Quietening pipes by water injection

Brian MAhoney · Dec 1, 2003

I am wanting to try further quieting an Irwin Quiet pipe.

Do I need to do any more than drill and tap the silencer for a pressure or water cooling fitting and then connect to the water coolling outlet from the cylinder head?

Also does anyone have any idea as to how noticable any improvement will be?

Brian

Scott Schneider · Dec 1, 2003

:unsure: Brain, The idea you have is correct and is used qite often by various pipe builders.

You need to be aware of a problem than can and will happen if the pipe you are using has too much back pressure within the muffler section. The water pressure you have in your cooling system is pushed against by the pressure within the pipe you are injecting water into and the two pressures against each other will reduce the overall flow volume of water threw engine. Most pipes that inject water into muffler have oversize exit pipe. If you are to do it I would on the irwin use a thin wall pipe pressure fitting and install in outlet pipe @ 1/2" or less from the end. You should see @ 5 to 8 DBa reduction in noise.

Scott

Kez · Dec 1, 2003

Would water in the muffler find its way into the engine exhaust port?

Thanks,

Kez

Russell Bear · Dec 1, 2003

That's what I was thinking. When the engine is running the water would most likely be converted to steam by the temperature of the exhaust to a point right. If the exhaust temperature is lowered enough by the water won't it eventually snuff out the engine? What about when the engine is running really rich and dieseling, could water possible enter the combustion chamber and damage the plug/head :huh: ?

Scott Schneider · Dec 1, 2003

Those are valid issues and while some will inject water in the header or edge of the diavergant cone for a torque increase they will shut off the "IN PIPE" water once you are at speed and running hard. Water even in vapor form has mass and is not directed back into engine, It follows the outward flow towards stinger and is not carried in the resonant wave activity within pipe.

But the humidity caused in the internal areas of pipe is not good for the engine once not running because the residual water will get into engine and rust rings or bearings if not dried out. It's best to just add the water at pipes discharge end to dampen the sound waves as they exit stinger.

Scott

Propjockey · Dec 1, 2003

Hmmm......I thought it was better to keep the exhaust temps up. :huh:

Scott Schneider · Dec 1, 2003

:blink: I will take a stab at that for you. The heat issue is about BTU's and the more heat you have the higher the output of the engine will be.

Then you look at the dynamics of wave energy that is the heart of a tuned pipe, the cooler the gas's within the pipes walls the stronger the wave activity and stronger the boost potential.

So as pipe gets hotter giving a higher BTU boost to the engine the signal strenth of the working waves is getting weaker. A double edge sword that has a ballance of both issues.

This is why to figure out any pipe design and tune the ones we have we must know at what speed the gas's travel in pipe and that speed is variable by changes in temputure and density.

:blink: By no means is this the whole story. :blink: Scott

Quietening pipes by water injection

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