Reducing weight of the spinning bits or minor power mods?
Discussion
Just mulling this over, on a n/a car thats not going to have a supercharger or turbo fitted would money be better spent on reducing the weight of the spinning bits? I read, no idea if true that you can multiply by four the effect of each kg lost compared to static weight loss. So say loose 2Kg a wheel and this has the effect of loosing 32kg from the static parts of the car. Add say a 5kg loss off the flywheel @ 20Kg, maybe 2Kg for alloy belled rotors 8kg gives you an equivalent loss of 60kg.
I notice the difference adding a 12 stone ~ 76kg a lot. Possibly more than a 10bhp increase from a equal lenght manifold for example. So is it better to approach n/a tuning by loossing rotational mass?
I notice the difference adding a 12 stone ~ 76kg a lot. Possibly more than a 10bhp increase from a equal lenght manifold for example. So is it better to approach n/a tuning by loossing rotational mass?
I've also read this is the case but it won't be a simple x4 effect because it also depends on where on the reciprocating parts you take the weight from - it's more effective if the weight is taken from the outer reaches of the part. It should mean that a 2kg saving on the ali bells would be more effective than wheels which are 2kg lighter, for example.
I doubt you'll get 5kg off a flywheel too, unless the stock item is exceptionally heavy.
I doubt you'll get 5kg off a flywheel too, unless the stock item is exceptionally heavy.
braddo said:
I've also read this is the case but it won't be a simple x4 effect because it also depends on where on the reciprocating parts you take the weight from - it's more effective if the weight is taken from the outer reaches of the part. It should mean that a 2kg saving on the ali bells would be more effective than wheels which are 2kg lighter, for example.
I doubt you'll get 5kg off a flywheel too, unless the stock item is exceptionally heavy.
Taking weight from the outer parts, that sounds right, but that'd make light alloys more effective that alloy belled rotors. I doubt you'll get 5kg off a flywheel too, unless the stock item is exceptionally heavy.
I'm thinking about my VX220, it does have a very heavy flywheel. Thorney motorsport list the OEM item machined as a 5 kg saving.
Scuffers said:
all laudable stuff, but you have to spend a shed load to make a significant difference in wheels, and have you ever put a tyre on the scales?
I would suggest the cash is better spent on dumping heavy non-rotating stuff, and start at the highest point in the car.
I've just fitted the below, a decent saving for not much cash at all I would suggest the cash is better spent on dumping heavy non-rotating stuff, and start at the highest point in the car.
Thorne Motorsport said:
Team Dynamics Pro Race 1.2's - The front wheel has been designed with a 20mm offset to widen the front track a little and give better front end grip and also provides ample clearance for the AP brake kits. Weighing in at only 7.3kg's the front wheel saves over 3kg's in weight over standard so turn in is far better.
The rear wheel weighs just under 8kg's (a 2.8kg saving over standard) and is slightly wider (7.5) so are perfectly set up for the car. These wheels are exclusive to TMS. Available in white, black and silver from stock.
There isn't anything heavy high up in a VX is there?The rear wheel weighs just under 8kg's (a 2.8kg saving over standard) and is slightly wider (7.5) so are perfectly set up for the car. These wheels are exclusive to TMS. Available in white, black and silver from stock.
My plan for the car now is Elise parts alloy belled rotors, Lightened flywheel when its clutch change time and the Elise parts sports seats on fixed runners, alloy rad and maybe a larger alloy fuel tank as range is quite limited. Not planning on any other significant mods, I see trying to get more power out of the n/a engine as flogging a dead horse (unless you turbo or supercharge it, which I have no intention of doing).
Herman Toothrot said:
Stonie said:
Herman,
If you're going to fit a lightened flywheel... you do know that the flywheel and crankshaft need to be rebalanced as one whole unit, which basically means an engine out job ?
Stonie.
Thats not true.If you're going to fit a lightened flywheel... you do know that the flywheel and crankshaft need to be rebalanced as one whole unit, which basically means an engine out job ?
Stonie.
Gooby said:
Herman Toothrot said:
Stonie said:
Herman,
If you're going to fit a lightened flywheel... you do know that the flywheel and crankshaft need to be rebalanced as one whole unit, which basically means an engine out job ?
Stonie.
Thats not true.If you're going to fit a lightened flywheel... you do know that the flywheel and crankshaft need to be rebalanced as one whole unit, which basically means an engine out job ?
Stonie.
Your saying you need to re-balance the crank when you change the clutch? If your doing a clutch change "properly" you should skim the flywheel, reality next to no one even bothers with that.
Changing the flywheel has no effect on the crank as long as it, itself is balanced. The other end of the crank will often have a harmonic damper built into the alternator / powersteering pump pully and you can upset things by removing this for light weight solid billet pullies. The flywheel isn't present to balance the crank, the crank itself should be balanced already. The fly wheel is just present to store kinetic energy so the revs don't dive when you lift off.
A very heavy flywheel can help when an engine is poorly balanced to start with but thats it.
Edited by Herman Toothrot on Wednesday 23 September 13:35
Herman Toothrot said:
braddo said:
I've also read this is the case but it won't be a simple x4 effect because it also depends on where on the reciprocating parts you take the weight from - it's more effective if the weight is taken from the outer reaches of the part. It should mean that a 2kg saving on the ali bells would be more effective than wheels which are 2kg lighter, for example.
I doubt you'll get 5kg off a flywheel too, unless the stock item is exceptionally heavy.
Taking weight from the outer parts, that sounds right, but that'd make light alloys more effective that alloy belled rotors. I doubt you'll get 5kg off a flywheel too, unless the stock item is exceptionally heavy.
Herman Toothrot said:
Gooby said:
Herman Toothrot said:
Stonie said:
Herman,
If you're going to fit a lightened flywheel... you do know that the flywheel and crankshaft need to be rebalanced as one whole unit, which basically means an engine out job ?
Stonie.
Thats not true.If you're going to fit a lightened flywheel... you do know that the flywheel and crankshaft need to be rebalanced as one whole unit, which basically means an engine out job ?
Stonie.
Your saying you need to re-balance the crank when you change the clutch? If your doing a clutch change "properly" you should skim the flywheel, reality next to no one even bothers with that.
Changing the flywheel has no effect on the crank as long as it, itself is balanced. The other end of the crank will often have a harmonic damper built into the alternator / powersteering pump pully and you can upset things by removing this for light weight solid billet pullies. The flywheel isn't present to balance the crank, the crank itself should be balanced already. The fly wheel is just present to store kinetic energy so the revs don't dive when you lift off.
A very heavy flywheel can help when an engine is poorly balanced to start with but thats it.
Edited by Herman Toothrot on Wednesday 23 September 13:35
A harmonic damper is not designed to balance out the effect of badly balanced flywheel. It is designed to iron out sympathetic resonance induced by the con rods at certain rev ranges and stop cranks acting like a spring under load. As a side affect of the designed purpose it will reduce certain vibrations from the unbalanced flywheel / load but that is not the purpose.
Now modern cranks are so well made that the risk is minimised but in an engine that can rev as high as the 2zz? I wouldnt push my luck.
You are welcome to stick on an unbalanced flywheel - I wont.
I didn't say the harmonic damper was present to compensate for an un-balanced flywheel.
You've changed your tune anyway, a balanced flywheel now!?! Obviously the flywheels balanced. You said the crank should be removed and balanced to the flywheel which is nonsense.
You've changed your tune anyway, a balanced flywheel now!?! Obviously the flywheels balanced. You said the crank should be removed and balanced to the flywheel which is nonsense.
Edited by Herman Toothrot on Wednesday 23 September 18:51
2kg on ally belled disks
If you fit the standard AP disks which people like to do you can add weight from the standard set of disks , not remove weight.
best things to change for the most gains are the back box exhaust unit and the battery, then wheels, then take out all the speakers and head unit.
I think i saved about 100Lbs in total doing those few things thats 45kg.
If you fit the standard AP disks which people like to do you can add weight from the standard set of disks , not remove weight.
best things to change for the most gains are the back box exhaust unit and the battery, then wheels, then take out all the speakers and head unit.
I think i saved about 100Lbs in total doing those few things thats 45kg.
Edited by mrdemon on Wednesday 23 September 19:58
mrdemon said:
2kg on ally belled disks
If you fit the standard AP disks which people like to do you can add weight from the standard set of disks , not remove weight.
best things to change for the most gains are the back box exhaust unit and the battery, then wheels, then take out all the speakers and head unit.
I think i saved about 100Lbs in total doing those few things thats 45kg.
Interesting note on the AP disks, I was going on what Elise parts say about their own alloy belled rotors.If you fit the standard AP disks which people like to do you can add weight from the standard set of disks , not remove weight.
best things to change for the most gains are the back box exhaust unit and the battery, then wheels, then take out all the speakers and head unit.
I think i saved about 100Lbs in total doing those few things thats 45kg.
Edited by mrdemon on Wednesday 23 September 19:58
Exhaust back box is an interesting one, is the stock one particularly heavy?
In the n/a VX you only get 2x speakers and a head unit so probably 4kg max, better to keep the radio for when sat in traffc I think.
Herman Toothrot said:
mrdemon said:
2kg on ally belled disks
If you fit the standard AP disks which people like to do you can add weight from the standard set of disks , not remove weight.
best things to change for the most gains are the back box exhaust unit and the battery, then wheels, then take out all the speakers and head unit.
I think i saved about 100Lbs in total doing those few things thats 45kg.
Interesting note on the AP disks, I was going on what Elise parts say about their own alloy belled rotors.If you fit the standard AP disks which people like to do you can add weight from the standard set of disks , not remove weight.
best things to change for the most gains are the back box exhaust unit and the battery, then wheels, then take out all the speakers and head unit.
I think i saved about 100Lbs in total doing those few things thats 45kg.
Edited by mrdemon on Wednesday 23 September 19:58
Exhaust back box is an interesting one, is the stock one particularly heavy?
In the n/a VX you only get 2x speakers and a head unit so probably 4kg max, better to keep the radio for when sat in traffc I think.
ks again!At the risk of being the subject of Scuffers mirth.....
I didn't think (proper)balancing of the flywheel/crankshaft assembly was really neccessary unless you were thinking of running higher rpm than the stock engine was designed for?
Anyway, regarding reducing rotating mass or static weight vs minor power: I doubt the average driver on here would notice the difference. I'd put the money to another training session and some more track time: you'll get faster quicker, more cheaply and with more satisfaction.
I didn't think (proper)balancing of the flywheel/crankshaft assembly was really neccessary unless you were thinking of running higher rpm than the stock engine was designed for?
Anyway, regarding reducing rotating mass or static weight vs minor power: I doubt the average driver on here would notice the difference. I'd put the money to another training session and some more track time: you'll get faster quicker, more cheaply and with more satisfaction.
TIPPER said:
At the risk of being the subject of Scuffers mirth.....
I didn't think (proper)balancing of the flywheel/crankshaft assembly was really neccessary unless you were thinking of running higher rpm than the stock engine was designed for?
Anyway, regarding reducing rotating mass or static weight vs minor power: I doubt the average driver on here would notice the difference. I'd put the money to another training session and some more track time: you'll get faster quicker, more cheaply and with more satisfaction.
Oh un-doubted driver training is very useful. These things can be noticed though, a passenger or no passenger in a relatively low powered, low torque n/a car can make a dramatic difference, so a modest loss of weight can also be noticed.I didn't think (proper)balancing of the flywheel/crankshaft assembly was really neccessary unless you were thinking of running higher rpm than the stock engine was designed for?
Anyway, regarding reducing rotating mass or static weight vs minor power: I doubt the average driver on here would notice the difference. I'd put the money to another training session and some more track time: you'll get faster quicker, more cheaply and with more satisfaction.
The whole flywheel thing, if your building a no holds barred full on race engine then yes you could have it balanced as one unit but to suggest its necessary is just silly. Knowing the price of built engines I bet far, far more light wieght fly wheels are sold and fitted to bog standard un-opened engines and with no ill effects. I know virtually all modified MR2 turbos for example when fitting the uprated clutch you need once the boost is raised its the norm to pop in a fidanza alloy fly wheel.
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