Deciding on which flywheel to go with, the RB lightweight steel or the aluminum. It's an 86 N/A that I'm rebuilding now for a daily driver, hoping to get around 200hp. I've read the aluminum one will increase 0-60 times significantly, with a good clutch of course, but I've read that it also hurts drive-ability as well. Is the lightweight steel flywheel a happy medium? Or does it really even hurt drive-ability that much?

 

i like the steel one, its what the car should have had from the factory. its perfect for a street car, thats a DD (full interior, stereo, etc)

if you were building a track car that was street legal, the AL flywheel is better. car is a little lighter, you're expecting it to be less civil, etc

 

what are some of the downsides of having a flywheel which is extremely light? I'm in a similar situation and I'm strongly considering getting a lighter flywheel to increase throttle response while heel toe downshifting

 

The performance of the flywheel is based on its moment of inertia (MOI), which may or may not relate to its static weight or material. A low MOI flywheel will decrease the stability of the engine's rpm, which results in a rough idle, difficulty in stop and go traffic, difficulty accelerating up an incline from a standing start, faster clutch wear in city driving, but faster shifting and a much more rapid response when accelerating and decelerating while racing. A high MOI flywheel will increase the stability of the engine's rpm, which results in a more stable idle, easier street driving, less clutch wear in city driving, but slower shifting and slower response when accelerating and decelerating on a race track. Yes, some flywheels are somewhere in the middle.

The material may affect MOI, but otherwise it is more related to durability. Aluminum is lighter but it will wear faster. Some aluminum flywheels have steel friction surfaces and/or steel ring gears to increase durability.

Yes, but a good clutch is a 4.5" or 5.5" low-MOI racing clutch pack. This would be paired with a matching low-MOI flywheel. The total package would greatly increase racing performance, but you are looking at about $2,000 for something that is not very streetable unless you live in a rural area. You also can't slip a racing clutch like you can a street clutch, which is why you see race teams pushing their cars onto their trailers rather than driving up the ramps.
Racing Clutch and Flywheel

 

dont do a flywheel with a replacable friction surface. you'll have all kinds of problems. make sure its a 1 piece.

that whole moment of inertia thing, comes down to this. its slightly harder to climb a hill with the same throttle angle that you use with a heavier flywheel. the inertia, or desire to keep moving on heavier flywheel is greater. its an energy "storage" thing.

its also slightly touchier when leaving a stop light.

 

lighter = less mass = faster accelerating. in a race car you want the engine to rev as fast as possible, but sometimes in a street car too fast is too fast.

with the light steel flywheel, you get most of the benefits of the light weight, with no down sides. with the AL flywheel you get the down side that you need a little more revs from a stop, and its a little harder to be smooth. in a track car neither of these are problems, in a street car, they might be.

there is also a correlation with vehicle weight, the lighter the car, the less flywheel you need. for example i have an AL flywheel in a light (2100?) 1st gen and it feels much better there than it did in a 2600lbs GSL-SE.

 

I'm no expert but have a higher power 87 I left the 6 puck act and went to a ss disk and a heavier pressure plate I think it's a 420 ft lb I also use the act lightweight flywheel with this setup for 800 I can race and jump rpm as well as street it I do have a lot larger friction point compared to the on and off of that 6 puck

 

So for my stock 1990 vert, which I'm not all that worried about smoothness or certain aspects of driveability on (but it IS my daily, mostly freeway miles), would the aluminum one just be unbearable? Do the pros outweigh the cons?

I rarely give rides to anyone and tend to pound on the car a little sometimes.

 

On a stop and go, even at 500 rpm as long as the car is rolling, you can leave it at 2nd gear. With aluminum flywheel, you will occassioanlly be at 1st gear; otherwise chug-chug the rx7 goes. Also it requires a higher rpm to get out of first gear.

 

A lot of great information so far! I live in the city, so there would be more stop and goes, think i'm leaning towards the light weight steel flywheel though. Does anyone here have a daily driver with an aluminum flywheel?

 

keep in mind the above is just my opinion, although i've done both in a bunch of different cars.

if you do lots of freeway driving you could get away with a lighter flywheel.

 

I used to DD an FB and RX-3 (both with aluminum flywheel and 4 puck, 13-B sp/48 IDA). It bothered me sometimes due to noise mainly but since you have a FI, it may differ.

 

I was in the same spot as you when I put my car back together last year. I had always said I was going to go with aluminum but wasn't sure how tolerable it would be in a purely street car. In the end I went with the steel. I like it but it is a little harder to be smooth around town. Someone not used to a stick might struggle at first, as after not driving one for 10 months I probably looked like a newb at it for the first week. I haven't driven one with aluminum so I can't comment on that. Was afraid to spend the money and not like it. I like my steel one. Would I have liked the aluminum? Maybe, but may never know. I think you can't go wrong with the steel one. You get most of the benefits of a lighter flywheel without such a drivability penalty(from what I've read by people who've driven the aluminum one).

 

My first aftermarket flywheel was steel. Everyone said it would be too hard to drive with an aluminum one. The steel took a little getting used to but after a while it felt normal. I wanted more. My next one was aluminum. Once again I had to learn how to drive smooth and once again I got used to it. I loved it. If my current car ever gets a flywheel, it'll be aluminum.

 

I vote for Aluminum.
Here's another thread with more opinions: https://www.rx7club.com/2nd-generati...s-them-903268/

 

I do sometimes wonder now that I am used to driving it if I should've just got the aluminum one, but I'm not disappointed with the steel either. Problem is if I had got the alum. one and didn't like it I'd be stuck with it vs. this one which works good all around.

 

One thing I wanted to point out in that link when they talk about flywheel weights. They don't say whether those weights on the SR ones include the counterweight. if not then a 9.5lb flywheel plus the 4.25lb C.W. = 13.75lbs. Racing Beat's 12lbs Aluminum one is including the C.W. so the SR would be a touch heavier. It doesn't say on their site( SR) if that weight includes the C.W. Also the R.B. steel one is 17lbs including the C.W. Not sure if they make that clear but I weighed mine before putting it on the car. My point is when shopping flywheels find out if the listed weight is including the C.W. or not.

 

good point!

 

Good point. Also, as I have stated, the driving characteristic of the flywheel is based on the moment of inertia, NOT the weight.

 

Both valid points.
I should point out that my vote was based on my experience with the SR motorsports 9.5lb flywheel, (which I'm pretty sure is more like 13 or 14 lbs with the counterweight).
I don't know how the MOI compares to the RB units.

 

Just get the lightest cro-mo swiss cheese flywheel you can find. The ACT one is pretty good. It wont hurt drivability. By the time you put a H/D pressed steel pressure plate on it it all kinda evens out anyway.
That is unless you've got deep pockets and get a billet aluminium pressure plate, in which case, if you are modifying for performance, then you will appreciate the extra snappyness and will still have no problem driving around any "drivability" problems.

Unsprung puck (especially 4 or less) clutch plates can be annoying in stop start driving. 6 puck and sprung is best of both worlds.

 

I have rb steel lightweight flywheel with a stage 1 clutch, love it but i bet the alum flywheel might be better but i do dd my fc