Lets Talk Flywheels

[ChimpOnGas]

Hi all,

I'd like to start a discussion on flywheels.

'Ol Gasbag' is getting a new clutch soon as it's time to say goodbye to my unnecessarily heavy Helix unit, so with the box coming out and a new clutch going in now's the tine to fit a lighter flywheel.

Actually I've already done this very thing when the Helix was fitted a few years ago and was delighted with the results. I simply went to Rob Robertson of V8 Developments, he supplied me a machined down original cast iron SD1 flywheel, for those that don't know the 4.0 Chimaera is fitted with a completely stock 32lb SD1 flywheel which is in my opinion way too heavy for a car that only weighs around 1100kg.

The SD1 weighs around 1440kg and was designed to be a flexible family saloon so a 32lb flywheel makes perfect sense, the far lighter Chimaera on the other hand simply doesn't need all this flywheel mass and it also fair to say the car is likely to be driven in a very different way to the Rover.

Anyone with a 4.0 Chimaera who is having their clutch replaced should therefore give serious consideration to lightening their standard flywheel, my 32lb original had a full 7lbs taken out of it to give me a 25lb flywheel and I can say with 100% conviction there were absolutely to downsides, only benefits.

TVR clearly new all this back in the day as they also machined these cast SD1 flywheels but only on the 5.0 litre cars taking it down even further than mine to 22lbs, when I bought it from Rob Robertson he explained stopping the machining at the 25lbs mark was a safer limit to work to than TVR's 22lbs.

With my new clutch being installed soon I've now started to look at the flywheel again, I've concluded that I can remove a further 5-7lbs without any downsides, a flywheel weighing between 18-20lbs should in theory be ideal. Obviously with TVR stopping at 22lbs and V8 Developments setting their limit at 25lbs it seems pretty conclusive I would be ill advised to try and get my SD1 type cast flywheel down to my target 18-20lbs.

So that leaves me searching for new made lightweight flywheel of which there are quite few options, the problem is I can find nothing on offer in my 18-20lbs target weight.

The nearest thing available is the 15lb unit from V8 Tuner, but I'm a little concerned 15lbs may just be fraction too light as I do like a reasonable idle and good drivbility.

http://www.v8tuner.co.uk/product.php?id=773



Can people using this V8 Tuner 15lb flywheel give me their honest appraisal of it and how it affected the way your TVR drives, it may also be helpful to include your power & torque outputs as what might be fine in something making 300ft/lbs plus may not suit 'Ol Gasbag' with her 260ft/lbs of torque.

Please also educate me if an "off the shelf" flywheel in my 18-20lbs target weight is available.

Thanks in advance, Dave.

Edited by ChimpOnGas on Friday 9th October 09:54

[ChimpOnGas]

ClassiChimi said:

When you think about it that 3lb is a lot of weight to lug around!
Even at 25 that's still way lighter than standard,,
Food for thought!

I know, I know.

But lets face it a 32lbs flywheel is nuts in a car like this, so anyone with a 4.0 litre Chimaera would do well to get their flywheel shaved. Take it down to a safe 25lbs and they will notice a big difference just as I did.

So I'm now at 25lbs and it's working really well, no issues with low speed tractability and a super rock solid idle as well, best of all the engine picks up revs so much better.

But the question I'm trying to answer is could it be lighter still

My gut feeling is I could reduce it's weight by another 5lbs and it'll still keep the stable idle and good low speed driving manners, so to me a 20lb flywheel seems the ideal and I'm certaily fearful of going any lower than 18lbs.

The truth of course is I'm guessing really and the closest flywheel on offer is 15lbs anyway, so perhaps it'll be just fine

That's why I'm on here asking for feedback from anyone who's fitted this 15lb flywheel from V8 Tuner. I'm sure there's a few of you out there with it so it would be great to hear your honest feedback.

The issue I'm trying to avoid is discovering I don't like it after it's all bolted in, I know the whole thing is subjective as one man's fantastic is another man's undrivable but some real world feedback would help a lot.

Personally I feel it could go either way, I may love it or I may just find I've taken a step too far. The only real way to find out is to pay the £400 and try it, but before I do I'd love to hear from anyone with this V8 Tuner 15lb flywheel.

http://www.v8tuner.co.uk/product.php?id=773



Anyone

[ChimpOnGas]

Pupp said:

I've a couple of TVR 500 flywheels, including the one on the car. They were both under 22Lb and neither was a machined SD1 unit... bespoke castings I think.

I would have no hesitation going lighter still with a steel unit

Thanks Gary that's really helpful, so the 22lbs 5.0 litre flywheel was a bespoke casting for TVR, I never knew that

Perhaps that supports why Rob Robertson didn't want to take my standard SD1/4.0 Chimaera flywheel any lighter than 25lbs and the 5.0 litre ones are safe at 22lbs

Anyway, I'm in no doubt I can go lighter than my current 25lbs one without issues, but can I take it as low as 15lbs and still have a nice driving TVR?

It's a hard one to call

I guess I could source a 5.0 litre flywheel but it hardly seems worth it for the 3lbs advantage over my current one.

Feedback from anyone with real world experience of the 15lbs V8 Tuner flywheel would be much appreciated

[ChimpOnGas]

Sardonicus said:

Dave my flywheel is 6.5 kg and and I would give you an opinion on what its like but seeing as opinions are like arse holes and everyone as one it would be just that (thats not having a pop at Gary etc) however I will say dont go too mad you want to retain some FW inertia with that FI build you plan otherwise you will end up with an on/off switch not being awkward but without you experiencing it its going to be hard for you to gauge I have no regrets with my choice it compliments my spec perfectly and I certainly would not change it I can go from tickling along in 1st at idle to flooring the gas with no clutch action to instantly breaking rubber it really spins up nicely with thanks to that FW oh yeh 500 fly is def bespoke like Pupp states I have a pic

Edited by Sardonicus on Friday 9th October 14:26

Thanks for that Simon and you're quite right, as I've already said the whole thing is subject to personal taste and expectations so it's impossible to make my choice over a forum.

One half of me says I should play it safe and stick with my current 25lbs one, but there's also a devil on my shoulder telling be to grow some balls and buy the 15lbs unit.

It's a shame there isn't something in the 18-20lbs bracket because if there was I wouldn't think twice about fitting it.

I guess I'm going to have to make a choice at some point, and with the fantastically smooth way 'Ol Gasbag' is driving after our recent round of improvements I'm super tempted to think she'll be just fine on the 15lbs one from V8 Tuner.

Only time will tell if I've gone too light, the problem is it'll be an expensive mistake if I end up not liking it

NB: Simon, You Have Mail

Edited by ChimpOnGas on Friday 9th October 14:47

[ChimpOnGas]

Sardonicus said:

trangely enough Dave my brother was over on saturday and we fitted a 19 pounder FW he is surprised at the difference its made he will be wanting the other set of DIY heads fitted next I'm sure I know he will be reading this NO mail Dave

Check your junk mail Simon..

I also sent you a response to your S-10 tail housing query the other day and wondered why you didn't acknowledge it

That 19lb flywheel you fitted to your bother's car sounds ideal, can you PM me with where it came from?

Thanks, Dave.

[ChimpOnGas]

phazed said:

I just found the receipt for my forged aluminium flywheel that came from Abbey sports cars Ltd Which is V8 tuner.

My invoice is for £400 but I see they are actually £530 now!

I noticed they state that they are 11lbs in weight.

As a few people who have driven my car will confirm, the engine acceleration is extremely rapid and spins up instantly but it is still a pussycat to drive.
There is a very minor amount of shunting at about 1500 to 1700 rpm If you really look for it, which may or may not be caused by the light flywheel, apart from that you would never know that the flywheel is so light.

Thanks Peter, I guess it's fair to say you've got a significant slug more torque than me so that may well be helping.

But it has to be said 11lbs is one very light flywheel, so if you're still getting a nice drive maybe I could get away with the 15lbs one on mine?

I had a good chat with Simon an hour or two ago and he says stick with my 25 pounder, there's a lot to be said for this actually.... because.

A. It's proven

B. I'm not taking any risks I may not like it

c. It's free

To throw £400 at something only to find I don't like it and then have to pull the whole thing down again would be an expensive mistake.

The problem with all this is if I don't do it I'll always be wondering "What If?"

For sure if I don't fit the 15lb flywheel and stay with what I have I'll spend the next however many years torturing myself about all that crisp throttle response and eagerness to rev I could have had.

This is proving trickier than I'd thought, what we really need is someone with a 4.0 litre Chimera who's fitted one of these 15lbs flywheels and can be honest about how it changed things both good & bad.

Anyone

Edited by ChimpOnGas on Friday 9th October 18:30

[ChimpOnGas]

TV8 said:

Hi Dave, some info here. Lots of other cars use the RV8 so the info could be out there somewhere re the 4lt with light flywheel
http://www.britishv8.org/Articles/Introduction-to-...

I would go for it personally.

Thanks, good article, actually I read it earlier today and its what lead me to conclude that 20lbs was about right for 'Ol Gasbag' and the power she makes.

I also spoke with the my friends at Lloyd Specialist Developments who like Simon have a 4.0 litre with the 15lbs flywheel.

Two opinions I respect they both said there are some downsides going this light.

I guess it all depends on what someone personally feels is acceptable, and without trying it that's something I'm left guessing on.

Its a tricky one for sure

[ChimpOnGas]

77racing said:

SILICONEKID345HP said:

There`s a nice aluminium one sat in Engineer1949 garage ,it came out of Nicks car .Can you remember the post ?

I have that same style on the back of my Rover and it rev's up like a GSXR, awesome.

Well I guess that's fantastic, but only if you're looking to build a TVR that revs like a GSXR.

I'm not!

As always I'm looking for the perfect compromise between a car that drives like a pussy cat around town yet picks up revs with controllable eagerness that delivers the best throttle response I can achieve.

Building a one trick pony is one thing, building a TVR that delivers both super smooth drivability and the performance characteristics we all yearn for is somewhat more of challenge.

It's what the likes of Porsche spend thousands of hours on the dyno trying to achieve, more challenging still is they are trying to achieve these goals while still hitting the very challenging Euro emission rules and fuel economy targets.

These super demanding and conflicting challenges is what interests me, they become my reference for the things I'm trying to achieve with my TVR.

A Chimaera is actually a super practical all rounder GT/sports car in the old school vein, as such it's my belief a Chimaera represents an excellent development platform to build the ultimate classic car.

I don't want a race car, I merely want a Chimaera where all it's already excellent traits of usability and performance are enhanced not removed.

Will I like the 15lbs flywheel?

Does it match my development "all things to all men" design brief?

Hard to say really without trying it

[ChimpOnGas]

Pupp said:

I could understand all this agonising if the rotating and reciprocating mass on the crank and crank-borne components was small. Then the differences between 19 or 15 pounds might have a really significant impact. That's just not the case however; the crank is massive, the damper is massive, the clutch is bloody massive too. All else being equal, if it wasn't for the need to have a ring gear for starting and a face for the clutch to drive off, I think the flywheel could be prety much dispensed with

Great point Gary.

[ChimpOnGas]

SILICONEKID345HP said:

This one had to be removed ,it was undriveable on the road but great for track .

http://www.pistonheads.com/gassing/topic.asp?h=5&a...

Replaced for this one .

Edited by SILICONEKID345HP on Saturday 10th October 19:06

In that link he talks about going to a 12kg flywheel, that's around 26lbs so heavier than my 25lb one.

I still feel 15lbs may be a step too far for what I want, 20lbs remains my target as something is telling me this would be the best compromise.

I wonder if I the solution is to have a 20kg one made, I think they are made to order anyway so the 15lb one with 5lbs more materialb left on the back of it should be spot on.


It would still be 5lbs lighter that what I have now and 2lbs lighter than a 5.0 litre one.

In theory it should also have less of a negative effect on drivability while still giving some engine responsiveness benefits I will feel.

Well that's the theory!

[ChimpOnGas]

BoostedChim said:

This is my 500 fly when I picked it up, that's 8.8kg on the scales. I had John Eales balance it neutrally so I could use it on my 4.0, it needed 8 holes drilling at 180 degrees to the existing 6 and was 8.7kg (19.1lbs) at the end. My advise would be to keep an eye out for a 500 version and factor in £120 for balancing and posting if your budget will stretch to it at the same time as the clutch.

Very nice solution indeed, 19lbs is right smack in the middle of my 18-
20lbs target range.

Gary (Pupp), will you sell me your spare 5litre flywheel?

[ChimpOnGas]

Ok, all sorted girls and boys

Before I explain I'd like to thank you all for listening to my agonizing over wanting something lighter than my current cast iron 25 pound flywheel, yet not quite as light as the 15 pound steel one on offer off the shelf

It was all solved in a highly educational 5 minute chat with the engineer himself.

As I've always said... it's the guy in the brown coat with a pencil behind his ear and a micrometer in his top pocket who really knows what's what!

The first lesson I was given was in inertia which lead to the following statement....

"I could make you 15lb flywheel that made your TVR drive like a tractor, it's not so much about the weight but where I choose to leave that weight when I make your steel flywheel"

Of course this lesson from the expert immediately made perfect sense to me so we chatted some more about what I have now (25lbs machined down SD1) and what I was trying to achieve as an improvement over it.

I made it clear I needed to keep just enough of that "pulling off the junction" and town driving flexibility to ensure the car remains nice and streetable.

Quite quickly the expert says....

"I get it, I know exactly what you want, if you're looking for throttle response improvements and quick revving engine characteristics over what you have now without going as far as the 15lb one I have ready on the shelf... I will simply make a 19lb one that does the trick perfectly".

The expert gave me so much confidence he knew exactly what I wanted I didn't bother to challenge him where he was leaving the additional weight, suffice to say he confidently ended our conversation by saying...

"I've been turning and balancing steel flywheels for everything under the sun for over 30 years, trust me, you will get the exact animal you want"

I think the real lesson here is... there's no substitute for knowledge and experience, a quick chat with the man himself left me 100% confident I've done the right thing and I'll get what I want".

Now that's what I call good old fashioned service, from a good old fashioned engineer

[ChimpOnGas]

"Flywheel Fred" (thanks for that Peter ) is The Man!

Fred actually makes flywheels for everything from a type 35 Bugatti to a Ferrari F40.

Not content with this he also makes the flywheels for Mclaren that go in their MP4 GT3 cars.

I feel honored Fred is making one to my exact specifications for 'Ol Gasbag'

And even more so that.. (based on our chat) Fred also offered to add his own top secret enhancements to my spec driven by the extensive knowledge he's built up over years and years of turning some of the worlds best flywheels.

If Fred & I have got all this right 'Ol Gasbag' has lost another 6lbs (in the right places) off her already lightened flywheel but will still pull away from the lights and trickle through town like a pussycat.

Lets hope we've found that perfect sweet spot of revability, throttle response and drivability

Only time will tell

[ChimpOnGas]

ClassiChimi said:

I drove Peters car,,, I couldn't tell any difference, it's a pussy cat at slow speeds and come to think about it, blipping the throttle on down shifts,, the engine responded tremendously well Dave,,
When do you think you'll be getting your present from Old Fred
I can't wait to see how it fairs,,, sounds spot on to me.

But Alun, you're not comparing apples with apples here mate.

The thing with Peter's car is it makes like 428 torques, which if you really sit down for a minute and think about it is totally bonkers in a car this light!!!

To put Peter's torque into perspective...

• A 1997 - TVR Cerbera 4.5 produces 345.4 lb-ft per tonne

• A 2002 - Ferrari Enzo 6.0 V12 makes 355.3 lb-ft per tonne

• And a 2014 McLaren 650S 3.8 V8 Twin Turbo makes 375.9 lb-ft per tonne

And what of Peter's TVR Chimaera then?

Well that makes a tarmac shredding 411 lb-ft per tonne!!!!

And at just 1,500 RPM Peter's car is already making 90 lb-ft more torque than 'Ol Gasbag' can muster all out at 5,250 RPM!!!

A Chimaera is a very light car so 'Ol Gasbag's" 260 lb-ft of torque still gets her up the road very niclely thanks, but with 411 torques for every tonne of mass to move I doubt Peter needs anything much more than a bottle top on the back of his engine to give a super smooth drive.

Now lets look at a 2013 Ferrari LaFerrari 6.3L V12 that trumps Peters TVR by delivering 411.1 lb-ft per tonne, or does it

Well no it doesn't, because that Ferrari needs its engine spinning at 8,750 RPM to beat Peter's peak figure which comes in at a mere 4,000 RPM.

Now I know that Ferrari engine builds revs fast, but can it really get to 8,750 RPM before Peter reaches 4,000 RPM?

I doubt it

Anyway, Italian cars are for Ghays and posers, TVRs are for real men!

[ChimpOnGas]

phazed said:

Even worse Dave

Nearly 460 torques.

Holy Mother of God Peter

That's actually 50 torques more than that crazy 6.3 litre LS3 Cerbera I drove, these old Rovers still have it for sure!

[ChimpOnGas]

Done!

Flywheel ordered from Fred

Fred charged me an extra £26.40 for the custom job but assures me he's working some of his special magic on the thing to make sure it's just what I need.

Fred is a proper old school engineer but is not stuck in the past, as such he prefers to work in metric measurements.

This means what I'm getting will actually be exactly 8.6kg, which translates to 18.96lbs in old money

I will keep you all updated on how my custom 8.5kg steel flywheel performs in 'Ol Gasbag'.

Be patient folks, while it is being machined from a new forged chrome moly steel blank in a few days it won't actually be fitted until December when all my other S-10 gearbox mods and lighter clutch are installed by Lloyd Specialist Developments.

I'm hoping everything will come together to deliver a super slick gear shift, a feather light clutch and an even more responsive engine, but very importantly for me one that still drives nicely at low speeds too.

Will I get my cake & eat it?

Here's praying I do

[ChimpOnGas]

OleVix said:

I had the original 12.6 kg one in my 400, milled that down to 10 kg and felt the difference, but could have taken off more. As I said I now have the 6.8 kg one in my 4.6. Nice idle and no problems with pootling along. Mass removed translates to acceleration, do it!!

Good to have your feedback Ole, much appreciated.

In the end I've gone for a half way house, I'm having a bespoke 8.6kg chrome moly steel flywheel made which translates to 18.96lbs in old money.

I started with the comically heavy 32lbs cast iron Rover SD1 flywheel TVR stuck in all 4.0 litre Chimeras which I then had machined down to 25lbs, as when you did something similar Ole this made a massive difference to throttle response and the way the engine picked up revs.

I was really impressed with this simple and cheap modification but always felt I could have gone a little lighter than 25lbs, the problem is you are close to the safe limit of machining at 25lbs.

You were brave to take your standard cast flywheel down to 22lbs, my understanding is TVR had to produce their own casting to get the 5.0 litre flywheel to 22lbs.

So I've gone from the silly 32lbs flywheel to the way way better 25lbs one and now rather than going for the 15lb one I'm playing it safe somewhere in the middle at 19lbs.

That's still a full 6lbs lighter than what I have now which I feel it should be the sweet spot for my 4.0 litre car.

If anyone would like to buy my V8 Developments supplied 25lb flywheel it will be available in early January, if you have a 4.0 litre Chimaera this 25lb flywheel is a cheap mod you will really feel.

If you're gearbox is coming out for a clutch replacement fitting my cheap to buy 25lb flywheel is an absolute no-brainer!

All inquiries by PM please

[ChimpOnGas]

spitfire4v8 said:

My personal choice would be to go with the lightest flywheel you can. As mentioned above, the other rotating components all have significant mass, and don't forget you have 4 firing events per revolution smoothing things out, it's hardly an ATCO mower or Fiat 126.

You can also ramp up the ignition map below idle on closed/light throttle to increase the power below idle and prevent stalling too.
The energy stored in the flywheel may help you when pulling away, but a heavier flywheel will only inhibit the acceleration rate thereafter, meaning more energy used to accelerate the car and more fuel required than with a lighter unit, though I accept that this is a law of rapidly diminishing returns.

Point taken, I respect your opinion and experience in these matters.

For now I'm very comfortable with my 19lbs choice, and I'm confident it's right for my needs.

But as the engineer who's making my flywheel said...

"I can always easily spin your 19lb flywheel down to 15lbs at a later date, but if you take the 15lbs one off the shelf and you don't like it there's no option to add material back on"

He also suggested letting me try the 15lb one in the future and taking my 19lb one in exchange if I liked it better, or taking the 15lb one back at no charge if I didn't.

The real way to find the best weight for an individual's tastes and driving style would be to take sacrificial flywheel and keep shaving half a pound off it at a time, until you found the point at which you went half a pound too light.

You could then have a new flywheel made to the exact weight that sits just the right side of the lightest point where sufficient drivbility is retained.

Of course flywheel weight is all subjective, what's considered the perfect weight will vary greatly from driver to driver and from car to car, one man's too light is another's way too heavy.... and vice versa.

Lets see how I get on with my bespoke 19lb cut, one thing is for sure it'll definitely be a good 6lbs better than what I have now, and what I have now was already a massive improvement over the original and comically heavy millstone.

And best of all..... I still have option to go lighter from there if I ever feel the need to do so

[ChimpOnGas]

UPDATE







This morning I popped out to the garage and weighed my V8 Developments flywheel, something I'd been meaning to do for ages

Admittedly my scales aren't the most sophisticated in the world but I did check them against a dumbbell of a known weight and they do actually prove themselves to be spot on. While the scale marks go up in one pound increments and the needle sits between the 22lb and 23lb mark it is a fraction over the half way point.

I conclude my V8 Developments lightened flywheel is approximately 10.3kg which equates to 22.7lbs, to avoid debate I'm happy to er on the side of pessimism and call it a 23lb flywheel.

A standard 4.0 litre flywheel must therefore be 30lbs as V8 Developments confirmed they took 7lbs out of mine to give me their 23lb lightened version, I can also assure you once fitted it made a big improvement to the way the engine picked up revs with absolutely no drivability downsides.

It's also been proven the very rare 5.0 litre flywheel used by TVR weighs in at 8.8kg which is 19.4lbs, so my V8 Developments lightened flywheel is significantly lighter than standard one used in the 4.0 litre cars and only just over 3lbs heavier than the specially cast 5.0 litre TVR one.

If you've been following this post you'll know I was cautious not to go too light, both people I spoke to separately who have the 15lb steel flywheel available off the shelf from V8 Tuner said they do need to raise the revs slightly more than normal when pulling away from a junction, I didn't want this so I had a bespoke all steel 8.5kg flywheel made which equates to 18.74lbs.

So what I have now is fractionally lighter than the elusive 5.0 litre flywheel and I would also imagine it to be much stronger being chromo steel rather than cast iron. Essentially I've gone from the ridiculous 30lb millstone fitted to 4.0 litre Chimaeras down to the massively better V8 Developments lighted one at a shade under 23lbs, I've then cut the weight still further by over 4lbs from there to give me an 18.74lbs flywheel with still no negative impact on dravability.

I wouldn't want to go any lighter and it has to be said the steel flywheel wasn't exactly cheap, so my conclusion is a V8 Developments lightened flywheel at a shade under 23lbs offers by far the best bang for your buck. Indeed anyone changing the clutch on their 4.0 litre car is well advised to fit one of these V8 Developments lighted flywheels because they'll definitely feel the difference without sacrificing any drivability.

Best of all a V8 Developments lightened to 23lb flywheel won't break the bank, mine currently sits redundant in my garage acting as a static reminder to the significant benefits of reducing the engine mass of a 4.0 litre Chimaera

Hope this helps people?

Dave.

[ChimpOnGas]

mateypeeps1 said:

So, best part of 4 years later, I am considering the same thing. Am changing the clutch in the next few weeks, and a lighter flywheel to improve response seems like a no-brainer. Pretty certain my std 400 has the original millstone fitted. All opinions welcome. car use is just fun road/touring and occasional novice track day. 20 Lbs / 9kg seems to be the optimum figure, most of the more expensive steel items seem to be more like 15Lb / 7kg. Is that too light for a boggo 4 litre?

I'm running 18lbs now, its a custom flywheel I had TTV Racing grind for me from chro-mo billet steel.

http://ttvracing.com/

I've very happy with it, but I think I could sill go lighter.

TTV are the UK flywheel experts, don't mess about with anyone else, TTV will sort you out.