AL. Flywheel: One last time...

[Joel]

In the nicest possible way I'm going to disagree with Jason with the increase in HP issue. Since HP is a measure of work done, lightening the reciprocating weight won't make a difference, however if will make a difference in the length of time required for the motor to reach the rpm at which it will produce said horsepower.
That said I've just ordered one and expect it to make the motor more responsive both when out of gear and in the lower gears, especially first gear where the heavy flywheel is particularly noticeable.

 

[Joel]

Agreed on that Jason

 

[Greg D]

Airbornerx7: You are correct in your belief, that it will make a difference in RWHP. (not engine HP) (Does anyone disagree that by removing weight from the flywheel makes more power available to the rear wheels to accelerate the dyno jet drum faster?)

Jason: Rotating weight is much more important than dead weight when considering the effects it's removal would have on ET. A good rule of thumb is for every 100 lbs of non rotating weight removed, you could expect to see a reduction in ET of .1 of a second in the 1/4 mile. Engine speed rotating weight is said to be 3-4 times as significant as dead weight. Drive shaft speed rotating weight is about 2-3 times as significant as dead weight and wheel speed rotating weight is about 1.5-2 times as significant. (this depends a lot on the PMOI of the item your reducing the rotating weight from and where on the item the weight is coming off, I.E. bar bell effect) My aluminum flywheel is approx 17 lbs lighter than the OEM flywheel. 17lbs x 4(factor) = 68lbs or about a .06 to .07 of a second reduction in 1/4 mile ET. (best case scenario)

I recently replaced my stock flywheel with an aluminum flywheel. My reasoning was; prior to the aluminum flywheel, getting out of the hole (on the street with stock tires)was quite a challenge. The car would spin the tires unmercifully on the launch and when I hit second gear the tires would break loose and spin wildly again. This kills ET. Now with the aluminum flywheel, the car doesn't spin near as bad on the launch and the second gear change is just barely a bark. An aluminum flywheel may not be the way to go if your primary a "slicks and skinnies" guy. Then the reduced kinetic energy in the heavier flywheel may cause the engine to bog down off the line.
For the guy who is cruising down the road (at any MPH)and someone comes up and wants to play, an aluminum flywheel IS beneficial.
If a heavy flywheel was good, why wouldn't someone be selling flywheels that are heavier than the OEM unit for the Viper?

Just my 2 cents.

 

[Greg D]

Hey Shey
Think about it this way, If you subscribe to the fact (and I do believe in what you say here) "because once that flywheel is spinning, it's momentum (ability to sustain speed) is greater than the AL flywheel and would require less effort to sustain the rotation." then wouldn't it be true that it would be easier (translation: requires less HP) to increase (or decrease) the speed of the aluminum flywheel which in turn would free up the extra HP that was previously required to increase the speed of the heavier flywheel, so it can now be used at the rear wheels?
It sure would be nice if someone actually performed a before and after dyno run. Otherwise it's all just theory.

 

[Joel]

I've got to come back here. The lighter flywheel cannot make a difference to flywheel or rwhp. It will allow the motor to spin up faster and reach the revs at which max hp is produced but will not affect the value of that hp. This may show up an anomaly of the dynamometer which was discussed in a post a couple of months ago. If the lighter flywheel shows an increase in percieved rwhp, what does a change in rear axle ratio show...the same. Bhp is the power of an engine to do work and its
max value is at one particular steady rpm. Held at a steady rpm the reciprocating mass will have no effect. Thats kind of hard to explain but I'm 99% sure I'm right but only about 30% sure I've clarifyed things

 

[Joel]

"Joel,

I think me and you are on the same wavelength. I wish I could remember more of my basic physics! Wouldn't the heavier flywheel also have more energy stored in it at a given RPM due to the fact that it is denser than AL?"

Yes, thats spot on, but it can only release that energy when it decelerates and likewise will absorb energy to accelerate it so at a steady rpm that flywheel is not having any effect.

 

[jamie furman]

Well I can answer this question, I was told to get an aluminum flywheel and my car would pick up horse and et in the 1/4 . Well I didn't gain anything but a big bill, about 1500 installed and the engagement and disengagement of the pedal was so weird and uncomfortable I took it back out as soon as I got home from the track.It might work good on a road race car but I hate it on a street car don't waste your money.Also you will not notice more response and the engine won't feel nearly as torquey.I did the before and after not on the dyno but at the track lost 1 mph and ran virtually the same et.I figured I could do that for free, why pay for it?

 

[Ron]

<FONT face="Comic Sans MS">Jamie;

My experience is quite different than yours. Perhaps there were other issues as I see no reason why the engagement and disengagement would change so much or at all for that matter. Perhaps you were experiencing clutch chatter which is normal until the disc mates with the flywheel.

I personally was never told that it would add HP or lower ET, just improve the throttle response. I experienced exactly what I was promised by Jon B., no more no less.

Clearly at $1,500 you did a remove and replace solely for the AL flywheel install, which many have said isn't worth it. @ $395 ~ $450 while you're in there already, it's a lot more palatable expense.

All that said, I do agree that it's not a must have or even the best $400 I've ever spent. An improvement, yes but not more than that. For me, there was no downside though but the cash. </FONT f>