31 replies to this topic

[oliver122]

hey guys , i thought about spinning my flywheel on the lathe just take abit off it lighten it , i was wondering what the pro's and cons of doing it , as my uncle has asked aswell so was going to explain to him to

thanks in advance guys

[Andyagl]

I have heard of people lightening the iron flywheel a little, but cant do it much because it will get too weak.

I used a Ultra light steel flywheel on a project of mine, idle was lumpy (I did also have a different cam though) , but the engine revved so freely afterwards. I thought it became much easier to drive, didn't have to be so heavy on the foot to accelerate.

[Guess-Works.com]

And don't forget once you've machined a flywheel it will need re-balancing.

Using a lighter than standard flywheel reduces the rotational mass of the the crank assembly, this reduces the amount of torque which is used to turn the assembly, therefore making it available to the drivetrain. As above this generally means the pickup of the engine is quicker. On the downside, because you have reduced the rotational mass, then you have also reduced the inertia ( flywheel effect ) of the assembly, so it will also slow down quicker, this is great for a performance engine where it needs to accelerate and decelerate quickly, but not so good if you want to cruise along the motorway at a constant 60-70 mph.. in this case you will use more fuel and induce more wear on the engine because you will always need to be 'on the throttle' to maintain a speed.

[Gr4h4m]

I never noticed the down sides when I fitted one to my car. I picked the minispares one and a light back plate. Mpg is the same before and after. The car does pickup quicker when your on the loud pedal.

[minimarco]

... is great for a performance engine where it needs to accelerate and decelerate quickly, but not so good if you want to cruise along the motorway at a constant 60-70 mph..

I wonder if there is a flywheel where the weight(or balance, mass towards the center or edge) can be controlled electronically? Or maybe centrifugally. Or maybe have two or more flywheels you can switch from, as you would shifting gears.

[Carlos W]

Like a dual mass flywheel?

[Deathrow]

Like a dual mass flywheel?

Not quite as those two masses can't be detached from one another, unless there is a different type to those used on diesels.

I think what he means is extra weight which spins freely on a bearing but can then be joined to the fixed flywheel somehow, possibly by a friction material like a second clutch?

[MrBounce]

When I was getting all my engine bits machined I was asked if I wanted my flywheel lightened. I asked him for his advice and was told that if using primarily as a road car not to bother.

So I didn't.

[SolarB]

but not so good if you want to cruise along the motorway at a constant 60-70 mph.. in this case you will use more fuel and induce more wear on the engine because you will always need to be 'on the throttle' to maintain a speed.

That's an interesting theory..........

[jaydee]

I like to have a light fly on my engine as it makes it rev a bit more free, it make quite a bit of difference above 4500 rpm.
Depening on full engine spec, you're gonna loose some torque under load with a light fly, and the engine wont like to run smoothly at idle and at constant revs like 2500rpm.
So evaluate accordigily.

[racingbob]

for fast road engine dont bother

you will lose torque

lightened flywheels are for high performance engines with big cams

my engine is just balanced has mg metro cam stage 3 head maniflow stage 2

goes great with heaps torque

[Artful Dodger]

If you have a pre a plus flywheel then defiantly do it. I took 100 thou off the face and then the huge band off at the back. Made quite a difference in weight but I didn't want to go mad on the milling machine putting holes in it because if it goes horribly wrong it will be nasty to balance.

[mk3 Cooper S]

Switchy throttle input control, reducted run on effect and rougher idle are the downsides.

[mab01uk]

Be careful lightening standard flywheels if you don't really know what you are doing........if it lets go big time on a RHD Mini you are sat right behind it!

[mk3 Cooper S]

Be careful lightening standard flywheels if you don't really know what you are doing........if it lets go big time on a RHD Mini you are sat right behind it!

Good point, A friend of a friend lost his foot back in the day when his flywheel came off !!!!