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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 ports , and 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 rotation , the 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, rpm , based 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. The differing patterns and cut options diamond cut, spiral cut, and an aggressive Alumni-cut will yeild different results, and for that matter, varying the rpm of the tool rotation will have optimal results with different cut patterns.
We have several customers that find it necessary to invest in custom carbide burrs www. CC Specialty has several CNC machines and related equipment, and we still use the tools we sell for any porting and polishing, and even the detail work we do on tools and equipment around the shop.
We have several customers that do porting work, by hand, that has out performed cylinders modified by the latest and greatest CNC and CAD design machines and software. The addition of boost ports may be another consideration. Turbo and even s upercharger setups of various configurations can be very useful, however, they are often more complicated with 2 stroke tuning than with 4 stroke applications on a tangent, I did witness a 50cc turbo 2 stroke bike that would do over mph, but I digress.
Weather and humidity also play a big role because they can change air density as well. Temperature will change air density by causing an increase when the air is colder and a decrease when it warms up. Fun little side note, our race group at CC Specialty got reminded of this the hard way in jetski racing. We had a monster of a cc ported and race ready out in Texas, where this little red and yellow bullet would scream and fly faster than just about any parallel twin known, but when we brought it to Alabama for a sponsored race, it stalled every time, went back out to Texas for repairs, and BAM!
There are several terms you will need to become familiar with when you start modifying 2 stroke cylinders so please go over this link and the related pages: MacDizzy is also kind enough to provide you with some very useful engine building formulas www.
Read this article and check out the excellent illustrations. This guy knows a few things about Porting and Polishing. Follow this link and be a more informed tuner http: I have read some great advice and insight on certain forums. That being said, I have read a good deal of pure BS and poorly educated speculation as well. One of my favorite is that porting makes little difference, and to be honest, if I was worried about beating you in a race, I would tell you the same thing: I don't know that I would consider this information the indisputable truth and it is fairly specific to these particular smaller cc cylinders, but it can be a very enlightening as to observable relations in altering 2 stroke port timing, enjoy: Relation of port timing to peak RPM , and Port timing for a specific 48cc cylinder , this doesn't apply to all cylinders obviously , and Piston "ramp" modifications because some guy want to do similar mods, A very DIY way to increase compression , and Port time duration as related to a specific cylinder , and exhaust port shape related to this specific cylinder.
These two links are a great guide, and will help you and your understanding of porting and polishing. This first link will discuss terms and the 2 stroke cycle. The next link will go over some basic principles behind the goal of porting and polishing ,. I might have a slightly different approach for some of the subjects, but his explanation for porting and polishing is great! I recommend knowing what you got before you start changing it too much.
If you are unable to find a template for your project at this site, there are ways to cut out templates on CNC machines. A template can help tremendously, since what may appear to be a simple enlargement of the port, might actually involve several complex radius changes. At any rate be sure to measure twice and cut once, the aluminum is easy to take out of the cylinder, but tricky to put back in. Increasing horsepower by increasing the amount of fuel and air that your motor can move in and out is only one piece of the puzzle a very big piece, but still just part of the goal.
Take into consideration the pulses that occur in particular on the intake side during normal engine operation, often these pulses will change based on rpm. Expansion chambers on the exhaust are a big consideration!
Lubrication and cooling need to be taken into account, some of our customers use our tools too also increase the openings for the oil flow and modify the cooling systems water jackets on liquid cooled in various ways.
Even the gear ratios for the transmission will need to be considered, since the power production characteristics will be altered at this level of tune. I am not saying it is perfect but it is very handy for the DIY guy out there looking to do some 2 stroke porting www. Do it yourself DIY porting and polishing for the beginner and intermediate tuner. Here is a quick video about some of the basic tools I will use for porting and polishing youtu.
Seems alot of the stuff i read on there, some guy says all i need are some files and maybe a dremel, another says i need the stuff you sell. I'll tell you this much. Check out the Mixxer. Hi, Really enjoyed this article, thank you. Did the app ever get finished? Hey Brian, Thanks for your inspirational post. Hello guys, as it is relevant to this article I would also like to share with you my web application for learning German vocabulary. If you need help in improving your app, just message me!
Hi, recommend you http: The website is totally free. Is studying German the best way to start or are there Austrian German resources you know of? I am in the same boat as you when it comes to learning German. My in-laws on my wives side are all German and I want to be able to understand them when we visit even though they all speak pretty good English. Have you tried the old FSI language course? That is what I am currently working through. You can find different versions of it online — it is public domain — but I am using the one on http: I hope that helps and good luck!
From what website did you get all the vocabulary and everything you needed? I am learning german. I am taking german lessons at my school two times a week, I find german a really interesting language. We have practice a couple of good stuff here. Worth bookmarking with regard to returning to. I ponder what amount try out you add to produce this type of fantastic educational web page. We have become a member of the rss feed and also sit up for hunting for excess of your great posting.
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This is actually a pretty awesome article. I think another aspect to memorizing the words vs meeting your language partner is that memorizing the words is a goal that leaves the process open whereas meeting the partner is a process that is straightforward to do because you already know how to do that. A study on incentives was done in Chicago along these lines. However if you paid the students based on attendance then the attendance increased because students knew how to increase attendance and as a by-product their grades did increase.
Just like setting a board un-specific goal which we will never have a chance of hitting. Just to clarify, for me, it is very specific and clear when I say memorizing phrases and words, because I use the memorization software, Genius on the Mac recommended by Maneesh. Not only that it has a built-in space repetition system which will continuously show phrases that I input incorrectly and will remind me phrases that I am about to forget. It also shows me the score of each phrases so I know how well I am memorizing the phrases.
So my objective when memorizing phrases is to change all the score to green, which means I have to get them right for at least 5 times. Hey Brian, this is a nice way of motivating yourself! We all need a few strong reasons to start learning a new language. And German language from my personal experience is not easy at all.
However, the idea of that kind of picture with your father—in-law is intimidating!!! I am only 4 months in Germany and I am trying to learn German from scratch. It is really hard. I am having courses every day and even though I can already communicate in a certain level, I find the grammar even more complicated day by day. But now I spend many hours on a German grammar trainer that I have recently found and it might be useful for you as well as it has a wide range of exercises on German grammar and is quite effective.
You can find it on this website: You can have the trainer as an application on your phone. Anyway, thank you for sharing your experience. It is so supportive for everybody facing the same challenge.
Thanks for your support Fatima! Will have a look at the website. Thanks for the inspirational story! Thanks for all the great tips and suggestions. Ooops… Looks like you guys forgot to link to this? Boy, can I relate to this story! American husband unable to learn German in a German speaking country Austria! Cool tips, though it is really beyond me why you lived in a country for a while and refused to learn the language?!
So anyone can do this! When I finish med school I will be implementing this into my life. Indeed, world travel will be made easier. Yup I am finishing med school as well this April. Learning a language and traveling to the country makes a world of difference. So go for it guys! Anki is free and cross platform compatible. Its for Spaced Repetition practice.
You can sync your progress to their service and its awesome! Yes, Anki is great and it comes with free downloadable German vocabulary — a great add-on for language studies! Thanks for the resources! If I am spending my limited time to learn and memorize something, I want the most effective tools, I tried both and hands down Genius wins big time.
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Before you go, join the 14, other system-hackers. You'll get a free guide to building a location-independent business. I am a living proof of this, since my wife Julia and I moved to Austria almost two years ago. So now I needed to find a way to incorporate this diagnostic in my daily memorization routine: Memorizing starts at 9 min 49 sec I was fully aware that the chance of someone watching me to struggle and memorize 30 phrases was very slim, but by putting myself in this position, people expected me to do it.
Business is a team sport. And learning a language is definitely a team sport. Here is what I mean: During the 3 months in my challenge: Thanks again for the great article and hacks Reply.
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