Lets Talk Flywheels
Discussion
15 pounder from TTV is in the post. As an ex-air-cooled 911 owner, I know pulling away in a light flywheel car for the first time can be like trying to drink a yard of ale for the first time - everybody stalls it, likewise everybody gets a face-full of Scruttocks Old Dirigible. Once. To avoid a repetition of the sheer level of humiliation involved, you have to get the hang of it really quickly. The engine is already balanced. So taking off a balanced SD1 wheel and fitting an equally balanced steel one shouldn't make any difference. Far as I'm going, anyway! If I'm wrong, I'll never admit it on here, just refit the millstone and keep quiet...
mateypeeps1 said:
... and fitting an equally balanced steel one...
That's the trick though, isn't it? Cause if it's not equally balanced, then you're worse off than before you started - 'cause then high revs is the place you don't then wanna be, and you've just fitted a device to get you there faster...
I have to say I absolutely love my 18.74 lbs chro/mo steel TTV Racing flywheel 
I couldn't imagine ever going back to the old 28 lb SD1 millstone the car came with from the factory, whatever you do to lighten this huge mass will make a massive difference to the way the engine responds to throttle inputs, indeed if you're replacing your clutch fitting a lighter flywheel undoubtedly represents the best 'bang for buck' modification you can make to a 4.0 litre Chimaera.
With help from V8 Developments I took the comically heavy 28 lb original down to 23 lbs, the 5 lbs weight loss was immediately noticeable with no drivability downsides whatsoever, I was so happy with the results when the opportunity presented itself I went another 4.26 lbs lighter settling on 18.74 lbs (8.5kg).
For safety it's not recommended to go much lighter than 22.5 lbs on the original cast flywheel, so this next weight reduction step involved going to TTV for a steel unit which gave even better results, and again there were absolutely no drivability negatives whatsoever. At the end of the day I played it safe 18.74 lbs (8.5kg), I now feel I could have just taken one of TTV's off the shelf 14.5 lb RV8 flywheels but that will have to wait until I address slight oil leak from the rear main, the good news is I already have the flywheel, I'll just get TTV to take another 4.25 lbs out of it.
By this time, and in three separate steps, I will have ended up going a whopping 13.5 lbs lighter than the 28 lb original millstone, and hopefully my lovely drivability will still be retained
I couldn't imagine ever going back to the old 28 lb SD1 millstone the car came with from the factory, whatever you do to lighten this huge mass will make a massive difference to the way the engine responds to throttle inputs, indeed if you're replacing your clutch fitting a lighter flywheel undoubtedly represents the best 'bang for buck' modification you can make to a 4.0 litre Chimaera.
With help from V8 Developments I took the comically heavy 28 lb original down to 23 lbs, the 5 lbs weight loss was immediately noticeable with no drivability downsides whatsoever, I was so happy with the results when the opportunity presented itself I went another 4.26 lbs lighter settling on 18.74 lbs (8.5kg).
For safety it's not recommended to go much lighter than 22.5 lbs on the original cast flywheel, so this next weight reduction step involved going to TTV for a steel unit which gave even better results, and again there were absolutely no drivability negatives whatsoever. At the end of the day I played it safe 18.74 lbs (8.5kg), I now feel I could have just taken one of TTV's off the shelf 14.5 lb RV8 flywheels but that will have to wait until I address slight oil leak from the rear main, the good news is I already have the flywheel, I'll just get TTV to take another 4.25 lbs out of it.
By this time, and in three separate steps, I will have ended up going a whopping 13.5 lbs lighter than the 28 lb original millstone, and hopefully my lovely drivability will still be retained
Agreed, but it is critical that the whole rotating mass is "perfectly" balanced...
Getting that wrong because of assumptions or incorrect information is a disaster, which is why often it's a crank-out job to ensure it is done correctly - which can significantly increase the costs over merely purchasing the FW itself...
Getting that wrong because of assumptions or incorrect information is a disaster, which is why often it's a crank-out job to ensure it is done correctly - which can significantly increase the costs over merely purchasing the FW itself...
Well actually, it’s not that critical. So long as the flywheel is balanced to whatever the usual standard is ie within a little, it’ll be ok. The whole point of balancing a crank is to ensure the crank weights equal the weight of the rotating masses, and half the weight of the reciprocating masses. And in my engine, they already are. I know this without a shadow of a doubt, because I am not seeing double with the engine running.The new flywheel is from the UK premier supplier. They only do flywheels, so I doubt they’ll send me an unbalanced one out of carelessness. From a balance standpoint, the engine does not know or care if the flywheel is fitted or not, so long as it’s balanced to an acceptable level. I have built probably over 100 engines in my time, both professionally and as a hobby. Back in the early days, most of them needed a rebuild because basket cases were all I could afford. And I have never had a crank professionally balanced in all that time. Because in most cases you don’t need to, the factory does it all for you. It’s an inexact science at best, and the bench balance does not take into account variables like cylinder pressure, ring to bore friction, component weight loss over time, oil splash weight, carbon deposit build up etc all these thing will affect balance, and you probably wouldn’t notice any difference. Example, in my enthusiastic youth, I obsessively balanced the bejesus out of a golf GTi engine ( noted as one of the most mechanically smooth engines of it’s time) I got the pistons with a gram of each other, dangled each end of the rods on string on super accurate scales, beggared about with combustion chamber volume matching, on and on, got myself in a right OCD froth.And it didn’t make a jot of difference whatsoever. Example two. Take a regular bike engine, revving routinely to 12-14K RPM. Strip it down, fit new pistons, rods rings etc etc using parts off the shelf. Would anyone rebalance everything? No-one I know, unless it’s a high-stakes race motor. Any parts from a reputable supplier are quality controlled to be within acceptable variation limits, you don’t need to get the digi scales out. As for completely stripping a perfectly serviceable RV8 for balancing as part of a 15 minute flywheel fitting exercise, bit OTT IMO, I won’t be doing it, even though the pubs are shut for the forseeable..!
^^This^^
There's really no problem fitting one of TTV Racing's off the shelf flywheels, they're flywheel experts and do not sell problems to their customers.
Keep in mind I've fitted one of TTV's lovely chro/mo steel flywheels and it worked absolutely brilliantly, my engine also remained super smooth! I tried to be clever and have TTV spin me up a custom 18.75 lbs flywheel, basically because I was too chicken to go to their off the shelf RV8 14.5 lb unit, while it works fantastically well and I absolutely love it I now think I can go lighter.
I want to hear feedback from mateypeeps1, especially on drivability, but my guess is his new flywheel will just give even better throttle response with no downsides despite being a further 4.25 lbs lighter than mine. As far as I'm concerned a lighter flywheel is an absolute no brainer, any weight you can take out of the original 28 lb millstone is going to give great results in a 1060kg TVR, and there's a lot of weight to remove before you even come close to running into drivability issues.
Let us all know how you get on mateypeeps1
There's really no problem fitting one of TTV Racing's off the shelf flywheels, they're flywheel experts and do not sell problems to their customers.
Keep in mind I've fitted one of TTV's lovely chro/mo steel flywheels and it worked absolutely brilliantly, my engine also remained super smooth! I tried to be clever and have TTV spin me up a custom 18.75 lbs flywheel, basically because I was too chicken to go to their off the shelf RV8 14.5 lb unit, while it works fantastically well and I absolutely love it I now think I can go lighter.
I want to hear feedback from mateypeeps1, especially on drivability, but my guess is his new flywheel will just give even better throttle response with no downsides despite being a further 4.25 lbs lighter than mine. As far as I'm concerned a lighter flywheel is an absolute no brainer, any weight you can take out of the original 28 lb millstone is going to give great results in a 1060kg TVR, and there's a lot of weight to remove before you even come close to running into drivability issues.
Let us all know how you get on mateypeeps1
Flywheels and clutch packs are usually neutral balance which allows owners to replace them without having to worry about the balance of an engine. If you really want to reduce weight but have a drivable clutch a small diameter multiplate could work but that might need gearbox mods. Sounds like a painful route to take.
I hear what you are saying regarding the balancing, but all the statements above are relying on the crank having been balanced in isolation of the flywheel - at which point switching one neutrally balanced flywheel for another is fine.
And that's great, if you know that your crank was balanced like that - you're good to go. Please see my point on assumptions in my post above.
For anyone who has had an engine rebuild, or does not know the provenance of their engine, the question then becomes how it was balanced - crank in isolation or as an assembled unit, as then the whole rebalancing point becomes pertinent...
Because this is not stripping an engine, and changing one factory-supplied part for another equal factory-supplied part - this is about having a pulley-crank-FW assembly balanced, and then removing 7kg from one end and somehow expecting there to be no discernable change to the overall balance..?
As an example, after my Power rebuild, I enquired about this exact topic as I wanted to run a light FW. The answer came back from Power that it would require the crank etc out for rebalancing with the new FW. So that was the advice that I received from Power regarding one of their rebuilds...
For those people in my situation (assembly-balanced rather than just crank), while I'm sure you can run a street engine unbalanced, it is neither optimal for the engine or for drivers perception of NVH, akin to driving with tyre-to-wheel-arch-contact or slightly warped discs - you can live with it, but it is a marred experience and one that reduces performance and component longevity.
Given the money that much of us spend on our cars to improve performance, reliability and drivability - for those people in my situation, or who are unsure of how it was balanced, the requirement for crank-out rebalance then becomes a very real possibility - or risk having an unbalanced engine that feels rough at higher revs, the very raison d'etre of a light FW's function.
Please understand that this is by no means saying that any of the FW's are poorly balanced in themselves - I would not expect them to be anything other than excellent - it's about whether the engine was previously balanced with the old flywheel attached to the crank or not, and the ramifications of then changing part of that assembly if it was...
It just surprises me how when someone enquires about changing wheels, loads of people post about offsets, unsprung mass etc - and yet whenever FW are discussed there is very little said about the balancing which may very well be required in order to achieve a pleasing outcome...
And that's great, if you know that your crank was balanced like that - you're good to go. Please see my point on assumptions in my post above.
For anyone who has had an engine rebuild, or does not know the provenance of their engine, the question then becomes how it was balanced - crank in isolation or as an assembled unit, as then the whole rebalancing point becomes pertinent...
Because this is not stripping an engine, and changing one factory-supplied part for another equal factory-supplied part - this is about having a pulley-crank-FW assembly balanced, and then removing 7kg from one end and somehow expecting there to be no discernable change to the overall balance..?
As an example, after my Power rebuild, I enquired about this exact topic as I wanted to run a light FW. The answer came back from Power that it would require the crank etc out for rebalancing with the new FW. So that was the advice that I received from Power regarding one of their rebuilds...
For those people in my situation (assembly-balanced rather than just crank), while I'm sure you can run a street engine unbalanced, it is neither optimal for the engine or for drivers perception of NVH, akin to driving with tyre-to-wheel-arch-contact or slightly warped discs - you can live with it, but it is a marred experience and one that reduces performance and component longevity.
Given the money that much of us spend on our cars to improve performance, reliability and drivability - for those people in my situation, or who are unsure of how it was balanced, the requirement for crank-out rebalance then becomes a very real possibility - or risk having an unbalanced engine that feels rough at higher revs, the very raison d'etre of a light FW's function.
Please understand that this is by no means saying that any of the FW's are poorly balanced in themselves - I would not expect them to be anything other than excellent - it's about whether the engine was previously balanced with the old flywheel attached to the crank or not, and the ramifications of then changing part of that assembly if it was...
It just surprises me how when someone enquires about changing wheels, loads of people post about offsets, unsprung mass etc - and yet whenever FW are discussed there is very little said about the balancing which may very well be required in order to achieve a pleasing outcome...
Edited by Dominic TVRetto on Thursday 4th June 15:52
Interesting posts will be doing the clutch on my Griff soon will definitely lighting my flywheel did it on previous wedge question which clutch did you use looking at Tvr powers. Alloy unit just over 420 dabs,or Racetech version 380 Griff is 4.3 with LT 77 box your feedback appreciated thanks fellow Tvr owner. Sorry no chimaera
For my purposes, fitting a lightened flywheel is all about improving the response of the engine, mainly in the lower gears. As the Revs increase, the effect will be increasingly less. But I have researched enough to know it will have a marked effect on acceleration, and that’s what I’m after. A bit more snap. I don’t expect it to achieve much at the top end of the rev scale. I did notice on a track day at Cadwell that although the old tub did perform quite well,it did take a noticeable while to spin up out of slow corners. As far as flywheel choice goes,I was going to go for a lightened std item, but they are a compromise because they can only be taken down to about 20Lbs before integrity becomes a worry. So the TTV V8 lite steel item at slightly under 15lbs was the choice. It can take either 10.5 or 9.5 clutch diameters, and comes pre-drilled and tapped, with dowels. Another interesting feature of this purpose-made item is that the bulk of the material thickness is concentrated around the hub, with a nice machined taper on the rear face out to the integral ring gear. This design also favours rapid engine response, because it’s light where it counts, at the periphery. A lightened std wheel would likely not have this feature,being machined uniformly. They’re cheaper, sure, but the steel one is in a different league for not that much more. There is also a tell-tale blind drilling on the outer edge, almost certainly for balancing, and the small amount of material removed confirms that the original billet had a nice uniform weight distribution from the off. In fact, I doubt it even needed doing, but this is a quality item, and the TTV guys did it anyway as part of the manufacturing process. I am fitting a standard 9.5” Borg and Beck clutch. Nothing fancy, it’ll do, I am not going for forced induction of anything heavy duty, just want to make my boggo 400 as good as it can be on a realistic budget. Will update when the remaining parts arrive, and I can get on with fitting it.
Dominic TVRetto said:
I hear what you are saying regarding the balancing, but all the statements above are relying on the crank having been balanced in isolation of the flywheel - at which point switching one neutrally balanced flywheel for another is fine.
And that's great, if you know that your crank was balanced like that - you're good to go. Please see my point on assumptions in my post above.
For anyone who has had an engine rebuild, or does not know the provenance of their engine, the question then becomes how it was balanced - crank in isolation or as an assembled unit, as then the whole rebalancing point becomes pertinent...achieve a pleasing outcome...
An engine builder or factory would do an internal balance. It's common sense. The add on's can also be balanced. No need to take it apart to do a re-balance unless it was running badly. And that's great, if you know that your crank was balanced like that - you're good to go. Please see my point on assumptions in my post above.
For anyone who has had an engine rebuild, or does not know the provenance of their engine, the question then becomes how it was balanced - crank in isolation or as an assembled unit, as then the whole rebalancing point becomes pertinent...achieve a pleasing outcome...
Edited by Dominic TVRetto on Thursday 4th June 15:52
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A few pics of the ongoing process. A good time to get a good view of one's chassis condition, too, with the gearbox and prop shaft out of the way. V pleased with mine, good to know. Took the opportunity to change the rear main seal while the flywheel was off, and finally found a good use for the original heavyweight - makes a good pressing tool to fit a new seal squarely, just ease the lip over the flange, then mm by mm tighten 4 bolts evenly. All you need to do then is tap it gently in square and flush with a bit of suitable timber. Also fitted some 50mm square battery leads while the bell housing was out of the way, this is going to be one good starting Chimaera, new starter also. Clutch arriving tomorrow
mateypeeps1 said:
A few pics of the ongoing process. A good time to get a good view of one's chassis condition, too, with the gearbox and prop shaft out of the way. V pleased with mine, good to know. Took the opportunity to change the rear main seal while the flywheel was off, and finally found a good use for the original heavyweight - makes a good pressing tool to fit a new seal squarely, just ease the lip over the flange, then mm by mm tighten 4 bolts evenly. All you need to do then is tap it gently in square and flush with a bit of suitable timber. Also fitted some 50mm square battery leads while the bell housing was out of the way, this is going to be one good starting Chimaera, new starter also. Clutch arriving tomorrow
Got it all back together yesterday, fired up very readily and settled to a steady idle at about 11-1200 RPM, haven't noticed that before, but perhaps it's part of the cold start program. Nice throttle response, much more immediate, which is what I was hoping for. Gear selection has improved, maybe due to the new oil and greased linkage, clutch felt lighter and with more feel, might be due to the new reinforced release fork. What was a pleasant surprise is how controllable pulling away from a standstill seems to be, because the revs are so immediately available, you can sort of 'blip' the throttle whilst slipping the clutch, to within 50 rpm or so, whereas trying the same thing with the std item would see the RPM going way too high, then taking too long to settle down again, hard to explain but it's definitely different in a good way. Test drive on some country lanes showed pretty much what I was expecting, car feels much lighter on it's feet and zippy, gone is the lumbering, Range Rover rumble up the RPM scale, now it feels more like a bespoke sports car engine. So far, no downsides, am well happy. And it's as smooth as it ever was, no balance issues whatsoever, and I didn't expect any. Good mod for a few hundred quid, although a bit labour intensive.
Gearbox linkage is no problem if you remove the transmission tunnel cover inside the car. Just get the centre console out of the way, over the door release knob. I lost my patience trying to undo the grub screw, (smaller than my smallest key of 2mm), so I just applied a stanley blade to the gaiter seam. Ease back the glued edges of the carpet to expose the cover, which slips over the handbrake and gear lever, the knob just unscrews. Retained with about 6 phillips screws, and a fair amount of sealant, so it's a case of easing up the edges gently with a screwdriver, being careful not to break it cos it's fairly brittle, but it will come away eventually. Then all is revealed - 2 x bolts and nylocs. Here's the two best tips though:
A. Be warned about the sleeved linkage connections. IE, when you remove the bolt, there is a nylon anti rattle sleeve that runs inside the bore of both the change stub and the linkage, and a couple of shims. Use a suitable sized pin punch to tap it out. Otherwise you may be under the car trying to drop the box and it'll be hanging on this hard to see sleeve. Cost me a couple of hours beggaring about before realising what the problem was.
B. The fabled bell housing rose joint connection of the change linkage did not need to be disturbed on my car. Heard a lot about this, and it is indeed a right PITA to get at. In the end I undid it from underneath, struggled for ages to get it to the end of the nyloc so it could finally be spun off using fingers, and the promptly found it was a completely unnecessary waste of effort. All that was needed was to remove the shifter bolt and sleeve, the linkage then lifts up and out of the way. There is a little guide stub on the link that is a simple push fit into the corresponding ball socket on top of the box.
I removed the box from the bell housing, 4 bolts. Glad I did because the bell housing needs turning through 90 degrees or so to clear the chassis rails, much easier with the box removed. Reassembly is a straight reversal of the dismantling process, I found it was helpful to refit the clutch slave cylinder to hold the release bearing up against the clutch cover, otherwise it is too easy to dislodge when attempting to line up the shaft. Goodness knows how anyone does this job on axle stands, you have my undying admiration. I borrowed a mates two poster, bought a gearbox column jack for about £75, and it wasn't too bad. Jack is useful for refitting the exhaust too. Oh yeah, and if yours is a T5, drain the gearbox oil before removing the propshaft, or thou wilst be truly anointed with holy ATF...
A. Be warned about the sleeved linkage connections. IE, when you remove the bolt, there is a nylon anti rattle sleeve that runs inside the bore of both the change stub and the linkage, and a couple of shims. Use a suitable sized pin punch to tap it out. Otherwise you may be under the car trying to drop the box and it'll be hanging on this hard to see sleeve. Cost me a couple of hours beggaring about before realising what the problem was.
B. The fabled bell housing rose joint connection of the change linkage did not need to be disturbed on my car. Heard a lot about this, and it is indeed a right PITA to get at. In the end I undid it from underneath, struggled for ages to get it to the end of the nyloc so it could finally be spun off using fingers, and the promptly found it was a completely unnecessary waste of effort. All that was needed was to remove the shifter bolt and sleeve, the linkage then lifts up and out of the way. There is a little guide stub on the link that is a simple push fit into the corresponding ball socket on top of the box.
I removed the box from the bell housing, 4 bolts. Glad I did because the bell housing needs turning through 90 degrees or so to clear the chassis rails, much easier with the box removed. Reassembly is a straight reversal of the dismantling process, I found it was helpful to refit the clutch slave cylinder to hold the release bearing up against the clutch cover, otherwise it is too easy to dislodge when attempting to line up the shaft. Goodness knows how anyone does this job on axle stands, you have my undying admiration. I borrowed a mates two poster, bought a gearbox column jack for about £75, and it wasn't too bad. Jack is useful for refitting the exhaust too. Oh yeah, and if yours is a T5, drain the gearbox oil before removing the propshaft, or thou wilst be truly anointed with holy ATF...
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