polished or rough inlet??

i now work at the aprilia shop owning the fastest rsv1000 in the country and i was told that to maximize the turbulence of the mixture before entering the engine, the rough surface(not polished) allows more turbulence/misture and hence a much more complete combustion in comparisionto a polished inlet?? Basically the difference on a dyno rreading on a vfr 400 was 3.5 bhp at 4000rpm and 8.0 at 11000 rpm?? basically he lose 8 bhp from polishing the inlet! i know the exhaust should be polished as ypu want the gas to flow out but if you port a inlet for instance on a typhoon 125 engine ,that i'm about to rebuild, after porting the inlet sho uld i leave it as rough as possible??

 

Right good question...

moisture clings to a polished surface (think beads of water clinging to a polished car bonnet)

A scenario happens in an engine especially during periods of low air velocity, called fuel drop out...this basically means the fuel can actually drop out of suspension and puddle on the port floor.

A shiny port surface will allow the fuel to cling to the port surface as a liquid, which will eventually run into the cylinder passing through the engine unburnt...

A rough ground finish to the port surface means the droplets of fuel cant puddle on the port surface, meaning they get introduced back into the air stream

 

so for better combustin and performace polished outlet and rough inlet then??

 

a rough ground surface is sufficent for maximum efficiency on inlet ports :nerd:

you can polish exhaust ports, it wont be detrimental or anything, but i always think its a waste
really, as its gonna coke up anyway...

 

It s al very interesting ,a smooth golf ball will not fly as fast as the ones with
all the dents in ,and sharks have hundreds of very small rough scales ,even
nuke powered subs have a deliberately rough paint job to reduce friction
So just because the goldfish swims round and round the bowl
does not mean that one just man might become an army?
Right back to me BEER :unsure: :unsure:

 

Lol! a pitted golf ball will fly twice as far as a smooth one.
The shark skin surface texture is actually due to denticles (named after the tooth like structure).
The phenomenon that keeps the fuel in suspention is called boundary layer seperation.
Drilling a line of holes along the trailing edge of a down-force wing on a car actually reduces drag.
There is no proper name for the back of the knee.

Much to learn you have grasshopper. :rofl:

 

learnt something new today

 

LOL (whatever that means ) no where and in no implication did i state or imply
in any shape or form or as a fact or any statment or statement of any fact that or implied
that a golf ball with dimples (or as you called them pits) doesent travel as far , and as ANY
one knows any object of the same mass useing the same force ,for it to travell or fly twice the distance MUST travel Twice as fast so there ? get out of that smart ass

 

Your physics is flawed, it`s not directly proportional but inverse square law, simply hitting an object twice as hard does not make it travel twice as far.or as fast, intial accelleration will be higher but because they both have the same mass they both have the same inertia to overcome.
To make any object of the same mass travel twice as far in a parralel plane given the same conditions of gravity/mass etc you would have to hit it four times as hard.
As you should know accelleration is a square law and not a linear progression, the falling object senario of standstill to terminal velocity of 32mps per sec dictates that an object accellerates at a non linear rate untill it reaches it`s terminal velocity and this is governed by its resistance to wind and not it`s mass, as demonstrated on the moon by Armstrong dropping two objects of wildly differing mass (a hammer and a feather)in a vacuum (no resistance) under low (1/6th the earth) and both hitting the surface at the same time.
A truck and a person will both fall at a terminal velocity of 120mph if thrown from an aircraft however the person will accellerate quicker to it`s terminal velocity of 120mph before the truck (and thus hit the ground first) because of the better aerodynamics.
It is possible to overcome this terminal speed by streamlining hence its possible for a person in free-fall to be caught by another in a dive or indeed to dive out of a plane and land in a falling car or catch a bean-bag (all been seen on tv before).
The pits or dimples on a golf ball create a boundary layer and lower its wind resistance,much like a sky diver in a tuck, no more energy expenditure would be needed to make it travel twice as far and by the way the perfect number of dimples required equally spaced around the periphery happens to be 82 (next time you find a golf ball count them) after years or research.
To overcome the resistance neccessary to make a similar shaped (no dimples) and sized object (golf ball) fly twice as far you would need to expend a force of nm/x to the power of 2 (eg 100metres equalls 30nm but 200 metres would need 30 x 30 nm (900)and not 30 x2nm (60) OR it would need a golf ball of half the surface area .If you reduce the mass then it would halve the inertia needed to get it moving from a standstill but halve the kinetic energy so but for the sake of arguement we are talking objects of the same mass.
Bottom line you need to push it four times as hard to get it to go twice as far.

And yes I am a smart arse.

 

theres a smart arse and then theres taking the sheer piss :w00t:

how many people on this forum will actually understand that? :wtf:

 

It`s not mean`t as a piss take.. Back to the original point I think.

If you cant go for shear mass of porting, eg opening the ports to the point where the mass of flow overcomes the need for finesse or simply fitting larger intake valves and higher cams (4t) or welding and grinding the transfers at the base of the barrell and case to a proportion of 150% (intake to transfer area in the cylinder (2t) then it is better to have a rough grained surface on the intakes.
On a flow bench this creates a series of small vortices that agitates the fuel/air mixture and keeps it in suspension plus makes it flow faster through the tract (sort of rolling over small ball bearings,the boundary layer, a very rough analogy but suits).
Exhaust, mirror polish, the fuel/air mixture is spent (4t) or been mixed by squish/max head velocity and has enough turbulance to keep it suspended until it forced back in just before the piston closes the port by the very efficient expansion pipe you are running

 

what a read :tup:

 

Agreed imp:

 

I peed, I mean indeed.

 

i think most people should be able to understand that he is only talking about velocity and newtons laws of motion abit of GCSE science and A level math