Printable Version of Topic

Posted by: RonnieJ Dec 21 2010, 05:54 PM

My 1.8 is being rebuilt to 2056 and my mechanic ask me today if I want the fly wheel lightened. I got a couple different answers on the club site and thought I would ask on the world site to help me make this decision. I just use the car on the street.

Posted by: SirAndy Dec 21 2010, 05:59 PM

There's your answer. For a street car, i wouldn't do it.

A lightened flywheel will increase your throttle response, both on and off throttle. The car will much less "coast" when letting off the gas but rather the rpm will drop much more quickly.
For a daily driver / street car, overall drive-ability will suffer with a lightened flywheel.

However, you should probably have it resurfaced, while you're in there ...

Posted by: r_towle Dec 21 2010, 06:14 PM

idle will suffer and require you to keep feathering the throttle.
Mileage will suffer due to less rotating mass.

In an autox car, its great...
Drivability does suffer...and its a PITA to take everything out to replace it...
Rich

Posted by: RonnieJ Dec 21 2010, 06:33 PM

Thanks, I'll tell him no thanks.

Posted by: Matt Romanowski Dec 21 2010, 09:59 PM

I'd disagree with Andy and Rich. You can take some weight off with minimal effect and still have it completely driveable. A couple of pounds won't make it a monster that is un usuable.

Posted by: SirAndy Dec 21 2010, 10:06 PM

Where did i say that?

It's a bit of a stretch to go from "For a daily driver / street car, overall drive-ability will suffer with a lightened flywheel." to "a monster that is un usuable", don't you think?

Posted by: Jake Raby Dec 21 2010, 10:06 PM

But the real question is, will this engine be dynamically re-balanced after the material is removed from the wlywheel? Is the engine being dynamically balanced at all?

A couple of pounds can be removed without compromise, but if not done properly it can be detrimental.. Many lightened flywheels end up eliptical due to being improperly "zeroed" when being chucked up in the lathe... Can't balance something thats the shape of an egg.

Posted by: r_towle Dec 21 2010, 11:02 PM

must be a pretty scary thing for a trained machinist to start up a lathe with a flywheel that is not centered...

I have several flywheels of different weights...all for 914's
I have a couple that are super light...
by far the most streetable is the heavy one...the car idles perfectly and it runs smooth and easy on the highway.

Rich

Posted by: Drums66 Dec 22 2010, 01:27 PM

...I did it!!(only street)I'm sorry..I like it!

Posted by: brant Dec 22 2010, 02:20 PM

I loved my lightened flywheel on a street car
made it fun to rev/drive

I'm installing another one in 2 weeks on the current project.

Posted by: Jake Raby Dec 22 2010, 02:31 PM

Even .003 out of index is enough to create imbalance issues.

The only way to dial in these flywheels is in a 4 jaw chuck with a dial indicator, on the main seal surface of the flywheel. A 3 jaw chuck, generally doesn't cut it.

Posted by: Matt Romanowski Dec 22 2010, 03:53 PM

Rich - On a four jaw chuck, it's not hard to be out a couple of thousandths and it's not scarry until you realize you junked a part.

Posted by: Al Meredith Dec 22 2010, 08:19 PM

On my 912E 2056 I lightened the flywheel a little (maybe 3 lbs) and I can't tell a difference. Jake's shop balanced everything as a complete unit.

Posted by: Jeffs9146 Dec 22 2010, 08:30 PM

I had one that had 3.5 lbs removed and it was much more spunky to drive! I enjoyed bliping the throtle a bit when starting from a dead stop!

Posted by: Joe Sharp Dec 22 2010, 08:56 PM

Posted by: bam914 Dec 22 2010, 09:03 PM

The one on your 912e is about 12# and the one on your 914 is 15#. I liked the 11# one I ran on my 914 for years. But everyone has a different opinion.

Posted by: JimN73 Dec 22 2010, 11:24 PM

Mine is lightened to 12 lbs, I like it on the street. Idles fine, I tend to 'blip' the accelerator when stopped because I like the way it revs up.

Posted by: palmer_md Dec 22 2010, 11:39 PM

Funny this topic showed up today. I am in the middle of pulling everything and lightening the flywheel is on the list of things to change about the car.

Does anybody have a recommendation for where to take the flywheel and assembly to have the flywheel lightened and then rebalanced as a unit? I live in northern California.

Posted by: JimN73 Dec 22 2010, 11:54 PM

I used a company in Livermore called Top of the Hill Performance Center. Recommended by Rich at High Performance House in Redwood City. It's a fun place to visit, they do Nascar and sprint car engines as well as big V-8s and Ferrari and exotic rebuilds.

I know there are other shops in other areas that do a good job, but I have a personality defect. I like to see what's going on, I like to look at the parts when the machinist is looking and I like to have things explained to me when I'm looking at them. they called me several times to look at and talk about what was going on.

They don't dp as much Porsche stuff as they used to, but Doug (the Porsche Guy) knows the engines. Nothing escapes his scrutiny. I bought heads from Jake, Doug insisted on checking them to make sure they were as advertised. Balanced from fan to clutch at a reasonable cost.

If it's not too far to go, you should give them a call. I'd go back again.