To lighten or not to lighten?

[Vintage75]

I'm looking for a bit of advice from the people among us that have had their Flywheel lightened, Pro's and Con's.
I know you can loose a little Torque but gain a free'er revving engine.

This will be the flywheel from my Monza,
So a 3Ltr,cam in head straight 6 #boatanchor

I'm wondering if it's worth it as it's not a performance engine and I won't be doing track days but a quicker revving engine would be nice.

Let the debate begin!

[rwdrules]

when i fitted the 23v to my monza, Used a custom flywheel to enable me to use the 265 box with the 24v motor,it weighed just 6.8kilos,the thing just revved so easily i couldnt believe it,as for torque didnt notice any loss of it

[Vintage75]

Wow. 6.8kg!
I'm not looking to go that light but I like the idea of losing a bit of weight from it. I've not weighed it but it's really heavy, about the same weight as my wife's DS3.

[mrbounce]

I would get some advice from the machine shop who'll be doing the work. I know it's a lot smaller engine but when I got the Midas engine machined, i spoke with the guy and he asked what I'd be using the car for. He said that as I wouldn't be doing any Motorsport (Fast road only), a lightened flywheel for my application wasn't necessary. Have a chat with the man in the know. Mine suggested bottom end balancing would be more beneficial for the set up I had. 

Remember though - every engine is different - what works for one may not work for others. Talk it over with the machinist 

[ChasR]

On the flipside of the coin a mate of mine had a Nissan S14a 200SX. It was a nice car with lots of tricky parts.

However, that was a pig to drive around with the lightened flywheel. It really didn't like being at lowish RPM.

But as said, every car and engine is different. If you have a DMF installed be prepared for quite an increase of engine noise too. With a single mass flywheel originally fitted this will be fine.

[stealthstylz]

Taking a bit of weight off is usually fine, really lightweight ones are a pain though. I think a lot of people don't realise that although the engine revs up faster it also drops revs faster, which is why super light ones are a pain at low speed.

[dusky]

You don't lose torque btw. You only use inertia. Engine brakes quicker and accelerates quicker.
I really like to shave a few kg's of the flywheel. It makes the car feel a lot more performant

[inthedark]

If you're going for it, give them the crank with the flywheel
and have them balanced together.

[tristanh]

Apr 8, 2018 19:50:38 GMT dusky said:

You don't lose torque btw. You only use inertia. Engine brakes quicker and accelerates quicker.
I really like to shave a few kg's of the flywheel. It makes the car feel a lot more performant

What that man said.
Everyone bangs on (wrongly) about losing torque. My standard reply is, I you made the flywheel heavier, would you gain torque? Of course not.
My Mk2 GTI with a tuned for and cammed engine has a lightened flywheel, drives perfect. I fitted one to a g/f's totally standard mk2 and she didn't notice only it was freer to rev.

I use a guy called Martin Emment, aka HotGolf, aka Gas n Gears in Bridgend in Wales.

[welshpug]

6.8 kg does not sound light, but thats subjective, what does the original weigh??

my zx'd oem one was 6.5 kg and the ttv billet steel one I have is 3.5kg.

[Vintage75]

Yeah, sorry, badly described!
Should have put that it can feel like a loss of Torque.

[chris y]

I can feel like less torque when slow speed manouvering.

In a Carlton GSi you can do parking or a three point turn for example without touching the accelerator because of the idle control valve, it adds air and therefore fuel to bring the idle back when i drops as you release the clutch.

With a light SMF there is less energy stored in the flywheel releasing the clutch causes the revs to drop much more quickly, so stored energy applies less turning torque to the gearbox. Driving on the ICV takes a lot more care.
If you arent good with clutch and accelerator balance you might have to rev more to pull away quickly, it can feel like less torque.


I have a Carlton with and a Carlton without SMF, the one with it revs far more snappily, if thats a good description, the standard one feels sluggish in comparison.
Acceleration is better too, during acceleration you add energy to the car but also a lot to spinning up the flywheel, that stored energy that isnt required for the weight removed instead goes to the back wheels. Feels like free horses.

I really like it apart from the noise.