Aluminum flywheel?

[Bill Bayard]

I'm thinking of installing a Fidanza aluminum flywheel.

Does anybody know just how much of a difference

I'm likely to see? Big difference? Not worth the trouble?

Anybody currently running one?


Bill

 

[Paul Thompson 'Hooligan']

Hi Bill -

just looked and the 2.0 Probe flywheel as standard weighs about 23lbs (same as std. 3.0V6 GTD item?) whereas the Fidanza item weighs in at just 9lbs - quite a saving.

Especially as the the weight is spinning at engine rpm over quite a large diameter. I guess the most obvious difference is that the engine will spin up faster during acceleration, although there must be a downside too - hill starts perhaps?

If you fit one - let us know how you get on as I know several people over here interested.

 

[Ross Nicol]

I run an aluminium flywheel Bill,faster acceleration at the expense of a smooth idle although I don't notice I don't have a smooth idle.I do notice how quickly revs drop off though.I wouldn't bother in a road car but great for racing.
Ross

 

[Bill Bayard]

I certainly appreciate the input, guys! Thanks!


Bill

 

[Julian West]

I'm looking forward to experimenting with my flywheel/clutch setup. The flywheel/ring gear is made in one piece nitrided (sp?) steel, paired to a geared starter & a twin plate clutch.

Compared to a stock 302 assembly my flywheel/clutch is a massive 17kg lighter (~35 lbs) plus a few lbs saved with the starter motor.

I'll pay a price with a fierce clutch ! but aside from the overall weight saving, there has to be handling benefits due to the reduction in gyroscopic effect.

Anyone care to comment?

 

[Ian Clark]

Hi Bill,

Yours is one of those questions that bring all kinds of answers and each can be correct without being the same. Reminds me of the big brake questions. I just saw some dyno testing on a cable tv show where fitting big brakes cost 5hp even though the rotating mass was the same weight. Makes you think.

Seems to me that a lighter flywheel will produce quicker acceleration of the engine and drop off as well. As for idle quality, so long as your using a heavy vibration damper you should be fine. Lighter vibration dampers can reduce horespower according to a test I've read.

About drivability, thats more difficult to gauge as you want the car as pleasant to drive on the street, a track car well that's another ball game altogther. For a street car a heavier flywheel will make the engine somewhat less sensitive to throttle modulation and clutch take-up so it should be easier to drive.

Then the other side of my brain kicks in and says: yeah but if you had less rotating mass, torque reversals would be less severe so your shifts would be better with a light flywheel. See what I mean?

We've had satisfactory street performance and no problems on lapping days with the McLeod aluminum 157th Flywheel. It's lighter than stock but not 9lbs either.

So there you go, hope I given you some food for thought.

Cheers

 

[Keith]

Hey Bill, for what it's worth, I switched to a lightweight aluminum flywheel and an AP F1 style triple plate clutch for my SBC set up, with the clutch rated for 500-600hp. With the large reduction in reciprocating weight, throttle response was markedly improved and I found engine braking also much more efficient without the inertia effect of a heavy stock flywheel. I noticed no difference in idle or balance but I was running an internally balanced set up anyway. The triple plate was good for about 12 racing starts with that hp, but without doubt, it was the best flywheel/clutch combination I've ever driven. Don't know about the street, but I can't see anything but an improvement in driveability. Hope this assists...

 

[Dave Wharran]

Bill,
I'm running a McLeod 157 tooth aluminum flywheel. No problems with street driving, idling, or other.

Dave

 

[flatchat(Chris)]

Hey Bill, your billet steel flywheel is 11.9lbs (5.4kg)pending the counterweight offset (28oz/50oz)and 10.75" O/dia.The heavy bit is the Porsche clutch,pressure plate and ring gear housing/assy. I reckon its good as is --any lighter and you'd need a fair bit of "Welly" to get it launched at the lights without it stalling /ubbthreads/images/graemlins/tongue.gif JMHO /ubbthreads/images/graemlins/grin.gif
Good question though

 

[Russ Noble]

Bill, a lighter flywheel always makes for a much more responsive engine, snappier gearchanges and much more satisfying driving IMO. My experience is that it will only affect your idle if you have a fairly wild cam grind and you can live with that by simply raising the idle speed a little. With any not too radical road cam, idle should be fine.

Regards

 

[Bill Bayard]

Gents,

You guys have given me PLENTY of food for thought. Now to

chew on, and digest the results!

Ian,

OK, so which is the RIGHT, right answer? /ubbthreads/images/graemlins/wink.gif

Dave, Ross,

Are your engines internally or externally balanced?

Chris,

I'm very familiar with how heavy that PP is. /ubbthreads/images/graemlins/frown.gif If I do this, I'll go with the whole 9 yds in aluminum. (FW & PP)
Remembering how heavy that bugger was, the last time I replaced a clutch disc, is exactly what got me thinking!

Russ,

I would probably suffer a bit at idle, as my cam is a little over the top for the street already. I could always adjust the idle up a bit though..... As to the increase in acceleration, the engine comes on so quickly now, that I find the rev limiter on more occasions than I'd care to mention! /ubbthreads/images/graemlins/tongue.gif With an all aluminum setup, I'd have to set the shift light to blink 1000rpms early in order to hit the sweet spot! /ubbthreads/images/graemlins/wink.gif /ubbthreads/images/graemlins/grin.gif

I'll pose this question to some Porsche racing experts, before I make a decision either way. They'd have a good idea of what the result would be for my application. I'll post their thoughts on the subject.

Thanks to one and all, for your input!


Regards,


Bill

 

[Dave Wharran]

Bill,
Mine is externally balanced with a 28 oz steel counterbalance weight. McLeod makes the weight bolt in so you can remove it for an internally balanced engine.

You are correct about the rate of acceleration of the engine. I had to set up a shift LED about 200 rpm below redline (400 rpm below the rev limiter) to stay out of the rev limiter in 2nd gear. Tough to not touch the rev limiter even with the light.

Dave

 

[Trevor Booth]

Bill,
Another suggestion. If you are using a twin plate 7" clutch use a standard flywheel, macine OD down to the same OD as the clutch, machine the back and or front to lighten it then get the flywheel from an automatic (flex plate) c/w ring gear, machine the centre out of it, machine a spiggot on your cut down flywheel and bolt the bored out flex plate to it.
Works very well without the expense of an alum flywheel.
I will be making one in the next few weeks and will post some photos
Cheers

 

[Lukas Matzinger]

If anyone is interested in the Fidanza flywheels for a SBF with 157 tooth and 10.5 clutch, I found a great deal on them. THey include bolt one 28 and 50 oz weights and can be run neutral balance as well.

SDPC2000.com has them for $250. YOu must go to the actual product page to find the correct price. After a bit of a discussion I had Summit beat their price so I am paying $257 shipped. Everywhere else you will pay at least $370.

Hope this helps someone!

Lukas

 

[Russ Noble]

I can confirm that the flex plate + cut down flywheel option is an excellent solution. I have been running this setup behind a 4.9 Rover in my TR7V8 for 3 years now, no problems.
Regards

 

[Bill Bayard]

I have just receivd an e-mail from Steve Seigel, a Porsche
ALMS(American LeMans Series) team mechanic. Below are his thoughts on adding an aluminum flywheel to my engine.

"Do not change to aluminum. It is extremely difficult to get a car moving with light flywheels. City driving would become unbearable. You wouldn't gain any "compression braking", and the acceleration benefits are almost unmeasureable in such a light car."

Straight from the horse's mouth!

This is not to say that somebody with a larger/heavier flywheel couldn't do it and be happy with the result. The Fidanza G50 flywheel is only 5.5 lbs. That's pretty damn light, compared to say an aftermarket Ford aluminum flywheel.

Not in the cards for me, I guess!

What the hell was I thinking anyway?
My car scares me now! /ubbthreads/images/graemlins/shocked.gif /ubbthreads/images/graemlins/grin.gif


Bill

 

[wpeter]

I agree with Steve. DON'T DO IT. If you have ever seen a race car exiting the pits you see them racing the motor to get out. You may think it is because they have a very high gear, and some of it is the gear, but the amount of inertia in the flywheel is diminished considerably with very light flywheels and that will undoubtedly lead to continual stalling on the street.
Bill

 

[Dave Wharran]

I agree...to a point. My aluminum flywheel probably weighs in at 15 lbs or so. Not 5 lbs. It is also a 10 1/2" single plate clutch, not a 7 " or smaller multi plate unit.
My engine makes torque at reasonable rpms. It doesn't have to be screamed up to 4K to not stall when the clutch is engaged.
What I'm getting at is that my car with an aluminum flywheel is VERY street friendly. It doesn't have a racing engine with a racing cam. It doesn't have a small racing type clutch that is either engaged or not engauged. The clutch is very progressive and very smooth. It makes over 410 HP and 410 lb/ft, so it isn't that tame. It uses standard ZF gearing as was used in Pantera's with 160mph around 6K rpm. It pulls out smoothly either forward or reverse on hills, and clutch engagement is VERY progressive.

The package has to be looked at...as a package, and making a broad statement saying stay away from aluminum flywheels on the street doesn't tell the whole story.
I love mine.

Dave

 

[Ross Nicol]

Bill In answer to your question I have a 50oz externally balanced crank.I have the Mcleod aluminium flywheel with balance weight bolted to it.I drove the car on the road quite a bit when I first got it going and with the original single plate organic clutch plate it drove and Idled well.I have had to fit a scintered Iron plate for racing off the start line and if anything, it causes shudder and fierce revving around the pits.So in my opinion the clutch make more difference than the flywheel weight when it comes to street driving.I have a tall first gear 2.23 and combined with 3.2 final drive makes for a bit of revving to get away.My 2c worth is fit the alloy flywheel but don't go anywhere near one of these off /on clutches.The Porsche guy may not have factored in the fact that v8's have a lot more torque than a porsche (at low revs) It's a bugger when you get so many differences of opinion eh!
Ross

 

[Bill Bayard]

Steve is basing his judgment on his experience with Porsche racing clutches, flywheels, etc. The engines they are running do have considerable HP and torque. They may be 6's,
but they aren't exactly slouches!

The lack of size/weight of a Porsche aluminum flywheel, does put things into that "Do I really want to do this?" category. Not only is there a small rotating mass, but a small clutch surface. At a guess, I'd say my flywheel is only 12" in diameter. Clutch disc is 240mm.

I can easily believe that with a larger, heavier aluminum flywheel, a car can be very tractable for the street, but in this case, the potential gain isn't worth the risk. My engine hits the rev limiter fast enough for me anyway.

It'd be a bit embarassing to stall out at every other green light, as Bill suggested might happen. I hate the smell of a smoking clutch, not to mention the fun of replacing one!

Ross,

As you said, there are a ton of opinions, all valued, but

each is based on a different car, engine, gearbox, and

flywheel/clutch combination.

Many thanks to all for your input!



Bill