Anyone Running a Lightened Flywheel?

[Chimpafrolic]

Well it's clutch time for my Chim, it will be getting an uprated Helix from V8 developments.

The job got me thinking about a lightweight flywheel.

I know the pros & cons, but before I go down this road I thought I would see if I could get some impressions from anyone that has lightened their standard flywheel.

As I understand it the standard RV8 flywheel weighs in at just over 30 lbs, but happy to be corrected on this.

Not wanting to go too light I was looking at getting a local machine shop to take about 6 - 7 lbs out of the original and balance it up.

The car is a pretty standard 4.0HC with one of Rob's Stealth cams.

Not sure how much meat is available on the original or even how well they take to machining to be honest.

Anyone done this?

[v8 racing]

spend said:

Have you got a standard Rv8 in your TVR?

I've never had to hump one of the heavy flywheels like the LR's from a TVR, but I've not pulled apart any of the budget engines so I suppose they might have been left with them (but doubt it would be very common).

Spend all the 400's and 450's came with the standard sd1 flywheel i know crazy!

[Chimpafrolic]

spend said:

Have you got a standard Rv8 in your TVR?

I've never had to hump one of the heavy flywheels like the LR's from a TVR, but I've not pulled apart any of the budget engines so I suppose they might have been left with them (but doubt it would be very common).

To be honest I have no idea what what flywheel TVR put in my 1996 4.0HC (serp).

I had assumed it would be pretty standard 2 wheel drive RV8 fair, & I doubt if TVR did much if anything with it.

But again, I stand to be corrected here.

Balancing the crank & flywheel as an assembly is obviously the right way to do things.

So I already have my concerns about the idea of doing much more than a skim on my flywheel without having the crank out too.

Already I am talking myself out of the idea, but perhaps someone can confirm if the idea has any mileage.

[dbv8]

v8 racing said:

Spend all the 400's and 450's came with the standard sd1 flywheel i know crazy!

Maybe this is why they are faster up the dragstrip

[Chimpafrolic]

v8 racing said:

Spend all the 400's and 450's came with the standard sd1 flywheel i know crazy!

Hi Rob, just sent you the money for the clutch.

Lightweight flywheel without balancing with the crank, bad idea?

[Simon says]

I have the feeling that if an RV8 TVR car suffers from the low speed lurch things will only get worse after you have removed worthwhile weight from the flywheel just an heads up as I am all up for lightning the reciprocating component mass,it does make quite a difference on how quick a four pot spins up for example especially when your trying to hook it up onto the start of a spikey cams powerband I have no experience of how the RV8 takes to this or how much you can safely remove from the RV8 fly

[Chris71]

Simon says said:

I have the feeling that if an RV8 TVR car suffers from the low speed lurch things will only get worse after you have removed worthwhile weight from the flywheel just an heads up as I am all up for lightning the reciprocating component mass,it does make quite a difference on how quick a four pot spins up for example especially when your trying to hook it up onto the start of a spikey cams powerband I have no experience of how the RV8 takes to this or how much you can safely remove from the RV8 fly

Good point.

But if you've got a modified induction system or remapped ECU that's claimed to overcome the erratic fuelling of the original design then you might as well reduce the rotating mass.

[900T-R]

I've got a lightened flywheel but then again, the whole rotating assembly was lightened, strengthened and finely balanced while the top end has learned to breathe properly, so in fairness I don't have any meaningful data about what a lightened fly on a standard engine would be like.

All I know is that mine goes up and down the rev range a lot quicker, and so did my former Saab with a lightened fly (9kg > 7kg)...

[Chimpafrolic]

900T-R said:

I've got a lightened flywheel but then again, the whole rotating assembly was lightened, strengthened and finely balanced while the top end has learned to breathe properly, so in fairness I don't have any meaningful data about what a lightened fly on a standard engine would be like.

All I know is that mine goes up and down the rev range a lot quicker, and so did my former Saab with a lightened fly (9kg > 7kg)...

OK so that's a proper engine built correctly from the crank up.

Not sure my idea of just bolting a lighter flywheel to the back of my crank when I change the clutch is such a great idea after all.

Can someone confirm how critical is it to balance the bottom end as one (crank & flywheel)?

[v8 racing]

dave your flywheel will be neutrally balanced so no problem fitting a lighter one at all, certainly no downsides all positives as far as i am concerned, in the real world it feels like you have gained around 20 bhp. just for interest weights
std sdi/tvr = 28ibls
our lightened = 21.5ibls
tvr 500 = 20ibls

[Alexdaredevilz]

Would V8D lightened mine when it was built in 2001?

[v8 racing]

Alexdaredevilz said:

Would V8D lightened mine when it was built in 2001?

More than likely yes, its very very rare that we/i would fit a standard one back on

[Alexdaredevilz]

v8 racing said:

More than likely yes, its very very rare that we/i would fit a standard one back on

Thanks, now I can sleep at night

[Pupp]

I run a 500 flywheel (weighed at 19lb) on my 4.6 with a peaky cam. Sure it shunts a bit due to the cam but is perfectly possible to drive around and the flywheel hasn't made anything worse.

It previously had what I thought was a 'stock' 400 flywheel but as that weighed 21lb I'm now not so sure it was stock

[Chimpafrolic]

v8 racing said:

dave your flywheel will be neutrally balanced so no problem fitting a lighter one at all, certainly no downsides all positives as far as i am concerned, in the real world it feels like you have gained around 20 bhp. just for interest weights
std sdi/tvr = 28ibls
our lightened = 21.5ibls
tvr 500 = 20ibls

Interesting, sounds like the way forward if funds permit.

[Chimpafrolic]

That's some catch Quinny.

To be honest the photo looks a bit fishy to me.

I see you are weighing it without the net.

Did you keep it or throw it back?

[Chimpafrolic]

Quinny said:

No it hadn't had it's chips, so I reused it

Lol, nice to see you still have some TVR swimming in your blood Quinny

I hear there are some lovely big fish making their way upstream from Newport Pagnell these days

[slideways]

spend said:

Pupp said:

I run a 500 flywheel (weighed at 19lb) on my 4.6 with a peaky cam. Sure it shunts a bit due to the cam but is perfectly possible to drive around and the flywheel hasn't made anything worse.

It previously had what I thought was a 'stock' 400 flywheel but as that weighed 21lb I'm now not so sure it was stock

I think Rob was over simplifying and that earlier models may have some 'better' parts ala HC's having verniers & the like - banking on anything in TVR land is always precarious Expect the worse & be pleasantly surprised when you find something better is my attitude.

Does seem when lightened at factory a lot of preserps came with sub 20lb flywheels & 21+lb in serps from top of my head. I do have an extra light one in the garage at 17lbs & it looks plain scary to me. TBH I wouldn't really fancy taking one down less than 21lb (to go anywhere near my own goolies anyway) as they do start to look a bit weedy in my mind... I'd never get the 'what if' out of my mind and end up hanging out the door to drive .

I'm with you on this one Dave! I took Mikes advice and got an SFI rated Mcleod Flywheel, I don't fancy any more shrapnel in my legs

[Chimpafrolic]

Right folks the Helix clutch is in along with Rob's lightened flywheel.

Although the lightened flywheel seemed a good idea on paper I did have two main concerns:

1) The balancing issue

2) Rough idle & loss of drivability

In the end I decided to go with it on the the back of Rob saying there really wasn't any disadvantages, only benefits.

The cost was very fair and it made sense to fit it while the clutch was being replaced.

So how did it pan out?

Well the first thing I can say is the standard 4.0 litre flywheel is stupidly heavy.

The best way I can describe the heft of this thing is it's like something out of an old For Zephyr or diesel Transit.

Robs flywheel is 6.5 - 7lbs lighter, so there is a massive difference when you pick them both up.

In fact I recommend not picking up the original unless you want to put your back out.

So far so good, at this stage I am thinking my new lightened flywheel could be the way forward, but I still had those two concerns in the back of my mind.

Well I have now driven the car for a few days, the first thing I would say is the flywheel really complements the Stealth cam rob fitted a couple of months back.

There are no vibration, no idle or drivability issues whatsoever, in fact it's smoother and very tractable, pulling from 1500rpm no problem.

The engine revs much better so you can bring it into the cam's sweet spot much quicker, 3000 rpm & over is awesome.

Flipping brilliant, thanks Rob.