2 stroke porting for torque

Porting and torque

Purchase the Porting Tools you need at our Online Store. You need to know what your are aiming for before you start shooting. Determining this goal up front will also help immensely in choosing the proper tools for the job at hand. Is your goal a basic level of porting and polishing? This is the minimum amount of modification I could recommend. As for achieving a full race level of portinghate to break it to you, but you will need to go a little further than just what you will find on this article.

I suggest at a minimum you invest in a nice porting and polishing kit www. Often I see this step treated like a minor detail, rushed through with little regard to method or consistency.

The key reason to chamfer a port window is to allow a smoother transition of the pistonin particular the piston ring across the port opening. This not only extends the life of this particular part, but also reduces wear and tear on the entire combustion chamber while reducing overall mechanical losses.

Below are some methods to consider: 1. Your approach should be to give every edge of the port window a consistent recess and angle. Use abrasives or other method to further smooth the corner of the chamfered bevel port opening. Remember cylinder liners are generally a much harder metal Cast iron, Nikasil, and so on than the surrounding, usually aluminum, cylinder. Use a felt buff and buffing compound to further smooth and deburr the chamfered edge. 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.

You're not putting a ramp on the edge of your port window. Dimensions I like to advise are 1mm to 1. Here are some online videos that can help you with chamfering bevel youtu. A rounded corner offers a much less abrupt angle to the piston and to air flow.

Increasing the radius at the corner of a port opening can optimize flow even if an increase in overall port size is not desired, or possible. It is also a great practice to add at least a slight radius to the upper roof and floor of certain ports, this slight curvature will also offer a less abrupt transition for the piston ring.

This usually applies to intake portsand sometimes exhaust ports, which are often bridged to reduce piston rock. The reason for this is the thinner metal of the bridge will heat faster and expand due to thermodynamics at a faster rate. This expansion can cause the bridge to bulge out into the combustion chamber and rub the bottom of the piston skirt. Very little recess is needed, about 0. The radius should begin and end approximately 1 to 2mm above and below the port.

2 stroke porting for torque

Some have limitations but they can start to show you the ideas and principles behind port modification and design. Another option is purchasing templates that have proven design, and making slight tweaks or modifications to them. The exhaust port timing, and the pipe, will determine a great deal about your cylinders performance.

In general the higher the roof, or top edge of the exhaust port window is, the higher the powerband will be in the rpm range. Typically a pressure wave return time is. If the exhaust port begins to open at 80 degrees of rotationthe wave would return exactly when needed at 10, rpm because at that point, the time it takes for the piston to move from 80 degrees to degrees is. If the exhaust port is modified to open at degrees of rotation, then the peak of the powerband would lower to around 9, rpmbased on the same timing principle.

Keep in mind that raising the roof or upper edge of the exhaust port will decrease the trapping volume of the cylinder. The earlier in the cycle that the exhaust port opens during the descent of the piston, also means the later in the rotation cycle that it closes on the up stroke. This also explains why Power Valves are great options for 2 strokes.Purchase the Porting Tools you need at our Online Store.

You need to know what your are aiming for before you start shooting. Determining this goal up front will also help immensely in choosing the proper tools for the job at hand. Is your goal a basic level of porting and polishing? This is the minimum amount of modification I could recommend. As for achieving a full race level of portinghate to break it to you, but you will need to go a little further than just what you will find on this article.

I suggest at a minimum you invest in a nice porting and polishing kit www. Often I see this step treated like a minor detail, rushed through with little regard to method or consistency.

The key reason to chamfer a port window is to allow a smoother transition of the pistonin particular the piston ring across the port opening.

2 stroke porting for torque

This not only extends the life of this particular part, but also reduces wear and tear on the entire combustion chamber while reducing overall mechanical losses. Below are some methods to consider: 1. Your approach should be to give every edge of the port window a consistent recess and angle.

Use abrasives or other method to further smooth the corner of the chamfered bevel port opening. Remember cylinder liners are generally a much harder metal Cast iron, Nikasil, and so on than the surrounding, usually aluminum, cylinder. Use a felt buff and buffing compound to further smooth and deburr the chamfered edge.

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. You're not putting a ramp on the edge of your port window. Dimensions I like to advise are 1mm to 1. Here are some online videos that can help you with chamfering bevel youtu. A rounded corner offers a much less abrupt angle to the piston and to air flow. Increasing the radius at the corner of a port opening can optimize flow even if an increase in overall port size is not desired, or possible.

It is also a great practice to add at least a slight radius to the upper roof and floor of certain ports, this slight curvature will also offer a less abrupt transition for the piston ring.

This usually applies to intake portsand sometimes exhaust ports, which are often bridged to reduce piston rock. The reason for this is the thinner metal of the bridge will heat faster and expand due to thermodynamics at a faster rate. This expansion can cause the bridge to bulge out into the combustion chamber and rub the bottom of the piston skirt. Very little recess is needed, about 0.

The radius should begin and end approximately 1 to 2mm above and below the port. Some have limitations but they can start to show you the ideas and principles behind port modification and design. Another option is purchasing templates that have proven design, and making slight tweaks or modifications to them.

The exhaust port timing, and the pipe, will determine a great deal about your cylinders performance. In general the higher the roof, or top edge of the exhaust port window is, the higher the powerband will be in the rpm range. Typically a pressure wave return time is. If the exhaust port begins to open at 80 degrees of rotationthe wave would return exactly when needed at 10, rpm because at that point, the time it takes for the piston to move from 80 degrees to degrees is.

If the exhaust port is modified to open at degrees of rotation, then the peak of the powerband would lower to around 9, rpmbased on the same timing principle. Keep in mind that raising the roof or upper edge of the exhaust port will decrease the trapping volume of the cylinder. The earlier in the cycle that the exhaust port opens during the descent of the piston, also means the later in the rotation cycle that it closes on the up stroke.

This also explains why Power Valves are great options for 2 strokes. Power valve setups can allow the exhaust port height, area, and potential volume to be varied. This will yield a much broader useful rpm range. Long shank cutters may be able to reach farther, but the shortest shank burr you can get away with will offer a greater level of control and precision.Forums New posts Search forums.

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Search Advanced search…. New posts. Search forums. Log in. JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding. Thread starter pepsifreak28 Start date Sep 11, Sep 11, I would like to start a sticky for porting I see a lot of people asking questions about porting. Okies now that you got that down we can move onto some more advanced stuff. I know lets wideing those openings a little!

Here ya go. Sep 12, Joined Apr 25, Messages Location nw indiana. Keep it at beginner level You have a good start, keep it going. There is a lot of porting info out there but it goes from beginner to more advanced to quickly for me.

When you start to port your engine the first thing to do is look inside the jug and at all the ports and see how you can improve the flow of air and fuel you should start to notice casting flaws and extra metal here and there I like to use a locksmith file set on weed eaters and small engines its easyier to get a file in then it is a dremel plus you dont take as much metal off as fast a chainsaw chain file works great too.

Joined Mar 22, Messages 4, Location iowa. Great thread guys! Have read most of this already but nice having it in one place to reference. Myself and others use carbide dremel bits for the ruff work, and various gritt sanding balls for the chamfer and cleanup. Have not yet figured out how to down size my pics or I would post what I use.

This is your post: tomtrees58 said:. Hddnis Addicted to ArboristSite. This is your post: This is your post on crystal meth: Any questions?

If you could break your posts into sentences and paragraphs it would make that information more accessible and understandable. Keep up the good work. Freehand YourPasswordIsInvalid.

I do my best but I am willing to help share knowledge the best I can if you or someone would like to rewrite it ,add to it ,redo the pictures feel free I won't be upset or mad just wanted to help explain things with porting and the do and don'ts let me know if you would like to resize the pictures or make them better sent me a private message and ill edit the post. Sep 13, Crankcase and Cylinder porting is probably the most controversial subject among Performance 2-Stroke engine builders.

The laws of physics have not changed and the mathematical formulas are readily available. The computer is one of the tools we use to compare engines and determine the changes required to improve performance.

The exhaust port designed by the computer is mapped out on a plastic template. Other cylinder mods are incorporated into the template. The template provides consistency between cylinders in one engine, and other engines. The template insures a perfectly symmetrical exhaust port. The template also provides a reference if port work needs to be matched later.

The cylinder is marked, and the cuts are made to the cylinder. The exhaust port is smoothed, sanded, then polished, and the exhaust flange matched.

2 stroke porting for torque

Port work involves matching all the mating surfaces and gaskets from the carb boot thru to the exhaust flange. Increasing the airflow thru the engine provides the most useable gains in Torque and HP.

Port work is not Black Magic!

2 stroke transfer ports information, along with porting and polishing tips

Port work IS; tedious, precision work, to perfect air flow!! We will work with your engine to achieve your goals. Then design specific engine mods for your riding, racing, and elevation. A squish test is required before the engine is disassembled. A compression test is recommended as a reference for comparison. With the engine apart, the parts can be measured, to determine the work required. Accurate and precise measurements of widths, heights, and corner radius, are required for the software inputs.

Precise inputs in the computer give reliable outputs. Crankcase Reed: Remove the reed cage and see if cylinder sleeve blocks airflow? Does the reed stopper cover the Boost Port? Needs Reed Spacer Is there a smooth transition from the reeds to the base of transfer ports? Cylinder Reed: Check for reed stopper covering Boost Port? Can the air move freely under the piston and around it to the sides?

Piston Port: Is the intake tract open and smooth for maximum flow? Consider piston speed before you decide what rpm the engine will run at. What RPM pipe s are available? Will your RPM choice require a custom built pipe Expensive?

Check the piston speed for the stroke in your engine. Some engines can be run much faster, others, are running near maximum piston speed stock. You can run faster speeds, but you risk reliability and longevity.

Changing the power of 2-stroke engine

Example 1: Polaris twin engine has a stroke of 68 mm and runs at rpm, what is the mean piston speed? Example 2: SX Yamaha triple engine has a stroke of Do you want horsepower or torque? Both, right!!Forums New posts Search forums. What's new New posts New media New media comments Latest activity. Media New media New comments Search media. Log in Register. Search titles only. Search Advanced search…. New posts. Search forums. Log in. JavaScript is disabled.

For a better experience, please enable JavaScript in your browser before proceeding. Porting and torque. Thread starter Ndigity26 Start date Jan 5, Jan 5, Ndigity26 ArboristSite Operative. After a saw is ported, they become faster but do they loose or gain torque? I wonder this because cutting fast is nice but a loss in torque would not be good, but a faster cutting speed and a gain in torque sounds pretty sweet.

I own a few saws, mostly husqvarna and one stihl and I was thinking of having it ported but then wondered would I loose torque and I guess also potential lessen the life of the saw. I know the ports well and I thats what I thinking of porting. I was quoted about Thank you once again for any and all feed back.

Joined Feb 3, Messages 6, Location east,tn. Joined Dec 23, Messages 39, Location N. Porting can take a saw both ways and also combine both if done by someone that really knows what has to be done to attain the target. There is gains to be made in either direction, its just what the customer wants and what type of use the saw will see. There has to be some tradeoff going from mundane to high performance.Changing the power of 2-stroke engine is really very simple when you know the basic techniques of 2-stroke engines.

Most of the errors is to choose a less appropriate combination of engine components so that the engine actually ran worse than standartever experienced? Since modifying the 2-stroke engines require not only a big budget in funding but also modification strategies. But the simple craftsmanship, careful, and postpone for later extreme modification could be the key performance 2-stroke engine.

Although invisible to the machine 2 is more simple than 4 stroke engines, with very few components, only the piston within the cylinder, but actually not very complex machine 2 in the calculation: The main use of motion dynamics in a gas engine to generate power. There are different phases that are very influential in the crankcase and cylinder block in at the same time, so the second machine was unable to work more efficiently just enough degree crankshaft rotation, compared with degrees of crankshaft rotation by engine 4 stroke is what caused the explosion 2-stroke engine power than the 4 stroke stung.

Secret 2-stroke engine power is the primary and secondary compression settings in the machine. This is why we often suggest the rat rider if you want to send the machine to work on all engines or motors should be packaged and gentlemen, because not enough just to modify the block or head only.

Let us examine how 2-stroke engines work in the gas dynamics:. The driving force of the piston is pressed into the crankcase gases to cause the petals open. Compression on a crutch is important to create a suction force on the reed valve, moreover assisted membrane such as V-Force reed valve with a lot of compression so that even low fresh gas mixture is able to easily enter.

At 90 degrees crankshaft angle, and the piston is in the maximum negative acceleration, exhaust ported open as a sign of the end of the business step. The hot gas will be wasted by itself out to the exhaust. Compression on a crutch began to weaken during the transfer port begins to open. The pressure in the cylinder must be reduced lower than the pressure in the crankcase with the aim that unburned gas can out of the transfer ports during the flushing.

Porting 101

Flushing begins. That is fresh out of the ported gas transfer and fused to form a cycle. The gas will move upward toward the rear cylinder and spins continue rinsing residual combustion gases from the power stroke. It is important that the rest of the combustion gases must be removed completely, to open up room for the mixture of fresh air into the combustion chamber. That is the key to making big power on a two-stroke engine. Now the fresh gas also wasted until the headers on the exhaust.

But this fresh gas will not get away with it because it has a compression pressure wave reflection from the end of the exhaust pipe design is good, to bring the package back into the fresh gas cylinder before the piston closes the port hole.

This shows how important it is 2 stroke exhaust design, calculations done to reduce the trial n error is needed. Being able to see the difference? Can make a picture of how to design a 4 stroke engine to be able to fight the 2-stroke motorcycle engine? Compression waves which bounce off the exhaust pipe carrying fresh gas back through the exhaust port now also serve as the inlet port is not it?

As the piston closes the port then the compression begins. In the crutch, the pressure becomes lower than atmospheric pressure, causing a vacuum and this will open the suction valve reed and put fresh gas into the crankcase.Portal Forums Photo Gallery.

Detune 2-stroke for more torque. Hi this is my first post. Great site and so much info and catagories! I have been searching this topic here, but not yet found a satisfactory post to my thinking.

2 stroke porting for torque

I have a trials bike Beta Rev3 that I bought with this mod done: 2x extra base gaskets and rejetted to suit. I understand that with the softened power and smoother at low throttle and not so rorty, its made it a better lower grade riders bike. The gaskets obviously lower the compression by lifting the barrel.

What I dont understand is by lifting the barrel, isnt it going to raise the exhaust port too and all other ports? How does this effect the port timing? Is the ignition timing effected? I plan to do this mod now to a vintage trials bike using an equivalent trail bike head and barrel also with a reed block spacer to soften the top end and gain a stronger mid range response engine for modern trials courses.

Am I on the money here or waisting my time? I reckon it is a worthwhile exercise and not modifing original parts to acheive this. Cheers, Roger. Re: Detune 2-stroke for more torque. I can't answer as far as how your will feel when this is done, but I can answer two of your questions.

You are correct in assuming that the port timing will be changed. It will be advanced which on a two stroke using the method you are using also has the effect of increasing the duration of the port being open.

This favors a higher top end. Your ignition timing will be unaffected. There is an argument supported by some spark plug manufactures that the position of the spark in relationship to the piston changes and takes on a characteristic of retarded timing to a small degree.

They argue the converse of that which is that a longer spark plug tip will take on a characteristic of advancing the timing. I know some people who build alocohol engines that say there is a difference, but I have not found it on a gasoline engine. I supose with some dyno time you could. The modification you speak of has not worked to produce better low end when I have used it.

I didnt use it for that purpose though. I tried an intake spacer on a YZ and it moved the powerband down slightly. I'm interested what your results will be. Thanks for the replies, I suppose my results will literally be trial and error sorry for the pun for my vintage trials bike. I plan to try one mod at a time to eliminate difference. Even to add a the dirt bike exhaust, as it will aid the power curve to that barrels porting as this is the shape of the aftermarket pipes anyway.

In trials power it behaves like an unmodded or a torqueyand that was the outcome wanted. If I remove one of the 3x base gaskets, it will behave slightly dfferent again, probably where it should be for me, but I have had no reason to change it or had to remove the top end yet. Yes Sub, it will move the power around. Sometimes what you are in effect wanting, which in your case seems clearer to me now, was a less abrupt lower end response.

I guess we did use the raised barrel for similar purposes afterall. I have used that on large two strokes KX and CR when too much low end response was not a good thing. Years back my friend had a Cotta


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