2 Stroke Wizard Tuned Pipe Pro V4.rarl
Two stroke engines fascinate me. They are so simple and fun that I've always enjoyed tinkering with them. There are many ways to boost the power, one of which is by installing a "tuned" pipe. The way a two stroke motor works causes them to be fairly noisy and a bit inefficient. A tuned pipe has a set of cones- Divergent (meaning the cone gets bigger) and Convergent (meaning the cone gets smaller) that are built to cause "echoes" or pressure waves to reflect back, which if done properly can increase the power of the engine. Check out this link, it will make a little more sense.
2 Stroke Wizard Tuned Pipe Pro V4.rarl
As the pressure wave reflects back, it has a similar effect to turbocharging or supercharging a 4 stroke- it rams fuel and air that leaked into the pipe back into the cylinder under higher pressure, causing the motor to have more power (more fuel & air = bigger bang). That's a very loose explanation, but there you go.
This is NOT an easy quick project. It requires a lot of big, expensive tools. I'm lucky enough to have access to a shop that has everything I needed. There are alternate ways to make pipes, which I will discuss at the end of this instructable.Skills you should have: -Ability to Weld -Ability to mark & cut metal ACCURATELY -Understanding of and ability to use Shears, Brakes, and other metalworking tools -Safe work ethic -Understanding of 2 stroke engines -Ability to use expansion chamber design software (OR, be really good at math or want to build 50 different pipes (trial and error)) -lots and lots of TIMESupplies: -Cold Rolled sheet metal- I used 18 gauge -LOTS of welding rod- I used a 110v wire feed welder -Rubber stoppers for isolation mounts -Misc. nuts and bolts for mounting -Duct Tape, shop towels, and band-aids. You never know! Tools: -Safety equipment- safety glasses, ear plugs, gloves, etc. -Measuring & Marking tools- marker, scratch awl, steel rule, dividers, etc -Squaring Shears -Electric shears or aviation snips -Hammer (ball pein works great!) -Stake table with appropriate stakes -Box and Pan Brake (could just use stake table but...) -Welder (something capable of welding thin metal!) and related supplies- wire brush, clamps, gloves, helmet, safety gear, etc. -Hack saw or metal cutting Band Saw -Drill or Drill Press & drill bits -Grinder and/or fileOther Usefull Things: -2 Stroke expansion Chamber Software- I used 2 Stroke Wizard by Build and Click. Cost $20.00, came with a 4T header design program and a cone printing program that breaks large cones up to fit on 8.5x11 pages you can cut out and tape together. Great program. I tried a few free ones, but the first attempt at making a pipe from those didnt work so well... -The Book Two Stroke Performance Tuning by A. Grahm Bell (apparently, not THAT A.G. Bell...) -Someone who knows what they are doing, so you can ask questions! In my case, that was advrider.com
I'm not going to go into great detail, but you can't just build a pipe and throw it on there expecting it to work well. You have to know a lot of things about your engine- port size and location, port timing, desired application, etc. You will have to figure out all of this information. Here is a VERY basic rundown of what you need to do: Before you can start at all, you have to know your port timing. Port timing is measured in degrees. You need a degree wheel, which you can print from here: Remove the head from you engine. Remove the engine side cover over the flywheel. Set the engine at Top Dead Center (TDC)- meaning the piston is all the way to the top of the cylinder as far as it will go. Attach the Degree Wheel to the flywheel, and align it with something on the engine or use a laser like I did. it doesn't matter where the wheel is oriented, as long as whatever it is oriented with is pointing at ZERO. See Picture 1. Rotate engine slowly in the direction it runs until you see the top of one of the ports. Make a note of which port is opening and the degree at which it opens. Continue rotating, taking note of when the ports open and close. You will have to do some math to figure out the Duration- the amount of degrees each port is open- and then you are *almost* ready to plug numbers in to your software. I did my port timing on Sketchup, which allowed me to draw lines at the degrees I measured, then use the protractor tool to measure the duration. The results are shown in Picture 3, with RED being the Intake duration, YELLOW the Exhaust duration, and BLUE the transfer port duration. ***Quick side note about 2 strokes- you will notice the yellow and blue are open at the same time. Exhaust starts escaping the cylinder, then fresh fuel and air is being pushed in at the same time which also helps push the exhaust out. The problem is that some of that fresh fuel and air also escapes out with the exhaust- which is the whole point of a Tuned pipe- the pressure wave is timed so that it will push most of that fresh fuel and air BACK into the cylinder through the exhaust port while the transfer port is closed but the exhaust port is still opened. Whew. Clear as mud!? One more thing we need to measure before we can begin- Port locations and sizes. This is a little harder. There are lots of ways to do this, but I'm just going to share with you how I did it on my bike. It's, well, sorta unique... Remove the cylinder as shown in Picture 4. you can see a few of the ports we need to measure. We need to know the height from the top of the cylinder, their location to each other, and their size. Line the cylinder with aluminum foil as shown in Picture 5. Try to keep the foil as un-wrinkled as possible. Take a balloon or a laytex glove, stick it over an air hose, and set it in the cylinder. Inflate the balloon, causing it to push on the foil and indent the outline of the ports. Let the air out and take the balloon out. As you can see (barely) in Pictures 6 & 7, the ports have been imprinted on the foil. Unroll the foil, and measure the size & location of the ports. You can see my results in Pictures 8 & 9.***Another quick note on 2 strokes- you can change the dynamics and power of a 2 stroke engine a LOT just with simple porting. I didn't 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. Again, it depends on what you want the engine designed for- you can't have a high rpm road race engine that will also perform well as a lugging slow revving engine. Whew. Got all the info we need, and we're finally ready to start the design!
Mounting the pipe can be a little tricky. Two strokes in general vibrate a lot, at a high frequency. The pipe is also containing pressure waves- expanding and contracting rapidly. This can cause parts to shake and metal fatigue, so you want to be sure the muffler you've spent so much time on is well mounted with strong brackets or "Hangers" to keep the pipe from shaking, fatiguing, and eventually breaking. To help absorb some of these vibrations, I built some "isolation" mounts. These are not true isolation mounts in that the bolt goes all the way through the rubber and bolts solidly to the frame. Basically, its just a large rubber washer that will hopefully absorb some of the vibrations.Building the Isolation Mounts 1. Drill a hole through a rubber stopper- the hole needs to be big enough for the bolt and the stopper needs to be big enough for your application. See Picture 1. 2. Cut the stopper in half- it doesnt need to be that tall! See Picture 2.Building the Brackets Once you have the isolation mounts built, you can start figuring out where to place your pipe hangers. According to the books, the best way to build the hangers is to use the same metal used for the pipe, but layer it so that it's twice as thick. This way, you also have two tabs to weld to the pipe- one on each side. See Pictures 3-4. You will need to build your bracket to fit where it needs to go- take your time and lots of measurements! If you are using isolation mounts, be sure to take into consideration that it's a lot thicker so the bracket will need to be out further.Attaching the Brackets To attach the bracket to the pipe, tighten the pipe to the cylinder and make sure the pipe sits where you want it to be. Tighten the bracket to the frame. Tack the bracket on to the pipe, then remove the pipe and finish weld the bracket. See Pictures 6 & 7.If you are bending or forcing the pipe or bracket into position, things aren't going to line up well when you remove the pipe and it can put pressure on the pipe causing it to fatigue and fail. Place brackets so that no large section of the pipe is left hanging freely- again, thats inviting metal fatigue both from the engine vibrating and hitting bumps while riding. In these pictures, the entire back half of my pipe is hanging free. I plan to add another long hanger behind the brake lever, as shown in Picture 7.
Now that you think your pipe is "done, it's time to test. Ideally, you dyno'ed your bike before you did all of this work, or you at least know how much horsepower your engine makes stock. Check the fuel, oil, and whatever else is important, and fire it up! See Pictures 4 & 5. VERY important Note!- Any time you make changes to the engine, there will be a domino effect- you change one thing, other things are now no longer tuned right. As was brought to my attention by maxpower49, I forgot to mention the domino of putting on a tuned pipe. Since a tuned pipe will generally flow more air through it, the jetting in the carb needs to be changed to match. If more air flows through the engine with the same amount of gas, it will cause a lean condition which can be VERY bad for your engine! This can be fixed by installing a LARGER main jet. With a custom job like this, it's a process of trial and error that involves a lot of swapping of jets and lots of spark plugs. It's safer to guess rich (too big on the main jet) and then move smaller in little steps than it is to go larger in little steps. Here's the quick version of how to jet your engine: Make an educated guess (and guess on the rich or large size). Install the jet and a NEW spark plug. Start the engine, let it get good and warm, and then shut it off. It works best if you can actually ride it for a bit to put the engine under load. Remove the spark plug and compare to the chart in Picture 6. You want the tip of the plug to be a nice chocolate brown. White or grey or totally clean means it's TOO LEAN, you need a BIGGER jet. Oily and black means its too rich, and you need a SMALLER jet. This could probably be an entire instructable in itself. Hmmm......Testing While its running, take a moment to inspect for leaks. One problem with welding it the way I did, if I wasn't paying close attention I would miss a few pinholes. They are very easy to locate when the bike is running- the pipe is under pressure so anywhere there is a hole, smoke will jet out. Mark the holes if any and be sure to weld them up. If you have access to a dyno, run some tests! If not, there's always the "seat-of-your-pants" dyno. I measured performance by speed- my bike would top out at 50 mph in 4th gear with the stock pipe. With the first pipe I built, it would hit 50 mph in THIRD gear, but the power band was so narrow that as soon as I put it in 4th the bike could barely hold 50 mph. Once you are satisfied with the location and performance of your expansion chamber, make it look good! Not just because you spent so much time building it, but because its metal, and it WILL rust. Thoroughly clean the outside of any oil, dust, or welding debris. A wire wheel on a grinder works great! Use a HIGH HEAT paint and apply a few good coats to prevent it from rusting. I haven't quite made it to this step yet, I'm still building the rearsets, kickstand, and custom brake lever for my bike. There you go! I hope you have enjoyed this instructable on hand forming an expansion chamber. Please check back for finished pics and the seat-of-my-pants report on how the pipe works. My goal is to be done by JUNE! The pipe is done, I just have to finish up a few other odds and ends.