Anybody know how many HP a lightened flywheel (act prolite/mazdaspeed/Rb) is expected to free up?

I dont think its going to free up any hp. It will just allow the engine to rev quicker, which may give you .1 - .4 fast quarter mile time.

A long time ago somone said about 10 hp in 1st gear, 6-8 in second, 4-5 iin third, 2-3 in fourth and about 1 in fifth.

Being able to rev quicker does free up horse power. and a .1-.4 faster quarter mile is a heck of a huge difference.

thanks

It doesn't free up any horsepower at all..........the car just revs quicker due to less inertia meaning you hit the powerband sooner. It does have side effects though....when I had one in my last car, the car didn't like to idle with the A/C on. You need that inertia to keep the motor running smoothly so there comes a point where lighter isn't always better, but shedding a few pounds won't hurt!

It doesn't free up any horsepower at all..........the car just revs quicker due to less inertia meaning you hit the powerband sooner. It does have side effects though....when I had one in my last car, the car didn't like to idle with the A/C on. You need that inertia to keep the motor running smoothly so there comes a point where lighter isn't always better, but shedding a few pounds won't hurt!

I'm not going to bother explaining it, take a physics course at your local cc or something, you can begin reading here:

http://auto.howstuffworks.com/gear-ratio.htm

I had a .xls spreadsheet - one could enter variables and show "the car would accelerate as if it had 'x' much power in 'x' gear...I've forgotten who created the spreadsheet - but it was made for a miata; you'll have to adjust stuff.

http://www.d-mphotos.com/movies/flywheelcalculator.xls

A long time ago somone said about 10 hp in 1st gear, 6-8 in second, 4-5 iin third, 2-3 in fourth and about 1 in fifth.

Being able to rev quicker does free up horse power. and a .1-.4 faster quarter mile is a heck of a huge difference.

i think that was me... and i stand by them


on another note...
also, if your car "revs faster" and its in gear while its "revving faster", then you are accelerating faster because of putting more power to the wheels/pavement or have a slipping clutch :Eyecrazy:

Interesting question. My 2-cents (flame suit ON)

From an dyno perspective, you might not see see any (some dyno testing is done at a constant rpm, or only slightly changing rpm where the flywheel's inertia wouldn''t affect the resulting torque much). Practically speaking, the engine is able to increase rpm faster which does translate into getting more energy to the rest of the drivetrain (vs the flywheel) during acceleration, so could be converted into a net hp difference. The effect is more pronounced at lower gearing, because the engine is accelerating faster (you go through the rpm range faster). The results will very with the weight/inertia of the car and drivetrain, including the flywheel.

The folks above seem to have some practical experience...it's a good start.

Maybe I should build a mathmatical model for this to see how pronounced it would be. Hmmm....

Lot's of discussion on this.

I believe at least 1-2 more HP is freed up to the rear wheel just from the fact of the reduced weight and the power need to move the fly wheel.

Quicker acceleration and 1/4 mile times are great improvements.

Unfortunately, there is a reduction of torque. Torque is needed on the top end and to pull a heavy load. Load increase as speed increases.

Many drag racers and track guys will take torque over HP.

Then others will tell you you don't need athe fly wheel if you increase your HP through other means such as FI.

Oh yea, do a search it's worht the reading. :mdrmed:

You don't have to guess. Theres a complete set of dyno charts for "before" and "after" LWFW, and in several gears posted somewhere in this forum. Try searching on "LWFW" for lighe weight flywheel etc.

Question for those with the lightweight flywheel... I've heard that switching to the LWFW makes the car shudder or jerk more as you change gears? Do you find this to be the case? Any other day-to-day impacts?

Question for those with the lightweight flywheel... I've heard that switching to the LWFW makes the car (#) shudder or jerk more as you change gears? Do you find this to be the case? Any other day-to-day impacts?None. After you adapt as a driver. (I will admit that nearly every one that drives my car stalls it the first time they try it. And my fly is not mega light. But you quickly adapt.)

ah!

here's the one...

http://www.rx8club.com/showthread.php?t=36105&page=3&pp=15&highlight=flywheel

Did nobody look at that spreadsheet?

:)

FWIW - Torque is worthless in terms of winning races. HP is where it's at.

:D

ah!

here's the one...

http://www.rx8club.com/showthread.php?t=36105&page=3&pp=15&highlight=flywheel

Thanks.

BTW, if the reduced rotating inertial losses due to lighter flywheelscan be translated to HP gains, would lighter weight/tires wheels also show up similarly on a dyno? I'd think it would. :scratchhe

Horsepower=(Torque X RPM/5252). I don't see any flywheel weight in that formula. Might help in engine response, making the car marginally lighter, but no HP increase.

Right, no hp increase in the motor, but allows for more of that hp to get to the wheels which can be thought of an increase in hp.

http://www.rx8club.com/showthread.php?t=89582

It definately helps out. i havent driven it with more than 1 passenger yet, but ill let you know..

Horsepower=(Torque X RPM/5252). I don't see any flywheel weight in that formula. Might help in engine response, making the car marginally lighter, but no HP increase.
I don't have the lightened flywheel, but I think those that do report it as "revving faster." So, using your formula, if the engine reaches a given RPM in less time than before, that would mean that you'd reach that horsepower in less time as well. That should result in faster acceleration, even though actual horsepower hasn't changed.

I don't have the lightened flywheel, but I think those that do report it as "revving faster." So, using your formula, if the engine reaches a given RPM in less time than before, that would mean that you'd reach that horsepower in less time as well. That should result in faster acceleration, even though actual horsepower hasn't changed.

Yes, that's basically the benefit. The same horsepower is available sooner because you can spin the engine quicker. Keep in mind that the flywheel does serve a usefull purpose - it keeps the engine spinning between power pulses from the combustion chamber. If you go too light, the engine will have a problem idling smoothly.

Horsepower=(Torque X RPM/5252). I don't see any flywheel weight in that formula. Might help in engine response, making the car marginally lighter, but no HP increase.

here's another good equation...

HP at wheels = HP at crank - flywheel inertial - transmission inertia - transmission friction - driveshaft inertia - differential inertia - differential friction - axel inertia - wheel bearing friction - brake inertia - wheel/tire inertia - tire rolling resistance

Still, my favorite equation is:

Gas Pedal + Foot = ZOOM! :D:

I'm going to just pose this scenario for those who don't think that a lighter weight flywheel frees up horsepower to the wheels. Technically you gain no power as the engine makes no more power. You are reducing drivetrain loss though which means more power goes to the ground so in terms of what gets to where it counts, you do have more. If you don't believe me, think about this.

Let's say that instead of a 20 lb flywheel, you have a 200 lb flywheel. Now lets also say that we pulled off 200 lbs from somewhere else on the vehicle just to keep the total weight the same. The car weighs the same and has the same total flywheel horsepower. Which one will win in a race? Of course it's not the one with the 200 lb flywheel. As someone pointed out, it can't rev as fast. That's because it lacks the power to get it moving as fast. Power is being functionally absorbed by the flywheel. This is seen as the effort to turn it. That means that less power is making it to the ground. Once you get it up to speed, you don't see that much loss as it takes far more energy to get it turning initially than it does to keep it going but it still does take power never the less. This weight is stored energy which is also harder to slow down.

The lower the gear you are in, the larger the gain will be perceived as. This has to do with the amount of "leverage" that the gearing gives you.

I think the best way to explain to people that a LWFW is a good thing is to simply point them to real race cars and professionals. I bet a F1 car's flywheel is almost non-existent.

The real questions to ask yourself:
1. Is the gain worth the cost?
2. What weight do I want?

For question 1 the answer is a resounding maybe.

For question 2 I can only say that I went with the RB 12lb flywheel because I was a bit worried about drivability issues but I was 100% back to normal with my takeoff after just 15min in the car with the new flywheel.

Lot's of discussion on this.

Many drag racers and track guys will take torque over HP.


can you elaborate on this plz? i don't understando

Come on guys, it's plain physics: T=L x F, while F=M x g. Decrease M, you decrease F, you decrease T, which simply means you need less power to spin the lighter flywheel (smart, heh ? :) ).

In theory and in practice, by installing a lighter flywheel you don't increase the crank HP, but you certainly increase the percentage of this HP/torque that reach the wheels, i.e. you increase WHP.

So, a lighter flywheel does not increase crank HP, but certainly increases WHP ;) And of course allows the engine to spin up faster, since its reduced mass proves less of an obstacle (less inertia)

It is plain physics but you're confusing energy with power. A flywheel is an energy storage device, it doesn't create, absorb or provide power. If you had NO flywheel, the horsepower delivered by the engine to the rear wheels at a given RPM would be the same (minus the frictional losses in the drivetrain and assuming you could keep the engine running). The improvement comes from allowing the engine to spin up quicker (which the lighter flywheel allows) which translates to HP being available earlier. In the end, the maximum horsepower (heavy flywheel, light flywheel or no flywheel) remains the same.

Reducing flywheel weight just re-shuffles the existing horsepower throughout the RPM range. If you really think that reducing flywheel weight increases RWP, then you should concentrate on reducing the weight of the wheels, tires, brakes and other rotating machinery in the driveline. Those items weigh an order of magnitude more than a flywheel.

It is plain physics but you're confusing energy with power. A flywheel is an energy storage device, it doesn't create, absorb or provide power. If you had NO flywheel, the horsepower delivered by the engine to the rear wheels at a given RPM would be the same (minus the frictional losses in the drivetrain and assuming you could keep the engine running). The improvement comes from allowing the engine to spin up quicker (which the lighter flywheel allows) which translates to HP being available earlier. In the end, the maximum horsepower (heavy flywheel, light flywheel or no flywheel) remains the same.

Reducing flywheel weight just re-shuffles the existing horsepower throughout the RPM range. If you really think that reducing flywheel weight increases RWP, then you should concentrate on reducing the weight of the wheels, tires, brakes and other rotating machinery in the driveline. Those items weigh an order of magnitude more than a flywheel.

We agree on your second paragraph, but I don't quite agree with your first comments. Of course I am not confusing energy with power. The flywheel is -in broad terms- a disc with a certain mass. In order to spin it, you need to transfer energy to it, which means applying a certain force. This force comes of course from the engine. So, reducing the flywheel's mass, you reduce the amount of force needed to spin the flywheel, assuming the other variables remain constant.

I'm not discussing whether the flywheel moves the powerband up or down, or relocates the point of maximum output. I am merely pointing out that reducing the mass of the flywheel increases the net amount of force with goes "through" the flywheel and finally spins the wheels (which is measured as WHP).

I had done a very generic calculation as to how much power is "freed up" by reducing the mass of a flywheel by a certain percentage, but it was done in Greek and cannot translate right now. I did this because I didn't want to take the assumptions of ACT or MazdaSpeed as granted. The result (my result) was that for every Kg of mass shaved off, about 0,5% of WHP is gained (actually it was 0,5% of wheel torque that is gained).

It is plain physics but you're confusing energy with power. A flywheel is an energy storage device, it doesn't create, absorb or provide power.

A flywheel is an energy storage device - storing rotational inertial energy. This energy is dependant on the inertial moment of the flywheel, and its rotational speed.

The flywheel is connected to the engine - which varies in speed.


When the flywheel varies in speed, its stored energy changes. The change in energy over time is POWER. :Eyecrazy:


When the engine spins up, the flywheel spins up increasing its energy, and the power that it takes to increase the flywheel energy is power that could be going to the rear wheels but is not. The faster the flywheel changes speed the more power it consumes - therefore the most gains from a lighter flywheel will be in first gear, and diminishing in every gear after that.

It is plain physics but you're confusing energy with power. A flywheel is an energy storage device, it doesn't create, absorb or provide power. If you had NO flywheel, the horsepower delivered by the engine to the rear wheels at a given RPM would be the same (minus the frictional losses in the drivetrain and assuming you could keep the engine running). The improvement comes from allowing the engine to spin up quicker (which the lighter flywheel allows) which translates to HP being available earlier. In the end, the maximum horsepower (heavy flywheel, light flywheel or no flywheel) remains the same.

Reducing flywheel weight just re-shuffles the existing horsepower throughout the RPM range. If you really think that reducing flywheel weight increases RWP, then you should concentrate on reducing the weight of the wheels, tires, brakes and other rotating machinery in the driveline. Those items weigh an order of magnitude more than a flywheel.

I think that you are the one confusing energy and power.

After reading the previous posts I'm beginning to see where you're coming from.

You think of the flywheel solely as a storage medium for potential energy.

Basically in your world you think that the engine can spin up the flywheel, energy goes completey into the flywheel and then can be transfered completely into the driveshaft upon engagement of the clutch.

It does store energy for the engine, it's sole purpose is to make it easier for humans to shift gears by keeping the momentum of the engine constant. But it saps energy doing it!

To put it simply, having mass at any distance from the center of any rotating object is going to need energy to spin.

Remember the good old days of the merry-go-round?

Now it was easy to spin the merry-go-round with no-one on it, you could make it go around really fast(giving it 100% of your energy), but it stopped spinning rather quickly.

-Because you had enough energy to perform the work required, factor in the amount of time it took you to get it spinning and we can calculate your horsepower!

Now when all your friends were on it, it was so hard to get spinning(giving it 100% of your energy) that you needed a grown-up to help you and even then it wouldn't spin that fast, but once it got spinning it seemed to go on forever.

-Because it was too hard/impossible for you to spin the merry-go-round you did not have the energy to perform the work required!

Now look at the speeds! the light merry-go-round went fast for the same amount of energy as the heavy merry-go-round needed just to get it started.

This is exactly what a flywheel is, its purpose IS to store energy, but what you neglect completely is the quantity of Impulse. Impulse is the amount of energy required to change the inertia of something.

Yes, changing the inertia of something does require energy! This is why it was harder to spin the merry-go-round with people on it!

Com'on dude I was a physics tutor.

Just for argument's sake.... Don't you think that Mazda, who is DESPERATE to rate this engine's horsepower higher than it is, wouldn't have put in a lighter flywheel from the factory just to get the higher horsepower rating? They don't because they know flywheel weight doesn't make any difference in HP.

Don't get me wrong, there are plenty of good reasons for a lighter flywheel from an engine response standpoint. You can deliver what HP you've got faster and earlier. Because of that you can end up with improved quarter-mile or lap times. But, in the end, you've still got the same HP you started with - just delivered differently.

Translation for Marines: Light flywheel, car go faster. Ooo rah!

lightweight flywheel costs more for mazda to make and they dont care about any mods that only increase whp bc they advertise bhp. 238 bhp sounds better than an estimated 210 whp with a lightweight flywheel

That's what we have been saying all along; that a lighter flywheel makes itself less of a parasitic loss on the drivetrain, which results in more power left for the motivation of the vehicle. It has also been noted here that flywheel weights are a consideration made for the sake of driveability, not power numbers. If you look at the typical RX-8 owner, or potential owner, you'll see that they are not usually interested in a vehicle that will win races off the showroom floor. They are usually interested in a well-balanced vehicle that looks good and will carry more than two people. The RX-8 has been designed and executed very effectively for the demographic which it was/is intended to attract. That's the reason Mazda selected the flywheel weight they have; so more people of a wider variety can drive the car comfortably.

One thing I would ask others to consider is exactly how chassis dynos calculate the whp of a given vehicle. They do it by calculating the acceleration rate of a pair of wheels with a known mass and extrapolate h.p. numbers first. They then calculate torque using the formula stated earlier. The important thing is that the dyno wheels function the same way an engine flywheel does. If the dyno wheels were made lighter but the dyno software wasn't made aware of the change, it would calculate higher whp/wtq due to a quicker rate of acceleration.

The point made about the perceived effects of light flys and transmission gearing is why we try to use a transmission gear ratio as close to 1:1 as available. This removes the transmission as much as possible from skewing dyno numbers. If we could we would also use a final drive ratio of 1:1 to come as close to engine h.p. as was possible.

Isn't it enough just to say that, for performance purposes, a lighter flywheel is a benefit and then each of us report on the particular flywheel we have chosen to use and our experiences with them?

CRH

are you still in mi????

i will drive you and your car to tampa... you pay for gas...

yes i can fly to detroit for free.... we need you here..


beers :beer:

Regardless of what one's mathematic calculations may indicate or their understanding of physics may cause them to believe, the bottom line is that reducing flywheel weight to the lowest tolerable by the driver ends up making a more efficient drivetrain. If all a lighter fly does is cause the engine to rev up quicker, what physical phemonenon is it that allows the engine to rev up quicker? If the engine's ability to rev up quicker is the only observable outcome of a lighter flywheel does that mean that the engine will pass through it's powerband quicker also? If so, what do we do then? I can tell you from personal experience that switching to SR's 9.75# fly did not affect the driveability to the degree that some around here tend to speculate and that the acceleration was enhanced to the extent of shaving .3s off of my 1/4 mile time in both N/A and nitrous modes. At my current power/weight ratio that equates an extra 15 rwhp. For those who are interested the light fly is one of the most effective mods we have available to us, especially for the cost.

CRH
Absolutely! I have the aluminum SR flywheel for my RX-7. Very noticable gain in acceleration. That's only possible if more power actually gets to the ground.

On the 13B nonturbo engines, you could get very large gains from a new exhaust. They were gains not possible with the Renesis. We're talking on order of 30+ hp from an exhaust alone. The 2 largest gains you could do to a nonturbo RX-7 was the exhaust and a flywheel. Everything else was less important. The acceleration gains were on par with that of streetporting the engine. That's right, a good flywheel could add the acceleration capabilities of a ported engine with the stock flywheel! I laugh at those that say a flywheel makes no difference in power to the ground. They need to actually drive one instead of speculate as to how something works that they have no experience with.

Just for argument's sake.... Don't you think that Mazda, who is DESPERATE to rate this engine's horsepower higher than it is, wouldn't have put in a lighter flywheel from the factory just to get the higher horsepower rating? They don't because they know flywheel weight doesn't make any difference in HP.

The flywheel is there to begine with the smooth out the engine vibrations between power strokes (actually, to keep it running) and increase driveability in a manual transmission car by making it harder to stall. Many people are willing to sacrifice a bit in both categories for more performance - many others are not.

Judgeing by the amount of people complaining of squealing brake pads on this forum from the braking system that produces the shortest distance of any japanese car, they were probably right in using a big ol driver friendly flywheel.

Others can correct me if I'm wrong, but I think this is the lightest flywheel they've ever used on a production rotary.
Paul.

^Don't you know? Can't you just go into the back room and weigh them all??? You're slipping Paul! ;)