Piston port 2 stroke tuning pdf

As the piston finally bottoms out, the intake port is uncovered. As the 2 stroke engine animation below shows, a two stroke engine in its purest form is extremely simple in construction and operation, as it only has three primary moving parts the piston, connecting rod, and crankshaft. Pdf in a two stroke cycle engine, the piston and its piston rings slide over the cylinder wall and its cylinder ports. The port heights, widths, areas, directions they flow, and relationships to one another all have a significant influence on how the engine will behave. A twostroke, or twocycle, engine is a type of internal combustion engine which completes a power cycle with two strokes up and down movements of the piston during. If you are aiming for these qualities, modifying your 2stroke engine is a great strategy.

Two stroke moped tuning two stroke timing moped tuning. A 2stroke is different of course since there is only a finite amount of fresh mixture available in the crankcase to be transferred up into the cylinder. A highcompression piston typically delivers more punch at the cost of some topend. A man named aaen olav aaen performance had some published work about piston port 2 stroke technology and performance. However, you shouldnt just pick any business that you can find anywhere. A two stroke, or twocycle, engine is a type of internal combustion engine which completes a power cycle with two strokes up and down movements of the piston during. Chainsaws are pretty basic and need to be to be lightweight. By taking your time an going through these steps you can insure a perfect and smooth transition of the piston ring into and out of the port windows. Two stroke performance tuning a disc partially cut away and attached to the end of the crankshaft opens and closes an inlet port in the side of the crankcase. Piston port is mostly on motors that came out before case reeds, because the intake couldnt make the hard bends to line up with the crank case. Tuned adjustableexhaust pipe for use on two stroke motorcycle was designed and tested. Do you want it to be full range, still strong at low rpm or do you want it for higher power at rpm even if that means you will loose some low rpm. Direct injection two strokes wait until the piston is above the exhaust port to inject fuel so none is lost. Polaris cfi 2 pistons and how long you should let it warm up controversial how to read spark plugs ski doo rotax series iii engine problems and solutions.

Service and maintenance manual 2 stroke 50cc 1e40qmb. A two stroke cylinder consists of exhaust, transfer, and occasionally inlet ports true inlet ports are only found on piston or rotary valve controlled engines. Transfer is sometimes called bypass as this port enables the fresh fuelair mix to pass by the piston and enter the upper cylinder. The twostroke engine is a common power source for small and.

If you are aiming for these qualities, modifying your 2 stroke engine is a great strategy. Enthusiasts, tuners, mechanics, gp, drag racing, mx, enduro. The scavenging efficiency of a piston port chainsaw is around 75%. Reason coolant is drawn into the combustion chamber on the down stroke of the piston. I was reading a thread about a 2 stroke versus a 4 stroke and it occurred to me that if the porting, or timing, of a 2 stroke could be changed, that maybe its maximum torque range could be lowered to an rpm comparable to the 4 stroke, and thus swing the same prop as the 4 stroke. The morbidelli 125 twin road racer is a rotary valve engine. How to enhance a 2 stroke engines ports with piston ramps. On a four stroke, the compression ratio is increased by using a piston with a higher dome. The bottom of the piston is allowed to be machined for port timing adjustment purpose. Exhaust and main transfer timing can be entered by mouse click on graph, or typed in. I made this video long ago, but forgot to upload it. To draw the port timing diagram of given two stroke cycle petrol engine. The advantage of a rotary valve is that it enables the two stroke engines intake timing to be asymmetrical, which is not possible with piston port type engines.

The coolant is drawn into the combustion chamber on the down stroke of the piston. Twostroke waveaction engine simulation motion software. Reason main causes are general overheating, the bike. The first type of 2 cycle induction is piston port induction. You should only rely on the experience of the very best.

The port is opened or closed as the piston passes up and down the cylinder. This is the real reason non direct injection two stroke engines smoke and have poor emissions. Oct 24, 2017 10 ways to gain power in a 2 stroke engine for free. Mz250 race preparation for the financially challenged. He is in my view a good candidate for reading due to his knowledge of vintage and modern 2 stroke piston port engines. Single piston deck height measuring and its importance in head and engine design cranking compression vs. Fuel intake how twostroke engines work howstuffworks. Everything you need to know about the twostroke cylinder. When the coolant hits the piston crown the change in temperature makes the aluminium brittle and it eventually cracks. In a 2stroke, we want to maximize the retention of that finite fuel charge. The transfer port is opened when the piston is moved from tdc to bdc and.

Time area is still the standard unit for 2stroke ports since at least 1971. Bottom of inlet port location entering a value will produce inlet timing figures. Tips on how to port a two stroke cylinder, what to donot do and how to do it right. Zl 115mm 40mm stroke type a piston top end con rod needle bearing 10 x 14 x. Pistons and rods pk80 engines two stroke manual guide. Piston kpv oem factory pistons and rings are the only ones approved. Pdf improving the performance of twostroke motorcycle with. For port work, one company that will help you is 2strokeporting. Two stroke performance tuning chapter 3 porting and cylinder scavenging today, when we take a look down the cylinder of a two stroke engine, we find. Aug 04, 2017 the challenge in replacing a piston comes in choosing the proper size piston for the dimensions of the bikes cylinder. Two stroke performance tuning chapter 3 porting and cylinder scavenging today, when we take a look down the cylinder of a two stroke engine, we find its walls literally filled with ports to handle the induction, transfer and exhaust phases of gas flow through the engine.

We cant afford to waste any of it by having it escape out the exhaust port. The first thing you need to do when tuning a two stroke is to determine its characteristics. For port work, one company that will help you is 2 stroke porting. Finetuning of a two stoke engine in full power configuration. Changing the power of 2stroke engine is really very simple when you know the basic techniques of 2 stroke engines. Scavenging ports optimal design of a twostroke small. The most common mistake is to choose the wrong combination of engine components, making the engine run worse than stock. Simple twostroke cylinder porting tutorial youtube. Once the piston uncovers the side transfer and rear boost port, the arriving lowpressure vacuum pulse from the exhaust draws airfuel up into the combustion chamber. Oct 17, 2017 tips on how to port a two stroke cylinder, what to donot do and how to do it right.

The former is used to tune the cfd3d models, the latter is employed for the final assessment of. Bottom dead center bdc the bottom of the pistons stroke. Those of us who have grown up in the japanese two stroke. The crankcase ofa two stroke engine is sealed off from the rranny. It enters via the intake port as the piston rises into the crankcase and then is transferred to the combustion area via the transfer ports as the piston descends and the piston top uncovers the. Piston diagnosis a rough guide 2 stroke maintenance. The cylinder pressure drops, and the fresh charge transfers thru the transfer ports, over the top of the piston, and out the. Compare that to a high performance two stroke with around 95% scavenging efficiency and you can to begin to understand how a crappy open port cylinder can still work relatively well on a chainsaw.

Has any one done any kind of porting or polishing to a 2 stroke cylinder themselves. The first example is the pistonported bultaco matador mk4 which, like most. A 2 stroke is different of course since there is only a finite amount of fresh mixture available in the crankcase to be transferred up into the cylinder. The basicexhaust tuning mechanisms was described w ith respect to a twostroke singlecylinder engine. Basic 2 stroke tuning changing the power band of your dirt bike engine is simple when you know the basics. Apr, 2015 has any one done any kind of porting or polishing to a 2 stroke cylinder themselves. You should read about how the two stroke enigne works before you attempt this. Two stroke cylinder porting tips watch this before you start cutting. The exhaust port opens and combustion gas starts down the pipe at supersonic speeds. A pressure wave of hot expanding gasses flows down the exhaust pipe. I have the book, but its nice to have as a pdf as well and a good reference for those who dont know about it.

Although there is really no shortage of books on the subject of 2 stroke tuning and preparation, i knew that an active software programme would be able to offer so much more. Fortunately, wiseco has taken the micrometer out of the equation with the racer elite 2stroke series pistons. Calculates port heights from durations, or durations from port heights. The exhaust gases usually pass out through a conventional camoperated poppet valve. Two stroke tuners handbook 2 another mistake commonly made, sometimes even by those who have enjoyed some success in modifying two stroke engines, is to believe in a kind of mechanistic magic. Pdf engine performance is strongly dependent on gas dynamic phenomena in intake. The piston port type engines intake timing opens and closes before and after top dead center at the same crank angle, making it symmetrical, whereas the rotary valve allows the. Dynomatontwostroke is a dosbased simulation that was originally released in the mid1990s. A twostroke cylinder consists of exhaust, transfer, and occasionally inlet ports true inlet ports are only found on piston or rotary valve controlled engines.

However, the two stroke cycle can be difficult for some to visualize at first because certain phases of the cycle occur simultaneously, causing it to be. In a 2 stroke, we want to maximize the retention of that finite fuel charge. Piston ring projection and catching in cylinder ports of two stroke. Bigger carburetors, higher compression ratios, altered port. Two stroke tuners handbook 2 another mistake commonly made, sometimes even by those who have enjoyed some success in modifying twostroke engines, is to believe in a kind of mechanistic magic. It allows simulation of engines with reedvalve, rotaryvalve and piston port timed induction systems. A myriad of different aftermarket accessories is available for you to custom tune your bike to better suit your needs. Bottom dead center bdc the bottom of the piston s stroke. Many people talk about a port area as a target value and indirect refers to a header area with an area factor for the port.

Two stroke cylinder porting tips watch this before you. Thank you for your interest in dynomationtwostroke designed for windows98xp. Loop scavenging scavenging is the process of purging the combustion chamber of burnt gasses. This illustration shows the rings with a 120degree gap. Port timing basics airgasoline enters the engine from the carburetor at a ratio close to 15.

It enters via the intake port as the piston rises into the crankcase and then is transferred to the combustion area via the transfer ports as the piston descends and the piston top uncovers the port opening to the cylinder. Enables all transfer port heights to be calculated automatically by just entering exhaust timing. In a 2 stroke the piston and exhaust port do the job of the exhaust valve, thats why 2 strokes are so prone to piston burning and seizing where 4 strokes are prone to burning exhaust valves. Pdf piston ring projection and catching in cylinder. There are many ways to boost the power, one of which is by installing a tuned pipe. Jan 28, 2015 many modern reedvalve 2strokes have a rear boost port running up from the intake port to the same height as the transfers. The advantage of a rotary valve is that it enables the twostroke engines intake timing to be asymmetrical, which is not possible with piston port type engines.

Symptom the piston crown is chipped along the top ring groove. The inlet port opens 30 after bdc and closes 79 after tdc. Developed by pedro, with more than 20 000 lines of code, all the knowhow applied to software comes from us and also a lot from the legendary portuguese 2 stroke tuner lufo racing, this software is directed for all 2 stroke. I only have a dremel and was wondering if i could do anything at all myself to my yz125 before i put it together. What is the use of transfer ports in a twostroke engine.

In other words, the ring gaps should not be on the side of the piston thrust as it rides the cylinder. Most of the errors is to choose a less appropriate combination of engine components so that the engine actually ran worse than standart, ever experienced. The piston continues its downward travel and the remaining charge in the crankcase is transferred at low velocity into the cylinder via the. Transfer port enhancement with piston ramp on page 117 of two stroke tuners handbook gordon jennings wrote how one could grind transfer and exhaust port ramps into the piston crown to test porting ideas without grinding on the more expensive cylinder. Port timing diagram of two stroke cycle pertrol engine ex. Contents chapter 1 introduction 9 chapter 2 the cylinder. Chordal width the effective width of a port, measured from the straightest point between sides. When the coolant hits the piston crown it makes the aluminium brittle and it eventually cracks. The basic principle of the tuned pipe is making use of the moving air masses in the exhaust to assist in the scavenging the process whereby the exhaust gases are removed and replaced with unburnt mixture of a 2 stroke engine. Bigger carburetors, higher compression ratios, altered port timings and expansion. Each intake port can be locked to a fixed timing relation with the exhaust port. That approach is a completely waist since port area dont give any information about port shape. It will simulate one of the cylinders of a multicylinder twostroke engine provided that the cylinders are identical in layout and dimensions and each cylinder has a seperate exhaust and induction system.

The ceramicmetalic compound protects the piston in 2 ways. Most knowledgeable people i have spoken with recommend a180degree gap with the ring gaps being perpendicular to the wrist pin. The only problem is finding his books due to them being discontinued and published only for a short period. He really talking abour a mixwre of fuel and oil if yoll rjchen rhe premix ratio 20. The piston s movement has pressurized the mixture in the crankcase, so it rushes into the cylinder, displacing the remaining exhaust gases and filling the cylinder with a fresh charge of fuel, as shown here.

There are three ports are present in the two stroke cycle engine. It requires values for stroke, piston height, conrod length, and wrist pin offset. They are so simple and fun that ive always enjoyed tinkering with them. The piston crown opens and closes the exhaust and transfer ports. The way a two stroke motor works causes them to be f. One side of the crankshaft uses a dry seal and the orher a wer seal. Assign fixed relationships between transfers and exhaust port. Airgasoline enters the engine from the carburetor at a ratio close to 15.

Implementation of an exhaust system for an opposed piston two. Detonation leaves many telltale signs for which the twostroke tuner should have. The mold number and the name of piston will be cast on the inside skirt surface. Piston port is the most simple design and has the carburetor located on the. Since modifying the 2 stroke engines require not only a big.