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Location:
Malaysia,Kuala Lumpur
Registered:
July 2002
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Fly Wheel - Is it True ?
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Fri, 07 January 2005 21:08
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I was reading somewhere over the net (can't remember now )
that lightening the fly wheel, doesn't really have a 'major' change in overall performance,only 1st & 2nd gear.
Can someone please confirm this. Look like I'm better off with the original size/wt flywheel
Cheers
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Location:
On your mum!
Registered:
May 2002
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Re: Fly Wheel - Is it True ?
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Fri, 07 January 2005 21:45
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AFAIK - a lightened flywheel makes a difference to acceleration in all gears.
In my experience a lighter flywheel is not that much better than stock in first and second gears because the engine loses revs easier as well (ie less momentum = drop clutch and revs drop quite easily).
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Location:
Montrose, VIC
Registered:
May 2002
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Re: Fly Wheel - Is it True ?
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Sat, 08 January 2005 07:54
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Depends how much you lighten it by - shaving a little bit off the standard flywheel doesn't do much anyway, and removing enough to make a notable difference is often dangerous. In that case, you should go for a new flywheel that is built much lighter - and it does make the car better to drive, except you can notice the difference when parking etc. - not as tolerant to being ham-fisted with the clutch.
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I supported Toymods
Location:
Epping, Sydney
Registered:
May 2002
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Re: Fly Wheel - Is it True ?
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Sat, 08 January 2005 07:57
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side note: button clutch + lightened flywheel is not heaps of fun.
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Location:
Montrose, VIC
Registered:
May 2002
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Re: Fly Wheel - Is it True ?
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Sat, 08 January 2005 08:18
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| draven wrote on Sat, 08 January 2005 18:57 |
side note: button clutch + lightened flywheel is not heaps of fun.
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It all depends what you're doing  Not so enjoyable for the 17 point turn, but fantastic when you're treating the car the way you know it loves to be treated...
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Location:
Brisbane / Gold Coast
Registered:
May 2002
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Re: Fly Wheel - Is it True ?
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Sat, 08 January 2005 08:30
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I went from the stock 7kg steel flywheel to an alloy 3kg one. I also changed to a close-ratio gearbox so all the ratios were different.
But 4th gear was exactly the same, and I could notice a lot of improvement in acceleration at all speeds. Well worth it.
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I supported Toymods
Location:
sydney.au
Registered:
August 2002
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Re: Fly Wheel - Is it True ?
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Sat, 08 January 2005 08:31
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so whats the best kinda clutch to use with a 3kg flywheel on a 4ag?
and bill: what brand ratio gears? 1, 2 and 3?
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Location:
Brisbane / Gold Coast
Registered:
May 2002
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Re: Fly Wheel - Is it True ?
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Sat, 08 January 2005 11:57
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| ae86drift wrote on Sat, 08 January 2005 19:31 |
so whats the best kinda clutch to use with a 3kg flywheel on a 4ag?
and bill: what brand ratio gears? 1, 2 and 3?
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I just use a standard clutch, it's fine.
It's a one-off I picked up in NZ. Not sure what the ratio's are but 1st gear is around 2.6:1 I think.
It's nearly the same as 2nd gear in a normal Sprinter.
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Location:
Adelaide
Registered:
December 2004
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Location:
Montrose, VIC
Registered:
May 2002
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Re: Fly Wheel - Is it True ?
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Sun, 09 January 2005 01:37
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Pity about the 6 bolt holes 
With an NA 4AG, you're never going to need a hard-to-use clutch, simply because a little engine like that needs revs to make power, as it can never have Kenworth-like torque to convert clutch plates to a sacrificial offering. You'd be doing pretty well to ever see more than 160-170Nm of torque from one...
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Club Member
Location:
sydney
Registered:
May 2002
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Re: Fly Wheel - Is it True ?
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Sun, 09 January 2005 02:36
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Im using the same flywheel as Bill, 3.2kg ( with ring gear mounted ) noticeable improvement in acceleration 1st 2nd 3rd with a standard ratio box. running a standard clutch with a heavy duty pressure plate.
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side note: button clutch + lightened flywheel is not heaps of fun.
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yeah I started with the brass button clutch and ended up pulling it out and put an organic in.. made bugger all difference in gripping up with the car so light anyway but oh so much easier on the street.
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Location:
Madrid - Spain
Registered:
August 2002
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Re: Fly Wheel - Is it True ?
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Sun, 09 January 2005 23:28
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The change in acceleration is a function of the gearing as well.
In low gears the flywheel has more authority over the entire drivetrain inertia, therefore low gear acceleration will benefit from a lighter flywheel.
In higher gears, the remainder of the drivetrain has a bigger influence (ie wheels effectively act like a heavier flywheel due to the higher gearing) therefore the effective reduction in the system inertia is less and change in acceleration will be smaller.
On the downside though lighter flywheels are harder to drive in traffic and if it is just a standard one that has been "lightened", the strength may have been reduced and you may run the risk of it exploding at high RPM.
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Club Member
Location:
sydney
Registered:
May 2002
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Re: Fly Wheel - Is it True ?
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Mon, 10 January 2005 06:45
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On the downside though lighter flywheels are harder to drive in traffic
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are you speaking from experience?? cause ive never had any problems driving a car with a lightened flywheel in traffic
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Location:
Madrid - Spain
Registered:
August 2002
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Re: Fly Wheel - Is it True ?
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Mon, 10 January 2005 20:29
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Well it could be that the only cars that I have owned with lightened flywheels had bigger cams and heavy clutches....
Logically speaking though, having less engine inertia means that the engine is more likely to be disturbed by external forces such as clutch engagement. Thats why standard cars have big heavy flywheels, not just for idle quality.
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Registered:
May 2002
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Re: Fly Wheel - Is it True ?
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Mon, 10 January 2005 21:57
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I read somewhere (probably in a zoom magazine so don't pay too much attention) that someone reckoned that every 1KG you shave of your rotating components is as good as 10HP at the crank increase. so 7KG flywheel to a 4KG flywheel = 40HP?.
The theory is correct but I don't know about the numbers.
Also, a lightened flywheel will make it harder to drive, without the momentum in the flywheel the car will stall easier if you let the clutch go too fast.
Tim.
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Location:
Newcastle
Registered:
May 2004
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Re: Fly Wheel - Is it True ?
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Mon, 10 January 2005 23:11
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lol, 7kg to 4kg = 3kg difference, not 4... so 30hp maby, but i doubt this, it seems to much.
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Registered:
May 2002
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Re: Fly Wheel - Is it True ?
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Tue, 11 January 2005 03:53
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sorry, the 4 was a typo, they said something about 3 KG flywheels up there.
I agree it sounds like rubbish, but I did warn you it was read in a zoom magazine 
Tim
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I Supported Toymods
Location:
south Melbourne/KL
Registered:
June 2004
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Re: Fly Wheel - Is it True ?
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Tue, 11 January 2005 04:11
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as i understand, lightening flywheel does not change horse power. a lighten flywheel is like lightening ur car. the dyno would still come out the same.
for example, have a 4age in a corolla vs a 4age in a commodore. the dyno sheet should come out almost the same but if u have a drag who would win....??
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: Fly Wheel - Is it True ?
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Tue, 11 January 2005 04:29
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| b1gb3n wrote on Tue, 11 January 2005 15:11 |
as i understand, lightening flywheel does not change horse power. a lighten flywheel is like lightening ur car. the dyno would still come out the same.
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ooooh k...
htf could it change actual hp?
lightening a flywheel (or any drivetrain component, crank and rims included) reduces the mass, and more importantly, the rotational inertia that must be accelerated by the engine at the same time as the rest of the car.
in lower gears, ie 1st/2nd, the rotational mass that needs to be accelerated makes up a larger % of the "effective total mass" (ie rotational + car) than in higher gears.
reducing the rotational mass means that the "effective total mass" of the car is reduced. since f=ma, the cars acceleration is increased.
you can do some simple calculations to work out what a given flywheel mass translates to in "effective total mass". i have done this before but forget the answer
at a guesstimate, the flywheel mass makes up about 20% of the vehicle mass in 1st gear, but feel free to do some calcs..
and fwiw, if the dyno ramp rate is fast enough, then the hp reading can be affected, since the flywheel effect at reducing wheel hp is ONLY in operation when the car is accelerating.. a dyno reading at a static rpm will give an unaffected reading.
Cya, Stewart
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Club Member
Location:
sydney
Registered:
May 2002
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Registered:
May 2002
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Re: Fly Wheel - Is it True ?
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Tue, 11 January 2005 06:45
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I didn't mean it would actually make more power, it's not a like we're putting any nismo stickers on it. I just meant the effects would be comparable to a HP increase...
Tim.
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Location:
New Zealand
Registered:
May 2002
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Re: Fly Wheel - Is it True ?
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Tue, 11 January 2005 07:42
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Would show you a pic of a real light flywheel but not mine to show.
Lets just say it is for a 20V 4AGE race motor and incorporates a triple plate clutch and auto flex plate. EXTREMELY light weight.
Callum
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Club Member
Location:
sydney
Registered:
May 2002
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Re: Fly Wheel - Is it True ?
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Tue, 11 January 2005 10:08
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lighter than 3.2kg??
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Location:
New Zealand
Registered:
May 2002
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Re: Fly Wheel - Is it True ?
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Tue, 11 January 2005 11:23
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Not sure on the actual weight. It is basically an auto flexplate (to hold the ring gear) with a flywheel only large enough to hold a 3 plate Tilton 5.5 inch clutch. The flexplate appears to have been modified as well as there are no attachments points for the tourque convertor. Apparently he has made a few of these, but requires very accurate machining.
Race only obviously.
Callum
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