John WRX

Been asked to post this by Frank (Redwrx) as he cant get to a pc.

What are the advantages and disadvantages of running with a lightened flywheel such as power increases and fuel consumption ??

Cheers.

Neilo

no real power increase but the revs will rise quicker thus aiding acceleration. On the downside, engine braking will be greatly reduced. Basically it helps the engine on the way up but can harm it a lot more on the way down....(as advised by Branko from BRD)

Aztec Performance Ltd

iTrader: (234)

We had this discussion some time ago and such was the difference in opinion (weighed in favour of ) that I brought a lightweight flywheel (4.5kg) only to sell it without it even making it onto the car. I then thought 'what the hell' and brought another ultralight flywheel (4.2kgs) and had it fitted to my car (along with many other bits).

The negatives that came up on the thread were:

*Makes the car idle badly
*Makes the car too hard to launch
*Doesnt make a difference to performance
*Engine braking etc etc

My experiences:

*Intially makes the car feel lighter and more free revving
*Idle - unchanged
*Performance? Not one for bhp (number) chasers, but makes a positive difference on the road.
*No problem with launching. Yes it takes more skill to stop bogging but I had no probs achieving consistant 1.7s 60ft at the drag strip.

I will most definatley be sticking with lightweight flywheels

Neilo

agree with BOB there, it depends what the cars going to be used for as well.

I think when the time comes i will get a lighter one, but only slightly....maybe the 8.6kg variety that seems to go round....horses for courses and all that...

John WRX

What about fuel consumption? thats his main issue.

Aztec Performance Ltd

iTrader: (234)

Havent noticed any difference in fuel consumption and cant see any reason why it should be effected?

stu_5

This has been discussed before.

Suprisingly engine braking should increase.

Friction losses within the engine are the same, but the momentum to keep it running at the same speed when you lift off has been reduced so the revs will fall faster- the same way they rise.

stu_5

If anything fuel consumption would also fall- engine has to do less work. Wouldnt expect to notice it on anything other than a test bed however!

Neilo

either way i was told it wasnt so good for the engine on the way back down.....??

stu_5

to be honest I'd be more concerned for it on the way up under load. The issue is the engines designed with the flywheel to act to help counter imbalances present within it. Never seen any problems on mine, but thats only with an oem item machined down by API. - Something similar to thats probably the best way to go on a cost/return basis.

If your really bothered however and are going for something very light at around 4.5kg- change the pulley counterweights at the front as well for lightened items to help bring it back in balance.

Aztec Performance Ltd

iTrader: (234)

David has mentioned before what you say stu_5

Mines running a dream so not going to bother messing around with it.

Bob

theotherphil

Same experience as Bob. I am also running a 4.2kg fw (Fidanza) with no problems. The difference in "pull" through the gears is like night and day - really noticable!

John WRX

up for Frank for when he gets home from holiday/work

timmyajmy93wrx

iTrader: (27)

well i hope it is good news for light weight flywheels i just bought an exedy 4.5kgs flywheel and a nice ACT organic clutch (420lbs capable). I already
have the GO Fast Bits lightweight pulleys at the front 'to balance it out'

have to see what a difference it makes when i get it done - sounds promising, then i will be off for a trip to see havey for a fmic!

tim

murfs

I'm thinking of doing the same, lets us know when it's all done and how you get on with it. I'm more interested in a quick start than big HP, and that should help.

Best of luck
Murfs

StickyMicky

i run a 7.5kg as performance item

i thought i noticed a marginal increase in MPG, but i cant be sure

it did make "heel and toe" much much easier tho

98prodrivewrs

Is it benificial to the engine meaning less stress on it

redwrx

Thanks for the info guys, and thanks John for posting this for me..

Frank

vulnax999

iTrader: (7)

Then buy a Diesel!!!

Mine is a lightened OEM one at 8kg ( By ASPerformance approx £100 exchange ) and is fine - no downsides and engine spins up a bit quicker, as less mass to get moving ( and to slow down too! ).
It's smooth and not jerky on pulling away, launches fine without bogging.

Very lightweight flywheels circa 4kg may have more issues?

As less metal to spin round, very slight fuel economy could be expected but offset by the better go!


I also got light front pulleys but not essential as the engine is not especially balanced front to back ( only rotationally ), so changing one end for lighter items won't cause any problems. Saved 3kg on front pullies but expensive way to do it!

redwrx

Hopefully getting the car done this weekend,

the flywheel is 25% lightened.

As for economy, i still need to get some kinda sense from it...... for work based 'expenses' trips.