Lightened flywheel
Discussion
I see an add on Facebook for RV8 flywheels lightened and balanced down to about 9 kg.
My engine has about 340 ft lb torque and about 300 Bhp
What benefits should I expect from such a light flywheel
What downsides will there be.
Where there is a + there has to be a - so let’s be straight and talk of any potential issues arising from using a light flywheel on the roads aswell as the benefits.
Thanks in advance.
Winter so it’s worth talking tuning mods
My engine has about 340 ft lb torque and about 300 Bhp
What benefits should I expect from such a light flywheel
What downsides will there be.
Where there is a + there has to be a - so let’s be straight and talk of any potential issues arising from using a light flywheel on the roads aswell as the benefits.
Thanks in advance.
Winter so it’s worth talking tuning mods
I’ve got a lightened flywheel on my griff 500, similar power to yours. Never driven a standard 500 but sitting still and blipping the throttle the revs rise pretty damn quick more in keeping in time with the throttle pedal and drop just as quick. No idea if it’s better or for worse though lol. Sounds awesome though 
How I see it:
The + is it revs quicker - you've driven Peter's car, as I have too - all i can say is that his flywheel must be made from papier mache,. as the tacho flies up the scale. I was constantly over-revving it.
The - is the revs drop quicker when you take the hoof off the gas too, I guess. The mass is helping to keep the engine turning steadily.
A proper engineer with letters after his name (not just in his pocket on a Saturday night
) will be along soon with the correct explanation.
The + is it revs quicker - you've driven Peter's car, as I have too - all i can say is that his flywheel must be made from papier mache,. as the tacho flies up the scale. I was constantly over-revving it.
The - is the revs drop quicker when you take the hoof off the gas too, I guess. The mass is helping to keep the engine turning steadily.
A proper engineer with letters after his name (not just in his pocket on a Saturday night
) will be along soon with the correct explanation.QBee sums it up nicely.
The lighter fly will allow the revs to rise more quickly than engine with standard/heavier flywheel.
The down side is that the revs drop equally quickly. Makes it trickier to do smooth downshifts and gentle moving off from standstill.....Are you using car on the road or track??
Nick
The lighter fly will allow the revs to rise more quickly than engine with standard/heavier flywheel.
The down side is that the revs drop equally quickly. Makes it trickier to do smooth downshifts and gentle moving off from standstill.....Are you using car on the road or track??
Nick
Thanks boys, pretty much what the science of lighter suggests.
The real question is will I shave a few tenths of my drag strip time remembering it’s a blistering 12.60 as it is
So the standard flywheel must be about 16kg’s and these lightened one’s 9kg so knocking off nearly half its weight which is a big difference.
My concerns are as Boosted pointed out, I might loose my lazy smooth as silk engine that’s really enjoyable to drive at slow speeds.
My MBE Ignition and fuelling is exactly how I like it as in you shut off and it’s off, no pops or bangs until down to 1700 then loads of them as mapped in but again requires a touch of throttle to activate, it’s like pops on tap
This is just fantastic on track and anywhere where you just want throttle control to slow you slightly, engines been rebuilt by Dom so full of compression anyway so de acceleration needs to be done quite carefully anyway even with the heavy fly.
Hmmm
I’m bloody going off the idea already. Seems a cheap and fairly easy mod if it brought a few benefits mind. 2/10th of a second would be nice
The real question is will I shave a few tenths of my drag strip time remembering it’s a blistering 12.60 as it is
So the standard flywheel must be about 16kg’s and these lightened one’s 9kg so knocking off nearly half its weight which is a big difference.
My concerns are as Boosted pointed out, I might loose my lazy smooth as silk engine that’s really enjoyable to drive at slow speeds.
My MBE Ignition and fuelling is exactly how I like it as in you shut off and it’s off, no pops or bangs until down to 1700 then loads of them as mapped in but again requires a touch of throttle to activate, it’s like pops on tap
This is just fantastic on track and anywhere where you just want throttle control to slow you slightly, engines been rebuilt by Dom so full of compression anyway so de acceleration needs to be done quite carefully anyway even with the heavy fly.
Hmmm
I’m bloody going off the idea already. Seems a cheap and fairly easy mod if it brought a few benefits mind. 2/10th of a second would be nice
Edited by Classic Chim on Wednesday 29th January 10:39
Mine makes similar power to yours. I put a lightened flywheel in last year, no regrets.
One thing to mention, I believe you can go lightened or super lightened. My understanding is that super lightened may be a step too far. I think supper lightened went down to about 5kg in weight. I went for similar weight to the one your looking at.
One thing to mention, I believe you can go lightened or super lightened. My understanding is that super lightened may be a step too far. I think supper lightened went down to about 5kg in weight. I went for similar weight to the one your looking at.
Alun you need to check what you have fitted 1st already witnessed a 450 with the bespoke TVR but cast iron lighter FW about 8.5 kilo's IIRC, the other thing is unless your existing FW is set at a neutral balance you will undo Powers work (speak to Dom) I use a steel 6.5kg FW and this will make for a loapier idle and will not improve low speed manners may not be much worse but even so not beneficial either (gear shifts are fine ) getting away quickly is an all or nothing deal but mastered after a short while but I have less CC's and more cam than you so not totally applicable would I go heavier? ........ NO definitely not its part of the whole character of my engine and works , looks nice though dinit ? 
already witnessed a 450 with the bespoke TVR but cast iron lighter FW about 8.5 kilo's IIRC, the other thing is unless your existing FW is set at a neutral balance you will undo Powers work (speak to Dom) I use a steel 6.5kg FW and this will make for a loapier idle and will not improve low speed manners may not be much worse but even so not beneficial either (gear shifts are fine ) getting away quickly is an all or nothing deal but mastered after a short while but I have less CC's and more cam than you so not totally applicable would I go heavier? ........ NO definitely not its part of the whole character of my engine and works , looks nice though dinit ? Edited by Zener on Wednesday 29th January 12:11
Zener said:
Alun you need to check what you have fitted 1st already witnessed a 450 with the bespoke TVR but cast iron lighter FW about 8.5 kilo's IIRC, the other thing is unless your existing FW is set at a neutral balance you will undo Powers work (speak to Dom) I use a steel 6.5kg FW and this will make for a loapier idle and will not improve low speed manners may not be much worse but even so not beneficial either (gear shifts are fine ) getting away quickly is an all or nothing deal but mastered after a short while but I have less CC's and more cam than you so not totally applicable would I go heavier? ........ NO definitely not its part of the whole character of my engine and works , looks nice though dinit ?
already witnessed a 450 with the bespoke TVR but cast iron lighter FW about 8.5 kilo's IIRC, the other thing is unless your existing FW is set at a neutral balance you will undo Powers work (speak to Dom) I use a steel 6.5kg FW and this will make for a loapier idle and will not improve low speed manners may not be much worse but even so not beneficial either (gear shifts are fine ) getting away quickly is an all or nothing deal but mastered after a short while but I have less CC's and more cam than you so not totally applicable would I go heavier? ........ NO definitely not its part of the whole character of my engine and works , looks nice though dinit ? Edited by Zener on Wednesday 29th January 12:11
dinit indeed. I’m pretty sure Dom will tell me to leave it alone,, I’ve asked him before. I’ll check with him again, maybe I can talk him into letting me have it
I’ll mention 2/10ths, he’ll scoff and say drive it better
He will honestly, takes no s
t off me Cheers guys
I think I’ll leave it until I’ve at least driven my car after chassis work.
Is it easy enough to replace fly in situ at a later date. I’d like one real bad
It would encourage me to finish porting my heads...
Classic Chim said:
STUFF.....
Is it easy enough to replace fly in situ at a later date. I’d like one real bad
It would encourage me to finish porting my heads...
Shirley it is easier to change the flywheel while you have the engine out of the car.....or have I been Is it easy enough to replace fly in situ at a later date. I’d like one real bad
It would encourage me to finish porting my heads...
................... 
It’s not just how much weight is removed, but WHERE it is removed from - one kg skimmed off the circumference is equivalent to 6/7/8 kg taken from the middle, and all the mounting holes are in the middle.
Faster acceleration and faster deceleration are the most noticeable changes, marginally less wear on battery and starter motor, easier HnT, but you will stall it a lot in the first few days after the lighter item has been fitted.
The effect of the weight reduction is multiplied by the gear ratio so the impact in 1st 2nd 3rd is significant, but 4th and 5th see a huge reduction in benefit compared to the first three.
Also, 1kg off the flywheel (rotational) is equal to 5/6/7/8 kg off the body (static)
I really like my flywheel, 5kg down from 8.5kg just makes the car feel more ‘alive’
Faster acceleration and faster deceleration are the most noticeable changes, marginally less wear on battery and starter motor, easier HnT, but you will stall it a lot in the first few days after the lighter item has been fitted.
The effect of the weight reduction is multiplied by the gear ratio so the impact in 1st 2nd 3rd is significant, but 4th and 5th see a huge reduction in benefit compared to the first three.
Also, 1kg off the flywheel (rotational) is equal to 5/6/7/8 kg off the body (static)
I really like my flywheel, 5kg down from 8.5kg just makes the car feel more ‘alive’
Alun, now is the time to do it if you are going to.
You won’t have any regrets. An engine your size. can only be positive. You have the engine already out and the gearbox split from it.
If you do in the future you have to drop exhaust, the prop shaft, the gearbox and then change the flywheel. That seems madness.
You won’t have any regrets. An engine your size. can only be positive. You have the engine already out and the gearbox split from it.
If you do in the future you have to drop exhaust, the prop shaft, the gearbox and then change the flywheel. That seems madness.
Olas said:
It’s not just how much weight is removed, but WHERE it is removed from - one kg skimmed off the circumference is equivalent to 6/7/8 kg taken from the middle, and all the mounting holes are in the middle.
Faster acceleration and faster deceleration are the most noticeable changes, marginally less wear on battery and starter motor, easier HnT, but you will stall it a lot in the first few days after the lighter item has been fitted.
The effect of the weight reduction is multiplied by the gear ratio so the impact in 1st 2nd 3rd is significant, but 4th and 5th see a huge reduction in benefit compared to the first three.
Also, 1kg off the flywheel (rotational) is equal to 5/6/7/8 kg off the body (static)
I really like my flywheel, 5kg down from 8.5kg just makes the car feel more ‘alive’
Where you remove material as everything to do with keeping the FW's integrity/strength ultimately & above all else Faster acceleration and faster deceleration are the most noticeable changes, marginally less wear on battery and starter motor, easier HnT, but you will stall it a lot in the first few days after the lighter item has been fitted.
The effect of the weight reduction is multiplied by the gear ratio so the impact in 1st 2nd 3rd is significant, but 4th and 5th see a huge reduction in benefit compared to the first three.
Also, 1kg off the flywheel (rotational) is equal to 5/6/7/8 kg off the body (static)
I really like my flywheel, 5kg down from 8.5kg just makes the car feel more ‘alive’
especially with a cast iron FW 
phazed said:
Alun, now is the time to do it if you are going to.
You won’t have any regrets. An engine your size. can only be positive. You have the engine already out and the gearbox split from it.
If you do in the future you have to drop exhaust, the prop shaft, the gearbox and then change the flywheel. That seems madness.
Just buy Peter's car, Alun, and I'm sure he'll throw in his lightened flywheel 'for free' You won’t have any regrets. An engine your size. can only be positive. You have the engine already out and the gearbox split from it.
If you do in the future you have to drop exhaust, the prop shaft, the gearbox and then change the flywheel. That seems madness.
Zener said:
John Eales will machine a customer FW for around 80/90 squids IIRC that one in the pic is an example , gave it to my brother for an Xmas gift years ago got him guessing
Cracked me up,, Your a good brother you are
Right now I know Anthony’s car and others including Peters( though I doubt the flywheel has much to do with the insane power output) all have lightened flywheels this bit about it revving or spinning up quicker, I can l tell when I drive mine it lags slightly on that spin up compared to these cars.
Once it’s revving and flat out I think it helps balance my engine and actually pulls better at higher revs compared to say a 5.0 which vibrates like mad in comparison, or the ones I’ve been in do. I hardly ever go to 5000 revs though so through the ranges I use it should be spot on.
I’ll contact JE and see if he’d like to lighten my fly. I might still bottle though, it’s not a slow car by a long way, I happen to be judging it up against the fastet 5.5 Chim in the world and Anthony’s which has a Matt Smith allover it, Zener: his has heads as big as a Chevy
quality cars of speed. Basically if I don’t do something about it Jacko Jackson4 with his alarmingly bright and very fast yellow 5.0 is going to stuff me up the drag strip everytime.
Edited by Classic Chim on Thursday 30th January 00:41
Edited by Classic Chim on Thursday 30th January 00:43
TwinKam said:
Just buy Peter's car, Alun, and I'm sure he'll throw in his lightened flywheel 'for free'
I’ve driven it flat out once, out the back at Bedford so Peter didn’t see me came past the pits all pedestrian like then nailed it again Too fast, it was slower then than it is now,,,,
Proper, still locked it up though, really quick effortless car to drive with the Scooby rack.
Imagine what it’s like to then drive my own, I’ve been chasing cheap power ever since
Edited by Classic Chim on Thursday 30th January 00:45
ETA I remember now, 140 mph down what isn’t the longest straight before the fast ish chicane, overtaking MX5 and Boxsters like they were standing still, I get it now, track days allow you to crush others dreams,,, including mine when I had to drive mine home
Seriously fast car above 100 mph let alone before that.
Edited by Classic Chim on Thursday 30th January 00:55
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