Light flywheel pros/cons

[TCJBOLDIE]

Have been agonizing over weather to install one behind my turbo motor for a wile and have read numerous articles but still undecided so hope someone with 1st hand knowledge/experience can help ?

I understand that the car will be harder to launch and will need a few more revs to prevent stalling and have to use more throttle or a lower gear going up hill to maintain speed and that there will be more engine braking as there is less stored energy so the motor will reduce revs faster when slowing or changing gears.

That it will help initial acceleration as there is less weight needed to spin the FW

There may be fear rattle at lo speed slowing or idle.

My thinking is that a LWFW will help the motor rev faster and help punching out of corners so the car will come on boost sooner due to the faster spin up

What I really want to know is will it affect top end speed as have been told that a heavy/stock weight FW is better due to the inertia/energy that helps to attain top speed.

 

[Guybo]

From what I read, rotating weight reduction affects the car like losing 4x the weight of non-rotaweigh components. The engine will be more responsive as less power is used to move that mass and it increases power at the crank.

 

[stamford]

I have to say for my nasp MG it was one of the best mods I've carried out. The response is so much better and quicker out of corners. I haven't noticed any downsides with mine as one would expect. However I can't say my car is blessed with lots of ponies but makes up for it in the handling department. No ill effects idling or driving up hills, nothing like some people think. No doubt this may vary from car to car and also the quality of the machined flywheel.

 

[HDi fun]

A good quality lightweight dual mass setup would be interesting. Can't see it making any difference at all to flat out top speed.

 

[old-git]

From what I read, rotating weight reduction affects the car like losing 4x the weight of non-rotaweigh components. The engine will be more responsive as less power is used to move that mass and it increases power at the crank.

Not quite. The affect of a lightened flywheel is dependant on where the weight is taken from (ie from the edge or near to the centre of a rotating mass). The further from the centre the more it is noticed. As an aside, the best place to remove rotating mass is from the tyres. Huge mass and large diameter.

A lightened flywheel does not increase power at the crank, but you may notice a difference after the flywheel on a dyno. Power is purely the result of how much fuel can be burnt efficiently. The weight of the flywheel affects how and where the available power is delivered.

There are a lot of uninformed/misinformed 'experts' on the web so be careful what you believe. It isn't as simple as less weight = faster car.

http://www.geocities.ws/ftrkeaka/TabooFlywheel.htm

 

[griffindai]

No issues with the last one but took a few mins to get used to it and stalled a couple times. Clutch was an upgraded Sachs friction disc, not sure how long it would have lasted if I'd gone for a paddle clutch though.

That was a £400 CNC billet wheel, a few of the guys went the cheaper route and had theirs machined down for around £70 iirc and seemed happy enough with the results

 

[TCJBOLDIE]

Thanks Steve,read all of the tech articles and there is some interesting stuff there

Here is imo a good article as well
http://store.uucmotorwerks.com/articles/FLYWHEEL-HOW-WORKS.htm

Re tyres front runners all round are not much good for circuit work

 

[old-git]

Yeah, seen that one. It just goes to show that it isn't as simple as a lot of people think it is. For example, I am anal about weight (just in case you didn't know ) but we went with the 4WD (heavier) flywheel as this will reduce the risk of stalling on the line. Once moving it will also reduce the rev drop at each gear change helping to keep the engine in its power band. A quick revving engine isn't required in drag racing, at least not with my setup.

 

[TCJBOLDIE]

FWIW my drag racing engine builder is advising against a LWFW

 

[old-git]

FWIW my drag racing engine builder is advising against a LWFW

I have done something right then

 

[TCJBOLDIE]

I have done something right then

Wish I could be as sure as winning Lotto as I am in no doubt that you have done all the research and crunched the numbers as well

 

[old-git]

I try my best, but sometimes even the experts can't agree. Therefore I have restricted by brains trust to a race car builder who also ran his cars in his own series (Global Lights) and was also a driver, an engine builder who used to work for F1 teams back in the 80s and was also a driver and, finally, a chassis/suspension specialist. It was the engine builder who recommended using a heavier flywheel and the car builder agreed.