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Old 11-24-2007, 07:39 PM   #1 (permalink)

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Default Two stroke 2 in to 1 pipes.

Does anyone understand how a 2 in two 1 two stroke pipe works as oppose to Using 2 seperate pipes.
Is it just a case of twice the size (or volume) and how does the back pressure from one cylinder work with the other cylinder??? Is the stinger twice the size??? could you use a 3 in to 1 on a triple???
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Old 11-25-2007, 07:45 AM   #2 (permalink)

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Default Re: Two stroke 2 in to 1 pipes.

I for one do not understand, but when I was building my first pipes, Crank Shop (pipe builder) advised me to go with a twin pipe kit, as it's not as tricky as getting a Y pipe to work properly. *I guess the pluseating action of the 2-stroke is critical in the first 12-15 inches of the pipe, and each cylinder needs backpressure and sonic return. *I tried the twins kit and they worked better than my first 3 singles but on the 4th try I got a single to work pretty good and it take up much less room than a twin, (was building for a Turbo). *
On my single I used the stock Y pipe and modified it slightly, keeping the length. *In the snowmobile world the rage now is aftermarket Y pipes. *Last year they started showing up in Arctic Cat 1000 engines because for the CC's they were lacking power. *With the slightly longer and straighter Y pipe they were able to get somthing like 10 hp. on that engine. *Now you can buy a Y pipe for most any twin and get more HP, I just swapped one on a Rev 800R.

Just about all the manufactures of snowmobile engines made triples with a 3 to 1 manifold. *No telling how that works.

The size of the Y pipe diameter, even on the aftermarket Y pipe is the same as the twins. *The difference is in the expansion chamber. *The single expansion chamber is not twice the size as one of the twins but is larger.

Lee, I thought you were using the stock Y pipe and stock pipe on your Pilot? *Is it not working out? *Because with Skidoo they make a very good stock pipe. *

Wayne
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Old 11-25-2007, 08:02 AM   #3 (permalink)

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Default Re: Two stroke 2 in to 1 pipes.

Lee,
I just went back and read your question on exhaust size. *I can measure the stock pipe if you want. *Do not go bigger on the stinger end this will reduce pressure and lose hp. *High altitude twin pipes have samller stinger size than stock pipes and they make more hp at altitude.

K-fab did a great job of answering your loud problem. *I too wrap my pipe with header wrap then paint the wrap with Barb-a-que paint. *This will do two things, take the high pitch noise from the expansion chamber and muffle it, but also keep heat in to help excavenge gasses.

I run my pipe wraped and with a MBRP can and it's loud but not too bad. *Not sure on the decible level as we don't test here in Alaska, but I can't ride it in my neighborhood.

I''ll try and attached a You Tube video, maybe you can get a sence of the sound.



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Old 11-25-2007, 08:40 AM   #4 (permalink)

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Default Re: Two stroke 2 in to 1 pipes.

Dam!!!! thats what i want. Only thing i remember from the old dirt bike days is keep the head pipe the same and make a larger cone section ,which will return a more powerful wave/ pulse which you will need when you feed two or three cylinders into one cone section. If your going to do your own pipes you need to read up on the latest theory, or copy one that you know works well.
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Old 11-25-2007, 10:22 AM   #5 (permalink)

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Default Re: Two stroke 2 in to 1 pipes.

Hi, Akpilot, I am using stock Y pipe but not stock skidoo pipe, My pipe came with the engine from when it was used in a hovercraft with a silencer that looks like a race can from a superbike.
I have bought a stock silencer from a skidoo from the USA about three and a half weeks ago but it has not arrived yet, I was going to fit that on to my pipe and see how much quieter it is and then lag the pipe.
If you get chance to measure the "stinger" (As I understand it that is the smallest diameter throughout the exhaust pipe) on a 800 skidoo that would help me thanks.
There is a guy a few miles from me named bob clews who has a small company called motivation (or motiv)who is big in to two stroke tuning and gets big horsepower from mainly gearbox karts and makes his own pipes, I asked him about a 2 in to 1 but he said he did not know how it worked because he never tried, seperate pipes are best for maximum power.
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Old 11-26-2007, 08:32 PM   #6 (permalink)

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Default Re: Two stroke 2 in to 1 pipes.

Lee,
I enclosed a picture of my pipe I built. *CPI (Custom Pipes Inc.) wanted measurements of what my expansion chamber circumferance every 5 inches to get a feel for what my pipe was doing, they were helping me try to get lag out of the turbo I tired. *
When I was building the pipe I measured every inch and took a circumferance of the pipe and tried to make it exactly the same as the stock. *Polaris and most snowmobiles use long sweeping bends, but the F-series from Arctic cat use a laydown style engine and thus use tight bends for their pipes. *On this pipe the first 15" is actually an F-7 pipe cut and squeezed down to match the polaris pipe as best as I could. *If I were to do it again I would try the larger diameter of the F-7 pipe at the tight bends, maybe I could get better results.

Later today I'll measure up my 04 Skidoo 800 pipe and post here. I'm at work now.

Wayne
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Old 11-26-2007, 10:37 PM   #7 (permalink)

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Default Re: Two stroke 2 in to 1 pipes.

You are using a turbo on a two stroke? How would that help, since the exhaust stroke is open later than the intake? Are you trying to pressurize the pipe also?
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Old 11-27-2007, 12:12 AM   #8 (permalink)

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Default Re: Two stroke 2 in to 1 pipes.

Turbo's have been used on 2 strokes for a long time. *The first time I heard of using a turbo is in 1997. *The turbos work great on a 2-stroke because of the exhaust back pressure that is normal with a turbo. *The back pressure that turns the trubine also keeps the intake charge in the combustion chamber. *Now with a super-charger it does not work well at all. *A few have tried but you have to reduce the stinger size of the pipe so small as to not blow all the boost out the pipe that it negates the benefit of the supercharger.
The turbo made huge amounts of HP, approx 220 @ 10#, too much for the pilot it would just stand on end when the boost came on. * What was really bad about it is the trubo lag. *The companies I was dealing with kept telling me that it was in the Billy-bob pipe I had made to fit the Pilot and just put on a stock pipe. *Well I made pipe after pipe and finally decited to put in a E.V. 800 with the last single pipe and so far it is much better. *Not as much power, but good throttle response.
Right now the turbo is on a sled that I'll be playing with this winter - if old man winter ever comes. *46 degrees in Anchorage alaska?
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Old 11-27-2007, 01:07 AM   #9 (permalink)

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Default Re: Two stroke 2 in to 1 pipes.

nice pillot man. create an thread and give us a lowndown on that bad mamajama
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Old 11-27-2007, 01:35 AM   #10 (permalink)

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Default Re: Two stroke 2 in to 1 pipes.

I am sure to get some flack about this but thats fine. Its not the backpressure you are trying to create. Its the pulsewave. Wether two stroke or fourstroke if you had a perfect exhaust for your engine it would bounce the percussion wave off the atmosphere at the end of the pipe and then back off the valve (four stroke) or piston wall (two stroke) as the wave does this and leaves the motor again it trys to create a suction that helps to draw the exhaust out. Then the next wave (in a perfect world in a perfect engine) would stop the fresh charge before it can be taken out of the motors cylinder.
A two into one setup may be able to use the other cylinders pulse to draw out of the first cylinder. This as stated above is a midrange thing and top end power is a separate pipes world. If backpressure was a power thing would top fuel dragsters have a backpressure setup or the little pipes that have a very carefulley measured length and diameter to make the pulse smack that valve at max RPM? Most people (myself included. I used to think this was true till I was shown) think that loud is faster. But some have had machines gain power with an exhaust and can only assume its backpressure. If thats the case porting would be nothing as the exhaust with backpressure slows down the enitre flow range thru a motor. Its why true pipe building is called tuning. The pipes have to be tuned to the cam (fourstoke) or porting (twostroke) to encourage breathing for power. Restricting flow is not good for power. The reason two stoke pipes tend to narrow down at the stinger end is to increase the speed of the tuning pluse to smack it off the atmosphere HARD for a better wave return pulse (This is why open stingers on a high end two stroke feel like needles being jammed into your eardrums. The HARD hit against the atmosphere.) The larger sections of pipe are to time (slow down) the pulse to hit the piston wall at the perfect time to bounce there to make power. Thus the two stroke term "On the pipe" is when the porting and the pipe start hitting this together and you know what a good two stroke on the pipe does. *High end (rpm) porting on a motor with midrange (rpm) pipes may have backressure but the pulse will be off and the motor will not be at its potential. Its why top engine builders offer the porting and pipe for the RPM range you will be riding at. *

Turbos simply increase pressure in. Thus more out (and the more out the more the turbo gets to its primary impeller and can increase the "IN"). As they do not tap the crank HP they are assumed to be free HP but they do take power to use. (If you think they do not look at a turbo pressure gauge and then show me where you can get ANY machine anywhere that will make that pressure for free!!!!) Superchargers can and do work on two strokes but they press more in with less restriction out so you do tend to make a "Sloppy engine" that lets fuel into the exhaust. But still makes power. As the superchargers are more of an intake only thing to many builders have just used "regular" two stroke pipes and they allow fuel to get thru the cylinder unburned as they are not tuned for the extra pressure the supercharger induces. Scince a turbo requires a complete redo of the whole intake/exhaust the system gets tuned for power. Otherwise why bother with the turbo. *That said there are good turbo setups and bad ones. Even a bad one will work as thats its nature but the good ones are very strong. * Bill
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