light weight flywheels

[Walko]

Hi All


I am hoping the collective wisdom may point me in the right direction regarding a lightweight flywheel.

Can anyone advise whether they are worth the additional expense.


Michael

[djbrand1]

I purchased my car with a light weight flywheel installed. The benefits are, the motor seems much more rev happy, and loves being run out. However, the negatives I see are the chattering at idle and the finesse needed to start out smoothly in first gear. Another side effect I've had pop up while the car is still warming up is that in between shifts sometimes the revs drop so quickly that the motor stalls. This happened to me after installing the Steve Wong chip, so maybe just an idle adjustment is needed, but doesn't happen all the time.

If you track your car, that is where I think you will see the benefit. Heel and toeing is much easier as only a quick stab of the go pedal is needed to match the revs. This is where the old school 915 transmission shows it's weakness though. It is a bit slow to shift to catch the "blips" between shifts. I imagine with the stock flywheel the engine would be a bit slower to rev down.

[JohnJL]

It can make the car more rev-happy but in many cases you'll need to do some software/tuning adjustments and/or adjust your driving style to avoid stalling the car when you get off the throttle. Especially in traffic, in stop-and-go or approaching a stop sign.

[tobluforu]

On my 72, I have zero issues with the fidanza and the car running, would I do it again, no as the install was a joke.

[Dueller]

Engine braking is reduced when decelerating....not necessarily a bad thing, but something you will adjust to quickly. Allows acceleration more quickly coming out off turns. That being said, if you are a casual or even slightly brisk driver probably not worth the expense as a bone stock 911 offers peformance level that far exceed the abilities of 99% of their owners. Myself included.

[Flieger]

Engine braking is increased with a reduction in inertia as from a lightweight flywheel.

[kwikt 911]

Didn't notice much diff between the stocker and the Fidanza. The original is already light. The car is a 72 911. Maybe in a newer car it makes a difference. Now in my 968 I went from 30lbs. to the 12lb fidanza flywheel and the difference was night and day. It actually brought the car to life........ along with some annoying rattling.

[Walko]

Thanks for the input.
Tobluforu what was the installation issue

Can anyone advise what the weight savings will be

The car is a 3.0Carrera which has the same crankshaft as a 2.7

Thanks
Michael

[Ronnie's.930]

I just typed in "light weight flywheel" into the search engine for this forum and saw many threads on the subject (including failures) on just the first two pages . . .

[don gilbert]

what you need is this PMS forged steel one..100.00 bucks. never been installed.

[Mahler9th]

The Fidanza has gone up in price through the years, and in at least some applications you have to slightly modify the case for clearance. More recently, my friend and engine builder has seen failures of the Fidanza.

I have a lightened stock 915 flywheel for my race car application and for a number of seasons had a Fidanza on my list. No longer.

Patrick Motorsports is what I might get if I decide I need to have something. More likely I will have a little more material carefully taken off of my stock unit by one of the experienced Porsche machinists that I know. The difference in MOI between a slightly lighter version of my already lightened factory unit and a Patrick is measurable I am sure, but perhaps not worth multiple hundreds of dollars in delta cost.

I have a full WEVO racing clutch kit sitting in my shop (borrowed from a friend), so if I really want light, I can give that a try. It is a nice kit, but not for the faint of heart on the street.

For any "mostly" street car, I would just have a competent machinist familiar with Porsches remove a little material. We have tons of those folks around here in NorCal. Two of my favorites are Ted at German precision and Mike at Pacific Performance Motorsports.

[Fishcop]

Walko

I'm very happy with this - Welcome to Windrush Evolutions - WEVO - Porsche Products The Streetlite, not the racing version Mike's mentioning above.

Fleiger, you have LESS engine braking with LESS enertial rotating mass.

[kwikt 911]

Just weighed my stock 72 flywheel. A whopping 8.5lbs. maybe that's why I can't feel any diff with the Fidanza(I think 5lbs)

[proffighter]

Originally Posted by Fishcop

Walko

I'm very happy with this - Welcome to Windrush Evolutions - WEVO - Porsche Products The Streetlite, not the racing version Mike's mentioning above.

Fleiger, you have LESS engine braking with LESS enertial rotating mass.

WRONG!!! Less mass let decreasing the rpm's faster. Have you ever run a motorcycle like a GSX-R? High CR and low mass = quick response in both directions.

To double my statement: I replaced my stock clutch with a Fidanza aluminum flywheel and a KEP alu PP, what a difference! Engine breaking increased very noticeable

[Fishcop]

Happy to be wrong. Have owned several R1s and 851s in the past. But the 13:1+ CR of a bike engine is a bit different to an 8.5:1 CR of an old 911.

I did notice some increased "rev-ability" on my engine with a lightened flywheel. I did not notice any better engine braking... But then again I don't particularly like using engine braking in routine driving. Brake pads are cheaper than engine builds

[tobluforu]

Walko, If I knew before hand that I would have to file down the case then I would not have bought a fidanza.

[ruwoodbury]

I just purchased the lightweight pressure plate and flywheel from Patrick Motorsports that will be installed in a couple weeks. It reduces the total clutch assembly weight from 40.65 lbs down to 24.4 lbs. Looking forward (with some trepidation) to the result. I'll report in May.

[KTL]

Have to be careful with the "aluminum" flywheels when used with a high clamp force clutch like Kennedy for instance. The massive leverage of the clutch can flex the flywheel. Like this




And that flywheel pictured above is NOT aluminum.......

The later models from 84-up benefit most from the clutch/flywheel upgrade. The 915 clutch assembly is already not too heavy. So it's hard to lose a lot of weight from it. That's why most of the guys with the older cars say they didn't really notice a benefit.

But the clutches on the later cars are MUCH heavier. So there's some weight to be lost in both the flywheel and the clutch. However there's a reason Porsche made the clutch & flywheel heavier- it makes shifting a bit easier (to catch the revs at the right point) and dampens noise. Noise reduction is the primary goal with the dual mass flywheels.

[Grady Clay]

The fun (and easy) bit about lightweight flywheels and clutch is you can try and change.
R&R engine and trans is easy.

Up front, Pelican djbrand1 nailed it.
Different weight (rotational inertia) for different use.
Porsche had it ‘right’.

Starting with ’70-’71, Porsche uses a very light weight aluminum clutch and a reasonably minimal flywheel.
The 911 was lightweight.
This continued through the ‘70s with the clutch becoming heavier with CIS mild cams.
With the 911SC, the clutch was almost all iron and the flywheel had extra mass around the peripheral.
This works well for street (and mild CIS) use.

Yes, if you are willing to be careful (not abusing, slipping the clutch) taking off from a stop a mid-year, 3.0 911SC and 3.2 Carrera can be fun with a lighter clutch-flywheel assembly.
You must pay attention.
Everything must be in perfect working order or you will be using ‘clutch slip’ to compensate for imperfect running and clutch operation.

Also in this equation is the weight of the car.
I’m perfectly (well, almost) happy with probably stock clutch and flywheel on my 3.2 (MaxM) SC for 100% street use.
My 2.8S MFI with a 906 flywheel and lightweight ‘69S clutch is still acceptable in the sub-2000# 914-6.
It depends on your intended use.


We are very fortunate to have an incredibly wide range of choices for our Porsches.
We have some of the best race products possible available to use.
We also have the pieces that Porsche engineers decided were a good ‘engineering compromise’ for our street 911.
We all get to make choices.
Deviating from Porsche’s ‘street compromise’ requires trade-offs in drivability.
It depends on your intended use.

The extremes are very mild cams; large displacement; large number of cylinders – 4,6,8,12; appropriate FI (CIS, DME); and large rotational mass.
This makes for easy street (town) drivability.

The other extreme Porsche has tested with racing.
Wild cams, required displacement limit, ‘production’ number of cylinders (well 908 & 917 excepted), MFI and light weight (Titanium, Magnesium and Aluminum) everywhere remotely possible.
Even the hardware was lightweight.


Super lightweight makes for great racewinning cars.
Appropriate heavier components make for great streetable cars.
It depends on your intended use.
There are your own personal compromises in between.
Your choice.
Try it. If you don't like it, change it. But ... make an informed choice.

Best,
Grady

[Flieger]

Engine braking is due to engine friction and the work being done to compress the incoming air which is not being regained by combusting fuel when off throttle. This is a certain amount of braking torque which works to decelerate the car. If you remove inertia from the car then there is less kinetic energy to remove and a certain force will slow the car or the engine quicker.