Some would argue that the gains are minor with the lightweight assembly. I was most impressed with the area under the curve on both cars in the test (link below) in which 2 cars received lightweight assemblies. While the reduced parasitic losses amounted to only 9-12 hp and 9-21 tq at peak, the upper-midrange power was up and more dramatically down low off idle in percentage proportion (25% on the stock car just off idle-try that with any other mod). That isn't minor and for me confirms that the clutch swap made a bigger difference to me than headers did.

I notice no clutch engagement issues at all and always thought after installing it that people like to spread the same false rumors around that seem to exist when people comment on things they never tried personally.

I was told by cartek personnel that they have seen these flywheels warp under severe conditions. I state that as a possible issue for drag racers who also argue that a bog may exist with some set-ups. For my street-only vette, its a winner all around. The car once in gear is so much faster that it is hard to imaging anyone having one of these for street use could argue for a better mod especially if the car is in need of a better clutch due to wear or power mods.

The test I spoke of:
http://www.vetteweb.com/tech/0407vet_flywheel/

 

I Could Not Agree With You More!!!!

 

Which Clutch combo did you go with???
Jeremy

 

Go down to the dyno graphs, and click the leftmost one up.

In the first graph the TQ curve of the modified vehicle is higher than the unmodified vehicle from the low end towards the upper midrange. Then the TQ curve of the modified vehicle dips below the unmodified vehicle, and yet the HP curves do not dip below.

Since HP = TQ * RPM / 5252

Any time the TQ curves have the same value at the same RPM the HP numbers have to be identical.

This smacks of dyno graph manpulation.

However, I am fully on board that light weight flywheels do good things to performance.

 

The graph isn't torque/hp vs RPM, it's vs time therefore the formula you gave doesn't apply. The lighter flywheel gets to the descending part of its' torque curve sooner but the RPM is also higher at that point making the HP more...that's why its' hp curve stays above the stock flywheel hp curve. I will admit it's a little confusing to look at when we're use to looking at torque/hp graphs vs RPM.

 

Interesting my dyno runs took 11 sec.

 

Different motor, different car....as they clearly pointed out both cars were faster than their same-variable base runs. There isn't much of an argument that a stock LS1 base 2004 vette is slower than a modded/tuned Z51 2005 C6. Now Jim, if you want to do some baseline runs and install one to show us they make your car run slower then we have some useful info. The other variable is where you start the run. If you start at 2k like they did, which is very low, it will take a bit longer then starting at 3500. Where was your run started at?....2500? 3000? If you are referring to this run you previously posted:

[/QUOTE]

It appears that you started the run at 2500 (base) and 2700 (tuned) and it isn't valid to put your 11sec time into the mix. I know you're not a fan of alum fly's on the track but for a street car its a great mod. Obviously mt point is that it isnt a measurment to use to compare car to car but rather same car, same dyno, same day/weather. How long it took your car on a different dyno, different day doesn't say anything about what a lighter set-up will do for your street car. I wonder what you would use if you kept this car long enough to warrant/need a clutch. Bogs on the track don't hold water on a street car unless you test your zero to sixty on the street as the standard rather than in gear passing power.

I was at ECS in NJ while Chris was tuning his car...seemed to be 5-6 seconds but then he has an auto and 700rwhp.

As pointed out the dyno graphs show how many seconds it took to make peak power not RPM vs. power. I thought people would recognize (and appreciate) that a simple mod that doesnt cost much if you are in need of a clutch gains simply by reducing parasitic loss.

I have a spec 3/fidanza on my C5 and RAM sd 900/fidanza waiting to go in the C6.

 

OK, I can buy that.

 

It appears that you started the run at 2500 and it isn't valid to put your 11sec time into the mix....unless you just doubt and you want to reach for anything. I know you're not a fan of alum fly's on the track but for a street car its a great mod.

I was at ECS in NJ while Chris was tuning his car...seemed to be 5-6 seconds but then he has an auto and 700rwhp.

As pointed out the dyno graphs show how many seconds it took to make peak power not RPM vs. power. I thought people would recognize (and appreciate) that a simple mod that doesnt cost much if you are in need of a clutch gains simply by reducing parasitic loss.

I have a spec 3/fidanza on my C5 and RAM sd 900/fidanza waiting to go in the C6.[/QUOTE]

It's been many years since I was really active in racing but when we went from Al to steel flywheels we picked up a bunch on time. Why you ask, well that with the current C5 or C6 traction is a big problem and the 1st gear delta rpm is the greatest but short lived. The energy storage is mainly done in 1st gear when your more concerned with hooking up anyway so who cares how you spin up. The energy now stored in the heavy flywheel comes into play at the shift points and is transferred at that point, that’s a good thing with narrow delta in rpm’s for the remaining 3 gears. The al was great in circle track when in just one gear and accelerating out of corners down back and front stretches. With road courses you keep your rev’s up in a narrow range with the transmission along with the stored energy in the rotating flywheel. Where am I going wrong here? The car I ran when active was a 55 chev with a 327 and we launched at 7000rpms and no bog with the steel wheel.

 

I would have loved to see 1/4 mile times to put the argument to an end.

 

You would have to ask my X wife the slips where probably with all the other stuff she burned.

 

Application is where. It isn't a drag car and it isn't a circle track car. Its a street car where passing power is usefull and 7000 rpm clutch dumps aren't done. I don't feel any bog at all shifting gears and the run-up in all gears is faster. Keep in mind, they measured the hardest gear of all in a drrag race...4th for the time difference.

You keep using race performance as the standard and for those not interested in aggressive clutch shifts and hard launches and just looking for passing power this mod has no downside.

In my corvette, the aluminum flywheels made it faster. Phil97svt (this forum) runs one of these with 1.4x 60 foot times so until you show a CORVETTE that was actually slower from using one stop offering that as fact. I have had this coversation with you before and said my 68 dart runs one with no bog so why is that not countering your experience at all?

 

Not a personal attack on you sir, I was refering to the test....I wish they had used that as the test of the flywheel in the CORVETTES to show how the alum fly. benfits this car and not a dyno test which you dont drive on to get to work....not the 1/4 mile time slips for your drag car.

IE...run 3 1/4 mile runs and then swap the flywheel to see if there is an improvement. That still wouldn't reflect my street driving but it seems to be the universal language for some.

If the test involved a 4th gear run-up on the hiway to redline...150mph it wouldnt solve anything either....and.. does the bog negate the faster in-gear pull?

I beleive it wouldnt change your mind either way. Even if the car ran 3 11.75's then a 11.63 you would attribute it to something else because you felt a bog in a 55 chevy. BTW, nice car. I still have my Dart but I don't recall you saying if you still have the 55 do you?

 

That would help. There isn't enough info available in those dyno runs to quantify the advantages of the lighter flywheel. It's more marketing hooey than anything else.

You could take the mass polar moment of intertia of the two set ups, a stock acceleration run and calculate the apparant increase in horsepower and torque far more meaningfuly that they did on their dyno.

One reason for somone selling something to not do that is that it will show that flywheel lightening makes a significant differents in the lower couple of gears but almost no differance in the hiogher gears.

Doing it by the numbers, like I suggested above, would also give you a good idea how it would feel seat of the pants on the street.

 

Don't have the 55 anymore, was fun while it lasted. 5.38 rear gears made for an interesting street ride though. The circle short track acceleration model is similar to street acceleration, with a fixed gear. As far as testing on the track, yes way too many variables to draw a conclusion. Just that the bog was gone and no hesitation on power shifts from then on, along with faster times. Didn't do the math at that time but conversations with team mates and compititors over the years made the case. Then throw in 34 years of college teaching math and physics may have something to do with it also along with the words inertia and that little tell tail equation e=(1/2)((M(C*C))

 

...and guys cut 1.4x 60' times with an aluminum flywheel....10.77 all motor.. stock displacement....Phil97svt.

If it was a corvette you had this issue with then I would credit the example. I have no bog with a track only 426 hemi/68 dart/w6.13 gears and no bog in my forged 348 2001 vette. Why don't those examples count. By the way I am licensed in NYS to be a teacher....yes math although I don't teach which means nothing since you can juggle numbers all day long which still doesnt answer if the bog some people experience (and I don't) outweighs the very proven quick rpm run-up in gear. Further I like to resort to the inertia principle that states an obect at rest wants to stay at rest which is mass related. Reduce the mass both the rotating and the weight of the car and it has less inertia. You can't model everything that happens in a drag strip launch in a single equation that fits your need here. If you are trying to say that adding weight to the flywheel is going to make you run faster 1/4 times then go ahead and add the weight. I think your car bogged due to a poor choice in stroke for a drag motor.

I would like to point out from the very start of this thread I specified that this was not to be looked at from a drag race perspective.

I said exactly this:


If you change the flywheel to an aluminum one your car will be faster on the street where I said from the beginning that I don't do high rpm clutch dumps nor was I recommending it to those that do hard launches. There are guys on this forum who do use it on the track and they state they have no bog.

Jim, I want to be clear on one thing; I enjoy the debate

 

Rockers, gears, flywheels, UD pulley....I seem to get a fight on all these issues and then you see a car run 10.77 all motor by a backyard mechanic running all of the above or a guy puts 480 to the wheels with stock displacement with a 224/228 cam using a UD pulley, 1.7 quick cranes, alum flywheel....and it is always a guy running 12 second 1/4's fights the recommendation every time with their expertise which is NEVER had by using the mod in question on a CORVETTE. Look and see just how many of these 'scam' mods are used on cars in the tens and in the nines then tell me they don't work or use it and show how it didnt work.

You know tuners read these threads but contribute nothing to them. They have flywheel experience and say nothing. The real rip-off is there, not in the writing but in the absence of sharing knowledge. How many guys on this board are running an aluminum flywheel and bothered to say how good it is? I get thanked by the ones that wont run these scam mods in the form of a kick in the azz for trying to turn this into a tech section instead of the listen-to-how-my-new-exhaust-sounds section.

I'm getting ready to be a read only member here.

 

This is another interesting thread with some interesting data and anecdotes as well. The '55 in the picture is/was also a very handsome car. I hope that the wife didn't burn it! The story reminded me of a time I ran a guy in a '56 years ago when I was in high school. Among the few things that I remember about the car were that it had a 327, a big gear, an aluminum flywheel and it definitely didn't bog. It took off like a rabbit. I didn't catch him until well into 3rd and only then because my brand X 6BBL, big-block wedge had so much power it made up for my driving skills. My tires spun a lot. His didn't. Regretfully, I had en excellent view of his progress.

I don't know anything about race cars but after listening to all of this, if I had to replace a clutch on my street-only C6, I'd put in the aluminum flywheel. It just makes too much sense. Most things that can be done to reduce weight also improve performance. This one seems like the rule and not the exception. Heck, I even remember a carbon fiber replacement for an aluminum driveshaft. I think that this was for some kind of Vette. Reducing driveline weight must mean a lot to some people.

I must confess that the "mass polar moment" thing has me stumped, though. I'm gonna hafta go watch March of the Penguins and call a math teacher to find out what that means.

As usual, thanks for the entertainment!

 

It's just a way to hang a number on how much torque it takes to accelerate a flywheel. If you know the mass moment of intertia of a flywheel you can calculate how much torque it takes to accelerate it at any rate far more accurately than you can measure it on a dyno.

Dynos like Dynojets actually are just big flywheels with some instrumentation added. The readings you get from a Dynojet are calculated from how rapidly you acclerate the big ol' Dynojet flywheel.

 

Thanks! Now, I get it. I can see why that might be the best test. The elasped time to speed data seems like a useful surrogate, though.