place to save weight on a G50 is the pressure plate, not the flywheel. I think the factory 3.2 G50 pressure plate is made out of lead? It's extremely heavy!

Back on topic..... Good thing about 915 trans. is the wider selection of clutch components. G50 doesn't have nearly the variety.

[Bill Verburg]

The differnce in percieved hp gained from loss of rotating weight will depend on the gear you are in
check this out

[randywebb]

Yes, percieved is the key point.

The lighter wt. components will not affect the power delivery to the rear wheels - except in a transient -- i.e. for a few seconds.

To really solve the power loss issue you would have to re-engineer the drivetrain for lower frictional losses, different gear cuts, yada yada....

[Randy W]

I have a factory '73 RSR flywheel like the one Kurt pictured. It is much lighter than the lightened 3.2L flywheel I have for sale in the classified section, but it is 6 bolt and does not have a DME sensor ring so will not work for Motronic cars. Also a NOS RSR flywheel is not cheap (paid $500 for mine). It will work great for the 2.8L autocross race motor I am having built where all rotational mass is being minimized and most of the autocross course is run in 2nd gear.

[randywebb]

"all rotational mass is being minimized."

Ok - I wanna see that! Just don't tell me what the bill is, because just the thought might knock me senseless.

And what about recip. masses?