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YOUR RESEARCHIs LWFW safe after LN Bearing retro fit?
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Use extensively as a track car
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A LWFW is a good mod to employ in an engine that is used extensively as a track car.
Leading evidence: 'Use extensively as a track car' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Check tool' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Suggestion
The factory RMS checking tool that the dealer uses measures the out of round condition of the crank to the case.
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Suggestion
As the out of balance is a buckling that starts at the crank pin connection on the crank, so when you use a LWFW despite the fact that your car feels like a race car always observe the manufactures RPM limit and don't overspeed the motor.
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Suggestion
I'm not sure a race team using a LWFW is a very convincing argument for street use.
Use measures the out of round condition of the crank
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Suggestion
The factory RMS checking tool that the dealer uses measures the out of round condition of the crank to the case.
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Suggestion
As the out of balance is a buckling that starts at the crank pin connection on the crank, so when you use a LWFW despite the fact that your car feels like a race car always observe the manufactures RPM limit and don't overspeed the motor.
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Suggestion
If you are worried about vibration issue, talk to Randy Aasco (the manufacturer) about it...he will tell you about all the race teams that use their product.
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New controversial topic:
There were threads mentioned that installing LWFW, compared to the dual mass OEM, would upset the balance the M96 engine leading to failure. If a LN bearing was installed, because it makes sense as a while you are in there mod, would the LWFW be a safe mod?
The LWFW doesnt upset balance of the motor, it reduces harmonic dampening causing more vibration to be transmitted through the engine components.
If anything, you will be safer after the IMS bearing with a LWFW or factory dual mass.
I've read if a LWFW is installed it is wise to have the crank/FW assembly balanced together to prevent excessive vibration which could lead to early failure.
I love my LWFW. I highly recommend this mod for the guys that don't mind increasing the sporting nature of their car. If you are worried about vibration issue, talk to Randy Aasco (the manufacturer) about it...he will tell you about all the race teams that use their product. I read every post on the subject for over a year, before I made the plunge. The gear noise is not bad. You really only notice the increased noise with the windows down and the transmission in neutral.
I'm not sure a race team using a LWFW is a very convincing argument for street use. Most race teams are willing to trade performance for some longevity since they rebuild engines more frequently than the average street car owner would be comfortable with.
Failures associated with the LWFW install do not share the same failed parts as that of an IMS bearing.
The failure we have experienced with the LWFW has been crankshafts broken in half, in these engines the IMS bearing saw no failure at all.
Crankshaft failures that have occurred with the LWFW rarely occur in street cars, all but one of the failures I have examined came from full time track cars or DE cars that see a lot of track time.
In all fairness we have seen crankshaft breakage in engnes with the dual mass as well, and in the earlier models the dual mass has bent the crank enough for the ring gear to touch the inside of the bell housing. The factory RMS checking tool that the dealer uses measures the out of round condition of the crank to the case. As the out of balance is a buckling that starts at the crank pin connection on the crank, so when you use a LWFW despite the fact that your car feels like a race car always observe the manufactures RPM limit and don't overspeed the motor.
regards
WTF!!!
The crankshaft can break in half??
I swear, I will not be sleeping this year either!!!
(I know my car is NOT a track car, or LWF but holy sheeeet)
This is more of a heavy gas pedal, not a light weight flywheel
A LWFW gives you faster revs sure. But the common one helps maintain the rotating mass and not throw more pressure on the engine. The dual mass helps absorb and apply rotating mass weather going up or down in rpms while shifting. Considering the 911 can't be shifted lightening fast I don't see the LWFW as much of an integral part of performance except for getting the weight of the car down. Although I think it can help to destabilize or shift the chasis around faster for managing the contact patchs for cornering. All in all if you aren't a master of the craft a LWFW is just bling bling making it so you can wind it faster out of gear. Maybe....maybe not. What do I know, I'm just an old man hehehe.
A LWFW is a good mod to employ in an engine that is used extensively as a track car. However the M96 has no crank damper (until the 3.8L)...so the FW provides this function. If you research crank dampers for other engines you may see more on the subject such as; Loss of power, harmonic vibrations, bearing life, ignition issues... faster revving, but some loss of power is actually common.
If a light weight flywheel, (even a perfectly balanced one from a top notch manufacturer) is bolted to an engine without dynamically balancing the entire assembly ... you may be playing with fire. Or you might be ok and the engine may not experience any failures. On the other hand.... if the minute changes in balance don't 'line up' in your favor.. you may get what Jake has posted above. The Porsche crank is made from powder... powdered metal. It's not a forged GT3 crank. Caveat Emptor.
I have experience in this area on non-porsche engines. Not trashing the LWFW idea, just saying it needs to be employed correctly. Via full dynamic balancing...w/ clutch also.
It's interesting to see Pac996 describe the 996 shifting like lightning... I think my 2 gearboxes have both shifted like a truck. I'm on shifter console type #3 and gearbox #2 in my attempts to get better shifting. Hmmm. Spring is in the air... getting track fever already
Yes the M96 cranks are not forged but the big issue that was explained to me was that the weakness is exacerbated by applying reverse pressure on the crank (which it cannot take at all).
Think of driver who habitually chirps the tires on a downshift and you see the light. He is sending a jolt right into the crank which eventually breaks.
I would have to wonder about that concept since chirping either way would create that issue. I'd be impressed that the Porsche Engineering Department was able to design a crank that took a rotational force in only one direction. If the crank is shearing, it doesn't matter which way (IMHO, which doesn't mean much).
But when you add sticky tires, better locking diff., higher friction clutch disc, you won't slip any of those items any more and just transfer that force to the crank.
A light just came on.
If you play with the dual-mass flywheel (even an old tired one), the main thing you notice is that there is some rotation allowed between the crankshaft mating surface and the clutch/pressure plate surface. When you hit the end of the travel (in either direction, meaning accelerating or decelerating), you hit one of the elastomers that reduces the shock of clutch engagement.
I always thought it was to make life easier on the transmission, as it inherently reduces the peak torque the transmission will see in an upshift, but now I see it can also reduce the BACK TORQUE transmitted to the crankshaft by the drivetrain when doing a harse downshift.
It can easily be such "torque spikes" which cause metal parts to fail in a spectacular manner...
I don't know guys a good 20 pounds of the dual mass flywheel is ridigd and directly bolted to the crank,
the top portion which provides the friction surface for the disc is allowed to articulate to provide dampening on the trans side. I think the proposition that a light flywheel is going to be be your unraveling is a wash, the Boxster I took apart to build a spec car had a broken crank with a dual mass and I haven't heard of any of the Boxster spec guys complaining of probems with the LWFL. Dramatic picture though in the eariler thread but I have seen pictures like that in V/8 and 4 clyinder cars that have been driven out of the rpm range.
great post regards
The Boxster Spec engines are 2.5 liter. These have the shortest stroke (72mm) of all M96 engines and therefore are by design the strongest crankshafts with the most rod journal overlap in comparison to their centerline.
This makes these cranks the hardest to break, where the larger engines, like the 3.6 liter with more than 82mm of stroke have much different overlap and are therefore weaker by design. The main journal sizes were increased when the crank went to 82.8mm from 78mm but not at the same ratio to that of the stroke increase.
So not only do the bigger engines make more power, but they also have 20+mm more stroke with only a .120 difference in main bearing diameter.
Sintered, powder metal? I've got a pic of a 996 crank and I see the wide flashing line -- ground away of course -- that is typical of a hot forged part. Cast parts typically have a thin flashing line and powdered metal a very thin one or none at all.
I'm surprised and frankly though I mean this in a friendly way still a bit doubtful the 996 crank's composed of sintered metal.
Sincerely,
Macster.
OMG the sky is falling. Porsche used sintered powdered metal cranks and connecting rods in the M96 motors!!
Exactly what does everyone think is in every other manufacturers engines?
Sintered powder metal rods common. Cast iron cranks ditto. Just sintered powder metal crank caught me a bit by surprise and with some disbelief.
I thought I had read the cranks were forged as I had read the rods were sintered powder metal and then "cracked". Porsche I believe perfected this cracked technique.
Sincerely,
Macster.
