2 stroke engine boost

this is translated with google translator, the original language is Spanish, it was very long to translate normally

BASIC SKILLS FOR PREPARING A CYLINDER :

ADMISSION :
Admission takes place , usually through an opening in the cylinder which is connected to the carburetor , and is called the third opening admission ; understood as 1st and 2nd opening the expulsion and transfer.
On admission to the third opening , which is the piston valve for controlling the input and the mixture into the crankcase , thus the admission duration is proportional to the height of the opening and its position in the cylinder.
With this control system , you can only perform a range of admission ; symmetrical and this is a limitation that does not allow for the best possible distribution diagram for asymmetric engine diagram , but permits the best symmetric diagram almost never matches above (with a symmetric diagram can not for example, increasing intake just a teaser , because each advance opening followed by a closing unwanted delay . This problem can only be resolved in rotary valve engines is generally the shaft or engine crankshaft , for example the typical simple scooter ) .
Another system is that the reed valve is simply one or more layers which open due to the depression created by the piston in the upward phase and closed by the effect of its elasticity when said depression stop ( idle ) and remains banging shut against its seat when the piston descending phase increases the pressure in the crankcase .
The type of material of the sheets is what promotes its elasticity and closing down its phase


CYLINDER :
To prepare an engine , you have to know what the engine can know through a very simple formula :

but there is another formula in which both the diameter and the stroke is expressed in inches

V = 0.785 . D ² . R . N where:
0.785 = a fixed number unchanged.
D = diameter of the piston in Centimeters
R = stroke in inches
N = number of cylinders
Then follow the previous example and as a centimeter is 10 mm divide by 10
D = 48 mm = 4.8 cm
C = 56 mm = 5.6 cm

THEN : V ² = 0.785 X 4.8 X 5.6 = 101.2838 C.C
IF YOU WANT TO HAVE ONE LITER LITER AS 1000 cc divide it by 1000 , I mean = 0.1012 83 liters .

One of the biggest problems is the spread of heat inside the cylinder and that 2 stroke engines have additional problems because they are warmer than other areas because as we saw above the fresh mixture cooling flows inside these areas , and is adds to the problem that the cylinder has holes inside (Willey ) with the elevated temperature can undergo twisting. To avoid this, the cylinder is provided with cooling fins for air to flow through them to cool the cylinder ( these fins should be clean , to favor the action of air ) for high engine speeds disperse more heat fins very thin and very close to each other and better low speeds and more thick fins spaced . The cooled water-cooled cylinders much better and you should pay attention to the pumping system to circulate water and cool in the radiator.
The problem that the heat produced in the metals is that dilates and some expand more than others depending on their composition. The expansion produces a lengthening and widening ( 2T engines normally run at 200 º centigrade THIS TEMPERATURE STANDARD BUT NOT ENOUGH ORIENTATIVA ) .
The expansion of a metal we know according to the following formula:

Dilation = Cet . D . T
Cet = Thermal expansion coefficient FOR EACH GRADE LINEAR metal in question
D = diameter of the sleeve in mm
T = temperature in degrees Celsius .

Example : The thermal expansion coefficient for each grade cast iron is 0.000010 .
D = 48 mm
T = 200 ° C then : Expansion = 0.000010 X 48 X 200 = 0.096 almost one hundredth of a millimeter
If the cylinder was plated aluminum would be greater dilation , dilation of chromed aluminum is about twice .

CYLINDER WEAR
Influence on wear : heat, rubbing materials and the piston speed

PISTON SPEED :
The piston speed is easily calculated using the following formula:

Vp = C . N / 30000 wherein:

Vp = velocity of the piston in m / s
C = Stroke in mm
N = number of turns of the engine R.P.M
30000 = fixed unit dependent on the units used

EXAMPLE: 58 race motor that spins at 9000 RPM then:
Vp = 58 x 9000/30000 = 522000/30000 = 17.4 m / s ( FORMULA IS GOING TO BE USEFUL FOR CARBURETION ) .

SHIRTS BY TYPES OF FRICTION MATERIAL
The cylinders , we saw that they were surrounded by a material that promotes cooling , this material is usually aluminum, for its light weight and ease of cooling.
Do construction can be three types:

Iron Shirt 1 ( cast ) aluminum body
The two parts are made separately , are prepared and placed inside the sleeve body for the body it is placed in an oil bath , higher than 200 ° approx. To dilate and embedding of the cylinder is simpler but requires the use of a press.

Casting 2nd centrifuged
It melts the aluminum body directly over the shirt .

3rd chromed aluminum cylinder
Currently is the most used is made and shirt body in a single casting and is applied through an electrolytic bath , a bath or hard chrome layer so called to distinguish it from the typical decorative chrome is bright this bathroom is like tenth least 1 thick. These cylinders are not easy to rectify , as it would give them a new electrolytic bath and that maybe we are not profitable.
THE REASON GIVEN CHROME BATH IS BECAUSE NO TWO SAME MATERIALS AS may rub ATOMIC AFFINITY FOR HIGH TEMPERATURE TEND TO "hook " ALMOST COMING TO A FOUNDRY . THEREFORE NEVER BE A PISTON SLIDE ALUMINUM ALUMINUM ON A SHIRT AS WELL AS IN A CYLINDER CHROME DO NOT USE SEGMENTS ( AROS ) CHROME AND A SHIRT ALSO CAST IRON CAST IRON RING . HERE IS WHERE IT JOINS THE STRENGTH OF THE VARIOUS MATERIALS , IF YOU HAVE CYLINDER CHROME CAST IRON AND SEGMENTS . CHROME CYLINDER IS MORE HARD SEGMENTS , THEREFORE, be spent SEGMENTS WILL BE MUCH FASTER AND MORE OFTEN THAN TO CHANGE BUT THE CYLINDER MORE HARD ON THE CONTRARY IS THE SHIRT IS CAST IRON AND CHROME RINGS , THE NEW RINGS AND CYLINDER WOULD be spent BEFORE AND WOULD be rectified , SO THE CHROME CYLINDER DURAN , IF YOU CARE , MORE THAN CONVENTIONAL CYLINDERS . ALTHOUGH HAVE CONVENTIONAL OTHER BENEFITS AS ARE THE GROUND AND IN MOST CASES, THE POWER disarm, THIS LAST DETAIL TO CONSIDER WHEN THE POWER TO MODIFY OR EVEN BUILD A SHIRT WITH A DIFFERENT DISTRIBUTION .

As transfers polish . -
We must be clear what is and what is polishing file : Polishing is to remove rough edges and file it down or removing material .
When we want to advance or delay the entry and exit of gases, ie vary the distribution of an engine , you can , as an option, enlarge the cylinder ports , both the intake and the exhaust . Transfers of transfer, are the little ones that connect the crankcase to the cylinder and whose function is to effect scavenging normally rarely enlarged, and only changed the angle so that the sweep is more or less rapid and direct, as explained in 2T engine operation .
Normally the cylinders are usually of two pieces, a shirt where the piston touches another block that is outside the cylinder lining is usually made ​​of aluminum and can carry fins, if air cooling or cavity through which the cOOLANT ( dirty water and corrodes aluminum , you can make mixtures of distilled water mixed with glycerin neutral , but not worth it , comes perhaps more expensive than the products sold ) .
The polishing is to remove all impurities or roughness remaining in the cylinder block casting to prevent soot buildup and promote fluid gases. There preparers who says it is not advisable to polish the transfer of transfer, because those ridges create a turbulence that favor the sweep , I think that's tastes and theories, I personally like polished .
To polish , you need to have a micro - motor or a mini - drill , which was installed some strawberries whose tip can be made of stone or diamond ( diamond is advised although the stone is much cheaper ) these stones the there are several coarse grain is to abrade or a refiner , as different shapes and sizes. Once reviewed and refined , is passed fine sandpaper to remove all stripes who have left the strawberries and since we are on task, if you do you can top with strawberries termination rubber , which also exist to wear and for brightening . The final result depends on the time you employ and careful you are. " If you strive much you can even comb because you reflect on the polishing so called " mirror polished " .



In these images , it can be seen as the entire duct and contouring as in the transfer of transfer, the center wall is tapered to avoid interference of the gases and the mixture
If only done polishing the ports , they should not touch the edges of the shirt through which the piston to prevent being rounded edges and snagging the segments or " rings " , it is also advisable to place a piece of cardboard attached to cylinder to prevent possible scratches in case of escape bore
As we mentioned earlier, one of the qualities of cast iron cylinder sleeve , is the possibility to disarm by operational readiness , building a new one if you already rectified to limit construction or other distribution.

The general idea with all the " preparers Beginners" is that enlarging the holes , you get more power and engine performance, this theory is partly true, and I say in part because sometimes hurts and engine performance worsens .

We must be very clear concepts of engine operation, and we know that engine performance so we can determine its size or position.
In different articles , we'll more or less , giving an explanation on the functioning of the different organs of the engine and some do an introduction to the preparation of that particular piece , but try to make a collection of modified parts in a specific section .
In the right figure we see two shirts of the same engine , the shirt of the Left , is the original shirt on the right and a shirt made and modified for better engine performance. It can be seen that what is wanted to achieve was a good sweep and trapped gas and so we chose to make a smaller transfer for the pressure and velocity of the mixture was superior and conduct a sweep and advance best to cut closing the sweep and to hold more gas quantity . These operations require a series of calculations for the operation is optimal , otherwise we run the risk of catching a lot of gas and burned and expelled , causing detonation and ignition problems .
The height can be seen or available in the cylinder are slightly different, as compared to higher PMI , that is, maintaining the opening but shortens or forward closure. ( Remember that the opening of the exhaust port as the transfers are performed when the piston is down , you can also observe the recess of settlement of the shirt is highest precisely to favor the expansion . )


HEAD . -

COMPRESSION RATIO INCREASE


The compression ratio indicates the order of magnitude that the air-fuel mixture will change in volume within the cylinder, when compressed. When the engine is running at a certain number of rpm , each time the piston descends from TDC ( Top Dead Center ) to BDC ( bottom dead center ) enters the cylinder , theoretically , both mixing volume as has the engine displacement .
At this point , the piston will start to rise from BDC to TDC , but during the climb, at 2 T engine , you find that the Exhaust Port is open for a while, while the piston not closed. During this time the mixture will escape without burning or compressed so that compression will not begin until the mixture of the exhaust port is fully closed . ( later will comment on this point)


Increasing the compression ratio achieved a power increase but be careful not to go to that there is no call laexplosión uncontrolled detonation ( see gasoline ) . for it is advisable not to move from a higher compression ratio to 12:1 in small engines.

The less cylinder engine has more supports compression ratio . This is because the effect of detonation appears more easily in larger displacement engines . There are some universal values ​​that should be reached by the maximum power that will provide hassle . These values ​​are suitable using unleaded 98 octane and you can see in the table. If the octane of gasoline is higher , you can even get to 17:1 as the famous " Dragsters "



The more compression ratio with a motor , the mixture will be more pressure when the piston is at TDC and release the piston with more force and speed.
This high pressure will cause a very rapid rise in temperature, and thus the gas molecules to flutter quickly. This upheaval cause rapid swelling of the combustion mixture producing high quality and high speed.
This is basically the reason that increasing the compression ratio we will get a higher peak power (also get more power to any number of rpm , not only in the maximum power rpm ) .
In the right chart , we can see . , Performance varies depending on the combustion compression ratio . With increasing compression ratio is improved in combustion efficiency , within certain limits .

So for example when passing from a compression ratio of 7:1 to 10:1, increasing 3 points, it shows great improvement in the power provided by the engine , yet passing from 10:1 to 13:1 , also increased 3 points, do not notice much improvement .





In these images the procedure to follow: image 1 is the piston TDC and in image 2 is filled with liquid to know the exact volume . It is clear that the way to increase the compression ratio is to reduce the volume of the chamber of the cylinder head , for this we use two methods are the lower base of the cylinder head thereby reduces the volume and the second method is fill the stock with the same material that is built the butt , usually aluminum, and then give the desired shape and volume , this method is more complicated but can be given to the dome of the head as desired to achieve a most effective sweeping .

In the images 3 shows a stock with normal dome in Image 4 a head with dome shifted also called high turbulence

How to calculate the cylinder volume when closing the exhaust.

As we mentioned above, until the Exhaust Port is not closed completely, the actual compression will not start .
The mixture volume was in the cylinder at closing of the exhaust port anger increasingly being lower due to the rise of the piston. When the piston is at TDC , the mixture will come to occupy the minimum volume : the volume of the combustion chamber in the cylinder head carved .
Measuring the compression height is easy. just need a vernier caliper , measure the height of the exhaust port , from the head of the piston when in the PMI to the top that is when closed and subtract that measurement to engine stroke .
Knowing the diameter of the motor and the compression height can calculate the compression volume using the formula used to calculate the engine with the modification that instead of using the full stroke is used as the race from the exhaust port is closed:


Rc = 64.77 + 6.82 / 6.82 / / Rc = 10.49

This means that if before we had a volume of 7.2 cylinder head and now a volume of 6.82 , we have reduced the volume of 0.38 cc .
Using the same formula that we have been using for calculating volumes but we can calculate the extent inverting planning in the butt to get the compression ratio :
HEIGHT = ( 4000 x VOLUME ) / ( 3.1416 x DIAMETER ² ) where:

VOLUME : The volume to reduce according to Example 0.38 cc
DIAMETER : The diameter of the cylinder 52 mm
HEIGHT : The distance in mm to remove the cylinder head.

Height = 4000 x 0.38 / 3.1416 x 52 ² / / A = 1520 / 84.95 / / A = 0.17 mm
This means you have to lower the top of the cylinder 0.17 mm . and obtain the 6.82 cc in volume if the cylinder head permits.

Issues to consider when increasing the compression ratio . -
As we were saying until now, the compression ratio depends on the volume trapped in the cylinder when the exhaust port is closed , so it is calculated from the time, but that's true in theory and influencing factors to enhance the trapped volume .

Can we really start to compress the fuel before the Exhaust Port is closed ?


That's fine of course not, but nevertheless when the motor rotates at high revs , the piston is moving so quickly that sends fuel so fast and less time to escape this open , because at that speed , the static volume cylinder caught is greater .


This fools that improves efficiency at higher rpm . Thus, under actual operating conditions , understanding our true relationship dynamically improves withincreasing rpm !
Rarely approaching 100 % efficiency of the engine, but with modifications to the exhaust port and a system with a " suction " adequate and well-designed shock , (either collecting or taking advantage of the sweep gas to effect complete evacuation by exhaust ) and the negative pressure created in the crankcase to push fuel through the transfer transfers ........ then we can reduce the losses of the " fill " (or pressure) before the exhaust port is closed at a certain rpm range of operation, in that case , we can even exceed 100% entrapment efficiency gas ! .
This means that for example a 125 cc engine , actually can trap more than 125 cc. fuel than the volume of the cylinder and then " compress " in much smaller volume above the piston prior to the spark .
The problem here is that this requires a suction and pressure system , synchronized with the exhaust and that occurs only in a specified range of power , when the engine accelerates outside that band power pulses in the suction and the systems download are out of phase and actually contribute to a loss in efficiency trapped .
Now knowing what actually happens when the engine is in the desired powerband , perhaps we can begin to see what is REALLY points to consider when getting a good compression ratio :

1 º . - How big is the engine. This means the volume in the cylinder with the piston at BDC ( in English is called BDC )

2nd . - What is the volume when the piston is at TDC ( TDC ) is the volume in which compressed gases trapped or what is the same, the volume of the compression chamber .

3rd . - What type of gas trapped dynamic efficiency is achieved according to the engine design . Here the range can be as low as 75% or even slightly higher than 110% on a tuned optimally .

4th . - How big are the transfers and exhaust port. Transfer the transfers of large , they tend to be less effective in filling because gases circulate with less speed and low pressure by sweeping causing trapping waste gas from the last combustion discharge expelled. Due to this as well, tend to make control of the process of combustion without detonation and / or - the ignition problems . Mainly for these reasons , you can get high compression ratios in engines with large Lumbreras without risking problems.

5th . - What is the fuel octane level will use the engine. The high octane and special fuels such as methanol have increased resistance to spontaneous combustion support " Detonation " " and can withstand higher compression ratios and can wait for the spark plug to fire them instead of" triggering " . If we use a mixture strict high octane fuel , we can raise a higher compression ratio . ( Typical compression ratios of typically 10:1 to 11.5:1 or even in some cases slightly higher . With fuel 100 octane, in the cylinders with a diameter of 70 mm can often tolerate a 13.5:1 . dragsters using a 110 octane fuel to the combustion chambers can tolerate well designed or 16:1 and 15.5 times higher. methanol in automobiles and those engines which use a mixture of methanol and nitromethane can reach 17:1)

A key issue to consider when lowering the head, is the distance between the piston and cylinder wall before you start the stock dome squish called for the piston head not trip creating a significant shredding motor. To avoid this, we must first reduce the stock, making the measure that has originally and angle.


SQUISH

A somewhat personal translation word might be " splash separation and angle ."

The word squish , is now becoming , a term quite used although some may not know exactly what is its importance in today's engines , both 2 and 4 stroke .

The squish , refers to the distance between the piston dome and the band or track that exists before the compression chamber itself. This band may be flat or have a certain angle and along with the piston , make a pushing function of trapped air toward the compression chamber . This pushing the compression chamber , allowing the compression process is faster favoring less compression work , higher compressive pressures , more work expansion , ignition coordination ... This means more power.
You should know that although the squish is beneficial, not always better , if there's much squish angle , it causes more turbulence that we can produce a severe shock causing detonation in the engine or a hole in the piston head .
To avoid these problems , we need to have a gas velocity " Meansquish ( MSV ) " with values ​​between 0-25 m / s getting good results with values ​​between 15 to 20 m / s . ( For an engine of 250 cc , the clearance between the piston and the splash band should not be less than 1mm in smaller displacement engines can be used smaller separations .
Separating the splash band is important for the gas velocity and often fall into the trap of not maintaining this separation when we lower the head to increase the compression ratio .

For this measurement , proceed as follows:
1 º . - Disarm the ignition and head
2nd . - Placed on the head of the piston 4 bits of lead solder or tin in a position opposite each other , ie 0 °, 90 ° . 180 ° and 270 ° , that sujetaremos a piston head with a little fat


3 º . - Mount the cylinder head with a new gasket and pressed with the contact pressure we're going to give ( this point is important , because if we give less pressure , we can vary the measure because later, when we give more pressure board yields and the stock is closer to the piston head ) .
4th . - We put the nut on and with a large tool to pry , turn the engine until the pieces of tin placed on the head of the piston touch the butt and we carefully with force until the piston exceeds the PMS and descend . (this must be done carefully because if we put a tin very thick, you may not have enough force to crush )
5th . - Disarm the stock and note in the position they were tins and measure . ( Usually usually have the same distance around the perimeter of the piston head , but in some cases vary the measures, so it is important to write it down )
6th . - Is measured with a micrometer tins and we observe that on one side are more flattened ( the overlap portion attached to the sleeve) and a minus side . By measuring the entire surface can know what is the exact angle with respect to the dome of the piston head ) .
7th . - This measure should be to spare the time to lower the head and only reduce the height and angle when you have made the appropriate calculations for good gas velocity ( MSV ) .

CRANKSHAFT


The crankshaft is very important in the 2 stroke because of its shape and design , we will get the necessary pressure in the crankcase for optimum performance of our engine . As already mentioned above in the " CHECK ENGINE 2 T " , space or volume not occupied by the motor organs is called " SPACE HARMFUL " so that space is intended to be minimal and to this end, gives the drive shaft of a steering wheel that make counterweights and filling to reduce that space , and the crankcase is designed to almost touch the crankshaft and that volume is minimal.
One of the changes that have the effect usually in an engine, is the lightening of its parts , as we illustrate later in the " IMPROVEMENTS " .
In the figure we see two crankshafts , one lightweight and one normal , if we decide to lighten a crank , it is clear that we have to fill the space that we have somehow lowered , so that the space Harmful, not excessive and not lose the effect crankcase pressure .

This filling can be made by filling the crankcase or crankshaft giving the caps some species . ( Will be illustrated later in the section improvements.

When we speak of a reinforced crankshaft , it does not mean fatter or thicker, but rather stronger or more resistant .
In all types of preparations , which is made to lighten parts , not only the engine but also the frame, but if lighten over , can achieve a delicate workpieces . High competition vehicles ( World Rally Championship , Formula 1 , motorcycle world ... ) use last generation materials (carbon fiber , titanium ..) materials that are expensive and used only an elite , achieving high strength and very little weight.

Cranks . -
The connecting rods are made up of three parts : foot rod ( which is the top, which houses the piston pin ) the big end (which is the lower part , which houses the crankshaft bolt ) and the rod body (linking these two parts ) . body length of rod that connects these two parts , no influence on the race, as the race gives the crank housing to the rod , which is more or less out of the center of the circumference of the crankshaft. What it does, is that the rotation is faster or slower , depending on their length.
rod that transmits only circular motion of the crankshaft and converts it into a linear (straight ) piston .
The length of the connecting rod, engine influences that is more or less rapid , but not only because I have to make travel more , but have less travel because the ports are more close to each other getting a distribution with faster sweeps .


In this illustration it can be seen the preparation of a rod from the aligeramento

oth the big end and the connecting rod are made of a metal " friction " or " BABBITT " which is usually a tin -lead alloy , and antimony with small amounts of copper and nickel metals are quite soft and need to are well prepared and LUBRICATED . Also used leaded bronze alloy ( leaded copper ) and other zinc , copper and aluminum with better mechanical strength than the conventional babbitt .
So if the babbitt is stronger than the original part , we can say that this piece is reinforced.
Keep in mind that the engines are able to withstand a given load revolutions and ultimately a brush and heat set , but the pieces do not come to the limit of their endurance , they have to ensure reliability and that margin is usually quite large , so that is where we have to build on that margin , preparing the pieces to get the most performance and of course create sufficient lubrication for the speed increase does not generate excessive heat

CARBURACION


DIFFUSER DIAMETER . -

The diameter of the diffuser is very important for the engine operation , some thought that increasing the diameter of diffuser , the engine ran faster because aspired more air and gasoline. The reasoning is logical but not entirely true , because you have to consider several factors.

The main thing is useful to know that the force of the piston corresponding to the maximum torque ' , is achieved in the diffuser there is a flow rate of at least 90 mtros / second , or what is the same, a rate of 324 Km / hour which allows vaporization and optimum combustion .

To obtain this rate , it is necessary that the diameter of the diffuser is not excessive because:

1 the amount of air flow when the piston descends aims have to be the same as that passing through the diffuser to achieve a continuous flow .

2nd the two volumes of the cylinder and the diffuser must be equal .

For that we must keep in mind that :

The volume 1 is always the product of the flow rate through the area (section)
2 The speed of passage in the diffuser is obtained by multiplying the speed of the piston by the ratio of the barrel sections and the diffuser or the squares of their respective diameters.

ie applying the formula:

Vd = Vp . D ² . / D ²

where:
Vd = speed diffuser.
Vp = piston speed .
D = diameter of the cylinder.
d = Diameter of the diffuser.
Suppose an engine with :

Diameter , D = 47 mm
Carrera C = 39.2 mm = 0.039 meters.
D = 21 mm diffuser
R.P.M , N = 11000

Calculate the speed of the cylinder ( remember that the race is placed in meters)

Vc = C. N / 30 / / 0.039 x 11000/30 = 14.3 m / s

Calculate the speed of the diffuser :

Vd = Vc . D ² / d ² / / 14.3 x 47 ² / 21 ² / / 14.3 x 2209/441 / / Vd = 31588.7 / 441 = 71.6 297052m / s

As the area of the circle is A = 3.1416 x R ²
then:
Cylinder Area = 3.14 x 23.5 ² = 1734.94454
Diffuser Area = 3.14 x 10.5 ² = 346.36059 .

As we said that the volume is the product of the velocity by the area then we have:

Cylinder volume = 14.3 x = 24809.7069 1734.94454
Volume diffuser 297052 = 71.6 x 346.36059 = 24809.7069

Then the volume of the cylinder is equal to the diffuser so we are meeting the basic requirement , the diameter is correct.

We will find the number of RPM corresponding to a speed of 90 m / s with the following formula :

N = 30.V. d ² / C.D ²

Wherein:
30 = fixed number (as measures used )
V = air optimum speed 90 m / s
D = diameter of the cylinder in mm
. diffuser d = diameter in mm
C = Piston stroke in meters.

N = 30 x 90 x 21 ² / 0.039 x 47 ² / / 2700 x 441 / 0,039 x 2209 / / N = 1.1907 million / 86.15 / / N = 13 821 RPM
It wants to tell us that when the motor runs at 13821 rpm in the carburetor are optimal flow 90 m / s

With this number of rpm we will check if the engine is running at these speeds , the speed of the diffuser corresponds to 90 m / s optimal .
cylinder speed
Vc = 0.039 x 13821/30 / / Vd = 539.019 / 30 / / Vd = 17.9673 m / s

speed diffuser
Vd = 17.96 x 2209/441 / / Vd = 39673.6 / 441 / / Vd = 89.9994 .....
Now let's do the same operation but sharing what the bore and stroke

Piston diameter D = 39.2
Piston stroke C = 47 mm = 0.047 meters
Diffuser diameter d = 21 mm
R.P.M N = 11000
then
Cylinder speed Vc = 0.047 x 11000/30 / / Vc = 17.2333 m / s
Diffuser speed Vd = 17.2333 x 1536.6 4/441 / / Vd = 60.0484 m / s

Ac = area of cylinder 16 x 3.14 384.16 / / A = 1206.8742
Diffuser area Ad = 3.1416 x 110.25 / / Ad = 346.3605

Flow rate:
Cylinder : Vc = 17.2333 x 1206.8742 / / Vc = 20798.4251
Diffuser : Vd = 60.04 84 x 346.3605 / / Vd = 20798.3938

R.P.M to find the flow of 90 m / s

N = 30 . V . d ² / c . D ² / / 2700 x 441 / 72,222 / / N = 16486.66 rpm

Roll speed check cylinder speed finding ::
Cylinder speed :
Vc = 0.047 x 16486.66 / 30 / / Vc = 25.8291 m / s
Diffuser speed :
Vd = 25.8291 x 1536.6 4/441 / / Vd = 90 m / s

CONCLUSION :

We note that the diameter of the diffuser is not a function of the displacement , but according to the VOLUMES , this is clear , as the engine displacement shown here are different since the Motor A, has a displacement of 68 cc and the B engine has a displacement of 56.72 cc .
If we apply the formula of the cylinder ( see Cylinder )

Displacement Motor A = 3.1416 . D ² . c / 4000 / / 3.14 x 47 ² x 39.2 / 4000 / / C = 68 cc
Displacement Motor B = 3.1416 . D ² . c / 4000 / / 39.2 ² x 3.14 x 47/4000 / / C = 56.72 cc

We deduce :

Piston speed
A = 14.3 m / s
B = 17.23 m / s
Revolutions per minute:
A = 13821 r.p.m.
B = 16491 r.p.m.
We clearly see influences cylinder construction ( bore and stroke ) engine performance
The smaller engine displacement is the same diameter diffuser and spins much faster at the same pass gasoline has more friction between piston and cylinder that rotates at a higher number of revolutions thus more wear and more heat produced by friction , by thus more expansion

Because the size of the carburetor will influence both the maximum power ?
To answer this we must consider two factors:

1. Fuel atomization . The faster the air flow through the carburetor , the better will be the gas atomization . On carburetors small diameter air speed is high and therefore the better the atomization of the fuel in the air

Two . Resistance to the passage . The faster the air flow through the carburetor , the greater will be the air friction with the walls . On carburetors small diameter air speed is high and therefore the air will have great difficulties circular .



As we see here two phenomena occur that are opposites. We improve atomization of gasoline with a carburetor very small, but at the same time we will be offering great resistance to the passage . We then reach a compromise. It has long been made ​​rigorous studies on this and came to the conclusion that for maximum performance , the air must flow through the carburetor at an average speed of 90 m / s . There is a graph that captures the relationship between the velocity of air through the carburetor and relative peak power will give us the engine
In the graph it is clear that the maximum power point corresponds to the above 90 m / s . If we use a larger diameter carburetor will air flowing at slower speeds and maximum power will be lower, but only slightly . Imagine a 125cc engine when air flows at 90 m / s through the carburetor , the engine provides optimum performance of 34 hp .

If the circulating air at 70 m / s , larger diameter carburetor , the maximum power of 30 hp serious offer about .
If we use a smaller diameter carburetor , air will circulate faster and maximum power will be lower , decreasing in a rather abrupt . In the above example if we did circulate the air at 140 m / s the maximum power that would offer to be about only 17 hp .
As shown in the graph and in the example , bad is a carburetor too big as one too small, but it is always better to spend a little bigger than a child. , Although it is clear that it is always best to use a carburetor to circulate the air at exactly 90 m / s , as this will achieve optimal engine performance .