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Old 11-27-2007, 12:33 AM   #11
67mustang302
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Default RE: Aluminum Flywheel - How much hp will it add

Horsepower is defined scientifically as force(pounds in the US) x distance(feet) / time(minutes). 1 horsepower = 33,000ft-lbs/minute, or that is to say it takes 1 horsepower to move 33,000lbs 1ft in 1 min, or it takes 1 horsepower to move 1lb 33,000ft in 1 minute, or it takes 1 horsepower to move 1lb 1ft in 1/33,000th of a minute. In order to move an object(which from a stand still requires acceleration) of a given mass(or weight, which isa resistance force, along with friction) a certain distance in a certain amount of time, you have to exert a certain amount of force. That's the essence of horsepower. So, if adding a lighter flywheel for instance produces or frees up noextra horsepower, then why does it accelerate more quickly? Well, because it weighs less, so you're exerting the same force over a LARGER distance in the same amount of time(revving to a higher rpm in the same time period) or you're exerting the same force over the same distance, in aSMALLER time period(revving to the same rpm more quickly). Plug that in to force x distance / time and you get more horsepower.

I think what's happening is force gets confused for work(lb-ft) or horsepower(ft-lbs/time). No more FORCE is being produced, which is your actual cylinder pressure during combustion that's pushing everything along, but there's less resistance in the form of mass, so the object you're moving(in the case of an engine it's all the internal moving parts and the flywheel, plus drivetrain components if you measure power at the wheels) either travels a greater distance in the same time perdiod, or travels the same distance in less time. Either way there's more horsepower, whether it's from more distance or less time, and more horsepower is also a matter of more torque. That gets into the fact that WORK = force x distance, whereas TORQUE = distance x force but is used to deonate work around a point of rotation, rather than a straight line(in that case, the line that is traveled is a circle with a given circumference, but torque is used with the standardized 1 ft radius, so the distance traveled is pi x 2 for the sake of a standardized measurement). So to get the same mass(in this case a flywheel) to travel the same distance in less time, you'd have to exert MORE force(increased cylinder pressure, or a greater distance in the same time would also require more force), either that or you DECREASE the mass of the resistant force(the flywheel and internal components) and exert the same amount of work, but in a shorter time period because of decreased resistance(or again, a larger amount of work in the same time period), so you produce more work because of increased efficiency(in an engine, torque) and thus, more horsepower.

Because....

Remember an engine is not an ideal machine, so for the purposes of power measurement, energy in(combustion pressure) minus losses due to inefficiency(in an engine, heat, mass and friction) = power out(what we measure as torque and horsepower). Heat loss can't really be controlled, it's just a result of the chemical reaction from oxidizing fuel, but mass and friction can. If we lower mass and/or friction, we're decreasing the resistance to the combustion pressure trying to push the piston down, and what we end up with is a more efficient machine that produces more torque/horsepower(but remember that the torque/horsepower we measure is the leftover USABLE power after the process is complete). Remember the engines back in the 60's were measured with Gross hp? It didn't account for a lot of the losses due to innefficiencies so you ended up with a higher than actual power rating, when you subtract the losses from friction and mass you get a smaller more realistic number.

Think of the ulimate resistance, a siezed engine. It won't run because the resistance from the friction etcexceeds the ability of either the starter motor to turn it over, or if it seizes while running, stalls for the same reason, combustion pressure isn't high enough to overcome the resistance and rotation stops, so the engine stalls and torque output drops to 0.

Mass can only be controlled so much though, parts can only be made so light with the available materials and at a reasonable cost and still be durable. So you try to reduce friction also, thinner rings with lower tension, better oils, better piston skirt coatings etc. That's one reason that the new LS7 from GM uses titanium rods. It obviously doesn't need the strength of an exotic metal like that, but they used it to free up weight to help boost power output from reduced resistance. It's simply more efficient.

The realisty is if you took an engine that produced an honest 300hp, and were able to make it into an ideal machine and it had a total efficiency of 100%(from friction and mass), it would put out somewhere in the neighborhood of 1,300-1,700hp give or take, depending on what the initial loss from efficiency was. If you could have a chemically ideal process and have no heat loss and convert all of the energy into pressure, as well as no loss from friction and mass, you'd have something on the order of 7,000-8,000 horsepower!! Engines lose upwards of 80% of the energy in the chemical process of combustion in the form of unusable heat, and then lose upwards of another 80% of what's left from that in the form of friction and mass inside the engine. So in actuallity the power that's put out at the crankshft, only represents around 5-10% of the POTENTIAL energy found in the gasoline of a well tuned engine. Some extremely well developed race cars have reached upwards of 15% or more. Engines, like ANY machine, are all about converting as much potential energy into usable kinetic energy as possible. Anything that can be done to reduce inefficiency makes the machine do what it does better. In the case of a gasoline engine, that's produce power that can be used for locomotion.

Cliff notes

All that is to say this, things like lighter internals and aluminum flywheels increase power in the sense that they reduce power loss from innefficiencydue tomass. Any mass takes energy(the ability to do work) to move. The less mass there is, the less work exerted to move it. So in an engine that produces a given amount of work(cylinder pressure), less mass means less work used to move the mass, and more left over to move the car(another mass). That's also why you can take a car and change nothing but it's weight. By making it lighter you've made it faster, not by increasing power, but by decreasing resistance. In that regard from a scientific standpoint, it could be said that the CAR'S(not the engine) horsepower has increased(obviously, since it traveled the same distance, a 1/4mi for instance, in less time with the same force). But for the sake of lack of confusion, a car's horsepower is refered to as power to weight ratio, and a car's "horsepower"(in the sense of how we use it as a statement) is the power the engine produces(or power at the wheels).

As long as it doesn't break, when it comes to producing power, lighter is always better. And so is less friction.
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Old 11-27-2007, 12:57 AM   #12
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Default RE: Aluminum Flywheel - How much hp will it add

Damn, i actually understood that lol

nice explaining
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Old 11-27-2007, 01:01 AM   #13
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Default RE: Aluminum Flywheel - How much hp will it add

Quote:
ORIGINAL: JMD

By my understanding of Newton's Law of Motion, an aluminum flywheel will add zero power, it will allow the engine to wrap up quicker by a few milliseconds, which may equate to a few hundredths of a second for aserious purpose built drag racing car in the 1/4 mile, but this difference in engine acceleration is all but meaningless on a street car of any description.

The extra weight of a steel flywheel vs. an aluminum flywheel is meaningless when it comes to friction or drag. The power consumed by accelerating the extra mass is returned once the flywheel starts slowing down.

This is kind of similar to a truck using lots of energy climbing a hill and then using virtually no energy when going down the other side, or kind of like anairplane climbing to 30,000 feet even for a relatively short flight, theenergy consumed climbing is recovered in decent.

A flywheel stores energy, it does not consumeenergy no matter the practical weight of the flywheelfor it's intended use.

Quote:
ORIGINAL: 67mustang302

Well, technically making things lighter inside the engine isn't actually creating more hp in the combustion chamber, no, but you're losing less hp from having to move all the parts around so you pick some up at the flywheel.But yeah, it's not increasing actual power produced, just the usable power that's left over.I think it's something like 80% of the power produced in combustion is lost due to heat, friction and internal mass of the engine. Not exactly the marvel of modern efficiency most people think it is....good ol internal combustion. Chalk another one up for the elctric motor....works for the railroads.
What you're talking about is the Law of conservation of energy within a system. And it's 100% true. Take the plane for example, suppose it weighs less, less power is used to climb to the same altitude, but when it descends back to where it started it accelerates from gravity(and possibly some engine power used)to a certain velocity, and it's velocity and it's mass(which is lighter now) will determine it's stored energy. That stored energy will be the same as when it started to begin with. But a heavier plane uses more power(or think of it as releasing more stored power) to get to that altitude, but recaptures that same amount of energy when it comes back down(same veleocity but more mass).

As for the flywheel, yes, it does store energy, but only once it's rotating. A flywheel of a given mass rotating at a given rpm has a given amount of stored energy, but it takes energy to get it rotating to that speed to begin with in order to store it.

With both the plane and the flywheel total SYSTEM energy is the same, but part of that system is the surroundings as well, which absorb and store some of that energy, mostly in the form of heat. Think of a rubber ball, you drop it from 3 feet and it hits the ground, releasing it's stored energy from falling, but it doesn't return back up to the full height of 3 ft because some of that energy was lost from the ball(not the system). It hits the ground and deforms, has friction etc, and releases a small portion of it's energy because of that, heat into the surrounding air/ground etc, and when that released energy causes it to bounce back up it doesn't go to the full height because some of the energy went into heating things etc, rather than bouncing the ball. Eventuall the ball stops bouncing after all it's energy is finally lost from the ball in way way, shape or form. The total energy in the system is the same, because the syste, includes everything that the ball came into contact with and which was effected by it, including but not limited to the ground and air molecules.

Back the the flywheel, trying to accelerate it in order to store the energy causes losses to other parts within the syste, including but not limited to heat and friction of internal components caused by the resistance of the mass itself, friction of the flywheel with the air, bearings etc etc. Greater mass = greater resistance, and greater resistance causes more pressure, and more pressure = more heat loss. The heavier flywheel offers more resistance, which means more pressure on all the parts of the engine that are moving, which means more pressure on things like oil in the oil wedge of the bearings, that pressure is converted into heat and the oil carries it away back to the pan, where it's then carried into the atmosphere. The total system which includes the atmosphere has the same total energy, but the engine itself has lost it to other parts of the system due to it's own inherant innefficiencies. So energy is lost in order to get the flywheel to a speed to store x amount of energy. You let off the throttle and it slows down, causing the flywheel to release the energy, but it has only stored the energy that was put into it, not the total energy released into the system. It's all still there inside the entire system, but the engine itself has less of it, and things like the oil and atmosphere has more of it.

It's a matter of 1+3=4 or 3+1=4. Total system energy is 4, regardless of which side of the + anything happens to be on. That's how an engine is, it loses a tremendous amount of energy to other parts of the system, oil, engine block, engine mounts into the car's chassis, atmosphere etc. The engine itself is so inniefficient that it loses much of it's energy into the rest of the system, primarily in the form of heat. Energy can't be created nor destroyed, but it can change forms. Engines change a LOT of kinetic energy into heat energy, that's what makes them so horribly innefficient. The engine by itself as a total system still loses no energy, but much of the kinetic energy again, gets converted into heat, hence the neccessity for a cooling system. Movement becomes heat elsewhere within the system.
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Old 11-27-2007, 01:10 AM   #14
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Default RE: Aluminum Flywheel - How much hp will it add

This is exactly what i've been learning at school for the past few weeks
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Old 11-27-2007, 01:31 AM   #15
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Default RE: Aluminum Flywheel - How much hp will it add

I had a totally awsome physics teacher in HS. She had worked for NASA, and even while teaching us was still writing grants for like JPL and others to get federal money for research etc. She actually made learning physics enjoyable.....we broke so many things in that class!! The problem is too many teachers make it boring, and people don't learn anything cuz they can't relate to it or see it in action to understand it. It was definately learn by doing.
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Old 11-27-2007, 01:37 AM   #16
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Default RE: Aluminum Flywheel - How much hp will it add

very true!!

i can't stand teachers who hand out worksheets and sit on their *** for the rest of the class
i'm in chemistry now so i'm not sure why we're learning about this physics stuff but oh well

i can understand 90% of the material on my own or from her lessons but once we do a lab on something it makes it 500% easier to understand


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Old 11-27-2007, 01:49 AM   #17
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Default RE: Aluminum Flywheel - How much hp will it add

My chemistry teacher that I hadused to work for a nuclear power plant. At least. I always got the impression that he did a lot more than that, but never talked about it. It's kinda funny, I went to this HS in a podunk little mountain town that's known for it's AG dept. But many of the teachers I had were amazing, with an unbelievable amount of knowledge and experience. They could have easily been university instructors, but chose instead to be HS teachers. Not that I'm complaining.
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Old 11-27-2007, 03:03 PM   #18
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Default RE: Aluminum Flywheel - How much hp will it add

http://store.summitracing.com/egnsea...115+4294840126

While there may be some marginal differences in hard acceleration when using an aluminum flywheel, the difference in price for a consumable product seems hardly worth the money to me... IMO the money spent here could be better spent in other places where a user would get more bang for the buck.... which is basically what I was trying to statein my first post...

While I don't disagree with your long explanation above, the loss of overall efficiencies when using an iron or steel flywheel in lieu of an aluminum piece are marginal at best.....

When this is taken into account in conjunction with the $300.00 difference in price when compared to it's cast iron counterpart,IMOadding "like 15 HP"can normally be done easier and cheaper by making other mods and improvements.

Themanufacturer claims that an aluminum flywheel is "like adding 15 HP", this to me is "like a tricky use of wording"... It may be "like adding 15 HP under ideal conditions in an all out 1/4 or 1/8 mile drag, but this is entirely misleading for a street car. I contend that the "like 15 HP" is not a middle of the road statement by the manufacturer,but, even if we accept this figure, we are talking about $20.00 a HP, in reality the figure is probably more than $50.00per HP. All IMO of course.

I also understand that some people have installed these and they can feel the difference, this I believe, but my point is that I just do not consider this the best place to spend an extra $300.00 Worth of mod money on a 300 HP car....

Another poster (sorry can't remember who for sure without going back and looking) here plainly stated that there are down sides to installing an aluminum flywheel, and these issues should be considered prior to spending $360.00+ on a flywheel.

I realize that I am probably taking this issue a little bit too serious, but it is not always in the best interest of a car owner to dump hard earned money in a modification that may not be the best option at the time..... Not everyone has an extra $300.00 to kick around.... $300.00 will buy a nice radiator, an nice intake, a big piece of a new carb, a nice performance clutch that will bolt to an iron flywheel, etc. etc....

I do not mean any disrespect to anyone here, I simply differ in my opinion....
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Old 11-27-2007, 03:36 PM   #19
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Default RE: Aluminum Flywheel - How much hp will it add

This tends to get messy once you start looking at the fact that a flywheel's inertia effect on acceleration is not the same from gear to gear, once you've got the car moving and neither the clutch nor the wheels are slipping.

You can "normalize" the effect if you first choose a constant rate of car acceleration and work backwards from things like tire size (revs/mile), axle gearing, and flywheel dimensions and weight. You'll end up with units of ft-lbs/g as "torque required to rotationally accelerate the flywheel at a rate consistent with one g of forward car acceleration". These results might look something like 65, 40, 25, 20, and 15 ft-lbs/g for a new GT with 3.55 gearing and a 20-lb flywheel. Times the actual forward car acceleration, this will give you the amount of torque that is siphoned off by the flywheel. Unfortunately, you have to iterate for this part of the solution, as torque lost to accelerating the flywheel means the car acceleration is less than you'd otherwise compute. Have Spreadsheet, Will Travel, to borrow from the business card on an oldTV western (or not).


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Old 11-27-2007, 03:38 PM   #20
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Default RE: Aluminum Flywheel - How much hp will it add

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ORIGINAL: Colorado_Mustang

Aluminum flywheels and lightened parts free up zero horsepower. They also add zero torque. They do allow the engine to spin up/down faster, but that's it. The way an engine is tested for power does not depend on how quickly the engine will gain RPM.

A lightened flywheel has a big disadvantage in both cruise mode, changing gears, and starting out from a light...it doesn't have the mass to dampen the fluxuations that occur during these conditions. You'll get less mileage on the highway, gear changes will be felt more, and the engine is more likely to stall if the clutch is let out a little too fast.

In a street car, an aluminum flywheel is a waste of money as a "performance" part.
Man here we go again another I read this and now I'm repeating what the theroy quote un quote states.....[sm=icon_blah.gif][sm=icon_blah.gif][sm=icon_blah.gif].....okay before speaking put one in your car then speak from experience....been there done that!!! 2 in fact ya wanna go for a ride in my aluminum flywheel equipped 66 and non equiped 92???? and I'll let you see if you can notice a difference......there was a night and day difference when I did the switch in my 66 with no change between shifts noticed....yeah that's right none!! I've read the theroy and was concerned with the swap of all the disadvantages I had read about but to my suprise the car didn't exibit what I was prepared for.. and no the engine doesn't stall if the clutch is let out two slowly on my car..again no change there and as for the thereoy of harsh gear shifts ....It's quite the opposite.......the less rotational mass will not be as harsh on tranny engagements and in the long run it'll length the life of the tranny as the impact of all the extra rotational mass is not there to lets say crash the party.. and heck my mpg went up!!! well I guess I should be honest here...it went up cause I put a 5 speed in to at the same time

In fact I've let people drive my 66 and if I hadn't of told them they'd never of guessed it had a aluminum flywheel.. I wait to tell them such only after the fact they've complemented me on how well it drives
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Old 11-27-2007, 03:38 PM
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