2 stroke porting theory

Carburetor on the engine 2stroke is life after modification ported and compression settings. Porting is a metal finishing process performed to the passageways of a twostroke cylinder and crankcases, that serves to match the surface texture, shapes and sizes of port ducts, and the timing and angle aspects of the port windows that interface with the cylinder bore. Bigger carburetors, higher compression ratios, altered port timings and expansion. Oct 04, 2011 changing the power of 2 stroke engine is really very simple when you know the basic techniques of 2 stroke engines. With my cr500, the rd200, and a set of cylinders on the way for it, and my newly acquired yz80 that needs a rebuild, i want to give porting a try, and see how it goes. The first commercial twostroke engine involving incylinder compression is attributed to. Having the mix flow to the proper areas and not to other areas contributes greatly to how much fuel is required and dictates the internal engine temperatures. Porting and polishing twostroke motorcycle engines. Our porting leads the way in performance and technology. This is from taylors book the internal combustion engine in theory and practice.

The morbidelli 125 twin road racer is a rotary valve engine. Diy moto fix website for fixing rebuilding repairing your. Im just trying to understand exactly how a 2 stroke can misfire when its getting the same quality mix every stroke. Chainsaw porting theory page 63 outdoor power equipment forum. Cylinder head porting refers to the process of modifying the intake and exhaust ports of an internal combustion engine to improve quantity of the air flow. Porting a modern 2stroke engine can improve the rideability of your machine as well as improve the power.

The piston crown opens and closes the exhaust and transfer ports. Piston port is the simplest of the designs and the most common in small two stroke engines. Unlocking the secrets of 2 stroke porting, part 2 how to trace and. Youd be doing well to find this much info about 2 stroke porting in any amount of time. Cylinder heads, as manufactured, are usually suboptimal for racing applications due to design and are made for maximum durability hence the thickness of the walls. I have had a large number of 2 stroke cylinders ported, and a fair number like 200 4 stroke cylinder heads ported generally from race cars. It was this concept which ultimately brought success to the twostroke, both as an economical power source for transport and as a powerful, lightweight power source for competition. The first 3 videos will cover simple mapping of the exhaust port and. The two stroke engine employs both the crankcase and the cylinder to achieve all the elements of the otto cycle in only two strokes of the piston.

How a 2stroke works your 2stroke motor is an air pump. He then has put his own programs together and applied to us mx 2 stroke motors. Brent at tdc 2 stroke has acquired data from from builders all over the world. After it is burned the exhaust gas exits via the exhaust port. An engines exhaust port can be thought of as a sound generator. The 2 stroke engine is a type of internal combustion engine where one power cycle is completed with two strokes of the piston during only one rotation of crankshaft. The old way, or low velocity porting if you will, followed suit with 2 valve per cylinder stuff where the mcsa was the valve seat. Schnuerle porting is a system to improve efficiency of a valveless twostroke engine by giving better scavenging.

A head can be engineered for maximum power, or for minimum fuel usage and. This led to the development of a 125 single employing a porting arrangement originally invented for twostroke diesels by german engineer dr. Diy moto fix website for fixing rebuilding repairing. This is the second of a series of videos on the topic of 2 stroke engine ports. So ill be the first to admit i know nothing about non nitro methane running 2 strokes. How twostroke expansion chambers work, and why you should care. 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. With my porting, head modifications, and pipe i am able to make 110. Changing the power of 2stroke engine is really very simple when you know the basic techniques of 2stroke engines.

A dremel is for wood working or engraving your favorite paper weight, but not for porting and polishing on a 2 stroke. This time we will learn about the second type of engine i. Cleaningup the rough edges of the port windows inside of the cylinder bore is really all you need to do to the port windows, as anything further, and youre messing with the port timing keep in mind, were out to build a little twostroke screamer, not make a boat anchor out of your cylinder. Port timing basics airgasoline enters the engine from the carburetor at a ratio close to 15. Has any one done any kind of porting or polishing to a 2 stroke cylinder themselves. 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. Jun 06, 2008 i consider myself to be a fan of 4strokes, but i have found myself with a few more 2 strokes than 4strokes. 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 only one crankshaft revolution.

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. Twostroke principles although a twostroke engine has fewer moving parts than a fourstroke engine, a twostroke is a complex engine with different phases taking place in the crankcase and in the cylinder bore at the same time. In this video i explain why a higher port not necessarily is a good. If you are aiming for these qualities, modifying your 2stroke engine is. Geared specifically for gp and kart racers, this hardcover treasure has turned out to be a great reference source for questions on the logic and concepts that pertain to tuning a 2 stroke for maximum performance. Drag port really has no meaning at all in the 4 stroke world. According your plot, the 2stroke evinrude etec 150 has less than 20% higher torque at 4,000rpm than the same capacity 4stroke f150 of yamaha.

Porting and polishing two stroke motorcycle engines. Since modifying the 2stroke engines require not only a big. Everything you need to know about the twostroke cylinder. The large majority of expensive work has been poor quality, with little attention to detail. The shape is based on different porting jobs i have looked at, and or ridden, it is actually pretty similar in shape to the stock port. This is the first of a series of videos on the topic of 2 stroke engine ports that you need to know if you are intending to modify your engine. Well i have been reminded lately that this is a dirtbike forum where i can ask questions so i figured id give it a shot. Hell take a competitors motor tune it to its best numbers on his dyno. I have over 38 years experience working with some of the best 2 stroke engineers in the world.

Thats over a 50% increase in horsepower and 11 ftlbs more torque. The port heights, widths, areas, directions they flow, and relationships to one another all have a significant influence on how the engine will behave. Eric gorr racing offers allinclusive porting packages for all types of 2 stroke and 4 stroke engines used in dirt bikes, atvs, snowmobiles, and shifter karts. This phenomenon was first discovered in the 1950s by walter kaaden, who was working at the east german company mz. I have a decent or so i think grasp on twostroke engine theory and operation, so i will not be too far behind. Best cylinder porting, engine porting, 2stroke porting, 4. The illustrated engine features a poppet intake valve. Because the duration of the porting will affect the engine rpm peaks ventury carburetor that fits should be done with caution.

This is in contrast to a fourstroke engine, which requires four strokes of the piston to complete a power cycle during two crankshaft revolutions. I know there are different porting methods for each section of the power curve of the engine. Files are great for busting out of prison or maybe a gal to do her nails, but not for professional porting of any kind. Processors with a lower number of cores will run the motax expansion chamber optimiser, as will the latest. 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. Whether youre into racing motocross or recreational dirtbikes, atv or snowsleds, for maximum performance, 2stroke cylinder porting from richs taylord porting puts the power in powersports. An excellent academic book on the theory behind performance tuning for 2 stroke motorcycles. The exhaust port opens and combustion gas starts down the pipe at supersonic speeds. This means that to run motax, you will need a post 2010 computer which is preferably a desktop, driven by an intel i7 4core processor. How twostroke expansion chambers work, and why you should. I didnt mess around with the porting yet, but a good port job combined with a tuned pipe work far better than just a tuned pipe by itself. Two stroke cylinder porting tips watch this before you. An excellent academic book on the theory behind performance tuning for 2stroke motorcycles. The way to calculate the return timing and length of the negative wave in a 2 stroke expansion chamber is by this formula.

I only have a dremel and was wondering if i could do anything at all myself to my yz125 before i put it together. 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. The internalcombustion engine in theory and practice. Eric gorr does all the porting himself and has worked with porting tools since the early 1970s and ported over 50,000 cylinders. Nov 20, 2010 some porting guys think this is dumb but really cant say why, others say its a good in theory setup. Wrt1d1x2sw where wrt1 is the wave return time for the first part of the wave, d1 is the distance from cylinder port to beginning of diffuser, and sw is the speed of the wave which is determined by the temperature and. Scavenging system redesign is more accurate, and doing so can entail complete overhauls of cylinder designs. Walbro carburetor repair, revision date 27 june 2010 page 2 figure 2. Discussion in chainsaws started by mastermind, feb 19, 2016. Ted boyko began porting cylinders 45 years ago, when the twostroke craze was at its peak, and hes still at it today. Scavenging ports optimal design of a twostroke small. Airgasoline enters the engine from the carburetor at a ratio close to 15. In my previous article, we learned how 4 stroke engines work.

Two stroke petrol engines are preferred when mechanical simplicity, light weight, and high powertoweight ratio are design priorities. Other than macdizzys site and camatv on banshee hq, nobody talks about their work. Unlocking the secrets of 2 stroke porting part 1 why do you map. Its amazing just how willing 4 stroke guys are to give out ideas. Drag port really has no meaning at all in the 4stroke world.

Eric gorr racing offers allinclusive porting packages for all types of 2stroke and 4stroke engines used in dirt bikes, atvs, snowmobiles, and shifter karts. More than all the other popular hopup shops combined. Quot you may end up with the bridge between the main port and the sub ports may crack if you open the subs wider. When tuning 2 stroke engines raising the exhaust port is common practice. The two extreme trouble symptoms were no fuel at all, or to much fuel that wetted the spark plug. For now, a net gain, however small, would be a fine starting place. Two stroke principles although a two stroke engine has fewer moving parts than a four stroke engine, a two stroke is a complex engine with different phases taking place in the crankcase and in the cylinder bore at the same time. I have worked with porting tools since the 1970s, porting countless cylinders and cases. Rating is available when the video has been rented. Heres how shaving off miniscule ammounts of metal can drastically improve your speed. A twostroke cylinder consists of exhaust, transfer, and occasionally inlet ports true inlet ports are only found on piston or rotary valve controlled engines.

Richs taylord porting offers allinclusive porting packages for all types of 2stroke engines used in dirt bikes, atvs, snowmobiles, watercraft and shifter karts. Maybe a rich mix wont burn well at all with a little exhaust mixed in, but burns very well with leftover rich mix from a failed previous. 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. We are known to use huge amounts of epoxy to redesign transfer tunnels to make power where the. Feb 27, 2015 the shape is based on different porting jobs i have looked at, and or ridden, it is actually pretty similar in shape to the stock port. We call upon twostroke genius ted boyko for the final word. Explanation of how the exhaust and transfers work together to produce the peak power rpm, and what to change to change that rpm. The cylinder pressure drops, and the fresh charge transfers thru the transfer ports, over the top of the piston, and out the. Tips on how to port a two stroke cylinder, what to donot do and how to do it right. Another quick note on 2 strokes you can change the dynamics and power of a 2 stroke engine a lot just with simple porting.

Chainsaw porting theory outdoor power equipment forum. Ive got kind of a strange twostroke theory question that i cant seem to find. The inlet portpassage delivers air into the engines crankcase, most commonly through a reed valve, on a dirt bike engine. The little high revving whiny motors im used to porting polishing and tuning, are way different than our larger displacement wood killing ones, and im out of my comfort zone. It was this concept which ultimately brought success to the two stroke, both as an economical power source for transport and as a powerful, lightweight power source for competition. Geared specifically for gp and kart racers, this hardcover treasure has turned out to be a great reference source for questions on the logic and concepts that pertain to tuning a 2stroke for maximum performance. That type still be found today, in other designs where theres not enough valve area to fully satisfy the demand of the engine, aka the block outruns the head. Not all porting is the same even the word porting has been mis used over the years. This led to the development of a 125 single employing a porting arrangement originally invented for two stroke diesels by german engineer dr. The porting arrangement of any 2 stroke engine will greatly effect all 3 of the things listed above. With the traditional lubrication technique of mixing oil into the fuel, they also have the advantage of working in any orientation, as there is no oil reservoir dependent on gravity.