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bottom end lighten an balence?
- Thread starter dunlop
- Start date
M
mini-valver
Makes it more stable and responsive when you're using some RPM, so it doesn't shake itself to bits. If I had my bottom end out, I'd definately do it.
M
mini-valver
They are yeah but if you're upping the rev limiter (Guess you have with the package the car is running) and you have the BE out anyway, I'd do it. I'd rather know I built the engine back as best it could be, afterall £70 isn't a massive amount of money!
ClioSport 172 Cup
Who quoted you £70!!?? This is usually a very expensive technical job. :/
Sam
Sam
The crank doesnt rotate in the oil though...
yes you get a mist build up, which can cause drag on the crank, but this is largely unaffected by aerodynamics. This is what the windage try is for.
Knife edging the leading edge of a crank is utter BS. The most aerodynamic shape for a body moving through a fluid (liquid or gas) is a tear-drop. The most effective shape for reducing trail drag is a knife edge.
So the most effective thing you could is round off the leading edge, and knife edge the TRAILING edge. This would make it aerodynamically ideal.
Whether you will see a gain or not is another story, let alone one which leads to a measurable power increase.
Same with dynamic balancing...
Why would an imbalance of a couple of GRAMS be relevant to an opposing combustion force which is in the order of TON's? Besides that, the effects intake manifold variations have on combustion will have a far more dramatic effect on balancing.....again combustion forces are in the order of tons, when balancing a crank you remove just grams. Same idea with coolant paths.....each cylinder is a different temparature, therefore has a different efficiency, and marginally different BMEP.
Its a "nice" thing to do while the engine is apart, but thats about it....
yes you get a mist build up, which can cause drag on the crank, but this is largely unaffected by aerodynamics. This is what the windage try is for.
Knife edging the leading edge of a crank is utter BS. The most aerodynamic shape for a body moving through a fluid (liquid or gas) is a tear-drop. The most effective shape for reducing trail drag is a knife edge.
So the most effective thing you could is round off the leading edge, and knife edge the TRAILING edge. This would make it aerodynamically ideal.
Whether you will see a gain or not is another story, let alone one which leads to a measurable power increase.
Same with dynamic balancing...
Why would an imbalance of a couple of GRAMS be relevant to an opposing combustion force which is in the order of TON's? Besides that, the effects intake manifold variations have on combustion will have a far more dramatic effect on balancing.....again combustion forces are in the order of tons, when balancing a crank you remove just grams. Same idea with coolant paths.....each cylinder is a different temparature, therefore has a different efficiency, and marginally different BMEP.
Its a "nice" thing to do while the engine is apart, but thats about it....
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ValverInBits
personally schooled!
Are you talking about crank balancing in your second paragraph? Obviously the force transmitted down the rods is going to be vast but if the crank is out of balance then the centripetal force would cause a "wobble" at higher RPM. Surely a better balanced crank can endure higher RPM?
I can see why a slightly unbalanced fly/clutch would have no detrimental effects to performance or NVH.
Are you talking about crank balancing in your second paragraph? Obviously the force transmitted down the rods is going to be vast but if the crank is out of balance then the centripetal force would cause a "wobble" at higher RPM. Surely a better balanced crank can endure higher RPM?
I can see why a slightly unbalanced fly/clutch would have no detrimental effects to performance or NVH.
M
mini-valver
If you're regrinding the crankc, using rods from another engine etc I'd have it all balanced.
Inbox emptied ben
as said its a nice thing to have done whilst apart, for the sake of nicness lol.
But thats about it.
many places recomend it, that doesnt mean alot though. have they any empirical proof (places that recomend it, im not talking about just GDI for example) that there is any reduction in NVH?
Dont get me wrong, its a service I offer aswell, but I always explain the theory behind why something works or doesnt work.
Ive built quite a few high revving engines, some balanced, some not....you cant FEEL any difference whatsoever.
And whilst i understand what im saying is going against the grain of "tradition", ive yet to see a sound explanation or any form of data prooving otherwise...
as said its a nice thing to have done whilst apart, for the sake of nicness lol.
But thats about it.
many places recomend it, that doesnt mean alot though. have they any empirical proof (places that recomend it, im not talking about just GDI for example) that there is any reduction in NVH?
Dont get me wrong, its a service I offer aswell, but I always explain the theory behind why something works or doesnt work.
Ive built quite a few high revving engines, some balanced, some not....you cant FEEL any difference whatsoever.
And whilst i understand what im saying is going against the grain of "tradition", ive yet to see a sound explanation or any form of data prooving otherwise...
M
mini-valver
Good post ^^
edit Brake lol not Break
rps13
Lightening and balancing a crank is appropriate for an engine enduring sustained high RPM,
race engines revolving at 10,000 rpm for example
at these speeds function of spark plugs, valvetrain etc are significantly impeded by the huge amount of vibration and and those few grams could save you from needing a new head after every lap.
dont do it!
BMEP- power/pressure after restrictions ( negative affects of heat, friction etc)
NVH- noise, vibrations, harshness
you should be familiar with NVH owning a clio!
race engines revolving at 10,000 rpm for example
at these speeds function of spark plugs, valvetrain etc are significantly impeded by the huge amount of vibration and and those few grams could save you from needing a new head after every lap.
dont do it!
BMEP- power/pressure after restrictions ( negative affects of heat, friction etc)
NVH- noise, vibrations, harshness
you should be familiar with NVH owning a clio!
ITB'd MK1
yes, we do. Various benefits in my opinion and experience, engine will run smoother, I've seen it many times. Less energy is wasted as vibration so ultimately transmitted to the wheels. Better bearing reliability (more noticable on engines prone to bearing wear/failure)
The engineers we use have this balancer http://www.cwtindustries.com/ I was their first customer to make use of it when it was brand new, I even helped unpack it
they're very proud of it.There's some videos in that link that give you an insight into what's involved with engine balancing
lol..was gunna say the exact same thing...does it pass thru the oil??? is there any meat on it to knife edge???
reading the rest of the thread after i posted lol....guess the crank isnt cuttin thru the oil
would also be worthwhile weighing the componants beforehand, some will obviously be closer to the set manufacturers tolerances than others, and a lighter version of what you already have would be taking very minimal weight off. i.e. my std williams fly with bolts weighed in at 5.2 kgs. after enquiring at several co.s the weight they take it down to was 5kg.....hmmm......worth it??? i think not.
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In my experience balancing makes a huge difference to the engine.
and you CAN feel it
a balanced engine will rev smoother and freer at higher revs than a std one...
having been on the dyno for many hours, i have found a balanced engine much smoother and more comfortable at high rpm than a std non balanced item..
std F4R engines dont like being above 6500 rpm, they become rough and feel uncomfortable, a balanced engine will wont feel this way...
for a high power high revving engine i would ALWAYS recomend balancing..
knife edging however..... never seen the gains from this.... its expensive and essentially pointless.
totally agree with stan on the shape however.... the teardrop is a very aerodynamic shape.... look at those silly helmets the speed cyclists wear...
and you CAN feel it
a balanced engine will rev smoother and freer at higher revs than a std one...
having been on the dyno for many hours, i have found a balanced engine much smoother and more comfortable at high rpm than a std non balanced item..
std F4R engines dont like being above 6500 rpm, they become rough and feel uncomfortable, a balanced engine will wont feel this way...
for a high power high revving engine i would ALWAYS recomend balancing..
knife edging however..... never seen the gains from this.... its expensive and essentially pointless.
totally agree with stan on the shape however.... the teardrop is a very aerodynamic shape.... look at those silly helmets the speed cyclists wear...
ITB'd MK1
It's not really something you do on it's own. Our "built" engines are balanced, and it's calculated into the price.
ITB'd MK1
yes
It's not really something you do on it's own. Our "built" engines are balanced, and it's calculated into the price.
i would like to get 428 cat cams into my car next year
was wandering how much on top if you can balance then engine also?
personally "we" dont balance anything... although I have been known to balance a broom on my nose..
our engineers do that for us.... and as dan says yes, and they are bloody good at it.
In an ideal world, where rods dont stretch, pistons dont rock at tdc, cranks dont flex or twist, then maybe.
As it stands all of the obove occurs.
And this isnt taking into account any of the variables ive listed above (cylinder pressure related).
But hey, every one has their understandings of engine dynamics, and their preferences on what works...
As it stands all of the obove occurs.
And this isnt taking into account any of the variables ive listed above (cylinder pressure related).
But hey, every one has their understandings of engine dynamics, and their preferences on what works...
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