Yep, This all makes sense to me now. I have been reading the LWFW threads sense I have been on this site. The heavy stock flywheel spools up you release the clutch and off you go with your head snapped back. Now if I put a LWFW into my pcar spool up the engine and release the clutch. Without the rotational mass that was on the stock FW the engine has to compensate and work harder to change the rotational force into linear motion. I can definitely see how it would help on the track with the engine already up in revs and the car moving already vs starting from a dead stop. I would be very curious what drag racing cars use. Personally I love the torque on my car and only track at De's at the most twice a year therefore I am not sure it would benefit my pcar. I remember when I rebuilt my 1973 FJ40 Landcruiser. The FW looked like it came out of a Caterpillar tractor (which is what the mechanic said he thought it came from when I had it resurfaced). That vehicle could pull a house off of it's foundation and was great fpr Rock crawling with tons of torque in combo with the transfer case. Now the LSD is a different story. I can totally see how it helps. Loved my lockers on my Landcruiser, tractor, gator, etc.

 

if you're not a track hound, i would advise against the lwfw til you have driven a car with it.

did this to an rx7 and i have to tell ya, it was quite annoying with the heft of the stock flywheel gone.

 

You do not lose low end torque with a LWFW guys. What happens is the car is out of the low end torque of the engines powerband so quickly that you don't notice it. The fact is if your ring and pinion ratio doesn't change and you see how fast the tach climbs that means your speed is climbing that much faster. Keep in mind that at 3200rpm in 2nd gear the car will go the same speed as it did with the OEM flywheel, it just goes through the rev band so fast you don't feel the torque the same. The LWFW is an awesome mod and I agree completely that this car should have come with this to begin with including a LSD. Some people will not like the noise of the LWFW, but I heard it on a 997 and it wasn't that noticeable like it was on a few other cars I did it to. The other drawback is the fact the car won't coast as efficiently as it did with the heavier flywheel therefore possibly affecting fuel economy while not under load. I will definitely do this mod along with the Quaife when the time is right.

Dave

 

There is a lot of misinformation in this thread.

A LWFW is a terrific upgrade, for several reasons, and it's relatively risk-free.

Power (also known as energy) within a car is a closed system, which means power/energy cannot be lost, it can just be applied elsewhere.

The power/energy coming from the engine (crank) must progress through a series of transactions before transferring that power/energy to the wheels. In this closed system, ideally, there would be zero energy transfer (loss) between engine power source and delivery of that power, the wheels. However, in reality, the power/ energy from the engine gets applied to spinning a flywheel before reaching the wheels. The heavier that flywheel, the more energy required to spin it. The more energy required to spin it, the less power/energy available for the wheels.

What does this mean: upgrading to a LWFW won't increase (or change whatsoever) your engine (crank) HP. It will, however, modestly increase the HP to your wheels, as fewer HP are lost in the transfer. Make sense?

Took me a LONG time to make it that simple, and of course that's a VERY basic and enormously oversimplified explanation, but it's got the basics.
Helpful?

In terms of sound or vibration from a LWFW: yes, with a stock muffler you can detect a mild chatter at idle if you listen for it. However, if silence in the cabin is what matters, and not performance, you are probably not a candidate for this upgrade. Or my AfterHours Mufflers. Or my EVOMS intake. Or any of the mods listed in my signature.
CATTMAN

 

Hey guys. I found this explanation and it seemed to make a lot of sense..

"FLYWHEELS: The actual horsepower of the engine does not change related to the weight of the flywheel. However, to increase the engine RPM, and accelerate the car, all rotating weight (as well as the entire car) must be speeded up. This requires power, and the heavier the part, the more power needed to speed it up. The less power needed to speed up the flywheel (and rotors, clutch, driveshaft, wheels, tires, car, etc.) the more power available to speed up everything else. The question we are asked frequently - "How much more horsepower will my engine have with a light flywheel" - is not the right question, because the answer is NONE. What you will have is more available horsepower to accelerate the car and yourself down the road.

The trade-offs are as follows: the heavier the flywheel, the smoother the idle, the easier the starting is from a stop, and the smoother the cruising/slight throttle changes are. BUT - the slower the acceleration is. The lighter the flywheel is, the harder it is to get the car moving from a stop (just requires a somewhat higher RPM before the clutch is let out - which wears the clutch faster), depending on porting, intake, and exhaust, the idle will be somewhat rougher, and some "jerkiness" may be noticed while cruising. BUT - you will be able to accelerate faster. This is true to a much lesser degree on fuel injected engines than on carbureted engines."

 

Good read. I was wondering why some people were regretting getting flywheels for the road (for a 350Z at least).

The engine RPMs will also drop a lot faster once you're off the gas as well.

 

Wait, 997's don't come with an LSD???

 

The na MY2009's do have a LSD option (standard on the gt3) as does the current turbo.

 

The 997.2 cars have it as an option now. The US 997.1 cars didn't get a LSD nor was one offered. The only 997.1 cars that had or was offered a LSD was the TT or the GT3/RS. Unbelieveable huh??

 

You could install an aftermarket one for about the same amount as Porsche charges for one on a new vehicle. You also get this really cool paper weight that kind of looks like an open dif

 

here's a video that shows you the diff between dual mass and single mass on a 997
http://www.youtube.com/watch?v=Er1eYuVe2zE
For more:
http://www.sharkwerks.com/products.php?pid=151

 

Alex: Nice video. I can see faster up-revs w/ the LWFW, but I was expecting quicker down-revs w/ it, especially in the first part of the video when you just blip the throttle in neutral or w/ the clutch disengaged.

 

Article on Flywheels .. Pros.. Cons
http://www.europeancarweb.com/tech/0...els/index.html

 

Great article, thanks for posting.

 

As always, you nailed it Cattman. But another useful abstraction is to compare the flywheel mass to the battery pack in my Prius. Both are simply energy cache's. People get all excited about the Prius being electric, but the real value is caching of energy to be used when it is needed. It just happens to use a battery to do it.
But back to the flywheel. The greater the weight, the larger the energy cache, much like a bigger battery. Engine power has to be used to 'charge the cache', i.e. spin up the flywheel and the heavier the flywheel, the more power has to be diverted from the rear wheels to 'charge' it. But that stored energy can be used to provide additive energy (observed as torque) once it is 'charged'.
All of this is a study in energy management. In theory, a zero mass flywheel would be most efficient because there is always energy lost when conversions take place (i.e. transferring energy in and out of the flywheel - or the battery pack in the Prius). But a zero mass flywheel is not practical. The engine would constantly stall because it needs flywheel inertia (cached energy) to make it to the next firing sequence.
As an aside, the only case where the Prius analogy breaks down is that it's cache (battery) can be charged by both the motor (like the Porsche) and the braking process (unlike the Porsche), which would otherwise be converted in to heat. Instead, it it converted to stored energy. The Porsche has no mechanism to do so.
This leads to a discussion about how the new GP cars use the KERS (kinetic energy recovery system) to use spare engine energy to charge a battery energy cache which is then used to add power when needed. But that's something else
Does this help?