single mass/lightweight flywheel GAIN
Thread Starter
Melting Slicks
Joined: Dec 2001
Posts: 2,437
Likes: 1
From: Gainesville Fl
single mass/lightweight flywheel GAIN
before everyone tells me to use the search let me say that im talking about how much gain in power people usually get with them on ZF6 speeds. i want to say the ZO6 crowd is getting some amazing gains with them. i want to say like over 10% power gain. can anybody fill me in on this?
Team Owner
Joined: Aug 2000
Posts: 40,156
Likes: 45
From: San Pedro CA
I think one of the mags did a test, the power gains were not that amazing.
Are you doing drag racing? comments from a few people here, the super light fidenza is not a great drag flywheel... too light. The F-body steel FW, machined .090 is the way to go. Or, for that matter, the DM. Seems to launch better. Could also be an issue of feel.
Road racing, the Fidenza is the bom.
Are you doing drag racing? comments from a few people here, the super light fidenza is not a great drag flywheel... too light. The F-body steel FW, machined .090 is the way to go. Or, for that matter, the DM. Seems to launch better. Could also be an issue of feel.
Road racing, the Fidenza is the bom.
Instructor
Joined: Sep 2004
Posts: 153
Likes: 0
Technically the single mass flywheel does not increase horsepower it reduces rotational inertia. Therefore the effect will be greatest when engine speed is changing the fastest in the lower gears. If you run the car on a chassis dyno in 4th gear the measured HP will not be that much different. If you measure it in 2nd gear the difference will be much greater.
I put a single mass flywheel on my 96 and at Buttonwillow raceway coming out of slow corners the difference was very noticable. Out of a 2nd gear corner onto a 3rd gear straight I gained about 500 rpm more by the end of the straight which is significant. On another part of the track where I am running out in 4th, there was almost no difference at the end of the straight.
Basically in 1st and 2nd the difference is significant, in the higher gears it is less significant.
On a dragstrip I am not sure that a light flywheel is the way to go. A drag race is won or lost in the first 60 feet and a heavier flywheel may give you a more consistent launch.
I put a single mass flywheel on my 96 and at Buttonwillow raceway coming out of slow corners the difference was very noticable. Out of a 2nd gear corner onto a 3rd gear straight I gained about 500 rpm more by the end of the straight which is significant. On another part of the track where I am running out in 4th, there was almost no difference at the end of the straight.
Basically in 1st and 2nd the difference is significant, in the higher gears it is less significant.
On a dragstrip I am not sure that a light flywheel is the way to go. A drag race is won or lost in the first 60 feet and a heavier flywheel may give you a more consistent launch.
Advanced
Joined: Feb 2003
Posts: 78
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From: AUGUSTA GA
the tranny in my lt4 hated the fidanza. it had a slight gear rattle at idle which was bearable but the zf6 growled and howled at various rpms so much that the couple of passengers that road in the car asked what in the world is wrong with your transmission! the car did rev noticably quicker with the fidanza but i did not notice any sotp power difference.i could not stand the loooouuud..... gear noise with the fidanza so i forked out the bucks and bought a new dual mass and oe clutch kit and returned to stock form.
Race Director
Joined: Aug 2003
Posts: 11,043
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From: San Jose Pat Tillman - American Hero
Originally Posted by CYLT4
the tranny in my lt4 hated the fidanza. it had a slight gear rattle at idle which was bearable but the zf6 growled and howled at various rpms so much that the couple of passengers that road in the car asked what in the world is wrong with your transmission! the car did rev noticably quicker with the fidanza but i did not notice any sotp power difference.i could not stand the loooouuud..... gear noise with the fidanza so i forked out the bucks and bought a new dual mass and oe clutch kit and returned to stock form.
Team Owner
Joined: Sep 2002
Posts: 22,209
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From: OBAMA IS HITLER
Originally Posted by Perfusion
Interesting info... I've got the sinking feeling that a new clutch/fw is in the future for my LT4, so this sort of reaffirms my suspicion that, in this case, OEM is better...or at least more tolerable
I despise the noise as well, its horrible for a daily driver. Mated to a black tag ZF (my '90) makes it even worse.
Le Mans Master
Joined: Jul 2001
Posts: 8,183
Likes: 3
From: Santa Maria, CA
I don't have actual numbers, just an observation.
I went from the DM to a steel camaro FW. The RPM's come up much quicker, thus keeping me up in the power band like I want. Combined with my granny shifting
gives me faster shifts and better timeslips. My MPH's were especially pleasing to me with the steel FW.
Launching does take alittle more technique now.
Auto-X was the same being that I am either on the gas hard or on the brakes hard.
I didn't go aluminum because of hearing that people had the centers tear out of them under high HP.
I went from the DM to a steel camaro FW. The RPM's come up much quicker, thus keeping me up in the power band like I want. Combined with my granny shifting
gives me faster shifts and better timeslips. My MPH's were especially pleasing to me with the steel FW.Launching does take alittle more technique now.
Auto-X was the same being that I am either on the gas hard or on the brakes hard.
I didn't go aluminum because of hearing that people had the centers tear out of them under high HP.
Melting Slicks
Joined: Dec 1999
Posts: 2,816
Likes: 2
From: Austin, TX
I have a Fidanza in my '96. I think everyone has made some very good points so far. In the 4th gear dyno runs I've done, I didn't see a difference at all. However, on the roadcourse, you can definitely tell the difference in throttle response and faster revving down low. I'm not a dragracer, so no clue there.
If it's a daily driver, I wouldn't recommend an aluminum single-mass. The noise annoys a lot of people. I personally don't mind it, and if you raise your idle a 100 or 200 RPM, it's even less noticable. I've heard that the single-mass steel FW (the shaved-down F-body unit) is a good compromise.
I think this question is very similar to the B&M vs Hurst vs stock shifter debate -- it really boils down to how you use the car and personal preference. I'm keeping my Fidanza
If it's a daily driver, I wouldn't recommend an aluminum single-mass. The noise annoys a lot of people. I personally don't mind it, and if you raise your idle a 100 or 200 RPM, it's even less noticable. I've heard that the single-mass steel FW (the shaved-down F-body unit) is a good compromise.
I think this question is very similar to the B&M vs Hurst vs stock shifter debate -- it really boils down to how you use the car and personal preference. I'm keeping my Fidanza
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Le Mans Master
Joined: Sep 2000
Posts: 6,303
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From: Bartlett IL
Originally Posted by bradvette
I'm fairly certain that the 13 lb. Fidanza is going to be ripped out of mine, I'm going back to DM, contacting carolinaclutch.com they charge $625 for factoy Luk FW and $75 for unsprung clutch disc....this is about 1/2 of what a dealer charges.
I despise the noise as well, its horrible for a daily driver. Mated to a black tag ZF (my '90) makes it even worse.
I despise the noise as well, its horrible for a daily driver. Mated to a black tag ZF (my '90) makes it even worse.
I did a TRANS-plant on my 84 Xfire and replaced the 4+3 with a Black Tag ZF-6 from a 1990. I used the Fidanza flywheel with an F-Body 11" sprung hub clutch from SLP. I get little gear chatter with mine. The better the idle tune, the less the chatter since the motor runs smoother. May want to check into that. Also, what trans fluid are you using? ZF Doc recommends the Castrol for BMW's which is what I used. The only place I get any rattle is at idle. Once underway, there's no noise other than the exhaust.
Instructor
Joined: Aug 2004
Posts: 104
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"Virtual gain" of lightweight flywheel
If I did the calculations correctly this is the benefit of the 13.5 Fidanza vs the 39lb. dual mass. I found a site that says a rule of thumb for kinetic energy reduction is 1 HP per 10 lbs of virtual weight reduction--It is a function of gear and rear axle ratio.
For the 3.45 gear:
Trans Gear 1 2 3 4 5 6
Virtual lbs lost 303 203 116 80 56 39
Equiv HP gain 30.3 20.3 11.6 8.0 5.6 3.9
For the 3.45 gear:
Trans Gear 1 2 3 4 5 6
Virtual lbs lost 303 203 116 80 56 39
Equiv HP gain 30.3 20.3 11.6 8.0 5.6 3.9
Drifting
Joined: Sep 2004
Posts: 1,638
Likes: 3
Originally Posted by GeosFun
Glad I have an automatic (yawn) 
Seriously, the lighter mass should require less power to rotate the FW during acceleration only. Everything else is probably negative.
Seriously, the lighter mass should require less power to rotate the FW during acceleration only. Everything else is probably negative.
Safety Car
Joined: Sep 2000
Posts: 3,524
Likes: 4
From: Hinckley Ohio
Originally Posted by CYLT4
the tranny in my lt4 hated the fidanza. it had a slight gear rattle at idle which was bearable but the zf6 growled and howled at various rpms so much that the couple of passengers that road in the car asked what in the world is wrong with your transmission!
gear noise with the fidanza so i forked out the bucks and bought a new dual mass and oe clutch kit and returned to stock form.
gear noise with the fidanza so i forked out the bucks and bought a new dual mass and oe clutch kit and returned to stock form.
Is this indicative of a transmission problem....
Does the motor idle rougher or miss/surge at low speeds.....
The problem has to be real as so many have experienced it, but why/how does this work.......I seem to get drive train/c-tunnel or whatever clanging from cam surge......are these phenomena related??
Race Director
Joined: May 2001
Posts: 14,165
Likes: 9
Bud,
It's not the weight of the flywheel but rather the lack of any dampening in it. You see the ZF-6 uses a flywheel that is in two parts which allows it to absorb some serious vibrations and help keep the transmission quiet. When you go with a lightweight flywheel it is one piece and every single vibration from the engine is transmitted directly to the trans. With an early model ZF-6 with straight cut gears this gets very loud and annoying.
BTW, if you get any clanging at all in your drivetrain it's simply because something is loose.
It's not the weight of the flywheel but rather the lack of any dampening in it. You see the ZF-6 uses a flywheel that is in two parts which allows it to absorb some serious vibrations and help keep the transmission quiet. When you go with a lightweight flywheel it is one piece and every single vibration from the engine is transmitted directly to the trans. With an early model ZF-6 with straight cut gears this gets very loud and annoying.
BTW, if you get any clanging at all in your drivetrain it's simply because something is loose.
Safety Car
Joined: Sep 2000
Posts: 3,524
Likes: 4
From: Hinckley Ohio
Originally Posted by Nathan Plemons
Bud,
It's not the weight of the flywheel but rather the lack of any dampening in it. You see the ZF-6 uses a flywheel that is in two parts which allows it to absorb some serious vibrations and help keep the transmission quiet.
BTW, if you get any clanging at all in your drivetrain it's simply because something is loose.
It's not the weight of the flywheel but rather the lack of any dampening in it. You see the ZF-6 uses a flywheel that is in two parts which allows it to absorb some serious vibrations and help keep the transmission quiet.
BTW, if you get any clanging at all in your drivetrain it's simply because something is loose.
Nathan, thanks for your explanation, it really helps but..
I must admit I really don't understand how some things work.....
LT1<4's also have front torsional dampers....dual mass on the LT4......I quess these are meant to dampen crankshaft vibrations.....this is a whole different topic.....always wonder what is the best damper up there for modded engines????
I wish I had better hearing......I have been told drivetrain slack....and C-tunnel is loose....I personally am not so sure that it doesn't come from the engine as in serious detonation....so simple in one way, but still not sure what to fix...
