| [ Total Views: 935 | Total Replies: 18 | Thread Id: 5549 ] |
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 karmannghia60
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| posted on April 22nd, 2003 at 09:08 AM |
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Lightened flywheels
There is a lot of talk about lightened fly wheels right now on the 356 Registry. Thought you might be interested that not a lot of people are
supporting the idea. Apparently while it helps with the acceleration, it doesn't help with engine/gearbox stress or fuel consumption amongst
other things. The fact that there is less metal to go around reduces the kinetic force developed hence a lot more stress on engine/gearbox to maitain
same momentum. One person also mentioned that he noticed there is a lot more noise in the cabin with a lightened fly wheel. Not sure about the last
one but the rest make sense. What do you think?
Raf
[Edited on 21-4-2003 by karmannghia60]
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KruizinKombi
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| posted on April 22nd, 2003 at 11:15 AM |
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I think that while lightened flywheels can be great for quick gearchanges and even acceleration, they tend to cause the vehicle to bog down on
take-off. Lightened flywheels work on certain vehicles for certain applications. I've never had any need for one.
It should also be said that flywheels can be over-lightened.
The only instance I can think of where I would like to have a lightened flywheel is to match up to a counterbalanced crank. I think if weight has been
added to the crank, it needs to come off somewhere else to compensate. 
Kruizin Kol
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kombikim
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| posted on April 22nd, 2003 at 11:47 AM |
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A good example of a "lightened" flywheel
that confronts you every day is the motor cycle engine, you will note that they go like hell but have to change gear a lot & need a few revs to
move off.
advantages are that you can pickup revs much quicker because of less drag - disadvantage is you lose them much quicker because there is less kinetic
energy
Good if you have a high BHP motor that you use in competition
I think it would be a pain for a reasonably standard VW with normal gear ratio's used on the road, use of 4th gear would become a rare occurence |
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aussiebug
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| posted on April 22nd, 2003 at 02:16 PM |
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A lightened flywheel takes less energy to spin up and less energy to spin down, so the engine response is a little faster.
But it also makes the engine "lumpy" at idle and when taking off in first gear - a heavy flywheel provides more inertia as the clutch is
released which means a smoother transition from clutch in to clutch out.
As an extreme example, the GP cars need about 13,000rpm as they drop the clutch, because 1. - the engine is very peaky in it's hp (comes
"on song" at maybe 15,000rpm) and 2. - the clutch is only about 5 inches in diameter - almost no rotating inertia to help get the car
moving.
[Edited on 22-4-2003 by aussiebug]
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Quickbug
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| posted on April 22nd, 2003 at 02:27 PM |
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In regards to the 1916cc with a lightened flywheel Raf, id never use anything else!
The 2180cc's flywheel is light enuff to be picked up by your pinkee finger alone...And no it wont break...Lots of other stuff will break before
it does...
The only disadvantage is it tends to slow you a lil quicker going uphill..
As for fuel consumption - since when was that an issue when modifiying?!?!?
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karmannghia60
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| posted on April 22nd, 2003 at 04:38 PM |
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Very true (about fuel consuption). if it was a problem you wouldn't go to 1916 would you 
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Quickbug
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| posted on April 23rd, 2003 at 12:17 PM |
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If fuel consumption is a problem stick with 1584cc.... or 1300cc......or *gulp* 1100cc.....
My god what am i saying?!?
:puke
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humpty
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| posted on April 25th, 2003 at 12:03 AM |
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I see the light(ening!)
Food for thought...
My little engine is only a 1776 but it makes good power. The spec is as follows.
69 CW crank, 9.5lbs FW, BERG Acheiver pulley, Engle 120 cam, Standard rockers (bolt together), ChroMo push rods, Stock Con Rods, Shimo modded 044
(40x35.5) & balanced all round & running 7.5-1 CR & 40mm Dells. I have always run ULP. Been on the road for over 10 years, Dragged in NSW
(9+ @ Oran Park), VIC & WA (14.8 @ Ravenswood, can't beat it @ Kwinana!), Hill Climbed in NSW & WA, Rally (Classic tarmac) in WA, loads
of sprints, autokanas & track time @ Wannaroo raceway. This car is daily driven (really!) has travelled across Australia 3 times (Perth to Sydney,
via Melbourne & Adelaide), gets 37mpg on the highway & 25 around town. It's a joy to drive & I wouldn't change this engine for
quids (though my EFI, intercooled/turbo 1915 is still in the works.. 3 years & counting!). So far this engine has completed over 200,000!
Light FW.....fphurt!
No problem here!
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OvalGlen
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| posted on April 25th, 2003 at 02:12 AM |
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so Simon you have added weight on the crank with counterweights, added weight on the pulley wheel with Berg" Rare steel " and taken it off
the flywheel.
So looks like you are just bringing it back to standard weight ? eh..
I run lighted flywheel too - but have c/w crank.
Regards,Glenn>
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humpty
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| posted on April 26th, 2003 at 12:01 AM |
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Light'en it man!
It's not just about total mass, it's about where it is and what it's doing. Lightening the FW removes the added weight from the outer
radious, which obviously improves RPM response but at the cost of the FW effect that VW needed to maintain 100kmh on the Autobahn. If you improve flow
(intake & exhaust) through the engine & maintain balanced harmonics (Added counter weights & heavy pulley etc) along the crank, the
improved hp & torque gained will also counter act any perceived loss of driveability.
If you want a bit better pick-up with mild (stock crank) engine the by all means lighten the FW, say 12-15lbs. Just make sure you balance everything
real well! If you want a Barn (Auto!) stormer with anything bigger than 90.5mm pistons, big cam & big valve heads, & you want to race it and
see high RPM (6k+), but also drive it in traffic, you must lighten the FW & CW the crank.
Just remember, Performance cost. But not just bucks, you also have to compromise performance verses longevity. And as my "little" engine
shows, you can have your cake & eat it!
PS: Just ask any of the old original Hellbug (Leigh, Keith, Shimo, Adam)crew how hard this car pulls & how drivable it is. Oh yeah...And she idles
sweet, now "lumby" V8 style idles for me...It's all in the balance & combination of parts.
[Edited on 25-4-2003 by humpty]
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70AutoStik
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| posted on April 26th, 2003 at 01:18 AM |
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karmannghia60: It sounds like the people on this forum you mention spend too much time playing Gran Turismo (or with themselves.)
A lightened flywheel allows the engine to spin up (or down) faster during gear changes, a valuable thing in racing. It makes stuff-all difference to
performance when the clutch is engaged (in any normal car - all-out race cars can see improved acceleration; hence the restrictions in many
formulae.)
If you're looking at a streetable vehicle, a standard flywheel with a radical engine can enable you to use more cam/porting.
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daz67
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| posted on April 26th, 2003 at 09:08 AM |
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Quote:
It makes stuff-all difference to performance when the clutch is engaged (in any normal car - all-out race cars can see improved acceleration; hence
the restrictions in many formulae.)
Actually, My real life experience over Easter 2003 was taking the Buggy over to Stradbroke Island. One Buggy had a Lightened flywheel, the other did
not, the one With could not idle off in soft sand like the one without. I appreciate there are a number of factors
that cause differences and this example may not be in keeping with the original post's. But I thought I would share for any other persons looking
to put one in their Offroader.
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humpty
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| posted on April 28th, 2003 at 11:45 AM |
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Response!
As I mentioned in the above reply...
"It's not just about total mass, it's about where it is and what it's doing. Lightening the FW removes the added weight from the
outer radious, which obviously improves RPM response but at the cost of the FW effect that VW needed to maintain 100kmh on the Autobahn."
If you want "quick pick-up of RPM's, lighten the FW, If you want stump pulling torque (especially from a small engine) the stock FW is the
way to go. Just remember, anything you modify on you car will be at a cost to something else....
To say that a light FW effects the drivability of an engine is total crap.....It is always how you drive it and what it's for! If your into
off-roading the a heavy FW is what you need, if you want to race on Tarmac you need quick RPM response.
That's all the there is to it.
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Phil74Camper
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| posted on April 30th, 2003 at 05:30 PM |
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Idling is also smoother with a stock flywheel, which is nice if you drive in heavy traffic a lot (ie. in Sydney any day of the week)
Of course you can't lighten the flywheel on an auto Kombi even if you wanted to (and you don't). It doesn't have a flywheel - the drive
plate bolts directly to the torque converter, which has the starter teeth ring welded to the outer edge.
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silver
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| posted on May 5th, 2003 at 09:37 PM |
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well it looks like i might put my standard fw back in. I knew that a standard flywheel was better for hills with the weight but i didnt know a
lightened one gave you less torque and worse fuel economy ...i drive my Kombi a lot over 500m a week or about 3 -4 tanks worth in city and open road i
wouldn't mind improving the economy and the torque and the hill climbing so unless there is an argument against it looks like it would suit my
use to reinstall the standard one
Keeping it real !
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KruizinKombi
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| posted on May 5th, 2003 at 10:01 PM |
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You use 3-4 tanks worth just to drive 500 metres??? :o:o:o
Gotcha!!! :P:P:P
Kruizin Kol
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Buggy Boyz
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| posted on May 5th, 2003 at 10:12 PM |
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| Quote: | Originally
posted by daz67
Quote:
Actually, My real life experience over Easter 2003 was taking the Buggy over to Stradbroke Island. One Buggy had a Lightened flywheel, the other did
not, the one With could not idle off in soft sand like the one without. I appreciate there are a number of factors
that cause differences and this example may not be in keeping with the original post's. But I thought I would share for any other persons looking
to put one in their Offroader.
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Hehe I hate to rain on your parade Dazza but I have a lightened flywheel, in fact it is about 10lbs and from memory it is lighter than yours
I can idle around in the sand cause I am a better driver :P
That and the fact I have a stroker in there with a few other mods and I built the engine to pull from about 600rpm to 4500 rpm. After that she
ain't got nothing. It is only a 2020 though and does use those crap 92 barrels everyone seems to hate so much. Seem fine to me, Time will tell, 1100 km and counting |
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silver
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| posted on May 6th, 2003 at 10:42 AM |
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Hmm..... maybe I should get a bigger tank!
Keeping it real !
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Baja Wes
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| posted on May 6th, 2003 at 12:31 PM |
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I've used lightened and standard flywheels and noticed little difference. Mainly cos the engine I put it on wasn't going to accelerate that
fast anyway.
My 1915 had a lightened flywheel, but always did so I don't know what it was like with a stock fw.
however my old 1835 had a lightened 6V flywheel on, then I converted it to 12V and put a stock 12V fw on. I noticed the heavier flywheel was more fun
when power shifting up gears, the extra weight of it would make it feel like the front wheels were trying to lift into the next gear. good fun  . The low down driveability didn't really change.
a light flywheel will make a high HP motored car accelerate quicker in 1st gear. that's about it. I can't see it helping on any kombi, or
any beetle with an engine smaller than a 1776.
a light fw will not effect the torque of the engine, and I will be extremely suprised if anyone noticed a fuel economy difference.
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pyr0
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| posted on May 6th, 2003 at 12:38 PM |
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i changed to a lightend flywheel on my old gemini and noticed a huge difference mabey because it was worked to the crap house :P |
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silver
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| posted on May 6th, 2003 at 02:31 PM |
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| Quote: | Originally
posted by pyr0
i changed to a lightend flywheel on my old gemini and noticed a huge difference mabey because it was worked to the crap house :P
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You are admitting to that..hehe
Keeping it real !
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humpty
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| posted on May 8th, 2003 at 12:15 AM |
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As for fitting a light FW to a bus......If you have a big cube engine with twin carbs or EFI then you will see better RPM pick-up. But of course you
engine will using RPM to move the car along the HWY as upposed to the "throw" effect given by the stock FW. (Have look at the drive wheels
on old steam locos...Thats how the keep going & one of the reasons they take so long to slow down!)
And I wouldn't recommend wacking a light FW on a stock 1600 or an engine that hasn't been built for it...You can't just stick one on
you old oil leaker and expect it to live....The balance would be mile out.
As for your mileage issue.....Keep you foot out of the carby if want better mileage! I believe the flywheel has little to no effect on MPG.
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70AutoStik
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| posted on May 8th, 2003 at 11:44 PM |
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Yes, Humpty; the effect of a lightened flywheel on economy, in technical terms, is a BCH. Kombis are not known for their speed of gearchanging: so a lightened flywheel isn't going to help there, either. And
the effect on a newly-built stocker would be detrimental, too.
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