Gains from machining flywheel

[Benjamin]

I am having my G200 rebuilt at the moment and we are planning on machining some weight from the flywheel. Anyone done this? What can I expect to gain from doing this?

From what I have heard, she will idle rough as guts and be a little harder to drive smooth, but I don't care as long as she goes like the proverbial off a shanghai.

Engine spec:
G200 - 88mm bore with dished pistons
32/36 Weber
Slightly ported inlet manifold
Hella shaven TX head
Reground cam (as far as she will go)
Genie extractors
Electronic ignition
High-volume oil pump

All this in about two weeks I will be on the road.
Cheers

[Frederick Stienheld]

Why do you plan to do it if you don't know what it will do? Basically your engine will rev up a bit quicker and in theory you will lose a bit of torque going up hills etc. but I doub't you'd notice the torque factor

[Benjamin]

That's why I am asking... derr! A couple of friends had suggested the mod. I was more curious as to what to expect from a Gemini, maybe even a rough estimate of power increase or otherwise.

The reduction in torque would make sense, but seeing as it is a G200 I can't imagine it being as weak as a G161.

[Reddez]

Easier revving up basically because you have less weight to have to overcome, but less torque because of the same factor. There is a fine line with this too, too much and your flywheel can shatter, particualrly if you have a high performance clutch, however if done right you may gain a little bit of top end power, what are you using the car for??? I'd keep the torque, more usable than top end power.

[Benjamin]

Mainly street, however I will be putting the car through club racing later this year. After driving a G200 which didn't want to rev, I would like mine to just have that little extra zing.

I have been driving a G161 for many years and so I am used to not having mountains of torque, or molehills of torque for that matter.

Driveability is not an issue.

[Frederick Stienheld]

Wank factor is an issue here, he wants to be able to say he has a lightened flywheel

[tx1975]

cast iron flywheels arent meant to be machined as will loose some strength, if u give it a hard time at club events and that u will prob crack it.
shattered flywheel=nasty :s

[Ben Wight]

Hey Ben,

I noticed two things being the general concensus, that being the engine will rev quicker, but make less torque.

Well the first is right, the engine makes x amount of torque, and if the rotational mass is less, the engine will accelerate quicker.

The second isn't, the engine will still make x amount of torque, no matter how much rotaional mass there is.

Therefore, if you come to a hill, there will be less roational inertia to and the engine will decelerate more quickly that it would with a bigger flywheel, but on the upside, it will also accelerate more quickly when you put your foot down.

Ben Wight

[GeminiCoupe]

Because of the flywheel being lighter and rotating quicker/easier, this would mean with a worked engine you'd get on the cam quicker?

[Frederick Stienheld]

yep

[smee]

Have a look in the workshop area under installing gearbox and clutch.
In there you will see a picture of the lightened clutch that was doing service in my rally car.
A huge amount of material was taken off the flywheel and a flex plate and drive gear from an auto gemini was attached to it. A shirt load of work went into this wheel and it made good gains. engine reved freely and quite high.

[Ben Wight]

Yes the engine will rev quicker, so the power band of cam would arrive sooner, but also finish sooner! In short, you get more acceleration.