Lightweight flywheels For NA: Pros and Cons

[Phoenix7]

I have the NA's motor out and I'm starting to put the replacement together and I think this is the best time to upgrade the flywheel...I'm looking to get input from those with lightweight flywheels and how light I should go.

The NA will not be daily driven but it will see some mild traffic once in a while.

[infernosg]

Sub for info.

I had one of Fidanza's 7.5 lb flywheels on my old turbo Protege (with an Exedy clutch) and I hardly noticed a difference. I had to give it a little more throttle to get it going and shift a tad faster but it wasn't anything inconvenient. I daily drove the thing too. I don't have any experience with them in a rotary though.

[Kentetsu]

I installed the Racing Beat lightweight steel flywheel on my 12a this spring. Feels okay, but I should've gone lighter. If I had it to do again, I'd take a look at the Fidanza Infernosg mentioned. :)








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[diabolical1]

i've heard all sorts of stories from one extreme to the other, but my experiences have not uncovered any drivability issues. on my MR2 Turbo, i never found myself having to slip the clutch any more than with the stock. on my Rx-7, i never detected any need to slip it more either. the only difference i detected there was engine deceleration between shifts, but it was only slight. admittedly, it could have been my mind's expectations manifesting itself.

i must add though, that i lived in Florida, so it's pretty flat. i see you live in the Bay, i've been San Francisco (spent a few hours in Oakland, too) and i know it's hilly, so that may affect your experience if you decide to do it. however, as long as you can adjust yourself easily, it shouldn't be a problem even then.
I installed the Racing Beat lightweight steel flywheel on my 12a this spring. Feels okay, but I should've gone lighter. If I had it to do again, I'd take a look at the Fidanza Infernosg mentioned. :)

this was the experience i had with the lightweight steel on my old 12A. i plan to move to aluminum for my next engine.

[jtbshaw]

Keep in mind that if you go lightweight FW, you will lose torque.

[IH8DSM]

It's a rotary what torque

[NoDOHC]

Keep in mind that if you go lightweight FW, you will lose torque.


Although the launch is a little weaker becuae you lose engine inertia relative to vehicle inertia (which barely changes with the little bit of weight you save) if you look at the engine and drivetrain as a whole, where would the lighter flywheel put the torque - if it were causing you to lose it?

Anyway, I went from a stock flywheel to the Fidanza, I picked up 0.2 seconds in the 1/4 mile. (13.4 to 13.2) with a completely stock RX7.

I didn't notice that the launch was that difficult with a stock-type clutch in the car.

I now have a RB 12 lb turbo flywheel in the car with a spec stage 3+ clutch and it is a bit challenging to get it moving without a smoky burnout, but I don't blame the flywheel.

Your idle may not be as smooth.

[Phoenix7]

yeah, the reading I've done says that they're not ideal for drag-racing so I am not too concerned about that.

How much does the Fidanza Aluminum flywheel weigh?

http://www.good-win-racing.com/Mazda-Performance-Part/15R-1003RX7.html

I found that one but there is no info on the weight...

DO you have any good places where I can pick them up at a good price?

[diabolical1]

Keep in mind that if you go lightweight FW, you will lose inertia.

though i think i know what you meant with your original statement, i also think this is more correct.

[diabolical1]

How much does the Fidanza Aluminum flywheel weigh?

http://www.good-win-racing.com/Mazda-Performance-Part/15R-1003RX7.html

I found that one but there is no info on the weight...

DO you have any good places where I can pick them up at a good price?

if i am not mistaken, i think RB subcontracts Fidanza for their aluminum flywheels, which i think they advertise as 12 pounds, but i don't remember if that's with or without the counterweight.

[Phoenix7]

I found an Exedy unit for less than the Fidanza too....But I can't find the weight even on the Exedy site.

I'm still doing some searching so I hope to find the info soon.

Question: can I use a TII lightweight flywheel with the NA counterbalance?

[diabolical1]

as long as the rear counterweight is correct for your rotors and front weight, then i think you can use virtually any aftermarket flywheel that will bolt to it.

[TitaniumTT]

Yup, you match the counterweight to the engine, and the flywheel to the trans.....

I had the lightest offering from SR motorsports, something like 9.5lbs, I had to rev slightly higher to get going in 1st, took a few minutes to get used to but nothing to bad. Reved faster, quicker shifting, but yeah the idle was messed up a bit.

All in all I'd do it again without hesitation.

[RotorDad]

I use the Exedy lightweight chromoly flywheel, not too sure of the weight. The car does rev faster & has quicker shifts. Never noticed the idle because mine was off anyways

[infernosg]

What happens to the idle? I never noticed anything on my other car so I guess this is something unique to the rotary? Are we talking "car will randomly stall" idle effect or something like "idle is more erratic"? I suppose nothing bumping up the idle 100 RPM or so wouldn't fix?

[diabolical1]

... I guess this is something unique to the rotary?

not really. from what i understand, Porsche 911s (at least the 964s and 993s) do the same thing when you use a light flywheel. however, i also understand that some people solve the problem by tuning or fooling the computer into thinking the A/C is on all the time. i guess that roughly equates to raising the idle, like you said.

[jtbshaw]

You guys must be coming from more of a mechanical engineering side talking about your inertia/"moment". I've always taken a more mathmatical/physics approach is why I mentioned torque. We are talking the same thing here.

All the lightweight FWs that I have used have always made improvements. Drivablility did change a bit, but nothing difficult at all. You do gain acceleration by going lighter. As B/TTT mentioned, I would do it again if I had anything with a stock FW.

[infernosg]

^^^ Aerospace Engineering, but isn't engineering just the application of mathematics/physics?

Moment = torque. Inertia is something entirely different, but I'm sure you know that. The only reason you have to give it more gas to get the car going is because it takes a certain amount of energy to get a 2900 lb car moving. Mass and rotational speed are independent, directly proportional variables of that energy so if you decrease one, you have to increase the other.

[jtbshaw]

http://content7.flixster.com/photo/11/10/94/11109453_tmb.jpg

Again, we are talking the same thing. Didn't mean to turn this into a physics/engineering discussion Phoenix.

[TitaniumTT]

What happens to the idle? I never noticed anything on my other car so I guess this is something unique to the rotary? Are we talking "car will randomly stall" idle effect or something like "idle is more erratic"? I suppose nothing bumping up the idle 100 RPM or so wouldn't fix?

Stock FW is what, 27 lbs? The stock ECU, I should mention that this only really relates to a stock edu'ed car, thinks you still have a 27lb flywheel and is thus tuned to rotate that mass. By removing mass you free up a little torque, so now it's taking less power to move that 9.5lb flywheel and the idle hunts around a bit, becomes irradic etc etc.

With a standalone, it's possible to get a perfectly smooth idle, it just takes time. Idle is the most difficult thing to tune. It's such a delicate balance between fuel, timing and BAC duty.

http://content7.flixster.com/photo/11/10/94/11109453_tmb.jpg

:rofl: I love that pic

Again, we are talking the same thing. Didn't mean to turn this into a physics/engineering discussion Phoenix.

Well, don't ever tell an engineer that a lightweight FW adds torque because they'll jump down your throat and say you didn't add anything, you free'd it up. THen you can say, alright motherfucker, here's a stock FW dyno, heres the same car after a lighweight FW. It added torque and hp to the dyno sheets didn't it? Then they say, you dumbass, you free'd it up...... and it goes back and forth all depending on how you interprete it.

[Rotary#10]

:icon_tup:Stock FW is what, 27 lbs? The stock ECU, I should mention that this only really relates to a stock edu'ed car, thinks you still have a 27lb flywheel and is thus tuned to rotate that mass. By removing mass you free up a little torque, so now it's taking less power to move that 9.5lb flywheel and the idle hunts around a bit, becomes irradic etc etc.

With a standalone, it's possible to get a perfectly smooth idle, it just takes time. Idle is the most difficult thing to tune. It's such a delicate balance between fuel, timing and BAC duty.



:rofl: I love that pic



Well, don't ever tell an engineer that a lightweight FW adds torque because they'll jump down your throat and say you didn't add anything, you free'd it up. THen you can say, alright motherfucker, here's a stock FW dyno, heres the same car after a lighweight FW. It added torque and hp to the dyno sheets didn't it? Then they say, you dumbass, you free'd it up...... and it goes back and forth all depending on how you interprete it.


Driving daily my gtus now with a RB 12lb FW and a ACT Street/ Strip clutch. Plus I do have vert wheels. Its fun to drive now, even more so with the flywheel on. I haven't really noticed my idle being erattic.
But thats what I've tell folks it just makes it easier to move what power you already have. For example you jog a block or two with two 40lbs bags of sand on your shoulders. Take the bags off the next block and jog. How do you feel? Lighter of course. Less effort for your engine to spin.
IDK about the gains in actual HP at the FW and at RWHP. That doesn't really concern me right now. I've read a few articles in theory it does. But Dnyo sheets are the evidence and facts of the matter if HP made it to the rear wheels.

[Kentetsu]

It was my understanding that the idle can become a bit rough because you don't have quite so much rotational mass to smooth it out. The idle, after all, is just a bunch of small controlled explosions, so it will have a natural lumpiness to it.

Picture trying to keep a merry-go-round spinning when empty. It might visibly slow between each shove you gave it, but it would be easier to move.

Now picture it loaded up with a bunch of fat harley dudes. It won't slow down much between pushes, but it would take a lot more to get it going.

:)

[Rotary#10]

It was my understanding that the idle can become a bit rough because you don't have quite so much rotational mass to smooth it out. The idle, after all, is just a bunch of small controlled explosions, so it will have a natural lumpiness to it.

Picture trying to keep a merry-go-round spinning when empty. It might visibly slow between each shove you gave it, but it would be easier to move.

Now picture it loaded up with a bunch of fat harley dudes. It won't slow down much between pushes, but it would take a lot more to get it going.

:)

:smilielol5: LOL!

[NoDOHC]

It was my understanding that the idle can become a bit rough because you don't have quite so much rotational mass to smooth it out. The idle, after all, is just a bunch of small controlled explosions, so it will have a natural lumpiness to it.

Picture trying to keep a merry-go-round spinning when empty. It might visibly slow between each shove you gave it, but it would be easier to move.

Now picture it loaded up with a bunch of fat harley dudes. It won't slow down much between pushes, but it would take a lot more to get it going.


This is actually an excellent description.

Now imagine how much easier it is to accelerate the merry-go-round without the Harley dudes on it and you have the lightweight flywheel benefit.

[Phoenix7]

I just picked up a FEED 12lb. flywheel....now looking for an Auto-transmission counter-weight (http://www.rotaryresurrection.com/2ndgen/tech_stockfly_vs_aftfly.html I Miss Landers :(

Thanks for the good feedback on this...

2 questions:

1. How the HELL do you torque the flywheel to 500 lb/ft of torque? I can remove a flywheel by myself but I don't know if I can torque it ON...

2. I noticed Landers said there are 205mm and 225mm flywheels...are you SURE I can use a TII flywheel (225mm) on the NA (stock 205mm) ??

[Sharingan 19]

no you cannot, and you should sell me your flywheel ;)

[Phoenix7]

I have a turbo FC also so it will end up being used either way... :001_005::driving:

but I just need to confirm that it'll work on the NA.

[infernosg]

There are different sized flywheels for the different clutch diameters. The 225 mm flywheel goes with the newer N/A transmissions and clutches, and I'm pretty sure they will not work with a turbo transmission, which uses a larger flywheel as mentioned below, and vice versa. Mazdatrix has a pretty good transmission narrative.

[Phoenix7]

I'm looking at mazdatrix right now...

NOTE: Excluding the TURBO, all the different flywheels and clutches, from 74 through 92, are basically divided by 215mm clutch (74-82), and 225mm (83-92), then by rear counterweight needed for the engine. We mix and match these all the time. This means if you want to put the larger diameter clutch assembly on a pre-83 application, just let us know - it is no problem. You just need to remember what diameter you have when you next purchase clutch parts.

[TitaniumTT]

Negative -

- Like I said before, you match the counterweight to the engine.... or the series rotors you have.

The flywheel MUST be matched to the TRANNY. If you have an N/A tranny, you need an N/A flywheel, if you have a TII, FD, RX8 tranny, you need the TII flywheel. The diameters are different and the starters will not engage.

This is why it's so easy to swap and mix and match trannies between cars.

[Phoenix7]

I missed that part in your post...well, it looks like this flywheel goes to my TII and not the NA. It's still a good deal but I am not sure I'm gonna spend more money to get a new NA flywheel. The stocker will go back into it.

[TitaniumTT]

It makes just as big of a difference if not a little more on an n/a car. I've heard multiple reports of RX8's picking up 9 rwhp on the dyno with a lightweight flywheel. That's over 5%. Not bad at all. Not to mention quicker revving when downshifting etc. I'd do it for sure.

[Kentetsu]

The guy I always turn to when it comes to flywheel questions is Jeff20b. You might want to consider shooting him a PM to run your plan by him, although I'm not sure if he's on this forum or not...

[Fidelity101]

DO IT

less rotating mass more faster revs!

I'm about ready to buy titanium flywheel nut and ti front pulley bolt.