Jamie_GT3

The .1 damper diameter is the same as the stock pulley diameter where the belt goes, the issue was the ATI damper had a large shoulder that interfered with the water pump housing on the .2. No need for a longer belt with the existing piece, it fits fine on all the .1 cars we've put it on including, PJS, John Chan, RSRanger, and my own. The .2 damper will have the same pulley diameter as stock, not over or under driving...

Understood about not wanting to add weight to a system, but it truly is a small percentage of additional gain. The total system even with a LWFW, clutch and clutch pack including the crank rods and pistons comes in around 60-70lbs, the 6 we're adding, is less than 10%.

As I've said before, I'm not trying to push these on people, just offering a solution if they so desire. My 4.2L would not survive street driving without it and many 3.8L/4.0L and aftermarket 4.0L and 4.2L engines can show what happens when they don't have either a DMFW acting as a damper or a harmonic damper installed.

We're pushing engineering as fast as we can for a low volume specialty part. We have a meeting again next week to push...

Chris from Cali

Don't you have some 30-yr old Macallan to drink?

John Chan

Machine shop lighten flywheel by taking material out from the outer area of the circle to reduce Inertia. Weight is one factor and distant to center of the circle is another factor for inertia. This damper has low inertia even it is at 6lb. This damper diameter is very small compare to the flywheel.
Do I count on Porsche to take care of their design flaw, I would not! Coolant fittings and LSD are good example. For the cup car engine, it is for high rev use and life goes by hrs, not much info can share with our street engine.
Bolts backing out can be fixed by locktie, but my worry is cracking the Al block in long. I just
Want to keep this car for long. Cheap insurance after seeing so many failed case, are u still believing in Porsche engineering?
By honest, every car has its own issue. If most of the design are perfect, many aftermarket will need to close down.

Ur20v

I will soon be one of those with this damper fitted and will provide independent VA findings to the group. (Thanks Jamie)

Has anyone lightened the stock DMFW, combined with this damper those running big bore, tuned engines might find additional benefit and still be below the reciprocal mass of OEM.

RedRSA

Thank you for the clarification regarding physical pulley diameter, Jamie; good to know that it will both fit and retain the stock drive surface diameter.

Regarding your stance on the concept/product, I applaud your efforts to identify a potential root cause of increased failures in the RS vice the GT3, and your work with ATI to develop a solution. I care about the longevity of my engine and need to increase my understanding - and that of my expert engine builder - before I introduce reliability issues by converting to a single mass 4.0 setup. And I obviously cannot install a corrective dampener that is still in development.

Determining what is real/factual is not easy. No one would deny that the 3.8RS and 4.0RS have experienced more reliability problems than the GT3 with the primary difference in parts being the SMFW. Isolating the root cause is difficult, because significant contributing factors such as over-revs are typically not disclosed. Increased vibration is certainly a plausible explanation for fasteners coming loose, as reducing NVH is the primary reason for installing the DMFW in the first place.

Personally, while official communications from Porsche certainly have merit, I think the Porsche bulletin disapproving the installation of the RS SMFW in the GT3 is based on expense managment and CYA, and citing that the GT3 engine was not designed to handle the SMFW seems like a stretch. There is very little known difference between the design of the GT3 and the RS. And while a different animal, GT3 Cup engines have been using the SMFW for many years with few adverse consequences.

So what is the key difference? Previous posters addressed the balance specifications. My engine builder is very experienced and builds 20-25 GT3 engines a year (mostly Cup, some street) and has seen no issues resulting from the SMFW. He does point out that his balance tolerances are significantly tighter, about 10% of the Porsche street spec.

This is becoming time critical for me. My engine will be out and new parts will need to be ordered within the next week. And there is only one opportunity to balance the whole system.

Jamie_GT3

What we've seen in our builds is that as the stroke increases the harmonic gets worse. Also as the rpm's increase the harmonic gets smaller. Cup engines don't typically have a problem as they spend most all of their life above 5k rpm and what we have is a low/mid RPM harmonic. Think highway speeds.

If your GT3 is predominantly a track car, then you have less to worry about. If your car is a weekend cruise the blvd/hwy then it's something to consider.

For now you may want to stay on the safe side and do the stock DMFW as we've seen few failures for flywheel bolts or cam bolts on the 3.8 GT3 with DMFW.

All of this is anecdotal statistics coupled with ours and our engine builders experience building 4.0/4.2L engines....

YMMV, good luck on your project!

RedRSA

My car is primarily driven on track and at higher RPMs, so there is less concern than at cruising speeds. That said, there are miles to the shop, etc., where I am at or passing through those ranges, and as low as 4k RPM on track when carrying higher gears through corners, though I try to stay above 4,500 RPM whenever possible.

I will need to decide in the next few days and will continue to collect qualified data until then. As you say, the conservative approach would be to stick with the stock DMFW. However, this will be my only chance to have the rotational mass finely balanced so I may not want to pass up that opportunity with the LWFW setup. Technically, if going this approach I could install the dampener later, after the product is finalized and proven on the 997.2.

mdrums

Hey Bob...can you comment on this further please. I'm might be mistaken but I read so,we here...can't friggin remember....that Porsche engines need the heavy factory fly wheel for the lower rpm street use and that higher end rpm track use the engine harmonics are better and the LWFW can be used without issue.

Makes sense in my brain but I know you have way more years on this than me.

Hope to see you soon

betonred

take a read of this too -

http://flat6innovations.com/index.php/broken-crank

Guest89

Flat 6 is a great shop, but Jake specializes in M96/7 engines, NOT the Mezger engines under discussion here...

Guest89

Since the advent of the DMF with the 964, Porsche has never installed a LWFW on a street version of any engine except the split case cars, AFAIK...

drbooba1

If the flywheel became loose with the fasteners perhaps the wrong bolt was used there are 2 lengths of 10 x 1.25 bolts one is longer than the other and will bottom out in the hole so close to the flywheel you will think it is tight that bolt came from a 928 the earlier 930 short bolt should be the fastener for the thin steel
RS style flywheel.

Regards

DRPM

So the stock 4.0 FW is not LW?

utkinpol

it is harmonic vibrations from an unbalanced crankshaft that is in the discussion here. not m9x, mezger, or in fact _any_ motor of any kind.

dual mass heavy flywheel is a band aid that is used to reduce effects from those vibrations as it takes skilled labor and effort to balance motor properly. any motor.

google any reputable racing shop for words 'engine balancing'. you guys just think you can bolt on any crap to your motor and it will live. well, may be it was so with old 993 and 968 cars as they were assembled with racing apps methodology, but now you got as much attention to details from Porsche as goes to an average Honda civic. Actually, I think it is way less attention, in fact, that civic motor gets, as most Japanese factories somehow got motor assembly quality issues under quite well control.

Marine Blue

I remember back in the day when balancing and blueprinting an engine was a way to increase horsepower. It makes sense since the engine could be safely run closer to its limits. Sounds like Porsche has taken a shortcut with the GT cars and not gone through the proper balancing. So instead of a damper shouldn't the real solution be to have the engine disassembled and properly balanced? I recognize the cost would be far more significant but I would also think the results would be better and engine life would be extended dramatically.