Was speaking with my engine builder today about engine balance and brought up the subject on lightened flywheels and underdrive pulleys.

 

I think everyone who currently has an underdrive pulley fitted must notice the more agressive engine note beyond 3000rpm.

 

The is because the at certain RPM's, the crankshaft will resonate violently and this usually overcome by the stock front pulley with harmonic balancer. The outer part of the stock pulley is supported by a flexible rubber bond which dampens the tortional vibration of the crank.

 

An underdrive pulley does not have a tortional dampener built into it and therefore cannot dampen the vibration resulting in rod and main bearing problems.

 

A lightweight flywheel does not have the same negative effect because it is not designed as a dampener and there is no need to have dampeners at both end of the crank.

 

Therefore, I'm removing my ASP front pulley and going for a JUN lightweight flywheel instead.

 

Steve

 

P.S I'm still upgrading until someone buys my Z

 

[This message has been edited by Steve E (edited 28-09-2001).]

Hi Steve,

 

That maybe, but I haven't seen or read any evidence to support any kind of failure. I checked this out on TT.net before buying mine, seems people have been running with them for years with no problems.

 

Also take into account that the crank in the Z is already more than capable and designed to full race spec.

 

So I'll still be fitting mine.

 

Hope nobody buys your car, nice article in CCC mate.

 

NICE CAR!

 

Tim

;-)

 

Cheerz

 

I'll compare the difference between flywheel and pulley when I fit it.

 

Steve

Steve,

 

I did wonder about the lightened flywheel, and would be interested in your impressions if you go ahead.

 

The Jun flywheel is about half the weight of the stock I believe (I have 7lb viz 14lb in my mind, but not certain I have this right?). The (extra) weight of the stock acts to provide torque and so is fairly easy to get the car off the mark, but looses power to the wheels. A lightened flywheel looses some of the torque, so could be more likely to stall unless additional revs are used. The gain is less weight to spin round, passing additional power to the wheels for quicker acceleration. It will be interesting to hear how practical the Jun lightened flywheel is for 'everyday driving'.

 

I wonder if anybody has had their stock flywheel skimmed, and by how much?

 

Cheers, Geoff

Steve, dunno if you've bought your Jun flywheel yet, i bought mine from Norris Designs £400.00 took 2 weeks.

Smithy

Steve

i like the sound of the lightened flywheel

it's always been a must for any race tuned type engine mod.

used to be the first thing to do ..In the old days.

Good move . a am sure it will improve engine pick up greatly.

Dazz...

 

 

 

Steve E,

 

I spoke to Holbay enginerring on Thursday, and they reckon a lightened flywheel will certainly give your more power, but you'll require more revs for normal pull-aways, AND you might find the aluminium wheel will warp, making your clutching very uneven. They recommend lightening your stock wheel, which will be loads cheaper than a lighweight one anyway. (Ok, it won't be as cheap as an ally one, but its a nice compromise)

 

Also.....how much was your one-piece prop shalf? I'm most interested in one of these since my center bearing is crap, and a second hand replacement would probably be just as bad.

 

 

------------------

Simon

If im not mistaken I think Nico said he was going to fit the UD pulley and lightend flywheel. He'll probably have to pull away at 6000 rpm

Paul

Hi,

I was going to add an underdrive pulley to my car, as on an NA it can make a good difference to the acceleration...However, on one of the US sites they claimed that it can eventually destroy your engine over time!

JEZ

click here for objective data on flywheel effectiveness

 

------------------

Later,

Phuong - EatRiceZone.com

Just a quick note about flywheels and safety!!!

 

NEVER modify the stock flywheel if you value your car and your feet.

 

Modifying the stock flywheel means cutting slots in it, and reducing the overall thickness. This reduces its strength considerably, and can lead to failure (normally at high RPM). The result is the flywheel breaking into quarters, and these will cut through the gearbox casing like its butter. It will continue thorugh the bulk head, feet, and eventually out of the car.

 

I friend of mine who is a tuner had a car in to work on which had the flywheel modified in this way. Luckily he was working bonnet side reving the engine, and not from the drivers seat. The marks in his garage wall are still visible as a reminder, and evidence to anyone who wants to modify there stock flywheel. Always fit an aftermarket flywheel which is designed to take the same abuse except made from a different material to reduce weight.

 

Leigh.

 

 

While we're on horror stories I know of a guy who had the propshaft on his TR7 go (standard one that is).. It decided to dig into the road, and rip through the floor of the car at about 80Mph... Scary!

 

Az

In reply to Leigh's horror story, of course it depends how much you lighten the stock wheel. If you try to match the aluminium version you're asking for trouble. But taking some of the weight off a stock is Ok. Plus you're really only interested in getting rid of weight near the edges as this is where the inertia is felt most (its travelling faster). But its not a DIY!!

 

Theres also primary and secondary balancing to consider (the wheel on its own and when fully installed with clutch etc)

 

My wheel has had 5 mmm skimmed off the outer surface mainly to get an RPS ceramic-metal clutch to fit properly. Off the line is a bit tricky or it could just be my crap technique!

Bloody hell, they are nightmare stories, think I'll stick with my ASP Underdrive Pulley thanks!!!

 

Tim,

 

There's still a possibility that the ASP underdrive pulley could fly off and go straight through your radiator and out the front of the car. It would probably take the ac condensor and power steering pump with it

 

 

...rather that than me feet Steve mate...LMAO!

 

Anyway, lightened flywheels? Me not being the most technically minded div! Don't you only have a flywheel for a manual motor, to interact with the clutch? Or do Autos have a flywheel to???

 

I know that an Autobox still has all sorts of clutches and gears but when you guyZ are talking about "lightened flywheels" you are mainly referring to the Manwell???

 

Tim - manuals have flywheels, auto's have flexplates. AFAIK flexplates cannot be lightened (they're lighter than a flywheel anyway I believe, and serve a slightly different purpose).

 

Az

 

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Stage: Rather Ill

CheerZ Az mate,

 

Just as I suspected, so I'll just stick with my ASP then...like I said in the first place!

 

Me being an Auto-Man etc. We know a TV program about that don't we? LOL

 

Good god, you remember AutoMan? That was that prog about the geeZer all made of electricity or something like that wasn't it?

 

Takes me back...

 

Az

oR THE Million RUPEE Man, unless you go to S.E Then you need to be the 10 Million pound man ?

 

------------------

BUFF MAN 300ZX SUPER HERO!!!! or is that DUFFMAN????

Oh man, Automan was awesome. Wasn't that the one with the little star thingy that drew out whatever he wanted. He had a really cool car that turned 90 degree corners instantly didn't he? I've been trying to remember the name of that for ages

 

Andy

Thats the one Andy - t'was a very cool show from what I remember

 

The car was excellent too...

http://www.chuckwagner.com/automan.html

 

The 'star thing' was called 'Cursor' BTW

 

Az

 

------------------

Stage: Rather Ill

 

[This message has been edited by aaronjb (edited 02-10-2001).]

Ahhh arto man, we halve Nito man in tokyo... he hald slame plowers

and the car was a vector w2

Yeah, thats right. Cursor

 

Craig, you're right, it was the first Vector I ever saw. It seemed to handle much better than the stock vectors, the cornering was lethal

 

I'm off to do a search on Digiguide for Automan. Problem with fond memories is that they tend to disapoint you when you re-visit them.

 

Andy

I remember having a top trumps card (remember those!?) with the Vector on it, and thinking "That's a fantastic car"...

 

I want one Lol

 

Az