rotarygod says he'd use the lightest flywheel he can find. No drivability issues for him he says. Just drive faster... WHICH is why I want his opinion warranty-wise and wear & tear-wise...

 

Yeah.. that would definitely be good.. Rotary god is well.. a god when it come to this stuff.. so come on.. reply

 

It isn't just how much it weighs but where the weight is on the flywheel that matters.

The pro ACT flywheel is about 4 lbs lighter than their 13 lb street. but it appears that all of that weight savings come from the OUTER EDGE of the flywheel!!

I would guestimate that the "moment" of the the pro version will be about half that of the street version and probably less than 1/4 of the stock flywheel.

The pro could be too light for street/traffic use IMO. At every stop sign you might have to rev it to 6000 RPM to get it to pull out smoothly instead of say 3000 RPM. Although getting the engine to rev to 6000 will be a lot easier. (I merely guessing here)

I would go for the street version of the ACT or pony up for the Mazdaspeed, IMO.

-Mr. Wigggles

 

I have a 9 lb. aluminum flywheel for my RX-7. This is not including the counterweight. I love it. It is not hard to get moving from a stop. You do not have to rev to 6000 rpm to get moving smoothly. Your driving style is hardly altered from its normal style. This is a huge false myth. Does it feel different? Yes. Is it difficult? No. The only thing bad about driving with one in traffic is pushing the clutch in all the time. This is because it is a standard transmission and has nothing to do with the flywheel. The only time it may even resemble an inconvenience is if you are going very slow at a low rpm and are on and off the gas such as in a small parking lot. It can get a little shaky here and the cure is to just ride the clutch a little. This is hardly bad for the car as it isn't under heavy power. Hard accelerating and shifting is so much harder on a clutch than riding it a little at low rpms and speeds in a parking lot. Big deal.

I would love to be able to run a much lighter rotating engine assembly and an even lighter flywheel. You have to drive one to really understand why. It completely chages the way the car feels. It takes it from feeling like a civilized grocery getter to a street driven race car. It is wonderful. I saw someone somewhere else on this forum say the sound was changed from original after a flywheel. BULL S#@T!!! That is impossible.

If you get a lightweight steel flywheel, you'll wish you bought the aluminum. The first flywheel I ever bought was steel because everyone was saying that the aluminum wasn't very streetable. I regretted it and later upgraded to aluminum. I've had 2 of them now on 2 different cars and wouldn't have it any other way. The people that say that aluminum is any hassle what so ever to drive on the street should probably stick to automatic transmissions. This is also a very noticable increase in wheel horsepower and acceleration. Horsepower isn't actually changed any but the usable amount that makes it to the ground is. Just think of it as decreasing drivetrain loss.

In my eyes, buying the steel flywheel is like buying the intake that only gives half the gain or the exhaust that only gives half the gain or the ecu that is only half tuned. If you're going to do something for performance reasons, do it properly. If driving comfort in traffic is your main concern, you should probably own an automatic transmission Cadillac and not a manual transmission sports car. You bought it because it was fun. Make it the most fun you can get for your money outside of a Nevada whorehouse.

 

So which flywheel would you reccommend?

Mazdatrix @ 12 pounds (with counter weight)

SR Motorsports @ 9.5 or 11 pounds (???) not sure... I'll call on it.

Or possibly another one....

 

I personally like them as light as I can get them. My aluminum one is from Mazdatrix and I love it.

 

I think this is my new theme for the day:

"You bought it because it was fun. Make it the most fun you can get for your money outside of a Nevada whorehouse."

- rotary god

 

Rotarygod's comments above bring about a good point: determine, first, just how far from stock comfort levels you are willing to deviate when selecting upgrades for your 8. In stock trim, the RX-8 has very low levels of NVH and it was engineered with this in mind. Noise, vibration, and harshness are issues which will turn away the average car buyer. Those of us interested in speed and performance are usually willing to sacrifice at least SOME level of comfort in exchange for a higher level of performance. The two most limiting factors in building a street/track car are money and willingness to sacrifice comfort for speed. Once you know your own limits, parts selection is made much easier. I have been able to comfortably drive with the SR Motorsports 9.75# flywheel. The only time it becomes an issue is precisely what Rotarygod mentions; tight parking spaces.

Charles

 

Rotary,

My comment was more on where the mass is located

The 9.5 lb ACT Prolite version



versus the 13.5 lb Streetlite version



Any mass removed at the outer diameter changes the moment by a factor of 4 versus mass removed from say half way towards the center. That is to say 10 lb 6 inch disk will feel 4 times as light as 10 lb 12 inch disk.

I don't know what your aluminum flywheels look like in RX-7, but there is a big difference in how how much inertial energy it stores (thus how it feels) if it is a 10 lb solid disk of aluminum versus the ACT pro version which has no weight on the outside at all.

I'm going to let someone else be the guinea pig here. I'll wait until someone actually gets the pro installed version.

-Mr. Wigggles

 

Yep I understand that. The stock flywheel has much more weight towards the outside and this definitely makes a big difference.

 

All right Charles and Rotarygod I think you sold me on the aluminum flywheel. I see SR motorsports has a great price as well. Even though it does not make any more H.P. it free's some up due to less drivetrain energy transfer. If it were Extra H.P. how much would you compare it to?

 

I accidentally lied above. I mistakingly said I had the Mazdatrix flywheel. I don't. I have the SR Motorsports flywheel. The 1st flywheel I had years ago was from Mazdatrix.

 

I still don't feel confortable with people using an auto counterweight in the manual transmission cars...

I work at a automotive manufacturing plant and I've seen catastrophic failures caused by unproper balance at less than 4000 rpm. By catastrophic I mean parts flying 20 ft in the air and breaking a lot of stuff in the process, imagine the same situation at 9000 rpm!!

 

Why? MAzdaspeed flywheel kits use that part number! For the balancer.

 

The problem is with the wrong weight counterweight being used. This is very noticable the second you start the car. The proper counterwieght will work just fine.

 

You guys are blowing this flywheel thing out of proportion. There are no driveability issues with a lightweight flywheel. I have been using a 9.5lb in my RX-7 for 7 years with no problems and its great on the street.

Im not sure why anyone would waste $529 on the SRmotorsports flywheel when you can get one for alot less.

Jason

 

When I bought one from them, it was alot less.

 

From ACT's website:

From your website:

Although the picture isn't correct, I am assuming you are referring to the ACT.

It is not the weight reduction that matters it is the inertia (i.e. moment of inertia) reduction that matters. Because it claims a 80 percent reduction in inertia and with the stock flywheel being 20.80 lbs, the ACT Prolite is essentially 4.2 lbs in comparison if the two were the same shape.

They make two versions for a reason. Until someone else tries out the Prolite for themselves, I plan to sit on the fence. I am sorry if that discourages anyone and I do hope that I am wrong.

-Mr. Wigggles

 

The only issue with a lightweight flywheel is you have to rev it a little higher to get the car moving. Maybe 500-1000 RPM.

Jason

 

With my SR fly and ACT clutch ***'y, I have no MAJOR drivability issues. I had to modify my clutch and throttle finesse a bit but, other than that, there is no reason why I would wish to change back to stock. I would tell those who might be concerned that if they think they are not ready to do such an install and make the necessary minute changes in driving technique, perhaps they are not the type of driver for which lightweight flys are designed and built. Stock vehicles are designed to suit a wide variety of drivers, thusly expanding the potential consumer base. The more experienced performance drivers know how to manage a more aggressive vehicle on the street. Not everyone has the experience to do this.

Charles

 

Well put!

Getting used to driving with a lighter flywheel is no harder than getting used to driving a different standard transmission car. They all feel a little different. My Civic fells nothing like my RX-7 does. It isn't even close to how the RX-7 was stock. My friends Camaro feels totally different than either car. Just get used to it. Big deal.

 

Well,

Like I said, I hope that me, ACT and Mazda (who designed the stock wheel) are all wrong and there are no "driveability" issues when switching to a flywheel that only has 1/5th the inertia of stock.

Time will tell when some people actually install the Prolite. If they don't have issues, I'll get it. Otherwise its the Mazdaspeed.

Thanks for the input guys.

-Mr. Wigggles

 

If i've learned anything from the forums, its that drivability is completly subjective. I personally love my super light flywheel on my rx7, no drivability problems, just had to reajust after it was put in. Whereas it would probably make someone out there bitch and moan and remove it because they dont like how it feels. Therefore no one can really tell you if its drivable "to you", just try and drive a car with one and draw your own conclusions. In my opinion lighter is better, i'd buy a 3 pound flywheel if i could find one...

 

If this was a 4 year old car with no warranty, I would go very light... However, if you want to keep your warranty get the Mazdaspeed... Spoke to Mazda; if you put a light aftermarket flywheel in an RX8 that is not approved by them you completely void your warranty... Some repairs can be very expensive, especially on a new model; the 6sp transmission in a RX8 is over 5k...

 

WOW! You guys have blown this way out of perspective. My brother is into cars and he did not even know it was a lite flywheel until I told him.