Hard facts about lightened flywheels

We recently recommended to a customer of ours that he not spend the money at the present time on having a flywheel lightened. We then received an E-mail from another vendor in the business challenging our opinion to this particular customer and the advantages of a lightened flywheel. We decided to run some real factual investigation into the pros and cons of such a flywheel by testing several and here are the hard facts from those test. Test engine: modified Mercury 300 drag. Heads 26cc. Compression as shown on snap on gauge with 24 volt starting system:168psi on all 6 cylinders Fuel: 100 LL av gas with additive. Oil: Klotz Super Techniplate at 32/1. Spark Plugs: NGK BR 9 HS10 Timing: 25 degrees max ECU: Merc A-63 w/56 lb regulator. ECU setting: 102.6 Fuel pump: weldon 90-120 psi aircraft grade fuel injection pump. Operating temperature: 155 degrees farenheit. All test were conducted in controlled enviroment at 80 degrees and 70% humidity on a Stuska A-600 turbine waterbrake powerhead dynomometer.
Test 1: stock Mercury aluminum flywheel as shipped with the engine. Peak horsepower at 8300 RPM 328.306 torque 204.829 ft lbs. Test 2: Factory Mercury flywheel lightened by Diamond Marine. Peak horsepower at 8300 RPM 328.303 torque 204.828 ft lbs Test 3: Factory Mercury flywheel lightened by unknown. Peak horsepower at 8300 rpm 328.283 torque 204.808 ft. lbs. Test 4:stock 16 amp steel flywheel, horsepower at 8300 rpm (we don't recommend this as there is a danger of disentegrating the flywheel) 329.121 torque 205.454 ft. lbs.
Test 5: stock factory left hand aluminum champ or S-3000 flywheel, horsepower at 8300 rpm, 328.313 torque 204.848 ft lbs. Test 6: Jay Smith lightened left hand aluminum flywheel, Horsepower at 8300 rpm 328.307 torque 204.839 ft lbs. We found that the stock aluminum flywheel made in reality as much or more actual usable horsepower as any flywheel tested except the slight increase that was noted in the stock steel unit which could be attributed to inertia from the added weight.Is the lightened unit worth the cost?? We believe it is an aid to engine longivity, especially in the upper 8000 rpm range and above, but as for a horsepower gain, there is absolutly no noticable gain at all according to our test. The Jay Smith and Diamond Marine units were both first rate and while the finish work on the unknown unit was not quite as neat they all performed well. There was a slight difference in the weight of the three with the Jay smith unit being slightly lighter than the Diamond Marine unit and the unknown unit slightly heavier than the other two. All three were considerably lighter than the stock aluminum units. This test in no way shows what increase or decrease in what the performance on an actual boat might be and was done solely for the purpose of an overall look at actual horsepower and torque readings. These test were done independently by Eagle One Performance Products and are neither intended to recommend or not to recommend the use or quality of any product by any of the vendors products that were used.
Eagle One Performance Products

[Edited by EagleOne on 07-28-2001 at 03:17 PM]

[us1]

We have never expected a lightened flywheel to make more top end horse power in fact it should make less. The #1 point in a lightened flywheel is to stop the top of the crank from coming off at 10,000 RPM. or for that matter at 8000 RPM. But what your test really doesn’t show is the torque gain on acceleration dew to spinning up a lighter mass. In an F1 boat a lightened flywheel is a noticeable gain in acceleration off the turn. On my dyno, as long as the motor is accelerating, the lightened flywheel will make 10 more HP over the stock S3000 type.

[Barney]

4 of the 5 test showed very similar numbers, the test #4 with the 16 amp steel flywheel was signifcantly higher, what's the reason for that?

I understand the NON recommendation for the possibility it may disentigrate, where would we find those 16 amp flywheels in use, so we know what to "watch out for"?


Are there applications you DO recommend a lighten flywheel such as spinning higher rpms?

[sosmerc]

where can I find out more about the Stuska A-600 turbine waterbrake powerhead dynomometer? Does it hook to the propshaft, or do you install the powerhead "on it" so to speak? I use both a K & O and a Land and Sea (never been very happy with the Land and Sea...terrible electronics, the water brake loading part of it is ok).

The earlier post had a misprint on the information regarding the steel flywheel as there was only about a 1 hp gain, we have edited that post. The 16 amp steel unit is from a 1983-85 200 2.4 merc. As for the questions about Stuska dyno's they are true powerhead dynomometers and are driven off the crankshaft on test stand housing which allows us to test things such as tuners, exhaust temperatures, water temps at several points on the block and much more without going through the lower unit or driving a water pump. Photos of our unit in use are shown in our shop tour on our web site at http://www.eagleoneperformance.com . For more information you can contact Stuska Engineering Company, the last address we show was 2930 s. Fox St. ,Englewood Colorado 80110 303-762-0553. Please excuse my errors in typing ,I smashed my thumb, it hurts like hell and the bandage gets in the way.
Noah Legear/ Eagle One Performance Products

[sosmerc]

keep your thumb away from the flywheel!!

[MERCMAN]

I DONT THINK ANYONE INTENDS FOR A LIGHTER FLYWHEEL TO INCREASE HORSPOWER. A LIGHTER FLYWHEEL HELPS THE STRAIN ON THE DRIVETRAIN AS WELL AS ALLOWING THE MOTOR TO TURN UP QUICKER. THIS ADVANTAGE MEANS ALOT TO ANY RACER WHO WANTS TO HIT THE FINISH LINE FIRST. EVERY LITTLE THING YOU CAN DO WILL ALWAYS HELP YOUR CHANCES OF WINNING. ANYONE WITH A LIGHT WEIGHT BOAT WOULD BENEFIT FROM A LIGHTER FLYWHEEL WHETHER THEY DRAG RACE OR NOT. ONLY HEAVIER BOATS WOULD NOT BENEFIT FROM IT. OBVIOUSLY THERE ARE VARYING OPINIONS ON THIS BUT I WILL STICK WITH THE MAJORITY ON THIS ONE.

[us1]

Hey Mercman, Your right, I was going to add that earlier but didn’t. A heavy boat will only benefit by diminishing crank strain, increased acceleration will be so slight, it will go unnoticed.

[MERCMAN]

JOHN , YOU DA MAN! I THINK WHERE GOING TO START THE "REAL HARD FACTS FAN CLUB" I DONT LIKE STEPPING ON TOES BY ANY MEANS BUT I FEEL THE GENERAL PUBLIC BENEFITS FROM THE WHOLE STORY INSTEAD OF JUST ONE SIDE. WHEN BOTH SIDES OF ANY OPINION ARE JUSTIFIED BY EACH PERSON (PROS AND CONS) IT REALLY HELPS OUT. IM NOT HERE TO SELL ANYONE ON ANYTHING.

"JUST THE FACTS MAM"

P.S. DO I MISS MY STV? MY ALLISON ? YES I DO BUT THIS (SKATER) RIG IS BAD TO THE BONE IN THE RUFF STUFF. IM GONNA GET ANOTHER BOAT THIS WINTER TO TOOL AROUND IN BUT I DONT THINK I WILL EVER GET RID OF THIS SKATER! I HOPE WHEN THE TIME COMES TO PUT TWINS ON THE 21 SKATER I WLL BE ABLE TO MAKE IT A FULL PROJECT TO SEND TO VIRUS FOR THE MAGAZINE! THIS WINTER WILL BE QUITE THE BUSY ONE FOR ME!

MERCMAN OUT: TALK TO YOU GUYS AFTER MY AWESOME DAY ON THE ISLANDS TOMMORROW IN THE SKATER!

[us1]

You’re so right, that’s the way to learn, listen to all the opinions and then form one of your own, or at least go with the majority. Have fun!

[racer]

I will have to agree a light flywheel was never meant to increase power, its for longevity and acceleration only.

[Techno]

As a baseline how fast can you spin on a stock flywheel and when should you switch to a lightweight?

[us1]

Mercury switches to the lightened flywheel at around 6000 RPM. Maybe you can push this higher but every few 100 RPM you increase putts 100s of LBS of twisting torque on the end of the flywheel as you accelerate and decelerate.

[Classic18]

Mercury switches to the lightened flywheel at around 6000 RPM. Maybe you can push this higher but every few 100 RPM you increase putts 100s of LBS of twisting torque on the end of the flywheel as you accelerate and decelerate.

Great thread(s)....I have one posted on this topic, but found this later. I'm building a SBC and want very good acceleration response. The current Mercruiser flywheel is very heavy and won't help my cause! I am interested in an aluminum/light weight flywheel just for the transient response from a stepped input.

Can anyone point me to a cost-effective low-mass flywheel (and coupler) that will bolt into a SBC/Bravo One powertrain? Thank you!

[us1]

I know nothing about Mercruiser flywheels. It's all about outboards baby. I'm sure the same principles apply. A lower revving motor and a heavier boat are not going to benefit much.

[90 5.0]

I have been told by some that have tested the merc aluminum vs a lightened on that on the aim dash they saw no performance gain. But as good quality factory flywheels get sparcer and sparcer buying a new diamond etc becomes more attractive from a longevity standpoint ie new magnets etc.

i have a 16 amp steel off an old 2.4 and I have a factory merc "small" aluminum 16amp. I plan to test both before the season starts and compare time data.

On my drag car, NMRA Pure street class 310ci small block ford the fidenza aluminum flywheel was worth as much as .3 in the 1/4 due to faster acceleration with 4.56 gearing and a liberty manual trans.

The motor spun very high for what most would consider on a car motor and loss of low end Torque was of no concern to us. Before I quit (due to constant rule changes thought the season) we were going t try and go to 5.13 gears.

I would leave at 8500 and cross the traps just over 9, we have pulled the motor to 10 on the dyno

just food for thought.

[us1]

Don't you just love racing and constant rule changes. I got real sick of that real fast.


I have been told by some that have tested the merc aluminum vs a lightened on that on the aim dash they saw no performance gain. But as good quality factory flywheels get sparcer and sparcer buying a new diamond etc becomes more attractive from a longevity standpoint ie new magnets etc.

i have a 16 amp steel off an old 2.4 and I have a factory merc "small" aluminum 16amp. I plan to test both before the season starts and compare time data.

On my drag car, NMRA Pure street class 310ci small block ford the fidenza aluminum flywheel was worth as much as .3 in the 1/4 due to faster acceleration with 4.56 gearing and a liberty manual trans.

The motor spun very high for what most would consider on a car motor and loss of low end Torque was of no concern to us. Before I quit (due to constant rule changes thought the season) we were going t try and go to 5.13 gears.

I would leave at 8500 and cross the traps just over 9, we have pulled the motor to 10 on the dyno

just food for thought.

[90 5.0]

Don't you just love racing and constant rule changes. I got real sick of that real fast.

It got the point that it would be more fun to light a grand on fire and throw it in the garage and go do something else for fun.

When inwas was trying to run it the class was new and getting way faster than they had originally intended. My heads became illegal, had to go build a new set port and test that set us back a couple races. Then our exhaust became illegal I just gave up. I couldn't financially keep up with the rule changes.

So I started fishing again, now I'm racing boats. Starting to wonder what have I done!!! LOL!!

[us1]

It's not only that. It's inventing some awesome new modification in the shop that kicks everyone else's butt and then at the next race all of a sudden it's illegal. I thought that's what racing was all about.


It got the point that it would be more fun to light a grand on fire and throw it in the garage and go do something else for fun.

When inwas was trying to run it the class was new and getting way faster than they had originally intended. My heads became illegal, had to go build a new set port and test that set us back a couple races. Then our exhaust became illegal I just gave up. I couldn't financially keep up with the rule changes.

So I started fishing again, now I'm racing boats. Starting to wonder what have I done!!! LOL!!

[90 5.0]

It's not only that. It's inventing some awesome new modification in the shop that kicks everyone else's butt and then at the next race all of a sudden it's illegal. I thought that's what racing was all about.

Or thinking outside the box and having a rule rewritten so you can't and your entire motor becomes illegal. The rule was 310 ci maximum, which is a 302 .060 over, but they never said how you could get the 310. So we ran big bore and short stroke cranks to make them scream rpm. Having your entire motor program become illegal was just the icing on the cake.

i had a motor building business at the time specializing in small block ford race motors. Having your own motor become illegal isn't good for business. I just finished the motors for customers i already had, shut down shop and went back working offshore again. It killed my love for building cars

[us1]

I love it when they made top
pinning your own pistons illegal because it made your motor out last stock top pinned and side pinned pistons.



Or thinking outside the box and having a rule rewritten so you can't and your entire motor becomes illegal. The rule was 310 ci maximum, which is a 302 .060 over, but they never said how you could get the 310. So we ran big bore and short stroke cranks to make them scream rpm. Having your entire motor program become illegal was just the icing on the cake.

i had a motor building business at the time specializing in small block ford race motors. Having your own motor become illegal isn't good for business. I just finished the motors for customers i already had, shut down shop and went back working offshore again. It killed my love for building cars

[90 5.0]

Yeah there's a few motor rules that make me scratch my head about

[Capt.Insane-o]

If you like stalling around the docks when shifting all that light weight **** is cool. :)

[CUDA]

Brendon Power flywheels are COOL:cheers:

[Capt.Insane-o]

A customer of mine has a 540 in a larger v bottom. The internals were put together with some left over stuff from a car project, j/e pistons, carrilio rods, eagle crank, high end parts that were lightened and balanced which was fine. It has a pretty aggressive cam and maybe a not so right intake and carb. It spins a 29 through 1.36 gears and wasn't the friendliest thing around the docks, he was at the end of his budget so we ended up taking his flywheel off which was an aluminum one with the steel insert removed and had a stocker balanced for the motor and it was much better during shifting chores. Lighter internals are fine but a motor that isn't particularly idle happy and without a self correcting efi system does benefit from some added inertia. The heavier flywheel didn't make a beans difference anywhere else other than idle. Keep in mind an 850 rpm max stable no load idle rpm is what you want for maximum drive reliability.

[90 5.0]

A motor combo that isn't right was the problem, a heavy flywheel is a band aid and fixed the issue.

Doesnt mean light weight flywheels on good combos are bad.

You could drive my drag car to the grocery store if you wanted too, or stand that bastard on the back bumper with a super light fidenza flywheel.

[90 5.0]

I also fish from time to time with a lightweight Mercury flywheel , no problems with the motor. It's tuned right

[Mr. Demeanor]

Does a stock flywheel have a zero balance or is it weighted to balance the entire rotating assembly?
I know when I had mine done I had it balanced with the entire rotating assembly by Falicon Cranks but that flywheel came apart.

[Classic18]

Does a stock flywheel have a zero balance or is it weighted to balance the entire rotating assembly?
I know when I had mine done I had it balanced with the entire rotating assembly by Falicon Cranks but that flywheel came apart.

Yes, the lightweight flywheel must be balanced with the rotating mass.

[Mr. Demeanor]

Yes, the lightweight flywheel must be balanced with the rotating mass.

So all these guys buying used flywheel or just buying a flywheel and slapping it on their motor are throwing off the balance?

[us1]

The Mercury flywheel is balanced just to itself.

[CUDA]

yes, the lightweight flywheel must be balanced with the rotating mass.

wrong!

[us1]

Everything rotating is balanced separately. So no it does not throw it off balance.


So all these guys buying used flywheel or just buying a flywheel and slapping it on their motor are throwing off the balance?

[Classic18]

So all these guys buying used flywheel or just buying a flywheel and slapping it on their motor are throwing off the balance?

Assuming you rotate the entire rotating assembly (which is best), If you replace the flywheel and don't rebalance the recip mass, it will throw off your balance.....unless its the same mass & location. If the mass is very low, should not have an effect

[Mr. Demeanor]

But, if you've had your entire rotating assembly balanced you probably should not swap flywheels. Thats the problem I ran into when mine grenaded but I have no choice but to throw a stock one on.

[Classic18]

Everything rotating is balanced separately. So no it does not throw it off balance.

I don't follow....if you add an extra bolt and nut to your flywheel, you will feel an imbalance....I would guess if the rotating assembly was balanced without a flywheel and the flywheel was on a neutral axis, no effect, but if its imbalanced, it would shake.

[Classic18]

But, if you've had your entire rotating assembly balanced you probably should not swap flywheels. Thats the problem I ran into when mine grenaded but I have no choice but to throw a stock one on.

I agree.....it can be a big b\deal, maybe not.....depends on the added mass...

[us1]

Exactly, That's why Mercury doesn't do it. The parts have to be interchangeable.


But, if you've had your entire rotating assembly balanced you probably should not swap flywheels. Thats the problem I ran into when mine grenaded but I have no choice but to throw a stock one on.

[FMP]

What you do with the recip depends on the configuration of the engine and how it's mounted. The rotating big end rod balanced with the flywheel balanced with or on it's own the flywheel will be the same. A balanced wheel is a balanced wheel. Merc

[CUDA]

This is Quality, less than 4lbs. approved for use in ODBA/DSRA/F1

[Mr. Demeanor]

Wish I could get something that pretty for my Yamaha without spending a fortune for a one off piece.

[us1]

That's exactly right.


What you do with the recip depends on the configuration of the engine and how it's mounted. The rotating big end rod balanced with the flywheel balanced with or on it's own the flywheel will be the same. A balanced wheel is a balanced wheel. Merc

[CUDA]

It's $1,000. when in stock

Nothing good is cheap

Nothing cheap is good .

[rude tim]

The only benifit to a lightened flywheel is crank flex. Dyno test will not show how a boat will perform on the water. Yes a lightened flywheel will spin up faster but the lost mass will allow the engine to dip farther when the prop loads. The real test would be in the water over a measured distance.

[Capt.Insane-o]

Unless he is drag racing this donzi with a data logger the difference between a light flywheel and a stocker is inconsequential. Flyweight stuff is great in a rig that is launched wave top to wave top with nasty rpm spikes. With 1.50 gears and 400 hp he is going to be up there in prop pitch and the heavy bite of a high pitch mirage bravo hydromotive or otherwise will negate much of a spendy flywheel. And it sucks to look like an ass around the docks.:smiletest:

[mrcrsr]

The point alot of people miss is it takes power to accelerate mass, that's why in a drag racing situation the lighter flywheel accelerates the boat quicker. Once the engine is up to speed it is not taking additional power to operate a heavier flywheel, but from a longevity standpoint a lighter flywheel is better, not having all the weight hanging off the top of the crankshaft, let alone what happens when the prop comes in and out of the water with the flywheel trying to twist the crankshaft

[FMP]

Take a 5hp motor with a 5 lb wheel ,run it a 4000rpm. Now replace that wheel with a 5000 lb wheel and see if it can maintain 4000rpm. Or build a flywheel which can draw mass from the outer edge toward the center while rotating.

A student stands on the center of a rotating platform that has frictionless bearings. He has a 2.0 kg object in each hand, held 1.0 m from the axis of rotation of the system. The system is initially rotating at 10 rpm. Determine a) the initial angular velocity in radians per second, b) the angular velocity of the sytem in radians per second after the objects are brought to a distance of 0.20 m from the axis of rotation, c) the change in the rotational kinetic energy of the system as the objects are pulled closer to the center of rotation. d) What causes the increase in rotational kinetic energy? (Assume that the moment of inertia of the platform + student remains constant at 1.0 kg m 2.)
Solution:

a) Use 1 rev = 2 http://theory.uwinnipeg.ca/physics/rot/img99.gif radians and 1 minute = 60 seconds to convert:


10 rev/min
=
(10 rev/min )(2http://theory.uwinnipeg.ca/physics/rot/img100.gif rads/rev )(1 min /60 s )




=
1.05 rad /s.




b) Use conservation of angular momentum. We therefore need to compute the initial and final moments of inertia of the system:


Ii
=
I (student + platform) + mri2 + mri2




=
1.0 kg m 2 + (2.0 kg )(1.0 m )2 + (2.0 kg )(1.0 m )2




=
5.0 kg m 2







If
=
I (student + platform) + mrf2 + mrf2




=
1.0 kg m 2 + (2.0 kg )(0.2 m )2 + (2.0 kg )(0.2 m )2




=
1.16 kg m 2.




Determine final velocity using conservation of angular momentum:



Iihttp://theory.uwinnipeg.ca/physics/rot/img44.gif = Ifhttp://theory.uwinnipeg.ca/physics/rot/img45.gif.



So that:


http://theory.uwinnipeg.ca/physics/rot/img45.gif
=
http://theory.uwinnipeg.ca/physics/rot/img101.gifhttp://theory.uwinnipeg.ca/physics/rot/img44.gif




=
http://theory.uwinnipeg.ca/physics/rot/img102.gif x 1.05 rads/s




=
4.5 rads/s.




c) The change in kinetic energy is:


http://theory.uwinnipeg.ca/physics/rot/img84.gifKE
=
KEf - KEi




=
http://theory.uwinnipeg.ca/physics/rot/img30.gifIfhttp://theory.uwinnipeg.ca/physics/rot/img96.gif - http://theory.uwinnipeg.ca/physics/rot/img30.gifIihttp://theory.uwinnipeg.ca/physics/rot/img103.gif




=
http://theory.uwinnipeg.ca/physics/rot/img30.gif(1.16 kg m 2)(4.5 rads/s )2 - http://theory.uwinnipeg.ca/physics/rot/img30.gif(5.0 kg m 2)(1.05 rad /s )2




=
11.8 J - 2.75 J




=
9.05 J.




d) As the student pulls the object in toward the center of rotation, he is doing work on the system. This work goes into increasing the kinetic energy of the system.

[Mr. Demeanor]

Take a 5hp motor with a 5 lb wheel ,run it a 4000rpm. Now replace that wheel with a 5000 lb wheel and see if it can maintain 4000rpm.. It would be able to maintain 4000rpm it would just take a LONGGGG time to get it up to 4000 rpm.

[FMP]

An infinite mass wheel and an infinitely small HP will take infinite time

[XstreamVking]

What I wanna know is, how do those ice skaters spin so damn fast with out a flywheel.....

[Mr. Demeanor]

367780
What I wanna know is, how do those ice skaters spin so damn fast with out a flywheel.....

[FMP]

Was going to post one with real nice shape just to give an example to the question above.

[XstreamVking]

That is not what I had in mind. I was thinking more like FMP.http://www.screamandfly.com/attachment.php?attachmentid=367780&d=1461285545&thumb=1 (http://www.screamandfly.com/attachment.php?attachmentid=367780&d=1487710123)

[Krazymaan]

The hardest fact about lightened flywheels... They look cool.

[Mr. Demeanor]

I know! My poor motor looks so sad. Kind of like its wearing an ugly hat.

[Mr. Demeanor]

Its only good for playing ring toss now.
367793

[Classic18]

We have never expected a lightened flywheel to make more top end horse power in fact it should make less. The #1 point in a lightened flywheel is to stop the top of the crank from coming off at 10,000 RPM. or for that matter at 8000 RPM. But what your test really doesn’t show is the torque gain on acceleration dew to spinning up a lighter mass. In an F1 boat a lightened flywheel is a noticeable gain in acceleration off the turn. On my dyno, as long as the motor is accelerating, the lightened flywheel will make 10 more HP over the stock S3000 type.

we run lighter recip mass on A sedans (pistons, flywheel...) for the increase in a Cel after a corner. Same physics...guess Newton knew what he was talking about. Not really any top speed increase, in fact slight negative

[Classic18]

What I wanna know is, how do those ice skaters spin so damn fast with out a flywheel.....

By using the product of moment of inertia and rotational speed

[FMP]

By drawing mass to center axes of rotation. Sample problems above
https://www.youtube.com/watch?v=LgI5AMQ347g

[tlwjkw]

i've been told for years n years tha lite weight came about for "slowin' down" ta turn more than any other reason.... any other benefit was jus icin'........

[FMP]

Why do I think someone tried to design a wheel with weights that could be drawn into the center hub? Hope it didn't scatter . Run wide open topped out and pull the weight in running to a turn, gain rpm. Hit the turn weights back outside. Decades ago

[rude tim]

Reducing Reciprocating mass will increase RPM not the weight of a flywheel. One must remember that a mass in motion tends to stay in motion. Unless your boat takes off and lands without dropping any RPM at all there will be no benefit with a lighter flywheel other than crank flex and looks.

[olboatman]

Reducing Reciprocating mass will increase RPM not the weight of a flywheel. One must remember that a mass in motion tends to stay in motion. Unless your boat takes off and lands without dropping any RPM at all there will be no benefit with a lighter flywheel other than crank flex and looks.

Isn't weight part of mass? The less weight should help get that mass in motion quicker.:confused: Gary

[FMP]

Wheel is rotating

[Krazymaan]

I know everyone doesn't have a digital scale. But I would like to see real life numbers. I'm always interested in why does your lightweight flywheel weighs 4.2 lbs and why does another lightweight flywheel for the same motor weigh in at 5.4 lbs. and they are supposedly the same flywheel. I'm betting its because thats what the buyer was told without real evidence. I know 1/2 lb isn't ultra critical, but its just interesting to know why it is what it is. Maybe they are all rough cut pretty close and the other grams are from removing material during balancing. I don't know but I am sure someone knows.

[FMP]

Jeff Dunn right? Forget his name.

[rude tim]

Rotational mass in this case flywheel will turn the same RPM lightened or stock, yes it will spin up faster if it is lighter but it will not spin faster. The point is unless your setup is able to never drop any RPM after you hit the throttle a lightened flywheel will not help the acceleration of your boat. Reciprocating mass will effect the overall RPM and acceleration.

The guys that do land speed racing at Bonniville and El Marage like to use heavy flywheels as this helps with getting the car to get and controll traction. The guys that road race like light flywheels for faster acceleration between shifts.

[FMP]

Unless factored to the config and mount correctly recip can shake you to bits

[olboatman]

I know everyone doesn't have a digital scale. But I would like to see real life numbers. I'm always interested in why does your lightweight flywheel weighs 4.2 lbs and why does another lightweight flywheel for the same motor weigh in at 5.4 lbs. and they are supposedly the same flywheel. I'm betting its because thats what the buyer was told without real evidence. I know 1/2 lb isn't ultra critical, but its just interesting to know why it is what it is. Maybe they are all rough cut pretty close and the other grams are from removing material during balancing. I don't know but I am sure someone knows.

I may disagree with 1/2 pound not being ultra critical( when you are drag racing).....thats over 20%! I agree Jeff Dunn may be the one to ask. Gary

[FMP]

Still like less twist on the top of the crank when cornering, chop etc.

[Krazymaan]

That may have been an uneducated typo on my behalf

[FMP]

Like freewheeling a bike front rim with your thumbs and index fingers holding the hub axel and feel the forces.

[Mr. Demeanor]

But with light flywheel your boat might tip over easier.

[Classic18]

��.

[HStream1]

A Lightened Flywheel will give you 200 to 300 more RPMs on the top end.


Rotational mass in this case flywheel will turn the same RPM lightened or stock, yes it will spin up faster if it is lighter but it will not spin faster. The point is unless your setup is able to never drop any RPM after you hit the throttle a lightened flywheel will not help the acceleration of your boat. Reciprocating mass will effect the overall RPM and acceleration.

The guys that do land speed racing at Bonniville and El Marage like to use heavy flywheels as this helps with getting the car to get and controll traction. The guys that road race like light flywheels for faster acceleration between shifts.

[Classic18]

So now my issue is where to get an affordable light flywheel and couple to fit in a SBC/Bravo combo.

suggestions??

[HStream1]

As far as why different light flywheels weigh differently?? That can be attributed to many factors. Were they done by the same person, Same machine with the same program? Diamond, Brendan, Jay Smith, Jeff Dunn all cut them differently therefore there is going to be a weight difference. Even if two wheels were done on the same machine with the same program. After balancing they will be different weights if only by a few Grams.

As far as a 1/2 lb not being ultra critical?? Well Myself as well as others spend alot of time and or money to remove ounces and even a few grams from Pistons and Rods to make sure they are all matched in weight and lighter than stock.

But for River Running purposes IMO its best not to Run a Lightened flywheel. The Up and down Flex due to RPMs will eventually cause stress cracks in the Magnets and possibly the Flywheel itself. Now if its a Billet Flywheel with encased magnets one has a better chance of that not happening.

This is a Stock mercury Lightweight Flywheel At 7.24lbs which is about average weight +- a few grams vs a Flywheel Jeff Dunn and I did for one of my race engines at 4.10 lbs. http://i465.photobucket.com/albums/rr18/jbcincnc/Light%20Stock%20Flywheel_zpscqizhyll.jpg?t=1487849454

http://i465.photobucket.com/albums/rr18/jbcincnc/15235637_1030366410407764_7984997679299533794_o_zpsdbskerl4.jpg


I know everyone doesn't have a digital scale. But I would like to see real life numbers. I'm always interested in why does your lightweight flywheel weighs 4.2 lbs and why does another lightweight flywheel for the same motor weigh in at 5.4 lbs. and they are supposedly the same flywheel. I'm betting its because thats what the buyer was told without real evidence. I know 1/2 lb isn't ultra critical, but its just interesting to know why it is what it is. Maybe they are all rough cut pretty close and the other grams are from removing material during balancing. I don't know but I am sure someone knows.

[FMP]

I've heard that

[Mr. Demeanor]

A Lightened Flywheel will give you 200 to 300 more RPMs on the top end.

Explain the physics on that.
Zero difference on mine and other on top end. There are in strong arguments for increased acceleration and better longevity but I have seen none for actual increased max attainable RPM.

[Mr. Demeanor]

🤡. Gyroscopic effect :D

[eli]

lighter is always better heavier never won anything, thinking about this when i,m pushing 1200 lbs of morter mix on a cart to the register at menards

[Mr. Demeanor]

lighter is always better heavier never won anything, thinking about this when i,m pushing 1200 lbs of motor mix on a cart to the register at menards Heavier wins in weight lifting, tractor pulls, sumo wrestling, ..... :D

[HStream1]

Very simply Law of Physics. Accelerating an unnecessary rotating mass requires energy, and the acceleration process saps some of the horsepower we have available to accelerate. Hence Faster Acceleration and Higher RPM's


Explain the physics on that.
Zero difference on mine and other on top end. There are in strong arguments for increased acceleration and better longevity but I have seen none for actual increased max attainable RPM.

[Mr. Demeanor]

Very simply Law of Physics. Accelerating an unnecessary rotating mass requires energy, and the acceleration process saps some of the horsepower we have available to accelerate. Hence Faster Acceleration and Higher RPM's That doesnt account for an increase in max attainable rpm. Faster acceleration yes. Higher max attainable RPM no.

[Mr. Demeanor]

Take a simple electric motor like a circular saw. Pull the trigger and it attains the same RPM with or without a blade in it. It will attain that RPM sooner without a blade in it.

[HStream1]

Yes it does if the engine is capable of attaining it. If as you say isnt true then based on Physics YOU explain how a motor that is turning say 10000 RPM while under load with weight and rotating mass can spin 12000 when that weight and mass is reduced or eliminated.



That doesnt account for an increase in max attainable rpm. Faster acceleration yes. Higher max attainable RPM no.

[Mr. Demeanor]

Yes it does if the engine is capable of attaining it. If as you say isnt true then based on Physics YOU explain how a motor that is turning say 10000 RPM while under load with weight and rotating mass can spin 12000 when that weight and mass is reduced or eliminated.
I cant explain it because no such a motor exists. The only time weight effects top speed is when it effects frictional drag. We can go round and round. This whole thread has been about exactly what I am saying. No increase in top RPM. Ill let someone else take a stab at explaining it.

[Mr. Demeanor]

We have never expected a lightened flywheel to make more top end horse power in fact it should make less. The #1 point in a lightened flywheel is to stop the top of the crank from coming off at 10,000 RPM. or for that matter at 8000 RPM. But what your test really doesn’t show is the torque gain on acceleration dew to spinning up a lighter mass. In an F1 boat a lightened flywheel is a noticeable gain in acceleration off the turn. On my dyno, as long as the motor is accelerating, the lightened flywheel will make 10 more HP over the stock S3000 type.

Ill just leave the first response to this thread here where someone with real experience answered the question pages ago.

[HStream1]

Im am so glad you posted that. Ill remain silent at this point. ROFLMAO.


I cant explain it because no such a motor exists. The only time weight effects top speed is when it effects frictional drag. We can go round and round. Ill let someone else take a stab at explaining it.

[Mr. Demeanor]

I wish you were right because I would love 200rpm by just lightening a flywheel. Hell I dont really like you and I still hope you are right LOL.

[HStream1]

John was extremely clear. Nothing he says disputes anything I have said. You disputed a Acceleration gain. But John clearly covered that. The question he didnt answer was RPM. Well back in 2001 we didnt have the Data Loggers that we do today to measure distance, RPM, speed, Time etc. My Data Logger says I gained 257 RPM's when I went to a Billet 4.10 Lb Flywheel vs a 7.2 lb Flywheel in 800 ft. When I ran it out to 1000+ I gained almost 300 RPMs.

I dont need to explain any more to you Chris. No matter what I say you will dispute it. Like you said You dont even like me. So that in itself explains how you will respond no matter what.


Ill just leave the first response to this thread here where someone with real experience answered the question pages ago.

[Mr. Demeanor]

I never disputes acceleration. You said 200 to 300 rpm gain. I disputes that. Are u reading the same thing I am? John says no gain except acceleration. You say gain in top rpm.
Whatever....

[Mr. Demeanor]

Wait, now your saying 200 to 300 rpm on 800' . Uiu originally said 200-300 rpm on the top end. That is completely different and possible. All along I've been saying max attainable rpm, no time or distance restrictions. You've completely changed your position.

[Krazymaan]

So no matter how you want to word it, putting on a lighter flywheel will always be an improvement. Irrelevant of what amp flywheel you have.

Do they make a lightweight 40 amp aluminum flywheel that weighs the same as or close to a 16 amp aluminum flywheel?

Then is the 9 amp even lighter, I never seen a 9 amp in real life.

So trying to get over technical here, Then if a 40 amp is in full amp mode, that would affect the RPM's more than a 16 amp in full amp mode, right? Therefore slowing your rpms just a tidge. The more amps drawn is more strain/resistance at the flywheel?

In general, do you need a matching Stator for the flywheel amperage?

[FMP]

So same question, will it spin 200less with the heavy wheel because that's all its got for that weight going wide open stretched out?

[Mr. Demeanor]

So same question, will it spin 200less with the heavy wheel because that's all its got for that weight going wide open stretched out?

Given enough room to let the motor reach max rpm (stop accelerating) weight of the flywheel will not effect it. Ive done it both ways same everything else and my boat is very sensitive to change. Ran the exact same number. My flywheel was a LOT lighter than a stocker too.

[FMP]

Take it to the extreme like the example I gave with the 5hp or the infinite condition.You might not get to full rpm because the rate of change is too slow. Shouldn't play with these weights but ?

[Classic18]

In my case with a sterndrive Bravo, my flywheel is appx 30 pounds..and I could get a 10 pound flywheel, but with a carb (as opposed to fuel injection), it's too much risk for dock adventures....so I'll stick to the heavier flywheel and look at lowering the other rotating mass (pistons, crank, etc)

[FMP]

Sorry classic, we went off on a tangent. Maybe you're right about the clown show at the dock or just set idle a bit higher?

[Classic18]

Sorry classic, we went off on a tangent. Maybe you're right about the clown show at the dock or just set idle a bit higher?

At a high level, my choice is a either standard flywheel and carb or fuel injection and a lighter flywheel.... guess I'll do the carb.

Dave