Benefits Of Using a Lightweight Flywheel
Posted by Matthew Marks on 2nd Aug 2024
In this article, we are going to go through what a lightweight flywheel is and the benefits of using one. There are multiple benefits, such as faster RPM changes, reduced parasitic losses, less rotating mass, and much more.
There is much to cover regarding flywheels, from their purpose to the pros and cons of lightening your flywheel.
Let's dive straight in and find out precisely what they do.
What Is a Flywheel?
A flywheel is a metal disc, usually manufactured from steel or aluminium, which bolts to the end of the crank on the inside of the gearbox bell housing.
On the other side of the flywheel is the clutch friction plate, which engages and disengages when the clutch pedal is depressed.
In aftermarket applications, the most common material is generally 4140 chromoly steel, as it's solid and lightweight compared to some of the mass-manufactured heavier steel options.
The flywheel's outer section has teeth that engage with the starter motor, bolted to the outside of the gearbox housing.
The flywheel has a few jobs; the first is to ensure the engine can stay running with rotational inertia when you let off the accelerator.
The second is to balance the engine as they are weighted explicitly for the crankshaft and allow the use of an electric starter motor, which engages with the outer ring of the flywheel to start the engine.
The last job is to transfer the power from the engine to the wheels through the transmission via the clutch friction plate.
What Is a Lightweight Flywheel?
A lightened flywheel is, as it sounds, a lighter-designed version of the stock flywheel.
The Stock factory flywheels have been designed for road use and are heavy to ensure smooth running and drivability of the engine. A heavier flywheel will create more rotational inertia, making the engine smoother. Still, the engine will react slower to RPM changes.
The opposite of this happens when you install a lightweight flywheel. The lighter the flywheel, the faster the engine can increase and drop revs, dramatically benefiting performance engines.
Choosing a lightweight flywheel is a considerable advantage if you have a modified car for fast road or race use.
You can vary RPM quickly, so you can change gear faster and get into the powerband faster.
There is a downside here, which we will cover in the next section.
Pros And Cons Of a Lightweight Flywheel
There are multiple Pros and cons of using a lightweight flywheel, which, like most car modifications, mainly depends on the use of your car and overall goals.
There are huge upsides if you use the car for fast road, track or race use. Still, it is always worth looking at everything to ensure you're making the correct decision to install one.
Below are the pros and cons of lightweight flywheels so you can decide whether it's worth investing in.
Pros Of a Lightweight Flywheel
- Decreases rotational mass
- Allows engine RPM to change quickly
- Faster gear changes
- Increases acceleration
Cons Of a Lightweight Flywheel
- Less driveable on the road than a heavier flywheel
- Are generally more expensive than stock
- The engine vibrates more at lower speeds
- You need more revs to pull away from a stop
The main thing to take away from this list is that you can use it in any application you wish. Still, lightweight flywheels are more suited towards aggressive driving than a standard daily driver.
I've used a lightweight flywheel on the road for many years. Although it doesn't feel as nice for daily use as a heavier flywheel, it has its advantages once the engine runs.
The biggest issue I found when using a lightweight flywheel on my road car was trying to pull away on a hill, as you have to rev the car much more than before. (FYI, your neighbours will not be happy at 4am)
Does a Lightweight Flywheel Increase Horsepower?
So the basic answer here is no, it does not increase horsepower at the engine, but it does reduce the rotational mass of the engine, which means you will need less horsepower to do the same work.
In this sense, although it isn't adding power figures, it's making better use of your power for faster acceleration.
You won't gain anything extra at the crank but should gain more at the wheels due to decreased parasitic loss over the drivetrain.
So, in a sense, it will technically increase wheel horsepower.
Is a Lightweight Flywheel Worth It?
Whether a lightweight flywheel is worth it comes down to what you use the car for, but in most cases, yes.
The benefits here generally outweigh the downsides; in terms of performance, you are nearly always better off going with a lighter option.
In fact, once you go with a more aggressive clutch, some manufacturers suggest pairing it with a specific lightened flywheel to get the most performance from both products.
Also, if your current flywheel has had it, and you are going for performance, it's a no-brainer!
The only time I suggest it is a bad idea is if your car is totally stock, you purely use it for daily driving and want the easiest, most comfortable experience possible.
Lightweight Flywheel Brands
There are loads of flywheel manufacturers on the market, and each has its own design and unique weight when it comes to flywheels.
We generally stick to a few manufacturers here, specifically selling Japanese performance parts. Still, other brands exist, depending on which car you own.
The most popular lightweight flywheel brands we use are:
Each one has its own advantages and disadvantages depending on which engine you have. For this example, we'll use the Honda K-Series to compare weights:
- Fidanza K-Series lightweight flywheel: 3.6kg
- Competition Clutch K-Series lightweight flywheel: 5.28kg
- Competition Clutch K-Series Ultra lightweight flywheel: 3.99kg
- RPC K-Series lightweight flywheel: 3.2kg
- Exedy K-Series lightweight flywheel: 4.3kg
As you can see from the list above, each manufacturer chooses their unique weight, which is good for you as you can narrow the options down easier.
Suppose you have used a 3.2kg beforehand and think it's too light for your application. In that case, you have a few options for going heavier but still lighter than OEM.
Conclusion
So there we have it, all of the pros and cons of using a lightweight flywheel and the situations where it is worth upgrading.
Hopefully, you've learnt something new today, but if you feel I have missed something, please drop us a message below, or if you need help deciding on a flywheel, please contact us.
We now actually have a specific discount code only for our blog readers for 5% off of anything on our Exoracing website; if you are thinking of getting anything, then use this code:
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Alternatively if you are looking to go more in depth into the performance world, then check out these related articles: