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Author lightened flywheel question
Greasemonkey
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Registered: 17th Apr 02
Location: Drives a Tractor
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29th Feb 04 at 00:03   View User's Profile U2U Member Reply With Quote

my Crank and fly wheel are off on monday to be lighned and balance to match, when they lighten the fly wheel they to put is simply, drill holes in the flywheel to remove a tiny bit of weight to balance it, is it worth me getting them to remove at least 1KG of weight off it, how will this effect my performance, will it cost allot
James R
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Registered: 4th Feb 03
Location: 205GTi16/306GTi16
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29th Feb 04 at 00:13   View User's Profile U2U Member Reply With Quote

The lighter the better to a point, sith a std case flywheel you basically want it as light as possible but no to the point were it will fall apart. The more the remove the more effective weight loss equivalent you'll get, normally you find a big improvement in first, second and third, but not really notice it in 4th and 5th, but you'll have to change gear mighty quick cause the engien can revdown just as fast as it revs up
Greasemonkey
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Registered: 17th Apr 02
Location: Drives a Tractor
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29th Feb 04 at 00:19   View User's Profile U2U Member Reply With Quote

sweet, i thought i would lose top end power cos i thought the weight and the inersia (spellin) of the fly wheel was a good thing, will i not lose touqe cos a heavy spinning fly wheel stores energy if you get what i mean the less weight the less energy stored????? or am i talking shite lol
clarkie
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Registered: 24th Jun 03
Location: Nuneaton Drives:1.4 sport
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29th Feb 04 at 03:57   View User's Profile U2U Member Reply With Quote

i shudnt think so, if n e thing u'd gain a bit of on the road torque, cuz if u think, doin 50 in third the floorin it, the engine aint got the extra weight of the fly wheel to turn, so it'd spin up faster, only down side really is u probably get lumpy idel cuz the fly wheel wont carry as much momentum
James R
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Registered: 4th Feb 03
Location: 205GTi16/306GTi16
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29th Feb 04 at 07:22   View User's Profile U2U Member Reply With Quote

NA the lumpy idle is bull, race engines on 3kgs flywheels and very lumpy cams idle fine, so a road car won't be a problem.
A lightened flywheel does nothing for torque it just reduces the inertia of the engine allowing to accelerate faster.
It doesn't effect power in anyway, no gain, no loss.
DangerousDave16v
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Registered: 20th Feb 03
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29th Feb 04 at 11:54   View User's Profile U2U Member Reply With Quote

wont it be more difficult to drive around town tho,like in traffic cos less inertia means it will be easier to stall, and you'll need to ride the clutch a bit
Marc
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Registered: 11th Aug 02
Location: York
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29th Feb 04 at 11:55   View User's Profile U2U Member Reply With Quote

I have a lightened and balanced flywheel, you wont lose top end.
miles
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Registered: 25th Mar 02
Location: plymouth Drives: Astra Sport
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29th Feb 04 at 12:20   View User's Profile U2U Member Reply With Quote

I've had my standard flywheel machined to reduce weight and had it balanced with my bottom end.

You want to give them your pistons, rods, bottom pully and clutch to balance as well.

I paid 145 for the lightened flywheel and balanced bottom end at a tuners down here.

They dont drill holes in it to lighten it, they drill the holes to remove mass for the balancing. They machine it to remove the weight, removing as much as poss from the outside.



Kris TD
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Registered: 25th Mar 02
Location: Ware, Hertfordshire
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29th Feb 04 at 13:41   View User's Profile U2U Member Reply With Quote

thought so miles, saw my uncle doing one at work a while ago, he had it on the lathe
Keith Piper
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Registered: 10th Apr 02
Location: West Sussex
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29th Feb 04 at 14:50   View User's Profile U2U Member Reply With Quote

My mate made me a flywheel from aircraft spec ali, with a steel friction plate. It weighs 3 kilos and has touched 10000 rpm. Visit www.qep.uk.com for more info
T5POL
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Registered: 22nd Mar 01
Location: Fife
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29th Feb 04 at 15:29   View User's Profile U2U Member Reply With Quote

*All of this was taken from http://www.jspeed.net/HondaFAQ.asp

Why should I lighten my flywheel?


The idea behind this is to reduce the amount of weight your engine uses power
to move. One heavy item to shave weight off is the flywheel. For street, it's
recommended to shave off about 5 lbs. For racing, you may consider removing
even more. The negative effect of lightening your flywheel is the loss of
rotational mass inertia when accelerating from a stop. Without careful
clutch and throttle work you may stall the engine more often. Be sure to
rebalance your flywheel after lightening.


From: mailto:fmlin@ccnet3.ccnet.com
"My friend had his B17A flywheel (18 lbs) machined down to 12 lbs. The
materials were taken off the back of the wheel, and mostly just the
rough castings removed."

From: lowell@smartt.com
"What you have to consider is the rotational inertia [when lightening], as
that's what's important here. My stock flywheel weighed in around 18lbs,
and I removed about 5.5-6lbs. The thing to look at though, is where did
the weight come off? Notice that there is an outer 'ring' on the back of
the flywheel and that's where a good chunk of material comes off. I machined
the back side flat, and just skimmed off all the rough casting surface on the
rest of the back so I don't think I compromised the strength in any way.
For the extra 2-3 lbs you'd save, I don't think a billet flywheel is worth
the insane price.

Just take it to a machine shop you trust, and have them cut the back of the
flywheel. Please don't drill any holes in it though. If you're really
worried, an SFI scattersheild would be the answer."

From: mailto:kurt.bilinski@GAT.COM
"use a light flywheel for "spirited" driving.

Entering a corner when road racing, normally you heel-and-toe downshift.
Since you're matching transmission rpm to engine rpm, the flywheel weight
would have no braking effect. Yet if you have a big heavy flywheel, it
will want to keep spinning, which means as you slow down, your brakes have
to also slow down the flywheel. So a heavy flywheel actually _hinders_
your braking, not helping it.

Your note about braking power isn't right. When road racing, you're
supposed to brake with the brakes, not the engine. The reason for the
shifting is to get you into the proper gear for the exit of the turn, not
to slow you down. That cool sounding downshifting noise came from the
early days when cars had very small brakes and they HAD to use the engine
compression as an additional brake. If you've ever let the clutch out
without matching tranny/engine speeds, while braking hard, you know the
problem with trying to use the engine for braking, instant spin.

For road racing, there is _no_ reason to have a heavy flywheel. It makes
the car heavier, the engine cannot accelerate or decelerated as quickly,
and it makes the brakes and engine work harder.

The only positive thing it does is allow starting from a dead stop easier
(especially on a hill) and helps when drag racing."

From: mailto:mcr@shore.net
"OK, here's the story. The flywheel is used to store energy specifically
for the purpose of evening out the the rather lumpy power output from
a reciproacting engine. (Like one push every 180 degrees of crank
rotation for a four banger.)

Heavy flywheels require more energy to change their speed. Light
flywheels require less.

Advantages of the heavy flywheel: engine rotation, particularly at
low rpms is smoother. Less gentle or skilled drivers are less likely
to stall from standing start. If one is dumb enough to want to use
the engine for braking (ie downshifting to reduce speed rather than
use the brakes) the heavy flywheel is more effective because it requires
oh so much more energy to increase its angular momentum.

Advantages of the light flywheel: #1, it's lighter. there's no such
thing as good weight. More accurately, there is no such thing as good
mass. Period. #2 because it has less mass, less energy is required to
change its angular momentum (less mass, less angular momentum) thus the
motor will rev freer.

**Was taken from:**

http://www.jspeed.net/HondaFAQ.asp




[Edited on 29-02-2004 by T5POL]

 
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