Lightened Flywheel questions
B*a*n*n*e*d
Joined: Mar 2002
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Re: Lightened Flywheel questions (AzN_Flava)
I don't see the big concern about being too light.
1) The difference is not that big when you take the flywheel/disc/pressure plate as a whole. 21lbs = 8lb flywheel, 1lb disc, and 12lb pressure plate vs. 31lbs for the same set-up with a stock 18lb flywheel. That's just a 33% decrease in weight.
I know this calculation is just an approximation since we are interested in rotational mass.
2)Honda cranks are forged and super stiff. Not the weak as cast **** found in other engines.
3) The main pulley/damper works really well on Honda's (at least the B-series).
4) With the lighter flywheel you can launch say at a more optimal RPM 6,000 and not spin the tires as much. Wheel hop and tire spin is a big problem with cars with decent power on street tires.
5) If you want your motor to last 200,000 miles then you are not looking to maximize power.
1) The difference is not that big when you take the flywheel/disc/pressure plate as a whole. 21lbs = 8lb flywheel, 1lb disc, and 12lb pressure plate vs. 31lbs for the same set-up with a stock 18lb flywheel. That's just a 33% decrease in weight.
I know this calculation is just an approximation since we are interested in rotational mass.
2)Honda cranks are forged and super stiff. Not the weak as cast **** found in other engines.
3) The main pulley/damper works really well on Honda's (at least the B-series).
4) With the lighter flywheel you can launch say at a more optimal RPM 6,000 and not spin the tires as much. Wheel hop and tire spin is a big problem with cars with decent power on street tires.
5) If you want your motor to last 200,000 miles then you are not looking to maximize power.
B*a*n*n*e*d
Joined: Mar 2002
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Re: Lightened Flywheel questions (Rocket)
A heavier flywheel will stop more vibrations (harmonics) on a crank by not allowing the vibrations from travelling from one end to the other. With a heavier flywheel the vibrations tend to stop when they meet the flywheel. This is how VW keeps their air-cooled motors from having excess crank harmonics.
Honda-Tech Member
Joined: May 2000
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From: PASADENA, CA, USA
Re: Lightened Flywheel questions (Hayasa15)
I am thinking about buying a lightened flywheel. Does brand matter at all?
--depends on you. Brand doesn't really matter, they're all pretty good. JDM or US aftermarket f.wheels.
Also does the weight matter?
--also depends on you. Usually 10-12lbs is the way to go. There are lighter ones though, which are made to be lighter
What i mean is can i damage the motor by using a flywheel that is too light?
-- no, you can't damage your engine with a lightened f.wheel.
Also what are the advantages to using an aluminum flywheel compared to using a cromoly one?
-- Don't exactly know, but logically a chromolly wheel would be stonger material & the Aluminum wheel would be lighter. (its past my bedtime right now)
Is it bad to just have the stock flywheel lightened instead of buying a new one?
-- HELL NO it's not bad! That's the cheapest most economic way to go with a lightened f.wheel. It's cheaper to do (at some automotive machine shops) over buying a brand new one. Approx. 12LBS is the maximum you'd wanna lighten a stock f.wheel, any lighter could cause thermonuclear breakdown (ask the machine shop guy, he'll tell ya).... 12lbs will give you nice snappy throttle response.
[Modified by Hayasa15, 12:06 PM 4/23/2002]
--depends on you. Brand doesn't really matter, they're all pretty good. JDM or US aftermarket f.wheels.
Also does the weight matter?
--also depends on you. Usually 10-12lbs is the way to go. There are lighter ones though, which are made to be lighter
What i mean is can i damage the motor by using a flywheel that is too light?
-- no, you can't damage your engine with a lightened f.wheel.
Also what are the advantages to using an aluminum flywheel compared to using a cromoly one?
-- Don't exactly know, but logically a chromolly wheel would be stonger material & the Aluminum wheel would be lighter. (its past my bedtime right now)
Is it bad to just have the stock flywheel lightened instead of buying a new one?
-- HELL NO it's not bad! That's the cheapest most economic way to go with a lightened f.wheel. It's cheaper to do (at some automotive machine shops) over buying a brand new one. Approx. 12LBS is the maximum you'd wanna lighten a stock f.wheel, any lighter could cause thermonuclear breakdown (ask the machine shop guy, he'll tell ya).... 12lbs will give you nice snappy throttle response.
[Modified by Hayasa15, 12:06 PM 4/23/2002]
Junior Member
Joined: Sep 2001
Posts: 611
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From: Believeland
Re: Lightened Flywheel questions (Rocket)
I don't see the big concern about being too light.
1) The difference is not that big when you take the flywheel/disc/pressure plate as a whole. 21lbs = 8lb flywheel, 1lb disc, and 12lb pressure plate vs. 31lbs for the same set-up with a stock 18lb flywheel. That's just a 33% decrease in weight.
I know this calculation is just an approximation since we are interested in rotational mass.
I know this calculation is just an approximation since we are interested in rotational mass.
2)Honda cranks are forged and super stiff. Not the weak as cast **** found in other engines.
3) The main pulley/damper works really well on Honda's (at least the B-series).
4) With the lighter flywheel you can launch say at a more optimal RPM 6,000 and not spin the tires as much. Wheel hop and tire spin is a big problem with cars with decent power on street tires.
5) If you want your motor to last 200,000 miles then you are not looking to maximize power.
5) If you want your motor to last 200,000 miles then you are not looking to maximize power.
B*a*n*n*e*d
Joined: Mar 2002
Posts: 7,765
Likes: 1
Re: Lightened Flywheel questions (allenp)
I like your style allenp. No sweat, your feedback is much appreciated by me.
I still differ with you on couple of your qualified opinions but it's all good.
I do agree that lightened flywheels will affect all engine components especially valve spring motion since the rotational acceleration gets propragated to the cams and thus increases the instaneous acceleration on valve springs. So stiffer valve springs will add life to an engine with a lighter flywheel.
I disagree on the sole purpose of the damper to isolate vibrations to accessories as the damper is an engergy absorbing device that "absorbs" vibrations and turns it into heat. Also the timing belt is directly connected to the crank but still benefits from having a damper.
I still differ with you on couple of your qualified opinions but it's all good.
I do agree that lightened flywheels will affect all engine components especially valve spring motion since the rotational acceleration gets propragated to the cams and thus increases the instaneous acceleration on valve springs. So stiffer valve springs will add life to an engine with a lighter flywheel.
I disagree on the sole purpose of the damper to isolate vibrations to accessories as the damper is an engergy absorbing device that "absorbs" vibrations and turns it into heat. Also the timing belt is directly connected to the crank but still benefits from having a damper.
B*a*n*n*e*d
Joined: Mar 2002
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Re: Lightened Flywheel questions (Rocket)
I haven't got a chance to visually study live crankshaft vibrations but I have studied their effects on the motor during tear downs.
[Modified by Rocket, 6:31 PM 6/4/2002]
[Modified by Rocket, 6:31 PM 6/4/2002]
B*a*n*n*e*d
Joined: Mar 2002
Posts: 7,765
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Re: Lightened Flywheel questions (Rocket)
allenp, what clutch/drivleline OEM do you work for? I am curious.
You are dead on about the purpose of springs in the hubs of clutch discs which is another common misconception.
Your study of rotational accelaration is of great interest to me. Hit me an IM if you like.
Thanks.
You are dead on about the purpose of springs in the hubs of clutch discs which is another common misconception.
Your study of rotational accelaration is of great interest to me. Hit me an IM if you like.
Thanks.
Junior Member
Joined: Jun 2002
Posts: 672
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From: CA, USA
Re: Lightened Flywheel questions (Rocket)
hey robert .....just wondering if the harmonic dampener ...has NO effect on the harmonics of the flywheel ...as stated .....WHY if the crank pulley comes lose ....do you spin all of your bearings ?????? we all know whos motor im talking about .....twice in one week .....DOH !! 
[Modified by allmotorgurl, 6:06 AM 6/5/2002]
[Modified by allmotorgurl, 6:06 AM 6/5/2002]
B*a*n*n*e*d
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Re: Lightened Flywheel questions (allmotorgurl)
I guess you know who's motor just has so much power that the crank is flexing like a ****. It's the rods bearings that seized correct? You guys migh want to try running a little more clearance in the rod bearings to handle the crank flex.
For those who are not in the loop the motor is the motor that I posted the dyno sheet on the post titled "Got torque, Vtec Kick (dyno sheet)".
[Modified by Rocket, 9:37 AM 6/5/2002]
[Modified by Rocket, 9:39 AM 6/5/2002]
For those who are not in the loop the motor is the motor that I posted the dyno sheet on the post titled "Got torque, Vtec Kick (dyno sheet)".
[Modified by Rocket, 9:37 AM 6/5/2002]
[Modified by Rocket, 9:39 AM 6/5/2002]
Junior Member
Joined: Sep 2001
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From: Believeland
Re: Lightened Flywheel questions (Rocket)
I'm around, if you want to IM me...
I work for LuK, Inc. in Wooster, Ohio (about 1 hr south of Cleveland.) We're a German-based company that manufactures dry clutches for about 50% of the North American market, and we also produce torque converter lockup clutches and torque converters for a portion of the market.
I develop the torsional damper, be it a damped clutch disc (disc with circumferential springs) or a dual-mass flywheel, for the vehicle in question. I work on Ford products. In developing the damper, I do extensive measurements in the vehicle, as well as computer simulation of the torsional system that is the driveline (engine, flywheel, clutch, transmission, driveshafts, wheels, tires, etc.)
Basically, I develop the damper to reduce noise from the transmission and driveline caused by engine torsional excitation.
I work for LuK, Inc. in Wooster, Ohio (about 1 hr south of Cleveland.) We're a German-based company that manufactures dry clutches for about 50% of the North American market, and we also produce torque converter lockup clutches and torque converters for a portion of the market.
I develop the torsional damper, be it a damped clutch disc (disc with circumferential springs) or a dual-mass flywheel, for the vehicle in question. I work on Ford products. In developing the damper, I do extensive measurements in the vehicle, as well as computer simulation of the torsional system that is the driveline (engine, flywheel, clutch, transmission, driveshafts, wheels, tires, etc.)
Basically, I develop the damper to reduce noise from the transmission and driveline caused by engine torsional excitation.
Honda-Tech Member
Joined: Jan 2002
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From: GSO, NC
Re: Lightened Flywheel questions (allmotorgurl)
Well the rule of thumb when modding engines has always been you dont get something for nothing. Another over looked point is that when people machine their flywheels they balance it without balancing the crank pulley as well. I have seen numerous engines suffer premature failure because of this!!
This is good info for everyone to see
This is good info for everyone to see
B*a*n*n*e*d
Joined: Mar 2002
Posts: 7,765
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Re: Lightened Flywheel questions (Rocket)
So you guys with the lightwieght flywhees are putting a lot more stress on your sprung clutch disc. Expect much shorter disc life. I have seen this first hand with my friends stock disc in his TypeR motor with the lighter Typer Flywheel (which isn't all that lighter). His disc basically got real beat and broke.
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Joined: Feb 2001
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From: Canada
Re: Lightened Flywheel questions (letsride)
allenp and rocket...
thank you for the very informative flywheel class 101...
like letsride said you don't get something for nothing...
faster rpms revs ... faster acceleration kinda... = more engine stress and shorter motor life...
i think this is definitely one of those personal bookmarks on flywheel questions!
good stuff !
thank you for the very informative flywheel class 101...
like letsride said you don't get something for nothing...
faster rpms revs ... faster acceleration kinda... = more engine stress and shorter motor life...
i think this is definitely one of those personal bookmarks on flywheel questions!
good stuff !
Honda-Tech Member
Joined: Mar 2002
Posts: 2,529
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From: deep in the heart of Texas
Re: Lightened Flywheel questions (Hayasa15)
Lightened flywheels and pullies do shorten engine life. They work great but be prepared to shell out for a new engine quicker then expected.
With that said I'm leaving off the UR pullies with the new engine. Want it to last a little longer then before. Still putting on the flywheel though.
With that said I'm leaving off the UR pullies with the new engine. Want it to last a little longer then before. Still putting on the flywheel though.
Junior Member
Joined: Sep 2001
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From: Believeland
Re: Lightened Flywheel questions (letsride)
Excellent avatar, letsride. My father and I are rebuilding a 1960 Austin 850, and my mom has a 2002 Cooper S on order!
A correction to an earlier assertion I made (and apologies to Rocket for the disagreement
) regarding crankshaft pullies. The crankshaft damper pulley, which drives the accessories, serves two primary purposes. One, as I earlier stated, is to damp out the vibrations going to the accessories. The other is, in fact, to dampen the crankshaft harmonics that exist in the crank. My statement that the pulley has no effect on torsional vibrations, while true in the sense I meant it, was too far-reaching and was not qualified properly. The crank damper pulley has minimal effect on flywheel, and thus driveline, torsional vibrations, only on the harmonics that exist inside the crankshaft between the flywheel and the crank pulley.
A correction to an earlier assertion I made (and apologies to Rocket for the disagreement
) regarding crankshaft pullies. The crankshaft damper pulley, which drives the accessories, serves two primary purposes. One, as I earlier stated, is to damp out the vibrations going to the accessories. The other is, in fact, to dampen the crankshaft harmonics that exist in the crank. My statement that the pulley has no effect on torsional vibrations, while true in the sense I meant it, was too far-reaching and was not qualified properly. The crank damper pulley has minimal effect on flywheel, and thus driveline, torsional vibrations, only on the harmonics that exist inside the crankshaft between the flywheel and the crank pulley.
Joined: Jan 2002
Posts: 2,018
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From: North/West, IL
Re: Lightened Flywheel questions (allenp)
The crank damper pulley has minimal effect on flywheel, and thus driveline, torsional vibrations, only on the harmonics that exist inside the crankshaft between the flywheel and the crank pulley.
B*a*n*n*e*d
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Re: Lightened Flywheel questions (SLPR)
Alot of good things have come out of this thread. Like I've always been told that if you run a lightweight flywheel you need more valvespring pressure. Now I really see why. That's awesome.
No more mysterious things like my valves pulled thru my retainers but I never over revved the motor. It's not just rpm but the "jerkyness" of the motion that puts stress on the moving parts.
No more mysterious things like my valves pulled thru my retainers but I never over revved the motor. It's not just rpm but the "jerkyness" of the motion that puts stress on the moving parts.