What weight flywheel for '99 Civic Si?

[rmcdaniels]

I'm getting ready to put a clutch and LSD in my Si, so I figured I should replace the flywheel as long as I have it apart. I'm seeing several major-name lighter replacements in the $200 range, from the Jackson Racing unit at 7.7 lbs, to the ACT Streetlite at 12.5 lbs. I understand that the lighter it is, the faster I can rev up the engine, but I've been told that a sub-10 pound unit can be very annoying in stop-and-go traffic. What's a good weight for improved performance, but without sacrificing too much drivability in traffic? I'd appreciate any opinions on performance and drivability from any one who is running with a lightened flywheel.

Thanks

[stu]

I had an 8 pound flywheel in my 96 GSR. You won't even hardly notice a difference. theoretically, it will take me gas to get the car moving, and the car will not hold momentum between shifts and when you let off the throttle as well as would with a heavier flywheel. But having had one before, I can honestly say that you may very well notice s difference, but it won't be a difference with any negitive effects when just driving around in traffic. After only like one day of driving, you won't even be able to tell you changed anything unless you go drive another car.

[THRICE]

Yeah, I have also heard that sub 10 pound flywheels are a bitch after awhile. I would just look at it like this. a 12.5 lb flywheel is still a very light flywheel. Not to mention ACT has a very reputable name. I think that anything below the 10lb range of flywheels is pretty much a waste of $ for the little difference that it will make. If you can find a flywheel that is between 10-14lbs without sacraficing durability too much, you're good to go.

[THRICE]

Stu beat me to it.

[stu]

The only reason I can even think of, as far as why you wouldn't want to get a flywheel under 10 pounds, is if you were going turbo. Otherwise I'd personally do it. flywheel weight doesn't have any negitive effects on superchargers as far as I know.

[marcrx5]

I got a 11 pound fidanza flywheel on my crx. Like stu said, after about a day, you don't even notice. I can't imagine an extra few lbs. making it horrible to drive.

[95GSRB18C]

i got a 12.5 lb on my integra. Cant really notice a BIG BIG difference, but its there.

[fodo]

I got an 8 lb one and it kinda sucks at higher speeds when you're trying to slow down in gear... :( i usually just take it out of gear and let it idle while slowing down...but for acceleration it's pretty good.

[rmcdaniels]

Thanks for all the info, given that the 8 lb flywheel is pretty close in price to the 12 lb one, I think I'll go for the lighter one if drivability isn't going to be seriously affected. Now I just haveto decide between the Jackson Racing unit and the ACT. The JAckson Racing unit is a little lighter, but I don't know about the durability compared to the steel ACT unit. At this point I'm leaning towards the ACT flywheel, but that might just be because it looks cooler. HAs anyone had any experience with either of them?

[Weston-work]

I have a 9.7 lb flywheel (Kaiten Karui 4.4kgs - $280 at Flatirons Acura, fits b-series engines)... I haven't had a problem with it. It acclerates better (most of the improvement is in the lower gears), revs drop faster (which is a good thing), it's easier to rev-match, and there's less stress on the clutch and synchros when shifting fast.

Something to consider is where that weight is placed on the flywheel. You'll notice that some have holes near the edge... that will make it act lighter. Some are aluminum, which is really light, but they have teeth made from a different metal bolted on... that will make it act heavier, and the whole thing is pretty ghetto as well.

Another thing to consider is that the clutch is bolted to the flywheel and rotates with it. The clutch (both my stock one and my aftermarket one) is about as heavy as my stock flywheel (said to be 18lbs). That means that when I replaced the flywheel with one that's about half the weight, I really only reduced the rotating mass by 25%, rather than 50%. But it's actually less than that, considering the pulleys and belts, and the load coming from the transmission. But it's still a nice improvement in acceleration, and the revs drop the perfect amount for quick shifting.


Here are the lightweight flywheel myths I've heard:

1) hard to drive in stop-and-go traffic
2) easy to stall the engine
3) slower going up hills
4) decreases torque and/or horsepower
5) the lower flywheel momentum slows you down after you shift (ie the excess momentum would speed the wheels up after the shift)


All of those are CRAP!

1) no problem for me or anyone I've talked to who has one on a Honda. Maybe a really grippy clutch would make things harder, but I don't have any trouble with my Exedy Organic Racing Clutch (said to be about a Stage 1), which is more than sufficient for most street driven Hondas. Some people think they need a Stage 3 clutch for their daily driven Honda with bolt-ons, and I'm sure that could cause problems, but that's their own fault (not the flywheel's).
2) see #1
3) BS. It's faster in general, nothing different than before for hills.
4) BS. If anything it would free up torque (like removing, underdriving, or lightening a pulley), but that I'm not aware of anyone dyno'ing immediately before and after to prove it.
5) BS. It's up to the transmission synchros to synchronise the engine speed and the transmission speed. So, I could see the thinking behind saying that it speeds up the wheels, but it really takes a lot of energy to accelerate the drivetrain (transmission - axles - brake rotors - wheels - tires) to then accelerate a 2600 or so pound car against friction from the air and ground plus other factors. The weak link is, and will always be, the synchros (unless you have a weak clutch), so that's where the excess energy goes... to put stress on them.

Ever hear of the b-series Honda 3rd gear synchro grind? This is because the stock flywheel doesn't drop revs fast enough for a quick shift from 2nd to 3rd. Some say that syncrho is weak, but my theory is that it's at least partially because the shift between 2nd and 3rd is the biggest difference in gear ratios (in my LS'es case, at least). BTW, my Integra would grind on high RPM shifts into 3rd before I put the flywheel in, but now it doesn't (unless I'm really quick, but that could be from the hydrolic clutch not reacting fast enough).

[stu]

Is that why I grind from first to second sometimes?

[Weston-work]

Possibly... But I've noticed that my rare 1st -> 2nd grinds are clutch related (either I wasn't quick enough on the pedal or the fluid is low or old). Of course, the 2nd gear synchro can get beat up just like the rest of them (3rd just tends to be the first).

[rmcdaniels]

I was thinking about that looking at the ACT flywheel with all the metal in the center and the open framework on the outside edge. It looked like it would act lighter, but that may just be what they have to do to get it close to the weight of the aluminum units. I also got a Clutchnet "FIBER-CARBON" sprung-hub disk and a Clutchnet pressure plate to go with it, which according to the Clutchnet people will handle my motor mods.

[Weston-work]

Oh, and be sure to get one that isn't going to fight with your starter teeth... Some flywheel teeth and starter teeth combinations tear each other up because the different metals have properties different enough to cause a problem.

And some people are pretty strongly against aluminum flywheels. They're sure light, but Aluminum's properties maybe aren't so good for a flywheel. Chromoly is pretty well accepted as the much safer alternative.

[rmcdaniels]

Sounds like the ACT chromoly may be my best bet. Thanks to everyone for all the input.

[THRICE]

And remember kids, change your transmission oil every 30K!!! I know that was random, but most people don't change it ever.

[prkrnt]

A guy sure can feel small in these conversations...

[hsunchen]

Originally posted by Weston-work


And some people are pretty strongly against aluminum flywheels. They're sure light, but Aluminum's properties maybe aren't so good for a flywheel. Chromoly is pretty well accepted as the much safer alternative.

I spent literally MONTHS and MONTHS researching light flywheels before I bought the Fidanza for my MR2 (and my CRX) - which is a aluminum product with a steel starter ring gear and replaceable friction surface.

What's "pretty well accepted" is that people don't agree what's a better material, but I'm very confident in my decision. Do your own research before you decide for yourself.

Another thing to consider - on my CRX clutch/flywheel setup, the pressure plate weighs more than the flywheel.

You have to spin the pressure plate too, since it's bolted to it, so keep that in mind that your rotating mass you have bolted to the end of the crankshaft ISN'T just the weight of the flywheel.

[Weston-work]

Originally posted by hsunchen
I spent literally MONTHS and MONTHS researching light flywheels before I bought the Fidanza for my MR2 (and my CRX) - which is a aluminum product with a steel starter ring gear and replaceable friction surface.

What's "pretty well accepted" is that people don't agree what's a better material, but I'm very confident in my decision. Do your own research before you decide for yourself.


Well, that's just what all the kids on the Honda message boards seem to say. Obviously, that's not the best source of information. It's not so easy to find legitimate racers or anyone who knows wtf they're talking about on most message boards.



Another thing to consider - on my CRX clutch/flywheel setup, the pressure plate weighs more than the flywheel.

You have to spin the pressure plate too, since it's bolted to it, so keep that in mind that your rotating mass you have bolted to the end of the crankshaft ISN'T just the weight of the flywheel.

Silly Hsun, I already said that. :)

[hsunchen]

Sorry Wes, I obviously didn't read your whole post carefully. Must be that "USA Today" I-don't-want-to-read-anything-too-long mentality kicking in.

I looked up my weights at home - 6.78 lb. for the Fidanza flywheel with pilot bearing, 7.17 lb. for the pressure plate. This is stuff for a '90-up Civic/CRX, which is the same as '92-95 Civic.

To sum up for "the kids" (and how old are you exactly Weston?) -

and remember the pros and cons I've listed are common OPINIONS of others; I don't care to hear your arguments about why I'm wrong, I'm just trying to give both sides of the table.

ALUMINUM

PROS -

1) more material to act as a heatsink, aluminum is a better material for heatsinking anyway
2) replaceable surface means they can in theory last much longer than a steel flywheel
3) Aluminum is usu. lighter than a CR-MO steel flywheel
4) Aluminum flys are usu. cheaper than CR-MO flywheels

CONS -

1) supposedly b/c of the difference in materials and the resulting different expansion and contraction rates from heat (steel friction surface, steel starter gear, steel fixing hardware) they can suffer from damage or warpage, or cause the fixing pins to fall out
2) some people claim aluminum is weaker than steel, so that makes it more likely to explode, flex or fail (again this is not my opinion, just what some people say!)
3) having the friction surface bolted on is another point of failure

STEEL/CROMOLY

PROS -

1) all one material, can't expand/contract at different rates
2) made in Japan by companies like JUN and TODA so it must be better
3) They have cool holes CNC-ed in them and look badass
4) I suppose there might be more but I can't think of any

CONS -

1) Being a very thin material, there isn't much to heatsink with and can tend to warp easily with repeated drag race launches.
2) Once it's warped or worn thin, it must be replaced.
3) Cr-mo flywheels are usu. more expensive than aluminum units.

THINGS THAT I'VE LEARNED THAT ARE UNDEBATABLE TRUTHS -

1) Clutchmaster flywheels are rebadged Fidanza products.

2) Jackson Racing flywheels are rebadged Fidanza products.

3) If you buy a Fidanza flywheel and have a problem or want the friction surface replaced, they WILL take care of you. I've had two Fidanza flywheels replaced/refurbished for NO CHARGE for no reason at all - their product wasn't at fault, they just did it for free anyway.

If you buy a JUN or Greddy or TODA flywheel and have a problem with it (warping), you WILL have to buy another one. Guaranteed.

Japanese vendors are well known for giving you "the Heisman" whenever there is any kind of issue with the product after it's been removed from the box - that's where their warranty ends.

And before I get accused of any JDM-bashing or whatever, here's a partial list of expensive jap-crap I've purchased -

SSR wheels, Racing Hart wheels
HKS cams
Greddy turbo kit (which I got "the Heisman" on when the wastegate actuator was found to be faulty at 2,000 miles!)
A'pexi GT spec exhaust, AVC-R
PIAA lights

etc etc.

[THRICE]

Originally posted by hsunchen
Sorry Wes, I obviously didn't read your whole post carefully. Must be that "USA Today" I-don't-want-to-read-anything-too-long mentality kicking in.

To sum up for "the kids" (and how old are you exactly Weston?) -

and remember the pros and cons I've listed are common OPINIONS of others; I don't care to hear your arguments about why I'm wrong, I'm just trying to give both sides of the table.

ALUMINUM

PROS -

1) more material to act as a heatsink, aluminum is a better material for heatsinking anyway
2) replaceable surface means they can in theory last much longer than a steel flywheel
3) Aluminum is usu. lighter than a CR-MO steel flywheel
4) Aluminum flys are usu. cheaper than CR-MO flywheels

CONS -

1) supposedly b/c of the difference in materials and the resulting different expansion and contraction rates from heat (steel friction surface, steel starter gear, steel fixing hardware) they can suffer from damage or warpage, or cause the fixing pins to fall out
2) some people claim aluminum is weaker than steel, so that makes it more likely to explode, flex or fail (again this is not my opinion, just what some people say!)
3) having the friction surface bolted on is another point of failure

STEEL/CROMOLY

PROS -

1) all one material, can't expand/contract at different rates
2) made in Japan by companies like JUN and TODA so it must be better
3) They have cool holes CNC-ed in them and look badass
4) I suppose there might be more but I can't think of any

CONS -

1) Being a very thin material, there isn't much to heatsink with and can tend to warp easily with repeated drag race launches.
2) Once it's warped or worn thin, it must be replaced.
3) Cr-mo flywheels are usu. more expensive than aluminum units.

THINGS THAT I'VE LEARNED THAT ARE UNDEBATABLE TRUTHS -

1) Clutchmaster flywheels are rebadged Fidanza products.

2) Jackson Racing flywheels are rebadged Fidanza products.

3) If you buy a Fidanza flywheel and have a problem or want the friction surface replaced, they WILL take care of you. I've had two Fidanza flywheels replaced/refurbished for NO CHARGE for no reason at all - their product wasn't at fault, they just did it for free anyway.

If you buy a JUN or Greddy or TODA flywheel and have a problem with it (warping), you WILL have to buy another one. Guaranteed.

Japanese vendors are well known for giving you "the Heisman" whenever there is any kind of issue with the product after it's been removed from the box - that's where their warranty ends.

And before I get accused of any JDM-bashing or whatever, here's a partial list of expensive jap-crap I've purchased -

SSR wheels, Racing Hart wheels
HKS cams
Greddy turbo kit (which I got "the Heisman" on when the wastegate actuator was found to be faulty at 2,000 miles!)
A'pexi GT spec exhaust, AVC-R
PIAA lights

etc etc.



Hsunchen,

Your pro-and cons aren't even actual things that people have said. It's random BS that you pulled from your knapsack. Your entire post sounds completely fucking rediculous.

"It's made in Japan so it must be better!"

Let me put it this way, Weston knows what the fuck is up and every single person on this board knows that whether they want to admit it or not. Even the experienced members. So far his posts have been intelligable and informative, yours have been sloppy, and misinformed.

BTW, Steel can, and does contract and flex at different rates fool. That's basic fucking physics. Ametuer. :rolleyes:

[exciv2000]

I did my research too and went with Fidanza over chrappoly for very good reasons. hsunchen is posting things not just from his knapsack, but common knowledge that you chromoly lovers obviously missed in your research. Your loss :)

[THRICE]

I never said that Steel was better than Fidanza aluminum flywheels. I simply was saying that if he was going to oppose Westons statement then he should have come up with some actual "cons" rather than just random comments from his own book. See what I'm saying? I want to hear actual reasons why Aluminum is going to be better than Steel. REAL REASONS.

[hsunchen]

Originally posted by THRICE

BTW, Steel can, and does contract and flex at different rates fool. That's basic fucking physics. Ametuer. :rolleyes:

Well of course it can depending on what it's alloyed with, and how thick it is, and whether it's forged or cast, etc etc.

Just trying to keep things simple - but excellent anger and aggression THRICE!

Channel your energy young jedi!:p

You are welcome to post the reasons steel is advantageous over aluminum - like I said, I couldn't come up with more, but I'm sure there are more pro's to Cr-Mo flys.

[THRICE]

All I wanted to see was some actual reason why aluminum is better. I too am looking for a new clutch and flywheel and I want to know what's best. :)

[Slava]

From what I've been hearing is that kevlar clutches are the best and the lightest. The cost a shit load but so far in the market they are well thats what I heard.

[rmcdaniels]

Good points all, but I believe there is another factor to consider, especially with regards to the mass of the pressure plate. When looking at how the rotating mass affects throttle response, don't you have to consider the distance of the weight from the center of rotation? The closer the weight is to the center of the rotation, the less acceleration/deceleration is required to change RPM, so the weight of the pressure plate, which is much smaller in diameter than the flywheel, does not count for near as much as the weight of the flywheel. Of course in the case of the Fidanza product, I would guess that the majority of the mass is going to be nearer the center where the steel friction plate is, but the weight of the material farther out towards the outside of the flywheel will count much more towards your performance.

Doing a little math (all base numbers are made up, because I don't have a flywheel handy to measure), if a flywheel is 18 inches in diameter and the friction material is 10 inches in diameter, then a single revolution moves the friction material 31.4 inches, while the outside moves 56.52 inches, or at 1000 RPM the inside travels at 43.61 FPS (feet per second) while the outside travels at 78.5 FPS. Now let's suppose that the inside portion weighs about the same as the outside portion, because while the inside has to be thicker to accomodate the friction pad, the outside has greater surface area as well as a relatively heavy steel ring gear so if the wheel weighs 8 lbs, then the outside and inside each weigh 4 lbs.

************************************************** ***
note to all engineers who read this: I know this model is far too limited to accurately describe the phenomenon I am attempting to describe, but for the sake of brevity and of keeping the math understandable to a significant percentage of the population I have drastically simplified every aspect to the point necessary to generate some basic numbers that will more or less accurately (from a physics perspective, not an engineering perspective) illustrate my point, so please don't flame me as an ignoramus, you'll have to get to know me much better before you can accuratelty plumb the depths of my ignorance.
************************************************** ***

If we suppose that the flywheel is turning at 1000 RPM at idle and we want to accelerate it to 5000 RPM, then we will be accelerating the outside by 314 FPS while we only accelerate the inside by 174.44 FPS. Now force equals mass multiplied by acceleration, so it takes about 697.76 lbs/feet of force to accelerate the inside, while requiring 1256 lbs/feet of force to accelerate the outside, so in this case, the weight on the outer edge of the flywheel counts about twice as much as the weight that is a little closer to the center.

The upshot of this is that the weight of the pressure plate doesn't count for near as much as the weight of the flywheel, and that the bad ass holes CNC'd into the chromoly flywheels may make a big difference in throttle response, especially considering the steel weighs about three times what the aluminum does. Of course the reason they can get away with making all the big holes is that high tensile/low carbon steel has about three times the tensile strength of high grade 6061 class aluminum (what Fidanza uses), so it's generally a wash between the two, but chromoly steel has about 40% more tensile strength than high tensile/low carbon steel, so I believe the chromoly flywheels can have the performance edge based on strength/weight because they can concentrate the mass in the center on the friction plate while leaving a very light framework of steel to support the ring gear. So if anyone is still reading at this point, I would summarize the pros/cons as follows:

ALUMINUM

PROS:

better heat dissipation, may make it less likely to warp/glaze/bubble under certain conditions
overall lighter
replacable friction surface
longer production history, people have been making aluminum flywheels forever, designs may be more well developed/tested

CONS:

not as strong per pound as coromoly steel, so more weight needs to be allocated farther out on it's diameter
multiple parts mean more points of failure, different materials may make it more prone to warpage under certain conditions


CHROMOLY

PROS:

all one piece, fewer points of failure, maybe less chance of warpage under certain conditions
higher tensile strength lets majority of mass be allocated towards the center (the friction plate), possibly giving better performance

CONS:

much poorer heat dissipation, may make it more prone to warpage/glazing/bubbling under certain conditions
friction pad can't be replaced, if you trash it, buy a new one
shorter production history, designs may not be as well developed and tested as aluminum flywheels

Pricewise I'm seeing both units in the $200 range, and it is good to know that the Jackson Racing units are a Fidanza product, because overall I like the quality and fitment of the JR products I have, but was concerned about them apparently producing a product that is not in their core specialty area (and they are on closeout sale now). Does anyone know who makes the ACT XACT products?

[hsunchen]

Originally posted by THRICE
All I wanted to see was some actual reason why aluminum is better. I too am looking for a new clutch and flywheel and I want to know what's best. :)

So I'm an "amateur" - and I freely admit I am, since I've only done clutch and flywheel replacement jobs on about 5 occasions - but you're looking for info on what's best?

I thought by your previous tirade that you were either a metallurgist, a mechanical engineer, a professional mechanic on a race team, or at least a MENSA member.

[THRICE]

No, I just know my stuff when it comes to physics and geophysics. I hate when people make broad based assumptions that steel doesn't give.

[THRICE]

Thanks rmcdaniels.

I have a question though. You are right on the factor that Aluminum doesn't retain heat to the degree that Steel does, but steel does have a higher density per square inch. It makes steel more durable in a sense, but at the same time it does not have the lightwieght feel to it and cannot desipate the heat as well as aluminum. I guess that's why alot of aircraft are made from aluminum, because it's light, and flexes far better. My question is, I don't understand how steel warps so easily if it is so dense compared to aluminum. Wouldn't you think aluminum would almost instantly warp? Or is the cooling benefactor that great?

[stu]

Kris, husnchen wasn't disagreeing with Weston, he was simply just posting all the things he has heard from when he spent time researching. And I have to tell you, when I read those kinds of threads, those are exactly the type of things that people say. His whole point was that there wasn't a lot of hard evidence either way out there, he wasn't argueing with Weston.

[exciv2000]

Watch out for those chromoly teeth vs. the steel teeth on the starter. that's a BAD combination for a lot of import owners.

[rmcdaniels]

I'm pretty sure the aircraft issue is primarily based on the flexing properties, given that they both have about the same strength for a given weight. You could make an aircraft out of steel, but the steel would be a third as thick as the aluminum and have a greater tendency to ripple under load, especially the thin outer skin and wing material (I generally prefer to travel in non-rippling aircraft). I read an article specifically about that when I was looking up tensile strengths of the different materials.

When it comes to lightweight feel, I really believe that with the capability to make the outer portion of the flywheel much thinner with chromoly, hence the skeletal appearance of the outside couple of inches of the ACT flywheels, that the heavier steel flywheels can give a very lightweight feel, because most of the weight is more towards the center, where it has much less effect. Unfortunately I can't drive them side by side to make an informed comparison, but based on strength/weight, a well designed chromoly unit could theoretically have less inertia that a lighter aluminum unit. Of course that's assuming the designs were equal, and I think that aluminum designs will tend to be better, if only due to their time in the marketplace. So I'll call that one a wash.

Unfortunately the warpage issue is my weakest area, you may have noticed the liberal use of "may" and "maybe" in reference to warpage, but here's what I do know:

Steel has a coefficient of expansion that is roughly half that of aluminum, so I wonder about the aluminum flywheels that are composed of multiple components; the steel ring gear, which I believe is pressed on, the aluminum main body of the flywheel, and the steel friction pad, which is secured with steel screws. It seems that in a component that is designed to get very hot at times, the elements would expand and contract at very different rates, potentially causing warpage or loosening the friction pad or ring gear. Of course you could attach the friction pad to the flywheel in some kind of way that allowed for some radial play, maybe use radially angled slots for the securing screws, but I would think that you would want it very tightly bonded to the aluminum for heat transfer reasons, because the friction pad is where most of the heat will be generated, which leads to the second thing I know.

Aluminum has a thermal conductivity rating about 5 times that of steel, so while steel is more dense and can soak up more heat, it is nowhere near as good at moving the heat away from the friction pad where it is generated to the non friction pad surfaces where it can dissipate into the air. So my guess on the steel warpage issue would be that it would be easier to overload the steel unit with more heat than it can move away from the friction pad and dissipate, thereby increasing the risk of damaging it. I'm also guessing that it would take a lot of punishment to do that.

Given my driving patterns, which typically consist of tearing around town with my engine screaming (although usually at no more than 10 MPH above the speed limit) and the occasional stoplight race if the person next to me is feeling froggy, I don't think I'm putting an excessive strain on my flywheel. After I finally get everything right with my car, I plan on occasional trips to a dragstrip to get some .25 mile times to validate any mods I make and occasional autox (maybe once or twice a month if I can find events) for the sheer unbridled fun of it, neither of which should (hopefully) trash a good high-performance flywheel, especially considering that I should be really beating on it for no more than a minute at a time. So at this point I'm leaning toward the chromoly unit for the performance potential and partly because the simplicity of a one-piece flywheel appeals to the engineer in me. If I were a professional racer I might have a different opinion, but I'm not. Actually I was kind of hoping to hear from someone who had driven with both types of flywheel, but I don't think I've seen a post by anyone that has so far.

[rmcdaniels]

I guess it would kind of suck to have a great flywheel that occasionally chews the teeth off my starter.

[hsunchen]

It's never a bad idea to replace the starter gear when you replace the flywheel. Esp. if the car has a lot of miles on it, like 100K plus.

I replaced the starter gear on my MR2 when I installed my Fidanza flywheel on the recommendation of MR2 tuners much more experienced than I.

Just like when you replace the chain on a bike, if it's sufficiently worn/stretched, you need to replace the cassette it meshes with for it to shift properly.

[THRICE]

Thanks for the information, I understand a bit better now. :)

[Weston]

Originally posted by stu
Kris, husnchen wasn't disagreeing with Weston, he was simply just posting all the things he has heard from when he spent time researching. And I have to tell you, when I read those kinds of threads, those are exactly the type of things that people say. His whole point was that there wasn't a lot of hard evidence either way out there, he wasn't argueing with Weston.

Yeah, he was just showing both sides of the debate. Hsun is a smart guy and I'm sure he's done more research on this topic than I have, so I would trust what he says.

[hsunchen]

Originally posted by Weston
Hsun is a smart guy and I'm sure he's done more research on this topic than I have, so I would trust what he says.

That's very nice, but really, I suggest people do their own research, whether it's online or whatever, and form your OWN OPINION, based on what arguments/evidence make sense to you.

I've had no problems with my Fidanza units, but if you research, you'll find that others have had problems with the locating pins coming out.

Fidanza has resolved this issue by loctiting the pins at the factory, but I could certainly understand if someone who had a problem with one of their units wouldn't put one on their car again if they paid them to.

For my MR2, what it came down to for me was that I found more testimonials about people with JUN steel flywheels warping them - usually after repeated drag race launches - than testimonials about Fidanza flywheel problems.

[rmcdaniels]

Yeah, I've been googling warping flywheels and the general consensus seems to be that the JUN unit has too little metal behind the friction pad, so it can't absorb very much heat, and since steel has such a low thermal conductivity rating the heat burns, cracks, and warps the friction area. I even saw one picture of burn spots on the side of the flywheel opposite the friction pad where it burned the metal all the way through, needless to say the flywheel was junk and JUN did not volunteer to replace it. I haven't been able to find anything about the ACT flywheel warping, but according to the ACT propaganda they put extra metal behind the friction pad to deal with this issue, and why would the nice people at ACT lie about something as important as that, certainly not to sell a lot of flywheels, although looking at pictures of the two units I can see that the JUN flywheel appears to have a lot more metal outside and inside the friction pad than the ACT unit, while they both weigh about the same. It looks like the ACT wheel put most of the metal in the friction pad area, which I believe should be a good thing, both for durability and performance reasons. I also called ACT and they confirmed that they make their own flywheels, so it should be easier to get support than with the Japanese product. I think at this point I'm working hard to talk myself into the ACT flywheel.

[exciv2000]

ACT is a great product, it won't let you down. They are world renowned and stand behind their work.

[rmcdaniels]

The 8.8lb ACT chrome moly steel unit is on and it's fine. The tech who helped me with the transmission was skeptical about ow the car would idle with such a light flywheel on it, but it idles fine. I did stall it once, but after a day of driving I've adjusted and it isn't noticeable. More noiceable is the increased spring rate of the new clutch, but it's not too bad either. I can't actually wind the car up now due to some boost/fuel issues, but I'll post if it makes a significant performance difference after I figure out how to get enough fuel to it.