I started this pipe building thread once before and didn't get much response.

This is what I think:
1) Everyone thinks that there is some black art involved and that the secret needs to be passed down thru channels.
2) The people that want to try it are scared off by everyone telling them how hard it is.

Well...I don't think that there is any black art involved. Art, yes, black art, no!

The info is out there. Several things factor into the making of pipes. It is said that the pipes must be built to the engine. Not true. You can alter a set of stock pipes to work with a modified engine, or alter a set of mod pipes to work with a stock engine.

There are several software programs available, some free, to do the calculations for you. Or you can do the calculations yourself. I prefer to use software. That's why it's here, right?

Granted, using software to design the pipes doesn't mean that they will be right on the money when you are done. The dyno still comes very much into play when the pipes are ready to try. But only slight adjustments should be necessary if you've done your homework.

I'm looking for any and all input that you may have on this. I am doing my homework and hoping to try my hand at it before winter. (key word being 'hoping' since I have a 'more than full time job') I'll pass on all lessons learned in the process.

idooski I for one am interested in a thread discussing pipe design and application. I was watching the progress of the other thread but it seemed to peter out too soon. I have a personal interest in pipe design as I participate in vintage class racing in my area where older performance items were more BS than fact. Right now I'm restoring a 1989 F Plus LT. I have been able to wake it up by installing larger carbs, Pipe / Muffler from a newer F Plus with a 617cc mill. Everyone I spoke to said the larger system would hamper the performance. As you probably already Know the '89 521cc motor was detuned so the introduction of the Mach 587 would not suffer. The earlier 521cc (type 537) was quite a rocket for its time. I have the 521cc (type 536) engine apart right now for an inspection and I have found it to be in great shape inside. Last year, when I purchased it for my son we upfitted 40mm Miks(correctly set up), installed a 507 valve (from an earlier Bombardier racing bulletin) and set up the primary to '88 specs. Although I don't have dyno results , the stop watch & radar readings are very positive. Where I have gained the most satisfying improvements with varying the length of the stinger (exit pipe) by inserting a smaller pipe into the stock 617s pipe's outlet through to the center of the expansion chamber and measuring the results using an infrared temperature gauge and performance results as mentioned above. Now that I have the motor apart, I'm going to bore out the rotary valve plate to 43mm and improve the tunnel porting in the cases. Any thoughts / opinions?

I'm definitely no expert on pipe building, but I have been reading a lot lately and talking to a lot of people. I do know that you need to get your engine pretty much where you want it before you get too serious about pipes. Working with the stinger like you are, you are basically working with restrictions. If it seems to work better with more restriction, it may be that you're not getting enough heat in the pipe or it needs to be wrapped. By having the stinger/restrictor sticking into the fat part of the pipe, you are effectively sending 2 different signals back to the exhaust port. The first when the positive signal hits the end of the restrictor and the second when it reaches the convergent cone. The second pulse is the stronger and the one you are most concerned with.

I'm hoping for help on this as much as you are. I'm still learning and I'll post as I get things sorted out.

idooski, thanks for the feedback I agree that getting the most out of the motor before piping is the best approach. This is a joint venture between myself and my teenaged son. It's good to share common interests this way. I am presently working on barter deal for some track dyno time in the fall to substantuate my work. My plate is full as summer is prime boating time and the weather here isn't co-operating as yet. Mercs love cold air too !

I completely understand all of that. I have a grown daughter and a 20' bass boat with a big block 225 merc. Yeah, buddy! She likes the cold water.

Don't forget to check back and keep us posted on your progress.

Keith

A good source of pipe info is Olav Aaen. He can steer you guys in the right direction. He also might be able to sell you parts/pieces to do your own set. He also has the data on all of the older sleds as he built pipes for them over the years. I too agree ayour own pipes could be fun. They are not THAT critical. The engine will run, it may not have all of the power it is capable of, but it will run ok. So, knowing that, what is the harm in trying? Just always keep your motor on the rich side and the pipe building should provide many hours of fun. That is exactly how many small buisnesses get started. You end up finding that you can do something "better" then what is currently out there. Reminds me of a company I know of........ seriously though, go for it and have fun!

Thanks Fast Mach Z! Do you have a # for Olav or does he have a web site. If you do, go ahead and post it for everyone.

Thanks,

Keith

Books by Bell, Blair, Robinson, Jennings are also good reads. Most the software is based on theory from these old books, Bell and Blair mostly. The "black art" you mention still exists IMO. I can build a pipe using bell based software, using the same inputs make one with blair formulas. End up with two differing performing pipes. Could prototype a straight coned dyno pipe that I'm happy with, then by the the time I bend it around to package it in a chassis, or clear the pipe next to it, the tuning changes. Another factor in the pipe software, and the porting software IMO, is that it based on theories that were bike based, usually single cylinder or . On a sled that engages at 4-5K you do not necessarily need to pull off a corner 1 gear too high for example. Also most sled motors usually are 2 or 3 cylinder and one cylinder can help "carry" the one next to it through the cycle. You can usually get away with taller ports on a sled. Another big sled factor is altitude, another is stinger diameter. Go "by the book" on stinger size and you WILL burn it down on a long hard snowmobile type pull. same stinger sizing would work great on short drag or more bike type short straightaway run. I could go on and on but I think you get the idea, the black art is understanding the cause and effect of the variables and making the adjustments for the application. Macdizzy.com is good site for this type of disscussion. cheers

Hillpounder...You're right all those books are good reading and I have them all. I still think it's just an art. The knowledge is there. The rest is art and experience. You do have to be carefull fitting the pipes in the chassis. There is a right way and a wrong way to cut and weld and still there is no quarantee. None the less, if you follow the formula's , you will most likely be close enough that you can 'tweek it in'.

Good observations on the difference between uses for these 2 strokes. We are using sled engines in a much different way than bikes when trail riding.

I've spent hours at MacDizzy's site and others like it. I think I must have 2000 bookmarks by now about 2 strokes.

I hope you continue to hang around and give your input and maybe help with some snags. The project is coming up soon.

Keith

:) Hello !

Tuned Pipe Operating Principle:
Tuned-pipe/Xpansion chamber exhaust systems are Helmholtz resonators. This is a fancy term for a big long tube that works like an organ pipe. Above a certain rpm, the engine exhaust pressure pulses (coming out of the cylinder head and going into the pipe) create a standing acoustic (sound) wave inside the pipe. Here's an analogy... When you sing in the shower, the sound will suddenly seem louder at certain notes. That is because the size of the shower is "tuned" to the particular note your are singing and begins to resonate (get louder). In the pipe, the sound wave bounces back and forth inside the big section and creates a lower pressure region right where it is bolted to the cylinder head. This lower pressure actually sucks the exhaust gas out of the cylinder thereby making more room for fresh charge of fuel and air. More fuel in the cylinder means: 1. more energy to drive the piston down, and 2. more power for you !! Tuned pipes are by their very principle of operation more efficient than other mufflers that simply reduce back pressure. Simple, low-restriction mufflers don't create low pressure at the exhaust port of the cylinder head like tuned pipes do. They just slightly reduce back pressure. Back pressure is the pressure that builds up at the exhaust port of the cylinder head when the engine is in operation. The exhaust wants to flow out of the exhaust port but the limited flow area in the muffler prevents it from flowing freely. For instance, when you try to blow through a drinking straw, you build up "back pressure" in your cheeks. Too much back pressure will keep a full, fresh charge of fuel/air mixture from entering the cylinder on the intake stroke. If a full charge of fuel/air mixture can't enter the cylinder then you will lose power. That's why excessive back pressure is a bad thing.

With a genuine tuned-pipe, expansion chamber installed, your engine will breathe better and have more power. Not only will back pressure be reduced, but the expansion chamber will actually pull the exhaust out of the engine. Because more air will be flowing through the engine with the pipe installed.
If the pipe/s is installed without an performance carb, you WILL get a very noticeable power boost, but it won't be the ideal set-up. The small opening (throat) on the stock carb will limit the amount of air that can flow into the engine at WOT. With both an performance carb and pipe installed, the air flow rates through the intake and exhaust will be matched, and you will get maximum performance.

Have FUN SWRules

:)

Idooski

Here is Olav Aaen home page :

www.aaenperformance.com

I hope this help you !!

Great explanation Lasse!! Now with all that said, have you ever built any pipes yourself? If not, would you?

I want to, not because I think that I can do it better, but because I like a challenge. I like to build things. Especially things that other people think you can't build. People like pipe builders that don't think anyone else can build pipes. You know?

so which is more important on a snowmobile,keeping proper heat in the pipe,the stingersize and length,pipe diameter or how it resonates

I'm not sure you can put an order on importance as they are all important. The one parameter that would kill ya if it were too small is the stinger dia. So...I guess that one would be more important that some, but...

I'm sure someone else can answer that better than I, since I'm just about to try my first set. ;)

Well stinger diamater is a direct relation to the resonance. The smaller diamater will not only resrict flow, but will reverb more pulse back at the port.

I have done allot of messing around with stinger and header changes. We would just tack in smaller stingers. Typically, it is good for drag racing but not good for long wide open runs.

The stinger is a pressure bleed pure and simple. Reducing it size will build more heat and pressure in the pipe. Because the speed of sound is affected by the pressure the air it is traveling through this increase in pressure can change the way the pipe works. The acoustic wave that exits the exhaust port (like the bang at the end of a gun barrel) needs to hit the convergant cone of the pipe and bounce back to the port. With the higher pressure it travels faster. The reflection is still a function of the convergent cone location, stinger diameter can only influence the speed of sound.

A cylinder without pipe tuning of say 100cc can at best compress 100cc of mixure. With pipe tuning the gasses leave the exhaust port and start to expand aided by the headpipe and first cone outward shaped taper, this expansion creates the low pressure that can help drag fresh mixure out through the exhaust port. Before the exhaust port closes the return reflected acoustic pressure wave from the convergant cone can stuff some of this fresh mixure back in the cylinder. This could be 50cc of mixure, or maybe with more careful pipe tuning 75cc ?So now our 100cc motor is compressing 150-175cc ! what motor do you think makes more power 100cc or 175cc?

Ok, now the compromises. My +50cc pipe has a nice wide powerband ( the ability to stuff the cylinder over a broad rpm range). The +75cc makes more power but will do it at a narrower rpm range. Can't have both sorry. Also this added stuffed mixure has been "polluted" by speant burned exhaust gasses and is prone to detonation. Also the added stuffed mixure raises the running compression. These 2 factors put me closer to the edge, good fuel timing jetting compression need more consideration.

This was just describing the effect of a pipe tuned for a motor running the same peak rpm. What if we tuned the pipe to do the same thing at at higher rpm? if you think of the engine as an airpump, and you want more air, you either turn the pump faster or make the pump bigger, right? with more rpm we&#39;re changing the pipe tuning even more, the compromise will be more peak rpm at the expense of low-mid. If your not willing to give up low-mid, the bigger pump would be better. of course no matter what pump you buy, they&#39;ll make a bigger one next year< LOL!

Idooski & company,

Here (http://www.pulserate.com/cone/) is a roadmap milestone on the ongoing quest to build the perfect pipe(s). ;)

I love it!!!!! Can&#39;t wait to try it.

:) Hello

Idooski,

Have you started building some Prototype pipes yet ??

SWRules

I&#39;m sorry to say that I have not started on building a set of pipes yet. As it stands, it doesn&#39;t look like it will happen this year. I already have too many things going on. And as you know, when you are doing too many things at once, there&#39;s a real good chance that at least one of them is going to be done wrong. I want to be sure that the projects I have going right now are all done right. I will continue to learn and store up information on pipe building and hopefully, I will be able to start on a set next year or late this sledding season.