Dual Mass, Single Mass Flywheel for Clutch
Discussion
Still no response?
This is an easy question for people who are clued up. I'm going to make a hash of it.
The DMF acts as a buffer between the engine crankshaft and the clutch, smoothing out spikes in torque thus reducing drivetrain vibration and protecting the crankshaft and gearbox. The impact of replacing the DMF with an SMF varies from one engine / gearbox combo to the next but obviously quite a few people have gone down that route over the years so you can google for experiences.
By nature of their design and function DMFs are heavier than SMFs so once converted to SMF you can expect the engine to gain and lose revs faster. With less mass to accelerate the engine will feel a bit more responsive. The clutch action and the level of vibration will probably feel a bit different.
This is an easy question for people who are clued up. I'm going to make a hash of it.
The DMF acts as a buffer between the engine crankshaft and the clutch, smoothing out spikes in torque thus reducing drivetrain vibration and protecting the crankshaft and gearbox. The impact of replacing the DMF with an SMF varies from one engine / gearbox combo to the next but obviously quite a few people have gone down that route over the years so you can google for experiences.
By nature of their design and function DMFs are heavier than SMFs so once converted to SMF you can expect the engine to gain and lose revs faster. With less mass to accelerate the engine will feel a bit more responsive. The clutch action and the level of vibration will probably feel a bit different.
I have owned a Mondeo diesel with a DMF, driven a Vauxhall Corsa VXR with DMF and have a Fiesta ST without a DMF although other Duratec Fords do have DMF
I can’t feel any difference, I expect I would if I changed the Corsa to non DMF but suspect it acts much like a cross between a harmonic balancer and a softer clutch.
I suspect you can run a harder clutch combo to take more torque and the DMF takes the shock out
I can’t feel any difference, I expect I would if I changed the Corsa to non DMF but suspect it acts much like a cross between a harmonic balancer and a softer clutch.
I suspect you can run a harder clutch combo to take more torque and the DMF takes the shock out
Dual mass flywheels are a comfort and efficiency development imo, very heavy two piece flywheels that retain high torque in modern cars while providing damping for the transmission and reducing driveline shocks in clutch engagement. They weigh circa 30lbs. The stored energy from their momentum assists with torque performance on a standard car. They use a solid clutch plate (no springs)
A single mass flywheel on the same modern car will require a sprung clutch disc which will damp some of the driveline shocks, but the springs are very much shorter so the damping effect is less, the flywheel will be steel, and lighter but this can vary, for instance if an aftermarket manufacturer makes them as a direct replacement for cost reasons, they may be naturally lighter by a few lbs. These manufacturers aren't producing them for performance, just practicality, they tend to not make much difference to transmission noise due to the similar weight. You may notice a slightly livelier pull away by default.
The other single mass flywheels produced for performance benefits still use a sprung disc, or should, and could be made from steel or aluminium. The latter has a replaceable friction surface, and is perhaps the lightest, although there are pro's and cons. Steel flywheels can be superlight which will only generally be used on race cars with raised idle speeds, the effect on the engine spinning up is huge, but also rpm drop which is quite sudden. The performance options for road cars might be 9-15lbs so you can see the weight benefits, they will produce transmission vibrations at idle caused by engine pulses, they can cause idle roughness or promote engine stalling due to lower inertia. The vibrations at idle can be stopped by pressing the clutch, and sometimes releasing it slowly it may ease but generally returns. The vibrations can be heard under load but more significantly on overrun, this can appear to sound almost like a scraping noise.
Steel flywheels may have the ring gear built/machined into them, they will have a series of holes either small, or quite large voids, they have a fixed friction surface and require balancing probably. Some people fear lightened flywheels exploding at high rpm which can cause serious harm. Alloy flywheels tend to be a high grade alloy and there are several types, usually with bolt on friction plates and replaceable ring gears, these seem to be fixed differently depending on the manufacturer. They can be machined from a billet which is likely to result in quite close tolerances and good balance.
These are only my observations from the last four years which includes researching them for my own car. I chose an aluminium flywheel from a U.K. source, and a sprung clutch disc. It was supplied with different mounting bolts to avoid fouling the timing gear on the rear of the crank, and longer bolts for the clutch plate on this particular item, to reduce the likelihood of pulling threads. These are very unlikely to explode but issues have occurred.
Mine has been fitted for almost two years, it has done about four track days and a couple of thousand general miles, on a ~270chp motor. I'm my humble opinion, brilliant. Gear changes are nice, some people rave about shift quality, it is better but not night and day imo. It is noisier. The car might stall every few days, this is caused by the cam though really, even with raised rpm, it will occasionally just defeat it, the flywheel doesn't weigh a lot, it can catch me out at random, but ultimately it is worth it and I'd fit it again tomorrow.
A single mass flywheel on the same modern car will require a sprung clutch disc which will damp some of the driveline shocks, but the springs are very much shorter so the damping effect is less, the flywheel will be steel, and lighter but this can vary, for instance if an aftermarket manufacturer makes them as a direct replacement for cost reasons, they may be naturally lighter by a few lbs. These manufacturers aren't producing them for performance, just practicality, they tend to not make much difference to transmission noise due to the similar weight. You may notice a slightly livelier pull away by default.
The other single mass flywheels produced for performance benefits still use a sprung disc, or should, and could be made from steel or aluminium. The latter has a replaceable friction surface, and is perhaps the lightest, although there are pro's and cons. Steel flywheels can be superlight which will only generally be used on race cars with raised idle speeds, the effect on the engine spinning up is huge, but also rpm drop which is quite sudden. The performance options for road cars might be 9-15lbs so you can see the weight benefits, they will produce transmission vibrations at idle caused by engine pulses, they can cause idle roughness or promote engine stalling due to lower inertia. The vibrations at idle can be stopped by pressing the clutch, and sometimes releasing it slowly it may ease but generally returns. The vibrations can be heard under load but more significantly on overrun, this can appear to sound almost like a scraping noise.
Steel flywheels may have the ring gear built/machined into them, they will have a series of holes either small, or quite large voids, they have a fixed friction surface and require balancing probably. Some people fear lightened flywheels exploding at high rpm which can cause serious harm. Alloy flywheels tend to be a high grade alloy and there are several types, usually with bolt on friction plates and replaceable ring gears, these seem to be fixed differently depending on the manufacturer. They can be machined from a billet which is likely to result in quite close tolerances and good balance.
These are only my observations from the last four years which includes researching them for my own car. I chose an aluminium flywheel from a U.K. source, and a sprung clutch disc. It was supplied with different mounting bolts to avoid fouling the timing gear on the rear of the crank, and longer bolts for the clutch plate on this particular item, to reduce the likelihood of pulling threads. These are very unlikely to explode but issues have occurred.
Mine has been fitted for almost two years, it has done about four track days and a couple of thousand general miles, on a ~270chp motor. I'm my humble opinion, brilliant. Gear changes are nice, some people rave about shift quality, it is better but not night and day imo. It is noisier. The car might stall every few days, this is caused by the cam though really, even with raised rpm, it will occasionally just defeat it, the flywheel doesn't weigh a lot, it can catch me out at random, but ultimately it is worth it and I'd fit it again tomorrow.
I have used a steel single piece lightweight flywheel on my supercharged Rover K in my Elise for many years, road and track.
Brilliant. Makes quick shifting much easier. The response on heel and toeing for downshifts is much quicker. In the end, the engine felt like it should in a sportscar.
If used in conjunction with a organic and sprung friction disk, there are no stalling issues in traffic.
In combination with a aggressively biting sinter metallic racing clutch, things become tricky. But then why would you need such a clutch in first place?
Civic folks seem to like them as it allows them to drop the clutch in first. In a Elise this type of behaviour makes little to no sense.
For track use, I'd replace a DMF with a reasonably light single mass steel flywheel.
My new engine for the Elise is a build Honda k20. I decided to keep its OEM 4.5kg single mass flywheel and install again a Honda OEM organic clutch.
This will yield OEM driveablity. Lighter options go down to 3kg, but I was told that 3.5kg is about the lower limit for road use in a Elise with a K20. For a more heavy Mini, I'd stick with something >4kg. As the Honda OEM FW is only 4.5kg, I keep it.
Before the EP3 Civic facelift, they used a 7kg FW. This is a different story. I would have replaced that.
Brilliant. Makes quick shifting much easier. The response on heel and toeing for downshifts is much quicker. In the end, the engine felt like it should in a sportscar.
If used in conjunction with a organic and sprung friction disk, there are no stalling issues in traffic.
In combination with a aggressively biting sinter metallic racing clutch, things become tricky. But then why would you need such a clutch in first place?
Civic folks seem to like them as it allows them to drop the clutch in first. In a Elise this type of behaviour makes little to no sense.
For track use, I'd replace a DMF with a reasonably light single mass steel flywheel.
My new engine for the Elise is a build Honda k20. I decided to keep its OEM 4.5kg single mass flywheel and install again a Honda OEM organic clutch.
This will yield OEM driveablity. Lighter options go down to 3kg, but I was told that 3.5kg is about the lower limit for road use in a Elise with a K20. For a more heavy Mini, I'd stick with something >4kg. As the Honda OEM FW is only 4.5kg, I keep it.
Before the EP3 Civic facelift, they used a 7kg FW. This is a different story. I would have replaced that.
Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff