#TechTip: Flexplates vs Flywheels

20 Feb 2016

Flexplates and flywheels are both vital components, but what are the differences?

Flywheels

Flywheels are generally used on manual transmission cars. If you’ve ever picked up a flywheel, you know they’re quite heavy, and there’s an important reason for that. They have 3 very important jobs, and those are:
1. To provide a surface for the clutch to grab- The flywheel is literally the surface that the clutch mates to. It is bolted to the output of the engine and it spins with the crankshaft.
2. To provide extra mass to help contribute to the rotational intertia of the engine- The reason flywheels are so heavy is because the increased rotating mass makes it easier to start a car from a stop without stalling. At the risk of more difficult starts, performance oriented individuals may choose to switch to an aluminum flywheel for weight reduction bro.
3. To provide gear teeth for the starter motor to engage to- All those pointy things on the sides? Gear teeth that engage with the starter to move the engine when you turn that key forward!

Flexplates

Flexplates are generally used in automatic transmissions, and they’re obviously much thinner and lighter than flywheels. These are what connect the output of the engine to the torque converter of the engine (basically the clutch of the automatic). The torque converter makes up for the mass that the flexplate doesn’t have.
Their main functions are to:
1. Connect the crankshaft to the torque converter
2. To provide gear teeth for the starter

Comments

Great article! another point you could add is that the torque converter adds some weight in the auto tranny, allowing the flex plate to be lighter

Solid point. Will do!

I always thought I had an above-average car knowledge, but I never knew flexplates existed. You learn something new everyday. More of this please!

Can do!

Love these little factoids Jake! Another thing that I would add is that a dual clutch could work with either setup—most have the single-mass flywheel, but the 8-speed DCT in the new Acuras uses a torque converter instead.

I could maybe do a whole write up on just DCTs. Glad you’re liking them!

Wow Gary posted something else besides Roast my car….. I’m not even mad that’s amazing

Flywheels also store kinetic energy between ignition events, “smoothing” the engine’s power output. Combined with the clutch springs, this turns the series of combustions into a steady flow of power, reducing backlash in the gearbox and making the car move down the road smoothly instead of in bursts.

it also makes the idle smoother and the operation of the engine better. thats why tuned engines with light flywheels sound so grumpy at idle.

Torque converters are not “basically” a clutch they are much more complicated do many more functions then a simole clutch, and besides, the clutches are inside the Auto.

While they’re more complicated, I’d argue that the torque convert is basically the equivalent of a clutch. They’re both the couplings between the engine and the transmission, one is just a fluid coupling and the other mechanical.

Here’s an big question i ever had. How the weight of the flywheel will influence in the general car performance. Like, I’m just replacing the flywheel to a lighter one, how much this will impact on overall performance. I’m saying that because where i live now this is a “thing”, replace or mod the flywheel to reduce weight. I really want someone to test this, also put an heavier one for cientific only.

Less rotating mass means quicker acceleration and also deceleration..I went from a factory 17lb flywheel to a 8lb flywheel..but I also upgraded my clutch to a dual surface Keller and carbon clutch…Either way it feels like a different motor the way it will Rev freely