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Lightened Flywheel or not?
- Thread starter Melanism
- Start date
JoeManNorth
Member
- :
- Mazda MP3 - Blue
From what I read on the net when i blew my tranny a while back was that a lighten flywheel will help your engine acceleration but you loose torque. But i guess most people gain with it as it is a very popular upgrade.
I do lots of hills (arround here and when i drive back home) so I rather have more torque so i kept the original.
I do lots of hills (arround here and when i drive back home) so I rather have more torque so i kept the original.
It has nothing to do with horsepower or torque, and will not actually affect either one.
What it will do is reduce the rotating mass in your drivetrain, allowing the engine to rev more freely. In situations where the engine speed is changing quickly (1st/2nd gear pulls or revving in neutral) you'll notice a bit more pep and pull from the motor, but this is NOT because you have increased the motor's power output, only because there is less mass in the drivetrain for the motor to accelerate. The principle is exactly the same as any other weight reduction mod, except that weight reductions from the drivetrain, especially at the crank/flywheel have a far larger impact pound for pound than reductions from the chassis.
On the other hand, in situations where the engine speed is changing slowly (higher gear pulls) the difference will be virtually unnoticable.
I know this isn't what exactly the OP was asking, but misconceptions about how a lightweight flywheel affects performance seem to be very abundant.
I also would be a bit more interested in the cons of a lightweight flywheel. I have previously heard that--while they are great on NA motors--the common wisdom is that they are not especially recommended for turbo motors because your revs drop more quickly between shifts so lose a bit more boost between shifts. But it seems like MSP owners love their lightened flywheels... Does your idle get a bit bumpier or anything?
What it will do is reduce the rotating mass in your drivetrain, allowing the engine to rev more freely. In situations where the engine speed is changing quickly (1st/2nd gear pulls or revving in neutral) you'll notice a bit more pep and pull from the motor, but this is NOT because you have increased the motor's power output, only because there is less mass in the drivetrain for the motor to accelerate. The principle is exactly the same as any other weight reduction mod, except that weight reductions from the drivetrain, especially at the crank/flywheel have a far larger impact pound for pound than reductions from the chassis.
On the other hand, in situations where the engine speed is changing slowly (higher gear pulls) the difference will be virtually unnoticable.
I know this isn't what exactly the OP was asking, but misconceptions about how a lightweight flywheel affects performance seem to be very abundant.
I also would be a bit more interested in the cons of a lightweight flywheel. I have previously heard that--while they are great on NA motors--the common wisdom is that they are not especially recommended for turbo motors because your revs drop more quickly between shifts so lose a bit more boost between shifts. But it seems like MSP owners love their lightened flywheels... Does your idle get a bit bumpier or anything?
Last edited:
flipmode815
Member
- :
- mazda, mp3, #908
I have a 6lb flywheel and stage 1 clutch on my mp3 and have had no problems.
JoeManNorth
Member
- :
- Mazda MP3 - Blue
I did not say it having less mass equaled more torque.. i said it would result in less rotational force wich leads to what dmention said. Having a HEAVIER flywheel will HELP with torque as when you are up to speed you have more rotating mass so when you hit that hill your engine wont bog down as much.. not saying that it's a HUGE difference but if you like hills, a heavier flywheel is better.. if all you do is drag then a lighter one would be better.
Front wheel drive cars dont drag well anyways.. but a LIGHTER flywheel could help you in a short AutoX course.
Front wheel drive cars dont drag well anyways.. but a LIGHTER flywheel could help you in a short AutoX course.
The rotational mass in your drivetrain is negligible when it comes to things like maintaining momentum up hills. Take your foot off the gas while cruising and watch how quickly the engine drops to idle--that's the momentum you're claiming will help you transition to a hill. The only time you will notice the difference between a lightweight and normal flywheel is when the engine is changing speeds--the more rapidly the engine is changing speed, the more you will notice the difference.
In the hill-climbing situation, if you were to maintain perfect throttle control such that your speed did not change as you transition from flat ground to the hill, there would be exactly zero difference between a lightweight and normal flywheel. In fact, in any situation where the engine is not changing speed, there is zero difference between flywheels. At least from a power/torque standpoint.
In the hill-climbing situation, if you were to maintain perfect throttle control such that your speed did not change as you transition from flat ground to the hill, there would be exactly zero difference between a lightweight and normal flywheel. In fact, in any situation where the engine is not changing speed, there is zero difference between flywheels. At least from a power/torque standpoint.
I've had the spec 6.8lbs flywheel for about a year and clutchmasters stage 4 clutch and couldn't be happier. The flywheel helps the car rev quickly and makes rev matching so easy.
The only downside is that you do lose a little low end but gain a lot up top.
The only downside is that you do lose a little low end but gain a lot up top.
JoeManNorth
Member
- :
- Mazda MP3 - Blue
the cetrentical force your engine has WILL help you when you get to a hill. Its simple math. It wont pull you up the hill and i mean, it wont be a crazy big difference but it will help. Think of it this way. When you are pushing a cart full of stuff, what do you do when you get to a hill? you try to get some momentum to facilatate going up it. Somewhat the same principal. But that's all I have to say on this matter.
So here's a question; I've heard various theories/statements/"experiences" about this, but what is the effect on mileage. Common sense (at least the way it makes sense in my head) tells me that a lightweight flywheel would increase mileage in the city and diminish it on the highway, but I've heard the contrary. What's your opinion??
Well, it's the rotational momentum, not centrifugal force that's in play here. And the momentum of the flywheel is miniscule compared to the momentum of the entire car. If your flywheel actually stored enough rotational momentum to make a noticable difference when transitioning into an incline, it would have to be large enough to be the equivalent of adding hundred of pounds of mass to your car, and the performance hit would be significant during day to day driving. Remember, every joule of energy that flywheel would contribute towards pushing your car up a hill, is a joule that your motor has to expend actually getting the flywheel going.
The milage differences you'd see with a lightweight flywheel will depend somewhat on your driving style. If you always put your car in neutral whenever you wanted to decelerate, you'd see a marginal increase in city milage (probably too small to detect), and no difference in highway milage. Reason being, the weight of a flywheel only makes a difference when the engine is changing speeds. At a constant speed, it won't make a lick of a difference in peformance. In the city, you'd be putting less of the engine's output into accelerating the drivetrain, but unless you are getting into stoplight challenges at each light, I'd have a hard time imagining a measurable difference in gas milage.
The milage differences you'd see with a lightweight flywheel will depend somewhat on your driving style. If you always put your car in neutral whenever you wanted to decelerate, you'd see a marginal increase in city milage (probably too small to detect), and no difference in highway milage. Reason being, the weight of a flywheel only makes a difference when the engine is changing speeds. At a constant speed, it won't make a lick of a difference in peformance. In the city, you'd be putting less of the engine's output into accelerating the drivetrain, but unless you are getting into stoplight challenges at each light, I'd have a hard time imagining a measurable difference in gas milage.
Last edited:
FunkyBuddha
Tuned by Slick Nick
- :
- 2003 Spicy Orange MSP
Jeeze...just get it. A bit of weight savings couldn't hurt.
i changed the clutch, lighten pulley, and lighten flywheel at the same time when my engine got off from my car.
My Engine (You can see the lighten pulley)
Lighten Flywheel& Daikin 750KG Clutch
My Engine (You can see the lighten pulley)
Lighten Flywheel& Daikin 750KG Clutch
Last edited:
Blitzkrieg
Member
- :
- 2001 Blue MP3 Protege #394, 2003.5 Yellow Mica MSP #1201
Lightweight flywheel in my opinion is worthy add-on especially if you are already doing the clutch.
Rotating mass takes energy to spin it from one RPM to another. Therefore, it takes power from the engine that could otherwise be used to accelerate the vehicle.
The significant measure of rotating mass is called the mass moment of inertia. To keep it simple, weight is bad, but weight farther from the center-of-rotation is much worse. The mass moment of inertia is measured by the mass (weight) multiplied by the distance between the weight and center of rotation squared. For instance if you had a weight of 10 pounds mass, 5 inches from the center of rotation, its' mass moment of inertia would be 10 lb x 5 in x 5 in = 250 lb in^2. That same 10 pounds only one inch from the center of rotation would only have a mass moment of inertia of 10 lb in^2 (96% less). This is why lower diameter flywheels are an issue and heavy larger wheels can have an effect.
When you were a child you may remember playing on hand pushed marry-go-rounds. Kids would stand on them and other children push to get them spinning. You may also remember that it was much harder to push when there were more kids on the marry-go-round and they stood near the edges.
Now for the stock flywheel. I am told the stock flywheel has a mass moment of inertia of 310 lb in^2 and I used this value in these calculations. Let me warn, the effect of rotating mass is not constant for RPM or road speed. In other words, the effect in 1st gear is different than second, and in any gear the effect changes with speed. This is why, if anybody quotes a given horsepower savings measured on a dyno, it is not accurate because chassis dynos DO NOT simulate accurate transients. They measure horsepower at the wheels just fine, but they can not measure the effect of a lightened flywheel, tires, or wheels. They will measure a difference, it just isn't accurate. But it is easy to calculate the difference.
From simple calculations the stock flywheel (280 lb in^2) takes 10-20 HP to spin it while accelerating in 1st gear. In second gear it takes about 5 HP. In 3rd gear it takes 2-3 HP. Therefore, if your lightweight flywheel had half the stock flywheel mass moment of inertia, you could save half the above values. To me, this would be more significant in a 1/4 mile run where the launch and 1st gear is very important. On a road course, not as important.
You might wonder why 1st gear is so much larger? The engine spins from idle to 6500 RPM in less than 3 seconds in 1st gear. It takes a lot of power to spin this mass to high RPM very quickly. In 4th gear, the flywheel takes 10-20 seconds to go from 4500 to 6500 RPM, therefore, much less power required.
Rotating mass takes energy to spin it from one RPM to another. Therefore, it takes power from the engine that could otherwise be used to accelerate the vehicle.
The significant measure of rotating mass is called the mass moment of inertia. To keep it simple, weight is bad, but weight farther from the center-of-rotation is much worse. The mass moment of inertia is measured by the mass (weight) multiplied by the distance between the weight and center of rotation squared. For instance if you had a weight of 10 pounds mass, 5 inches from the center of rotation, its' mass moment of inertia would be 10 lb x 5 in x 5 in = 250 lb in^2. That same 10 pounds only one inch from the center of rotation would only have a mass moment of inertia of 10 lb in^2 (96% less). This is why lower diameter flywheels are an issue and heavy larger wheels can have an effect.
When you were a child you may remember playing on hand pushed marry-go-rounds. Kids would stand on them and other children push to get them spinning. You may also remember that it was much harder to push when there were more kids on the marry-go-round and they stood near the edges.
Now for the stock flywheel. I am told the stock flywheel has a mass moment of inertia of 310 lb in^2 and I used this value in these calculations. Let me warn, the effect of rotating mass is not constant for RPM or road speed. In other words, the effect in 1st gear is different than second, and in any gear the effect changes with speed. This is why, if anybody quotes a given horsepower savings measured on a dyno, it is not accurate because chassis dynos DO NOT simulate accurate transients. They measure horsepower at the wheels just fine, but they can not measure the effect of a lightened flywheel, tires, or wheels. They will measure a difference, it just isn't accurate. But it is easy to calculate the difference.
From simple calculations the stock flywheel (280 lb in^2) takes 10-20 HP to spin it while accelerating in 1st gear. In second gear it takes about 5 HP. In 3rd gear it takes 2-3 HP. Therefore, if your lightweight flywheel had half the stock flywheel mass moment of inertia, you could save half the above values. To me, this would be more significant in a 1/4 mile run where the launch and 1st gear is very important. On a road course, not as important.
You might wonder why 1st gear is so much larger? The engine spins from idle to 6500 RPM in less than 3 seconds in 1st gear. It takes a lot of power to spin this mass to high RPM very quickly. In 4th gear, the flywheel takes 10-20 seconds to go from 4500 to 6500 RPM, therefore, much less power required.
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