On The Pipe

[Will Gallagher]

I was asked this Question by a New Boater last weekend and I really could not answer it. ” What exactly are we doing when we lengthen or shorten a pipe?” :unsure:

 

[Dorkhedeos]

well, im not sure if im right or not, but i think shrotening the pipe makes returning pressure waves come back faster, and if its too short, it might force exhaust gases back into the engine, making it lose power. making the pipe longer does the opposite. if its too long, the pressure waves dont get back to the exhaust port before it closes so it dont do nothing

 

[Bob Kensill]

Ideally,you are trying to make a pipe that doesn't fit any specific engine work with your combination. It is generally said that shortening a pipe will raise RPM and lower torque,and lengthening a pipe will raise torque and the engine will operate at a lower RPM. If it is difficult to get the pipe length just right,the pipe probably has the wrong cone lengths and angles for your engine. Most pipe manufacturers make a pipe that will work well on many different engines but is not designed for a specific engine.

 

[Lamar_Huff]

Refer the new boater to this website:

http://www.southernskies.net/page_info/run...rokeengine.html

This site explains it pretty well and the animation really helps it sink in.

Dorkhedeos is right, if the pipe is too long you basically have an expensive muffler. If the pipe is too short your engine will never "hop up" on the pipe.

Later,

Lamar

 

[gil sonsino]

Hi Will

This topic is not that simple as said.

There are many other factors that contribute for the high performance engines today.

It is correct when you say that a short pipe has a direct relationship with the loss of torque but we have to consider variables like nitro content, internal mods like raising timing, raising head volume,head clearance, type of boat as major points in this equation.

Otherwise my saw engines wouldn't be able to turn higher picthes at high rpms with short pipes and they do exactly that.

I do know that an average 67 heat boat(Any kind) has and optimun performance with a pipe at about 11"but when you go for speed this lenght drop to 10" or less turning much higher pitches so we have here different patters to understand the performance of our little motors.

To not make it difficult just try to experiment different lenghts,have a well tuned engine and a light boat with a proper prop!

Gill

 

[Jay Stone]

in effect, adjusting the powerband..

 

[gil sonsino]

That's it Jay!

Gill