mjr46

I agree that the money on a fairly stock engine can be best spent elsewhere..I only added one after the fact I had done every internal engine mod, external mod and suspention and drivetrain mod...this was a final supporting mod to the drivetrain..and was bought in conjunction with a aluminum driveshaft, heavier duty axles, aluminum rear end stud girdle and aluminum flywheel... and MM pan hard bar for my 85 gt...all together the mods really complemented each other and worked well as a overall noticable improvement......all I say when supporting productsIsuggest speaking from experience on what you have used and not read onlytheroy..because what you actually see and experience often don't line up hand in hand and defy what theroy states.. because a theroy is just that ...not fact which can be changed based on new and ever changing empirical evidednce

Norm Peterson

Mostly true, but you may need to have a slightly better "feel" with the lightweight unit to ensure both clean starts and minimal clutch wear. The NVH part (more vibration with a lighter unit) is probably true simply because crankshaft torque isn't really constant when you look at it over extremely short time steps (piston force isn't constant, and neither is the leverage offered by the crankpins). Mileage on the highway might go up, but if it goes up by enough to notice that means that you aren't holding a steady speed all that well either before or after. I'd believe a slight city-driving mpg improvement first.

In the somewhat more extreme, 5.5" triple disc clutches with small diameter lightweight racing flywheels are not considered streetable at all. Not enough inertia to get a street car moving without doing either a burnout or a lot of clutch slipping, and not enough durability to put up with the necessary slippage.

With respect to the 'consumable' thought, most aluminum flywheels give you a replaceable steel insert friction ring, so you need not replace the whole thing.

I might swap up to one for a semi-serious auto-X build, but probably not for pure street. Any chance of a swap for streey duty would probably depend on what the OE iron wheel weighed (a 40-lb'er I'd probably swap out when it came time for a normal clutch replacement, probably not if it was a 20-25).


Norm

Reverb

Take a look at this site http://www.pumaracing.co.uk/FLYWHEEL.htm it explains things very well (it's a british site, but they are very knowledgable). Theres some excellent articles if you scroll to the bottom of the home page too.

67mustang302

Yeah, I'd also agree that the cost of aluminum certainly needs to be weighed vs what the car has. Like norm said, many of them have steel insert rings too, so you just replace those when worn, no need to ever get it machined or buy a new flywheel, so in the long run of a vehicle's lifepsan, the initial cost may be offset by money saved, especially depending on how hard you drive and how often you change clutches/machine flywheels etc. For a stock engine it's pretty much a waste, but like mjr said, when you've done most everything else then things like aluminum flywheels etc start to have a bigger impact, and everything comes together.

Also, good posts by Norm, where've you been btw? Haven't seen you around lately.

Norm Peterson

Mostly lurking when I've had the chance.

With one exception - let's just say that an '08 GT of uncertain detail description is on a very short list (hint: that's at least onehint ).

And now, back to your regularly scheduled discussion . . .


Norm

ozarks06

Ford claims the aluminum flywheel in the 03-04 Cobras (which weighs 11.2 pounds) shaves 0.2 seconds from the 0-60 time. That is abig difference in performance, equal to quite a few ponies. Two-tenths in a quarter mile for a 3500 lb carwould be about 15 HP difference (at 12.9 vs. 12.7 seconds). If you can get one for $300, that is 'like' paying$20 per HP, not a bad price(like a cold air kit and tuner - $600, to gain 30 HP on an 05-08 Mustang GT). (And I realize we're not talking about any more torque from the engine, but HP is a factor of torque and RPM, so it is 'effective HP' you're buying.)

67mustang302

If Ford hadn't been lazy, and put the Termies on a diet and gave them screw superchargers instead, they woulda been low 12 cars easy. Still though, they have good performance for their price.

Colorado_Mustang

No one has stated that a lightened flywheel would decrease acceleration performance, as it will. It will not increase power. Lightening your car also increases acceleration performance, but does nothing for power. Both are efficiency considerations.

Unlike others, I've actually swapped out only the flywheel with a lighter weight unit. While the engine was peppier, it wasn't worth the hassle on the street. Five speeds typically have lower 1st gear ratios to help with the appearance of losing the smooth engagement with a lightened flywheel. The system must be taken into account, which is well beyond the quoted high school physics...and beyond beginning college physics classes that neglect many of the important variables.

67mustang302

The whole point of the basic physics was to show that usable horsepower can be increased by lightening moving parts in a machine, resulting in less inefficiency loss in the system. It takes power to move a car, period. If removing weight from a flywheel makes the car go faster, but the vehicle's weight remains the same(minus the flywheel weight, which had a larger impact on car acceleration than the total weight lost in the car because the flywheel is rotating and going through a series of gear reductions), then you HAD to have freed up power to propel the car faster. Remember that horsepower is force x distance / time, or rather work / time. The amount of work that you can do in a given time period is horsepower, so if a lighter flywheel causes you to cover the same distance in LESS time(faster acceleration) with the same amount of work, you produced more power. Or you could cover a greater distance in the same amount of time, you did more work and therefore have more power. Though in actuallity you'd be using power to move from one point to another, so you've converted potential energy(usable horsepower)into kinetic energy in the form of movement.

Remember, horsepower is not a thing, it's a measurement ofthe relationships invloved in a conversion process. Same with torque,which isa relationship known as work, which measures force and distance, horsepower measures force, distance and time. Changing mass, speed, time, force etc,all that changes the relationship, and therefore the power. I think the thing is too many people view power as something akin to an object, but it's much more abstract than that. Horsepower is simply measuring the relationship of a given force, exerted across a given distance in a given amount of time. Increasing mass in an object increases the moment of inertia, which means when the same force is applied there's more resistance to movement, so LESS distance is traveled in the same time period. That's why an engine with heavier internals/flywheel revs more slowly than one with lighter internals/flywheel. Less distance(fewer rpm's)with the same forcemeans less work, and therefore within the same time period,less power. Remember, the horsepower we measure from an engine isn't really a thing that's produced by an engine, but rather it's a measurement of usable potential energy that is left over from a process where chemical energy was converted to mechanical(kinetic) energy in order to release some useable potential energy.

With lighter parts inan engine,you're not really producing more power, so much as losing less energy to other parts of the system through the conversion process. That yields a higher horsepower rating, because there is more potential energy available after the process. But horsepower is a measurement, not a thing.Engines don't produce anything(other than exhaust gasses and heat), they CONVERT one form of energy to another. Horsepower and torque are just ways of measuring the relationship of the conversion preocess. It's more accurate to say that engines don't produce power, they LOSE power through the inefficiencies of conversion, and the horsepower and torque we measure is just what's not been lost after the conversion process. A more efficient engine doesn't make more power so much as it loses less.

ozarks06

My point was that Ford (presumably based on actual tests) claims that the lightened flywheel reduced 0-60 times by 0.2 seconds in the 03 Cobra. That 0.2 seconds (when applied to a 1/4 mile time in a 3500 lb car) is equivalent to gaining 15 HP(that is, it takes 15 more HP to cut 0.2 seconds from a 1/4 mile time in a 3500 lb car). Yes it comes from reduced rotational mass (lessenergy required to overcome inertia)rather than more engine torque, but 15 HP(or 0.2 seconds 0-60 time) from a $300 mod is not a bad investment (though a lot of work!). Whetheryou would get that from a small block (or any engine for that matter) depends on other factors (as Colorado_Mustang noted). But, in this particular application (03 Cobra) the improvement was pretty substantial.