I'm betting you have never driven an FD with a light flywheel

 

The stock flywheel if memory serves me correctly is ~23 lbs. So dropping to a 12 lb wheel will make a difference. It also makes a diference where the weight is on the wheel. The closer to the hub the better.

I remember reading 50 hp in first, 25 in second, 12 in third etc.

 

I say it is defintely worth it. I'm using the Racing Beat 17 lb steel flywheel as a compromise b/t stock and the ultra light flywheels.

Jack

 

Stocker is a bit over 20lb.

http://www.rotaryresurrection.com/3r...nter_info.html

Also you people talking about 9 and 12lb flywheels are forgetting to add the 4lb counterweight into that, which the stock flywheel has molded in permanently.

http://www.rotaryresurrection.com/3r...vs_aftfly.html

 

IF the stock FD wheel weighs 20.3lb and you're using a 17lb flywheel plus the 4lb auto ctwt, I fail to see how that is helping matters.

I think the 17lb was made for the earlier turbo II motors, some of which came with a HEAVY *** 27lb flywheel. On that motor, a 17lb flywheel plus 4lb counterweight would make a big difference.

 

I'm with Ramy on this topic, again

 

Kevin, are you sure the counterweight is 4 lbs? I have always seen 1 lb thrown around. I installed one the other day, and it didnt feel too heavy.....

 

10 lb 1-piece chromoly here (JUN). No regrets one bit.

 

I'm running a 9lb flywheel after my conversion and loving it. Although on hills it does tend to slow you down abit, a tiny bit. Nothing that I can complain about!

 

All the weights on that page were taken with a digital postage scale. All the counterweights weigh in at 4lb, give or take a few oz.

 

I put on a RB 9lb Flywheel about 4 years ago and would Never go back, whether for street or road track.

 

Hmm.... My motor is out right now, so the thought of doing this comes and goes. I have a stock-like(edit: RB street/strip clutch, so I'm told) clutch on there right now w/ ~7k miles on it. I'm not too keen on replacing the clutch until need be, should I do it all at once when I need to?

 

Keep the clutch, get a lightweight flywheel. I've never had any issues using a new flywheel with a used clutch disc.

 

Something's wrong w/ this picture...

 

Its mass is concentrated in the center. It was sold by Racing Beat for the FD, got mine through Rotary Performance in 1998. It's probably the same part they sell for the FC. Looks similar to the 17lb flywheel from Racing Beat that I had on a 1st gen 12A.

It wasn't as drastic as the change from the 1979 30lb flywheel to 17 lb but I still noticed enough difference.

Jack

 

I sat on this fence for 3 years. I kept stock because I thought "there is no way I am paying that much for something that won't make that much of a difference."

Then I bought an engine with lightened flywheel and sprung 6 puck on it. I had every intention of selling them. But after I rebuilt the engine, and a couple weak attempts of selling them I decided to go ahead and try it out.

And I am extremely happy with the change. I highly recommend it for a weekend street/HPDE car like mine. Daily driver may not like it but if I daily drove mine still I would do it.

The setup I have is much harder to drive than stock/act XT. At first I only got 2 out of 10 shifts right with it. After a couple thousand miles I get 8 out of 10. It makes you drive better I think - I am now rev matching, and heal toeing soo much better because you almost have to.

You can feel a difference big with a lightened flywheel.

 

When it comes to flywheels. Get the lightest (within reason) you can get your hands on. 9-11 lb is recommended.

 

I changed to a ACT SS clutch and a ACT streetlight flywheel when i did my clutch this spring. No problems at all with driving in start/stop traffic, but i think it revs faster.

I disagree with the people who state that speed matching is more important with a light flywheel. (lets clarify "speed matching" as a double clutch downshift). The original purpose of a double clutch down shift was to speed up the transmission input shaft to match the linear velocity of the gear teeth on the input shaft to that of the gear teeth on the output shaft, so that the transmission could be shifted into that gear. This is accomplished by shifting the transmission into neutral, engaging the clutch, stomping the throttle to use the engine to speed up the input shaft, disengage the clutch, shift into a lower gear and engage the clutch.

The need for all this was largely obviated by the invention of the syncomesh transmission, which is equipped with "syncronisers" to match up the gear teeth velocities and allow a nice grind-free shift. Still, routine use of a double clutch downshift during aggressive downshifts will greatly increase the life of the syncos.

So today, the primary use of a double clutch downshift is to match the RPM of the flywheel to the RPM of the clutch, so that when the clutch is engaged after the transmission is shifted, it does so nice and smoothly, and the clutch does not have to speed up the flywheel.

And so here is why i disagree with the "its more important to speed match with a light flywheel" statements: If you do not speed match during a downshift, then the faster turning clutch has to speed up the slower turning flywheel (and the engine to which it is attached) to the same speed as the clutch. Now, since it is widely accepted that the lighter flywheel with a lower rotational inertia (Polar Moment of Inertia for you engineers) allows the engine to rev quicker, then the same lower polar moment of inertia of the light flywheel allows the clutch to speed up the engine easier.

Therefore LESS IMPORTANT. Of course it is always more FUN to double clutch downshift.

Mike

 

^^We're talking about rev matching, no double clutching involved. Depress clutch, blip throttle, let clutch up.

 

I see no purpose for this "rev matching", as you describe it, other than showing off? Please clarify what the objective is.

Mike

 

Wear on the clutch maybe? If they are going near same speed on engagement there has to be less wear.

Since the flywheel is so light and I dont shift so "mad quick yo!" on downshifts my engine rpms drop very fast when I let off gas and depress clutch. Blipping the throttle just a bit makes the clutch engagement feel so much better. Maybe its my DIY motor mounts, jimlab diff mounts, or the 6puck clutch but just plopping the clutch out doesnt feel very good.

Besides being able to brake and have throttle control is one of the advanced skills of driving I haven't mastered yet and practice makes perfect!

And as far as showing off goes what would be wrong with that. That may be half of owning an FD...

Back to the topic of the thread though - I have 1 FD friend that has changed to lightened flywheel since they have driven mine.

 

When braking hard entering a corner, weight is obviously transferred to the front of the car, with less on the rear. The wide spacing between the gears means that unless there is some rev-matching between downshifts, the inertial imbalance between engine and drivetrain will always cause a loss of traction. A loss of traction with unweighted tires entering a corner can be a very bad deal.

This is during very aggressive driving on the track, obviously. On the street, it's pretty much a non-issue.

 

Maybe I missed something, but wouldn't rev matching, or blipping the throttle on downshift WITHOUT double clutching also tend to be easier on synchros?

 

Mike Nola, what you speak of sounds like it's right out of a late '70s article about double clutching prior to the advent of synchros. NO ONE double clutches anymore...

As Kento stated, rev matching is ESSENTIAL when you're entering a corner at a higher speed, and are reducing speed, and thus will be downshifting to a more proper gear for maximal corner exit speed. At that point, you want to make sure you DO NOT unsettle the car's balance, or (again like Kento said) you risk losing traction. That can be quite a scary thing.

One thing to add to what Kento said, however, is that I'm sure that the jolt of dropping gears and thus rpms suddenly from downshifting - say when you're braking due to traffic slowing then you're downshifting. If this is done w/o revmatching, there's a substantial jolt when you downshift. I'm sure that causes increased wear on the clutch, tranny, mounts, bushings, etc.

~Ramy

PS: It bewilders me that ppl don't revmatch, but it seems that (from my experience), the vast majority of ppl do NOT do it, let alone know what it is. I guess it's one of those things that you're only exposed to when you track your car?

 

i learned revmatching on accident, i was driving normaly and i was lazy or something, wasnt paying atention to what i was doing and shifted smoothly without using the clutch on an up shift, rpms fell just right. now i do it al the time when im lazy. i didnt use to know that rev matching is what i was doing, i just did it.