For Ken, what is a flywheel

[EricW]

Simple Ken, (the answer, not you) The flywheel is a large, heavy metal disk,
attached to the rear of the crankshaft.

Basically, the engine turns because the pistons push the crankshaft round and
round, but each piston only gets pushed once every two revolutions, so the
whole process would be a series of jerky motions if we simply relied on that
to keep the engine turning. We need something to smooth out the jerks,
particularly at low speeds where the time between firings is actually quite
long.

The flywheel being big and heavy, gains momentum as it is turned, and this
momentum keeps the engine turning in those brief moments between power strokes
while there are no firings going on.

The flywheel also has inertia, it resists changes in speed, so it smooths out
the movements of the crankshaft and lets the engine rotate smoothly and
quietly. It also provides a damned handy place to extract power from the
engine, being a big surface to mount a clutch on. A toothed wheel (the ring
gear) around the circumference of the flywheel allows the starter to turn, and
therefore start, the engine

Obviously, the heavier this disk, the more inertia it has, so it's slower to
accelerate, and the more momentum it gains, so it is slower to lose speed.
Lightening the flywheel on any specific motor allows it, not to rev faster,
but to gain revs faster, if you can appreciate that difference.

It comes at a cost however, in that the engine will not idle as smoothly, due
to the lesser effect of the flywheel.

I hope this explains it simply.

Eric

From chris.tankard@aderant.com Fri Apr 27 16:56:55 2007
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Subject: RE: For Ken, what is a flywheel
Date: Thu, 14 Jul 2005 08:47:06 +1200
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From: "Chris Tankard" <chris.tankard@aderant.com>
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A site that is really good at explaining things in plain English
howstuffworks.com


See : http://auto.howstuffworks.com/clutch.htm for info on clutches
with flywheels being covered (briefly) on page 3


________________________________

From: e-admin@mx5club.org.nz [mailto:e-admin@mx5club.org.nz] On Behalf
Of Eric & Ann West
Sent: 14 July 2005 08:23
To: MX5List
Subject: For Ken, what is a flywheel


Simple Ken, (the answer, not you) The flywheel is a large, heavy metal
disk, attached to the rear of the crankshaft.


Basically, the engine turns because the pistons push the crankshaft
round and round, but each piston only gets pushed once every two
revolutions, so the whole process would be a series of jerky motions if
we simply relied on that to keep the engine turning. We need something
to smooth out the jerks, particularly at low speeds where the time
between firings is actually quite long.


The flywheel being big and heavy, gains momentum as it is turned, and
this momentum keeps the engine turning in those brief moments between
power strokes while there are no firings going on.


The flywheel also has inertia, it resists changes in speed, so it
smooths out the movements of the crankshaft and lets the engine rotate
smoothly and quietly. It also provides a damned handy place to extract
power from the engine, being a big surface to mount a clutch on. A
toothed wheel (the ring gear) around the circumference of the flywheel
allows the starter to turn, and therefore start, the engine


Obviously, the heavier this disk, the more inertia it has, so it's
slower to accelerate, and the more momentum it gains, so it is slower to
lose speed. Lightening the flywheel on any specific motor allows it, not
to rev faster, but to gain revs faster, if you can appreciate that
difference.


It comes at a cost however, in that the engine will not idle as
smoothly, due to the lesser effect of the flywheel.


I hope this explains it simply.


Eric

[Ken McNoe]

Thanks Heaps Eric, that explained it very well!!!
Now it you could just describe a cardiac action potential I might just
understand that also!! =)

Ken McNoe

Phone: 09 483 8237
Mobile: 021 536 911

[Ken McNoe]

Thanks Heaps Eric, that explained it very well!!!
Now it you could just describe a cardiac action potential I might just
understand that also!! =)

Ken McNoe

Phone: 09 483 8237
Mobile: 021 536 911

[Greg and Shona Powell]

Eric - thanks for the explanation regarding the lightened flywheel. Would the
fact that the engine won't idle as smoothly have any adverse effects re wear
and tear on the engine?
Greg

[Greg and Shona Powell]

Eric - thanks for the explanation regarding the lightened flywheel. Would the
fact that the engine won't idle as smoothly have any adverse effects re wear
and tear on the engine?
Greg

[EricW]

It's all relative really, and rather depends on how much you lighten the
flywheel by, and why you are doing it. Anything you do to an engine has a cost
somewhere.

If you lightened it to the point where the engine would hardly idle at all,
then obviously the answer would be a resounding yes, but taking a pound or two
off an 18 pound flywheel, to enhance engine acceleration for competition, is
hardly likely to worry an engine used for racing or rallying,

The accelerated wear caused by the competitive use of the engine, and the
stresses involved in that, is going to be by far the most dominant factor in
determining wear and tear. The contribution of the flywheel to this wear would
hardly be measurable. It would be measurable in a modest reduction of flywheel
weight on a road car, but would not, I think, be major, unless you were silly
about it.

I would not, personally, lighten a flywheel on a street car I was going to use
every day, there is little point to it, but then, I am 57 years old. If you
had asked me forty years ago, you would have got a very different answer!

Regards

Eric

[Greg and Shona Powell]

Thanks Eric. I don't use my MX5 every day (can't have it getting wet) and only
bought it because I enjoy driving it (especially cornering). The primary
purpose for lightening the flywheel is to get a better take of so it sounds
like it might do the trick.My wife calls it my mid life crisis and it's a
battle getting her into the passenger seat as she doesn't like the fast
cornering.
Once I get the work done I will post an email letting everyone know how it is
going.
Greg

[Greg and Shona Powell]

Thanks Eric. I don't use my MX5 every day (can't have it getting wet) and only
bought it because I enjoy driving it (especially cornering). The primary
purpose for lightening the flywheel is to get a better take of so it sounds
like it might do the trick.My wife calls it my mid life crisis and it's a
battle getting her into the passenger seat as she doesn't like the fast
cornering.
Once I get the work done I will post an email letting everyone know how it is
going.
Greg

[bert wouda]

Hi Guys and Girls

I am reading with interest the stories about lightening the flywheel (s)
... what do you think to "gain" ( how many horses /KW !!! ) with
this " operation ".

Are you Guys planning to go to Le Mans etc ...

Greg if you really like cornering , ...have you lowered your suspension ,
fitted good shock absorbers and of course a good of tyres .

BERT
***********

[bert wouda]

Hi Guys and Girls

I am reading with interest the stories about lightening the flywheel (s)
... what do you think to "gain" ( how many horses /KW !!! ) with
this " operation ".

Are you Guys planning to go to Le Mans etc ...

Greg if you really like cornering , ...have you lowered your suspension ,
fitted good shock absorbers and of course a good of tyres .

BERT
***********

[Ian]

Bert...

You are exactly right!
I have owned and raced a Mazda Rx7 with a factory light flywheel and button
clutch.
A ligtened flywheel in a road going MX5 is going to have no effect on its
cornering abiliies.
A set of quality tyres, an 'expert' wheel alignment, and assuming suspension
bushes are all ok (and many aren't), a 25mm lowering will help.
Incidentally, I put mine on the shock tester the other day, and the Suspension
Shop owner, a respected race car builder of many cars over many years, told me
to stick with them. (These are factory shocks done 125,000 k)
We are lowering the standard springs by 25mm, and superpro bushing the sway
bars and end links as a first step.
My Goodyear NCT3 tyres, although hardly worn will be next for the heave...when
I can source some decent 15x 6 wheels at the right price

Cheers,
Ian

[Ian]

Bert...

You are exactly right!
I have owned and raced a Mazda Rx7 with a factory light flywheel and button
clutch.
A ligtened flywheel in a road going MX5 is going to have no effect on its
cornering abiliies.
A set of quality tyres, an 'expert' wheel alignment, and assuming suspension
bushes are all ok (and many aren't), a 25mm lowering will help.
Incidentally, I put mine on the shock tester the other day, and the Suspension
Shop owner, a respected race car builder of many cars over many years, told me
to stick with them. (These are factory shocks done 125,000 k)
We are lowering the standard springs by 25mm, and superpro bushing the sway
bars and end links as a first step.
My Goodyear NCT3 tyres, although hardly worn will be next for the heave...when
I can source some decent 15x 6 wheels at the right price

Cheers,
Ian

[EricW]

You are quite correct Bert, you might gain just the odd horse power or two,
which is no longer being used to drive the flywheel, but it will hardly be
measureable.

Lightening the flywheel on it's own will not do much, and certainly will not
help cornering, it is only effective as part of a package.

As I said, I would not do it to a road car, unless I was doing some serious
induction ignition and exhaust mods as well, all of which probably make the
car less docile on the road and hasten wear.

Eric

[Mikkels]

The gain is in rear wheel horsepower delivered during
acceleration. Especially in the lower gears. Flywheel mass
is increased by centrifugal force as the engine is revving.
This becomes a significant mass the engine has to accelerate
as revs increase. Reducing this weight means the engine
power can work on accelerating the mass of the car instead.

Meant to be worth about 0.5 secs 0 - 100 km and most of that
benefit is in the immediate acceleration in 1st and 2nd
gear.

Don

[...]

[Mikkels]

The gain is in rear wheel horsepower delivered during
acceleration. Especially in the lower gears. Flywheel mass
is increased by centrifugal force as the engine is revving.
This becomes a significant mass the engine has to accelerate
as revs increase. Reducing this weight means the engine
power can work on accelerating the mass of the car instead.

Meant to be worth about 0.5 secs 0 - 100 km and most of that
benefit is in the immediate acceleration in 1st and 2nd
gear.

Don

[...]

[Greg and Shona Powell]

The answer to your questions Bert is yes yes and yes
My baby sticks to the road like glue.
Got in behind a new XR8 Falcon coming through a windy gorge recently and had
to toot on him to let me past.
Greg

[Greg and Shona Powell]

The answer to your questions Bert is yes yes and yes
My baby sticks to the road like glue.
Got in behind a new XR8 Falcon coming through a windy gorge recently and had
to toot on him to let me past.
Greg

[Greg and Shona Powell]

Thanks for the feed back on the lightened flywheel. At a cost of $240 for the
new flywheel I am wondering if it is worth it.
I have been told that when the clutch is replaced some work also has to be
done on the existing flywheel (cost $50) so in selling the lightened flywheel
I am being told that the true cost of the lightened flywheel is only $190. Is
this true?
Greg

[Greg and Shona Powell]

Thanks for the feed back on the lightened flywheel. At a cost of $240 for the
new flywheel I am wondering if it is worth it.
I have been told that when the clutch is replaced some work also has to be
done on the existing flywheel (cost $50) so in selling the lightened flywheel
I am being told that the true cost of the lightened flywheel is only $190. Is
this true?
Greg

[Euen]

HiI Ian

Just a word of warning on re-bushing the sway-bay end links. The bushes on
the end links are not a standard replacement item. Mazda only sell the
links, not the bushes. The bushes fitted to the links are actually bonded
into the links and are an absolute pain in the a*se to get out. I suspect
if you have access to a hydraulic press it may be easier but I have had to
use a bench vice and it was not easy. Then had to use a small rotary wire
brush to clean out the residual rubber that was still bonded to the inside
of the eye.

Cheers
Euen

[Euen]

HiI Ian

Just a word of warning on re-bushing the sway-bay end links. The bushes on
the end links are not a standard replacement item. Mazda only sell the
links, not the bushes. The bushes fitted to the links are actually bonded
into the links and are an absolute pain in the a*se to get out. I suspect
if you have access to a hydraulic press it may be easier but I have had to
use a bench vice and it was not easy. Then had to use a small rotary wire
brush to clean out the residual rubber that was still bonded to the inside
of the eye.

Cheers
Euen