Its not arguing. It was a discussion. Just because someone disagrees doesnt make it an argument.

If the combined mass of an aluminum flywheel with your choice of pressure plate is still more mass than the next choice it has more stored energy. Aluminum, billet or steel, you choose based on what you run.

Gm engineers didnt come up with a winner for the LS7 combo since a lighter weight clutch holds the N/A record in a C6 after it was swapped out for a tex clutch that weighs 20 pounds lighter. Ed's car has the curretn h/c record and he replaced the heavy LS7 with a lighter Tex. Apparently weight doesnt make you lauch better and I would never credit the heavier flywheel is better becuase GM did it. I have an LS7 with an Alum fly and it doesnt bog with sticky tires at any launch rpm. Myth busted by everyone that drove one.

As with all mods people, drive the car with the mod you want and dont take advice on a mod from anyone that doesnt have that mod or personal first hand experience with it. I dont care who they reference or hwta they read as the source of the info; the fact is that they didnt get it from personal experience and shouldnt be offering it as fact nor should it ever counter the findings of someone who used 3 al flywheels with 5 clutches on 2 modern corvettes.

Just as with 4.10's I know of no one who got an Alum flywheel on the street who says it was a bad move. If you find someone who hates in on a track its more likely the clutch that is giving them greif not the flywheel its bolted to. I had used the Ram with and without it with no other changes and noticed no ill effects from it.....and I dont care what anyone says about xyz set-up in a car other than the C6 or C5.

 

I have to address this not to have a come back to you but to clarify to others that may read that and think its correct.

The total weight of the flywheel and pressure plate is a some total sum and the weight isnt constant for the pressure plate so vary the use of your flywheel to compensate can still result in the exact same amount of weight.

An engine once it has increased power will not bog with a lighter flywheel at the same point than a lower powered engine so thats not the constant you pass it off as either.

Lastly, no one said a lighter flywheel makes every car faster, in fact all I was forcing the issue on was that there can exist a condition where a pressure plate is too heavy and a lighter flywheel can compensate and yet not give up a single pound of total weight to another pressure plate/flywheel combo. In that case the al fly and pressure plate combo has the exact same amount of storeed enbergy and clutch assembly 2.

MY AL FLYWHEEL AND PRESSURE PLATE TOTAL WEIGHT IS NOT LIGHTER THAN THE CURRENT CLUTCH BEING USED IN THE FASTEST H/C CAR SO THE WEIGHT LOST BY THE FLYWHEEL.

Stop saying al flywheels are bad for launches until you see what pressure plate they will run and then judge the total wieght. Its not rewriting science, its using various tool as the variables they are meant to work in. You seem to think alum flywheels are bad for launches in all cases and shouldnt be saying that. There exists some power levels where ther wont be any bog with 1/2 the clutch assembly weight gone. No one size fits all.

You need to be able to have people disagree with you without thinking its an arguement. The cut and paste of info doesnt make anyone experienced.

 

not sure if this will help any but i plan on using the Mcleod Twin Street

 

wow alot of good info here . i have 2 zr1s both cars went almost.3 tenths faster with the alluminum fly wheel verses the stk one . i used the carolina pressure plate and ceramic disc . love the way the car revs too . for me it works better everywhere even in stop and go traffic. whats that old saying try it youll like it

 

My experience and those around me failed to produce the C5 or C6 that bogs on a launch. Based on that info, your experiece, and others like you, I dont think people who didnt try an aluminum flywheel should be posting info they got from 3rd parties about bogs on corvettes that I have yet to see.

Even people who may have a bog with any clutch, the simple reason is insufficient power. By far the vast majority at the track happen to have so much power that wheel spin rather than bogs is the norm. Far too many people reading the internet or going by experience on other cars (especially small ricer machines) tend to think the constant is less weight means more bog and it doesnt when you look at all ther variables.

Anyone ever hold the clutch disc itself in their hands? That has varying weights too and once the clutch is dumped the flywheel, pressure plate, clutch disc, drive sahft, crank, and everything with a drag on it all move as a single unit. Have a stroker? Well the flywheel is bolted to that heavier forged stroker crank. Whats wrong with adding weight with these parts and compensating for it with a lighter flywheel?

Sorry, in my book it doesnt mean a bog and I dont care what clutch manufacturer tries to make it out to be a constant, it isnt. Sometimes less flywheel is still heavier than stock and there isnt a given bog. So to the OP, it can be exactly what you're looking for at the 1/4 track if you have heavier other parts. In your case, you have more than enough power to not worry about bogs and will likely have wheel spin on your launches regardelsss of flywheel weight. You will not bog and would be gaining from lessening drive line losses. Most people report a minimum of a tenth and I have seen as much as 3 tenths from this mod. I have never seen someone get pissed off at having done it. Like 4.10's, most who get it love it. I'm sure that there are a few that dont but like i said before, they may be actually not liking the clutch's more aggressive nature since almost everyone gets the flywheel in conjunction with a much more aggressive clutch.

For those that didnt check his mods are:

Callaway Honker | Ported TB | Spin Ported FAST 90mm | LG G6x3 cam | Trick Flow 225's milled to 62cc | LG Pro Z06 Headers | Z06 Bullets | WCC lowering bolts | VR calipers | GS fender stripe | Black C6 wheels | MGW Shifter | RPM Stage III 4.10's | LG Tune

Yes skinnies are 'worth it' for weight transfer. Yes 500 for the flywheel is 'worth it'.

 

Well I'm one of those who did experience the bog after putting on the Fidanza/Spec II to replace the stock flywheel and clutch (failing after a 425 SAE rwhp) heads/cam swap on my C5. I tried three launches on ET Street 275 DR's, all bogged. First launch @ 3,000 rpm, dead hook and bog. Second @ 3,500 rpm, same result. Third @ 4,000 no spin, bog. With a stock rear IRS I was unwilling to launch harder as I have seen first hand two grenaded diffs.

Trying to throw dust in the air talking about how light is light doesn't change the fact that I reduced the rotating mass of the fly/clutch and lost energy in the launch. The new combo worked GREAT on the street, showed about a 10 rwhp gain on the dyno, but wasn't the best for me on the dragstrip.

 

Thank you for your input; it's nice to hear from someone else with 1st hand experience

 

Slipping a clutch on the launch is kind of the entire art. You have to hold the balance between spinning and not giving it enough. It isnt an off/on switch. The rev to 4000rpm thing and dropping the clutch shows me someone doesnt know the technique. Bogging any car is part driver error. I doubt very many 1/4 guys would say it was a reasonable launch method.

What makes you think the bog wouldnt be there with the steel flywheel? Maybe the car didnt bog before because it had a stock clutch that slips and the aggressive clutch is causing the bog from too little power with no slip. Beginners that think they have it down have 3 things helping them not bog: 1-street tires that spin letting the rpm's climb, slipping clutches that when dumped still dont grab, and 3 usuing lots of rpm and spinning off the line. When all three are taken away and they actually have to manually keep it from grabbing too fast is when you really became good at the launch. In this case we had all 3 handicaps...sticky tires, grabby clutch and unwilling to raise the rpms for the rev and drop method. Let it out at a controlled rate.

I usually look at the guys running fast times at the track to see what works not the 425rwhp guy with issues. Since my friend has it with a 10.0 et, it works in drag racing.

Now why didnt you comment for the guy that said he gained 3 tenths with it? That example didnt make your point?

C'mon man. Admit the statistics arent in favor of the nay's for actual users. I'm done here too before it gets into a bad direction. Youre probably already pissed.

 

Launching with less rotating mass is easier on the drive line than with the steel flywheel. If you launched 4000 with a steel flywheel aside from more mass with more stress, the same clutch may still have bogged since it isnt slipping like the stock clutch. You changed the clutch and flywheel together so it is impossible to tell which is more responsible for the bog you experienced. The most immediate remedy is to increase power to keep the car moving.

 

One bad thing about al fly's is that they can be more prone to warping from excessive heat.

 

Everything SpinMonster has said is true not only in the real world where he has experience, but also technically and can be proven by the math. The e-mails from the clutch companies were pretty sad quite frankly, they show a distinct lack of knowledge. A lightweight flywheel is king on the dragstrip...look what the fastest dragracers run.

When considering the launch, the inertia of the flywheel is not even half of the inertia in the whole "system". (Spin referred to this in an earlier post.) Of the two variables RPM and mass, RPM has the far greater impact on the kinetic energy stored by the "system". Let me run through a sample HP calculation on a lightweight flywheel vs a heavy flywheel.

To illustrate the effects of a lighter flywheel, let's take the acceleration of the Z06 from 5-60 MPH where the engine goes from 600-7000 RPM in 3.7 seconds (clutch engaged from a roll). Work is done ON the flywheel by the engine to increase its' kinetic energy (KE) with the amount of work done (KE added) given by the KE (after) minus the KE (before). KE=1/2Iw^2 (where I is rotational inertia and w is the angular velocity) from this link: http://hyperphysics.phy-astr.gsu.edu/hbase/mi.html
The rate at which work is being done on the flywheel is equal to the rate at which the KE is increasing. HP is the rate at which work is being done so we're left with finding the KE added and dividing by the time it took to add the KE to the flywheel to find the average HP required to accelerate it from one RPM to another.

flywheel/clutch: 60 LBs (~27.3 KG) and 13" diameter (~.33m). These are my estimates...close enough to get a good number but they are not 100% accurate. If you have the correct numbers, there's enough here to get the exact answer...I think I'm low on the diameter and high on the mass.
From the link above, I for the flywheel is I=1/2MR^2 where M is the mass and R is the radius of the flywheel/clutch.
I=1/2(27.3KG)(.165m)^2=.372 kg-m^2

600 RPM=(600/60)(2)(pi)=62.8 rad/sec
KE (before)=1/2(.372)(62.8)^2=733.7 Joules
7000 RPM=(7000/60)(2)(pi)=733 rad/sec
KE (after)=1/2(.372)(733)^2=99866 Joules
KE (after)-KE (before)=99866-733.7=99132 Joules
1 Joule=.738 ft-lb
99132(.738)=73159 ft-lb which is the total work done to increase the RPM from 600 to 7000.
To get the rate at which work was done, divide by the 3.7 sec run giving: 73159 ft-lb/3.7 sec= 19773 ft-lb/sec
1 HP=550 ft-lb/sec, so we have 19773/550=36 HP to accelerate the flywheel. If the weight of the flywheel/clutch is reduced to 30 LBs, it will only take 18 HP for the same acceleration...that's a free 18 HP! Of course the rate at which the RPM is sweeping is ~1730 RPM/sec which is much more than on a dyno, but you will see an increase on a dyno with a lighter flywheel. As you can see, the effect is dependant upon the rate of RPM increase. Therefore as you go up in speed/gears, the RPM rate decreases requiring less HP to accelerate the flywheel. By the time you get in 3rd and certainly 4th, the effect is so small (in comparison to the LS7's rated engine HP) it's considered negligible.

As you can see, mass is a first order determinant (linear) and RPM is a second order determinant (exponential). So while doubling the mass will double the KE, doubling the RPM will increase KE by four times. Now to tie things together using a flywheel/clutch at 60 lbs and rotating at 1000 RPM and analyze KE using 1/2Iw^2. Using only the M portion of "I", we have 60*(1000^2)= 60,000,000 units. The rest of the "system" consists of the crankshaft, rotating portion of the connecting rods (rods have rotating and reciprocating portions), timing gears, timing chain, cam, harmonic dampner, and all pulleys (most engines would include the alternator, but not here). Let's say the KE of the rest of the system is 1/2 of the flywheel/clutch giving it 30,000,000 units (giving a total of 30 lbs of mass equivalent to the rest of the system) making the total 90,000,000 units or 90*1,000,000. If we reduce the mass of the flywheel by 20 lbs, we now have a total of 70 lbs of mass leaving us with the equation 70*(x^2)=90,000,000 where x=RPM with the lightweight flywheel required to equal the KE of the system with the heavy flywheel at 1000 RPM. Grinding through the math gives us x=1134 RPM to equal the same KE...not a very significant increase. Most people tend to use more RPM than needed when driving on the street and would never notice a difference in drivability. At the dragstrip, a 3000 RPM launch with a heavy flywheel would require a 3400 RPM launch with a lightweight flywheel. The launch in the post above at 4000 RPM w/lightweight FW is the equivalent to 3530 RPM with a heavy FW. Again Spin is correct where he said in several posts that a bog after a lightweight FW installation has more to do with the new clutch grabbing better/quicker and requires the driver to use a little skill to slip it. My ZR-1 has trouble with wheelspin off the line so I launch at 2500-3000 RPM and slip the clutch up to 40-45 MPH.

The mantra of a lightweight FW requires more RPM is true but usually grossly overstated. Its' largest benefit is in 1st gear on the dragstrip. Road racing at courses that use mainly 3rd and 4th don't see much benefit in acceleration but rev matching on downshifts are made easier by the quicker revving. Smaller engines will see larger performance gains with a lightweight FW because it's a larger % of the "system"...but you may only need 1200 RPM instead of 1000 RPM on the street to leave a stoplight.

 

talked to my shop guy at a car meet tonight..he recommended i do the aluminum...looks i am going that route

 

i would be willing to be that you will be glad you did. when you get to the strip the first time you might seek out a vet guy that has your clutch set up and ask him for some hints. my 3rd zr1 that i just bought has the stk clutch set up , its getting changed asap the car feels like a slug compared to the other 2. it revs so slow. just get a good quality setup dont get cheap

 

Rich, I'm convinced that I need to figure out how to Vulcan Mind Meld with you and Guy somehow ....when me and Spin come to FL in January, dinner is on me.

 

Sounds great, where in FL will you and Guy be? I'd love to get in on some of the fun you guys have and sit down to dinner, first round is on me.

 

If you can afford to live in a waterfront house in Neptune Beach, the second round is on you too.

I will keep you informed.