Fly wheel weight pros and cons Griff 500
Discussion
Can someone explain to me the benefits of making the fly wheel lighter.
Just to clarify i have a Griff 500 which last time i looked had made 350 hp on TCS Rollers
If i go down the route of trying to find more power HP wise would it be worth taking some weight off said Fly wheel
And if so what weight is best to aim for and why ?
Many Thanks in advance
Pasco
BTW I need to weigh the one that sits on my garage floor but it has clearly had some weight reduction at some time or other
Just to clarify i have a Griff 500 which last time i looked had made 350 hp on TCS Rollers
If i go down the route of trying to find more power HP wise would it be worth taking some weight off said Fly wheel
And if so what weight is best to aim for and why ?
Many Thanks in advance
Pasco
BTW I need to weigh the one that sits on my garage floor but it has clearly had some weight reduction at some time or other
Your a Star 
Mat350 Why 14 Lb mate I took the flywheel off and bunged it on a lathe and removed all the material I thought I could get away with safely, I ended up at 14lb (or thereabouts).
One important point is on the 5ltr TVR engine, they balanced the crank externally with holes drilled in the flywheel and little weights added to the front pulley.
So I'd be careful about just fitting a lightened flywheel in isolation on these engines (only applies to the 5ltrs)
You can still do it but I think it would mean removing the entire crank and front pulley and getting the whole lot dynamically balanced again. and if you were going to go to that much trouble I'd use this chaps services;
http://www.vibrationfree.co.uk/
He balances the entire bottom end dynamically, pistons and all (no rings fitted) I know some F1 buddies of mine have recently used his services with impressive results.
Happy to hear a different argument on this one tho'
One important point is on the 5ltr TVR engine, they balanced the crank externally with holes drilled in the flywheel and little weights added to the front pulley.
So I'd be careful about just fitting a lightened flywheel in isolation on these engines (only applies to the 5ltrs)
You can still do it but I think it would mean removing the entire crank and front pulley and getting the whole lot dynamically balanced again. and if you were going to go to that much trouble I'd use this chaps services;
http://www.vibrationfree.co.uk/
He balances the entire bottom end dynamically, pistons and all (no rings fitted) I know some F1 buddies of mine have recently used his services with impressive results.
Happy to hear a different argument on this one tho'
Reducing rotating mass doesn't increase steady state power as you're already at the RPM your're measuring at, however it does increase transient / accelerating power as there's less mass to accelerate.
So the blip response will increase and this also tends to improve gearchanges as the load on the synchros is reduced. Its generally worth doing providing you don't go below the point where the beneficial torsional damping is lost and rpm stability is reduced to an unacceptable level.
So the blip response will increase and this also tends to improve gearchanges as the load on the synchros is reduced. Its generally worth doing providing you don't go below the point where the beneficial torsional damping is lost and rpm stability is reduced to an unacceptable level.
Unless you are interested in how the engine performs in Neutral 
I would have thought looking at wheel / disk / hub.. weights would yield far greater desired impact.
The flywheel weight is not only relative to how well the bottom end is balanced, but also the rotating mass. The engines have different cranks / rods / pistons which all have a different rotational inertia. Matts light flywheel was probably for a small journal 4.0 (lightest crank with least throw), a later 5.0 intrinsically has heavier parts and greater throw.. There is also a lot of balancing of pistons and rods done on some of the cars, as well as having them lightened along with the crank (if you go to those extremes
).
At the end of the day I'd rather lighten other rotational parts, and have the benefit of some weight in the flywheel to benefit starting. Unless you are boosting the engine, you have have missed the boat if you don't have a nice high compression before you go to the extent of lightening and balancing the bottom ends.
I am certainly adverse to the one size fits all flywheel scenario
I would have thought looking at wheel / disk / hub.. weights would yield far greater desired impact.The flywheel weight is not only relative to how well the bottom end is balanced, but also the rotating mass. The engines have different cranks / rods / pistons which all have a different rotational inertia. Matts light flywheel was probably for a small journal 4.0 (lightest crank with least throw), a later 5.0 intrinsically has heavier parts and greater throw.. There is also a lot of balancing of pistons and rods done on some of the cars, as well as having them lightened along with the crank (if you go to those extremes
).At the end of the day I'd rather lighten other rotational parts, and have the benefit of some weight in the flywheel to benefit starting. Unless you are boosting the engine, you have have missed the boat if you don't have a nice high compression before you go to the extent of lightening and balancing the bottom ends.
I am certainly adverse to the one size fits all flywheel scenario
The key point for me is Matt's that TVR took the quick and easy option for balancing the crank only via flywheel and front pulley and therefore if you're going to lighten the flywheel you'l probably end up with the engine out of balance overall and you'll loose more benefit than you gain.
You'd get more from having the whole lot out and having all of the moving bits balanced.
You'd get more from having the whole lot out and having all of the moving bits balanced.
350Matt said:
Reducing rotating mass doesn't increase steady state power as you're already at the RPM your're measuring at, however it does increase transient / accelerating power as there's less mass to accelerate.
So the blip response will increase and this also tends to improve gearchanges as the load on the synchros is reduced. Its generally worth doing providing you don't go below the point where the beneficial torsional damping is lost and rpm stability is reduced to an unacceptable level.
Thanks Matt and all the other contributors So the blip response will increase and this also tends to improve gearchanges as the load on the synchros is reduced. Its generally worth doing providing you don't go below the point where the beneficial torsional damping is lost and rpm stability is reduced to an unacceptable level.
So i have just weighed my fly wheel and it is 20lb
So taking into account re the comments regarding internal balancing and assuming that this would be done what should i be aiming for regarding weight reduction to help gain the characteristics you mention above Matt ?
rev-erend said:
Johno said:
The key point for me is Matt's that TVR took the quick and easy option for balancing the crank
Or you could just say - they took the cheap method..Pasco
Ultimately people tend to shave off whatever the flywheel can stand without exploding into a thousand bits and taking your feet with it.
Hence the availability of steel flywheels or even aluminium ones
If you were going to go down the route of a complete bottom end re-balance (which is what you'd have to do to keep it safe on the 500) then I would contact some experienced engine builders such V8 developments to see how much weight you can get away with. Sadly I can't punch some numbers into a calculator and give you a weight as torsional vibrations need to measured to gauge their severity.
Typically a manufacturer will start with a generic weight and test the engine with the torsional kit all hooked up then try different masses to achieve the torsional damping in the range they want.
You can calculate it but in my experience it'll be miles off what's actually happening.
A way forward would be to lighten the crank and flywheel as much as you can then fit one of these:
http://www.vibrationfree.co.uk/Rattler.htm
Ultimately people tend to shave off whatever the flywheel can stand without exploding into a thousand bits and taking your feet with it.
Hence the availability of steel flywheels or even aluminium ones
If you were going to go down the route of a complete bottom end re-balance (which is what you'd have to do to keep it safe on the 500) then I would contact some experienced engine builders such V8 developments to see how much weight you can get away with. Sadly I can't punch some numbers into a calculator and give you a weight as torsional vibrations need to measured to gauge their severity.
Typically a manufacturer will start with a generic weight and test the engine with the torsional kit all hooked up then try different masses to achieve the torsional damping in the range they want.
You can calculate it but in my experience it'll be miles off what's actually happening.
A way forward would be to lighten the crank and flywheel as much as you can then fit one of these:
http://www.vibrationfree.co.uk/Rattler.htm
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