FRporscheman

If the factory saw necessary to equip the 3.0L engines with either the S2 damper or the 968 DMFW, how are all you 3.0L turbo guys doing? What kind of flywheels do you run, what kind of engine balancing did you do, and how is everything running? Any vibrations at certains rpms, etc?

Do you think it would be better for a 3.0L turbo engine with a 951 flywheel setup to have a lightened crank, or would that make things worse?

333pg333

Interesting question. There was a bit of a discussion on this recently and Chris Prack more or less said that when we get our cranks lightened aftermarket, we run the risk of the whole thing being way out of balance. So when I got a lightened stock fly, knife crank, Arrow rods, different pistons, different clutch etc what chance the whole thing holding together? Can't say conclusively as it didn't go for very long each time but it's all going back in the next few weeks so I guess I'll find out.
You start to get the sense that a lot of us buy mods and slap them on thinking we're improving things when we may not be???

JET951

as far as why porsche used dampening devices was because these engines create a lot of vibration due to being such large 4 cylinders, the larger the capacity of the 4 cylinder the worse the vibration will get, when these were applied directly to the gearbox it creates what sounds like extreme layshaft chatter. to counter this porsche used either the damper on the early cars and the DMF on the 968.

thingo

I'm going to use a steel lightweight flywheel in mine, similar to the ninemeister, standard crank.

George D

There is nothing wrong with removing material (lightening) a crank as long as you balance everything prior to install. I am using a lightened crank, not knife edged, and a steel lightened factory 951 flywheel. The pistons are forged (Ross Racing) and the rods are forged by Oliver.

This does not necessarily create more hp, but it does allow the tq to come on earlier and the motor becomes more rev happy. If you are using a MAF sensor close to the intake and you lift quickly, the motor may be prone to stall as there is not as much mass to slow the deceleration. This is just my observation and talking with folks and their experience with these particular large 4 pot motors.

Here is a pic of my crank after machine work.

nick_968

I am still using the DMF on mine until someone comes up with a solution that is not compromised!

RajDatta

Nick, a 951 setup with an S2 vibration dampner is how the factory did it as well, so that would not be a compromise.
Do remember, all parts are stock weight though.
Raj

JET951

also remember the less reciprocating mass the less torque the engine will have. and torque is pulling power

333pg333

So assuming that someone has got all these new components, how do you then balance them? Also won't the balance shafts be out of whack as well due to these changes? Hahah hope I'm not driving around in a 3.0ltr tractor later this month.

nick_968

Raj

I opted out of the original plan to use the 951 setup as I did not want to lose the 968 fast clutch change and have to change out my 968 bellhousing. I am not having any probs with the DMF so far.

FRporscheman

LOL, yeah, I was thinking that there are lots of ideas going around that sound really great in theory and work well for other cars, like lightening the rotating mass, but I was wondering how it all plays out when applied to these unusual motors. I'm planning on building my 968 motor into a 8v turbo this summer, doing all the work myself, so I'm trying to figure out details like what flywheel stuff to use, etc.

333pg333

Yeah, I just don't get how you could balance all these parts without putting the engine all back together and checking everything, then adding or subtracting weights somewhere. Also with all the various components having an effect it's not like you're only trying to balance what you guys call a 'teeter totter' (I think?), there's all sorts of stuff moving around so how the hell can you balance it all???

RajDatta

Nick, I am sure your setup is working well. It will be interesting to see what the threshold for the DMF is. There is always a lot of debate on how much power these units can handle. My car had a DMF setup as well when I bought it. They modified the DMF and installed the appropriate triggers to make it work with a 951 harness.

Raj

sawood12

You can also counteract the effects of a light flywheel by clever standalone EMS programming. I read a report in the Porsche Post last year from a chap who swapped out his DMF on his 964 with a lightened single mass one. He had problems with it stalling and generally being tricky at low RPM. He then got a Motec upgrade by Ninemeister who then programmed the EMS to solve the problem. He now reckons the car is as civilised to drive as it was before with the benefit of a more responsive engine due to the lightened flywheel. Not a cheap solution I know, but useful if you've already got EMS.

333pg333

Yep, good point Scott although that's not really dealing with the balance of the engine, more masking it with programming.