Tuned Pipe Design?

[shoboat]

Boaters,

Just wondering if anyone out there has any updated tuned pipe design

information available? Or does anyone know where I can find more

information on the subject? I've read the Jennings information already.

Thanks,

Mark Sholund

 

[TimD]

Mark,

There is Prof. Blair's book which is more current than Jennings, and there are pipe design programs available also, but getting them set up for the small capacity engines and the fuel we use is critical to getting the correct results.

Tim.

 

[shoboat]

Tim,

The reason I'm asking is we need to build some torque pipes for the 21

Str.Away boats. Do you know where I can get a copy of Blair's book?

And do you have any names of the design software for tuned pipes?

Thanks,

Mark Sholund

 

[TimD]

Tim,
The reason I'm asking is we need to build some torque pipes for the 21

Str.Away boats. Do you know where I can get a copy of Blair's book?

And do you have any names of the design software for tuned pipes?

Thanks,

Mark Sholund

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Mark, do a search for "Design and Simulation of Two-Stroke Engines" by Dr. Gordon P. Blair. I believe it is still in publication.

I don't think software programs will be very helpful with designing a 21 torque pipe. They seem to work better on larger engines like 90's, when set up for the fuel.

The "frankenstein" method will be your best bet. That and lots of controlled testing.

 

[shoboat]

Tim,

It sounds like you guys have already looked into it. Thanks for the book

information, that should help a lot.

Kevin,

Thanks for the information.

Thanks Again Fellas,

Mark Sholund

 

[DaveMarles]

Mark, by 'torque pipe' do you mean a pipe to pull bigger props at lower rpm?

 

[izitbrokeyet?]

I found that Dr. Blairs Design book pretty much has the same info as Jennings. I found the Jennings 2 stroke tuners book to be a little better on the tuned pipe stuff since he's a little more practical than Blair.

 

[shoboat]

Dave Marles,

Thanks for the information,maybe we will have to try an English pipe.

Thanks,

Mark Sholund

 

[Hap Mulvany]

Larry Browman is working on tuning the intake This has an added benifit no more hydrauliced engines.

 

[lohring]

There is an applet for designing tuned pipes at http://www.mh-aerotools.de/airfoils/index.htm There is a detailed explanation of the formulas behind the applet there as well.

Lohring Miller

 

[EatMyShortsRacing]

Ahh the big question..... you can always tune for the appropriate rpm and engine displacement, but what effects on performance through the rev range do some of these dimensions give you? And what is the effect of rounding some of the cones??? like the good ol parabolic pipe theory???? And in all reality isnt the multiple angles on the diffusion cone supposed to approximate a parabolic or logrythmic calculation???

All this information has been available for years, yet people are coming up with new pipes???? Why???

Because theory and application differ. Where do you make the compromises on a pipe to gain more torque??? Where does all this figure in the calculations??? Almost anyone can design a pipe to resonate at their target RPM but you have to get the engine to that RPM for it to be effective.

I would be interested to hear if any other theories in pipe design including gradual curving of pipes have any effect.

 

[TimD]

The sophisticated pipe software available commercially today takes many things specific to the engine in question into account, such as port time areas, rod /stroke ratio etc. You will find that once a pipe is optimised for a particular engine, that the optimised pipe design will not give the same results on a different engine of the same capacity......

The next big advance in pipes for our applications will be pipes that have been designed and optimised for specific engines. It is already starting to happen.

Tim.

 

[EatMyShortsRacing]

you may have missed the point....

a lot of pipes these days (and some earlier pipes too) dont have the precise angles and flat areas as depicted in the software simulations. Parabolic rear cones and general smoothing of lines has been employed to varying degrees on different pipes. What I am getting at is what effects come from these designs???

 

[EatMyShortsRacing]

to take that further I would have thought that as the exhaust leaves the engine the most efficient way of the gas leaving would be through a trumpet shaped pipe like a reverse venturi. I have this funny feeling that the calculations supplied try to approximate this varying shape to a more 'constructable' model.....

 

[DaveMarles]

The next big advance in pipes for our applications will be pipes that have been designed and optimised for specific engines. It is already starting to happen.

Tim.

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Starting to happen? I've been doing that for years ! <_<

 

[Ian Inverarity]

you may have missed the point....

a lot of pipes these days (and some earlier pipes too) dont have the precise angles and flat areas as depicted in the software simulations.  Parabolic rear cones and general smoothing of lines has been employed to varying degrees on different pipes.  What I am getting at is what effects come from these designs???

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Criag,

Most of the Bolly Pipe designs that I have are parabolic pipes. What I have found is that good parabolic designs can have very good top end, very powerful, however they lack midrange, this is from the shape of the diverging cone. Given that Bolly designed the pipes for pylon racing, they are very good in that application. But a plane can get on pipe whilst being held stationary on the ground! The P92's you have on the twin come on very hard, but have poor midrange. This limits the props they can pull, the torque curve is not well matched to the needs of boat racing.

Ian.

 

[jydracing]

Hi All I have been watching this thread with intrest. I have been testing a lot of pipe designs and can say that in figuring up what works and what does not is not simple. there are so many verables out there a lot of them are forgotten about. for example hull,engine,prop,prop depth,engine angle,engine porting,combustion chamber, nitro content, type and amount of lubercant, water conditions, and oh lets not forget mother nature. is it hot ,cold , humid or not. are you running at sea level or high in the mountains are you running on the east coast or the weat coast or in the middle. all of this needs to be looked at.

Also i like looking at the engine mfg sites on the engines they list a max rpm and hp but they do not list at what rpm the engine is making the most hp and this is very important. you want to set up every thing around this. the rpm where the engine is making the most hp is were you will get the best out of your engine and pipe.

Well that is all for now just rember this is from my own test results and is not law. all i can say is test.test,test,test and when you think you got it test some more

see ya jimmy

 

[AndyBrown]

I've read all the books from Jennings to Blair and everything in between. Tested almost every pipe made. Made pipes from bar stock. Made dozens and dozens of Frankestien pipes. Tested them in many different combinations........

I think Dave will agree with this statement:

There is yet to be a book written that is nothing more than a gross guesstimate of how a tuned pipe really works.

And yes Dave has been designing "Application specific" pipes for longer than most have been model boating.

This is my opinion,.......but there are no "big advances" in pipe design to be seen....only small ones.

There are no bad pipes out there..... only pipes that have not found the right mate!

Parabolic (curved) cones can be used to fine tune a pipes effect. For instance, 5 to 7 degrees are pretty standrad angles for the divergent cone. However, some engines will respond better if the divergent cone is not one constant angle for it's full length. To what extent to vary the angles and where are dependent on the specific requierments of the engine and varibles of the total surounding universe.

Have fun....it's just a hobby!! B)

 

[DaveMarles]

I've read all the books from Jennings to Blair and everything in between. Tested almost every pipe made. Made pipes from bar stock. Made dozens and dozens of Frankestien pipes.  Tested them in many different combinations........
I think Dave will agree with this statement:

    There is yet to be a book written that is nothing more than a gross guesstimate of how a tuned pipe really works.

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I agree with Andy on that for sure.

My experience is that there can be many pipes that will work well on a particular engine/boat combination but only one really, really good one. If you can find or make that special pipe then you can have a big improvement. For best overall performance pipes are critical to within 1 or 2mm on cone lengths and getting the combination right is like trying to do a Rubiks cube blindfolded and with one hand behind your back..

Anyway, its often easier to modify the engine to match the pipe.

My 3 cents.

 

[VansRacing]

When Joey and I developed the "J" pipe, we learned the most by building 5 or 6 different pipes and spending all day at the pond testing. When we found that we had improved the pipe, we then analyzed that pipe design and then went back to the pond with more variations of the shape to prove or disprove what we had learned.

My 2 cents

-Carl