Muffled vs. non muffled pipes.

[StephenLilly]

Is there generally a distinct power difference between muffled and non muffled pipes? I would assume the trade off is that muffle has less power but it's not as loud? Looking at macs and novarossi for .18 is tz on a jae outrigger if anyone has any advise. Mine currently is a stock one off an old pro-boat RTR miss Budweiser hydro, might be fine? Also I've heard the header matters more? Thanks.

 

[Andy Brown]

Muffled pipes make MORE power. I ran 126.3 mph with one WAY BACK in 2001.

Header, pipe, and stinger design/size all matter. The smallest change to anyone part can have a very noticeable effect on power all across the power band.

My advice. Try all the pipes you can....or go with what someone suggests for your basic set up. It will work, but may not be optimum.

 

[StephenLilly]

Thank you Andy, that puts me on the right track! I may do a little more research and pick up a few different pipes and see what that results are.

 

[LohringMiller]

We also have done many tests with various muffling methods. Two strokes don't loose power from back pressure like four strokes. In fact, the right amount of back pressure helps the pipe "supercharge" the engine. A muffling system can be used to provide this back pressure. The easiest is an inverted stinger. Even better is an inverted stinger with a standard stinger muffler. Water injection at the stinger muffler improves the effect even more. It's not hard to do these things with over the counter parts. Dave Marles builds muffled pipes for gas and nitro engines that meet the strict European noise standards.

Lohring Miller

 

[Terry Keeley]

I use a length of brass tubing with a short piece of the next larger size soldered to the end, tube should extend to about the middle of the widest part of the pipe. For 3.5cc I use 11/32" (0.312" I/D), 7.5's 13/32" (0.375" I/D), 11cc and up including 27cc gas motors 15/32" (0.437" I/D). You may need to stretch the stinger slightly, on aluminum pipes you can heat it with a torch and use increasingly bigger drill bits to work it out, or if there's enough material you can just drill it out. You can use the next smaller size tube but watch for excess motor heat in hot conditions.

I drill a small (1/16") drain hole near where the tube meets the stinger, this way you can drain the pipe if you take a dunk or flood the engine. I like to use Locktite to hold it in and it works well if it's a close fit, others have said JB weld works if the fit is looser. This simple mod brought my 11cc rigger from around 102 dB to about 91. If I use a small stinger muffler (Muck, Prather, T-Mod etc) the result is a very quiet running boat of around 88 dB. I haven't seen any power loss or excess heat doing this since the '03 season.

 

[warlokboats]

Will you have to lean or richer the motor when you switch to a muffled pipe?

 

[Andy Brown]

Will you have to lean or richer the motor when you switch to a muffled pipe?

Depends on weather or not it changes the back pressure. If it makes more back pressure, the tank pressure will be increased.

Less back pressure reduces tank pressure.

Different pipes volumes and cones angle effect the mixture too. Just be prepared to adjust the needle when making any kind of pipe change or adjustment.

 

[gilbert galli]

in europe in fsrv, oval offshore and sometimes in hydro if the place is sufficient, it is used a tank with constant level whose flow is regulated by a float acting on a needle like a carburettor, the tank is presurized and pours its contents into the tank is the engine that sucks the fuel, the settings are less subject to the difference in pressurization

my 15cc fsro Costa hull

 

[Brandon Atwell]

Will you have to lean or richer the motor when you switch to a muffled pipe?

Depends on weather or not it changes the back pressure. If it makes more back pressure, the tank pressure will be increased.Less back pressure reduces tank pressure.

Different pipes volumes and cones angle effect the mixture too. Just be prepared to adjust the needle when making any kind of pipe change or adjustment.

So is there an optimum muffler design that coorelates to this added back pressure?

For example, we take a standard MACs pipe and place a standard add on muffler over it, or we take a cone similar to the cooper pipes and weld over it? Would you gain more by muffling the stinger, or gain more by essentially trapping the pressure released by the stinger into that cone?

Its funny because we always joked my 40 Tunnel got faster after putting a muffler on it. Maybe it was true!

 

[warlokboats]

Ok. Let me go at this a different way. If you take an ab nitro pipe run it and right after put on a ab muffled pipe and run it with no changes to anything else. what would it do to the needle? Make it rich or lean?

 

[RonShaw]

Ok. Let me go at this a different way. If you take an ab nitro pipe run it and right after put on a ab muffled pipe and run it with no changes to anything else. what would it do to the needle? Make it rich or lean?

The additional back pressure to the tank will make the engine run richer.

 

[Andy Brown]

Ok. Let me go at this a different way. If you take an ab nitro pipe run it and right after put on a ab muffled pipe and run it with no changes to anything else. what would it do to the needle? Make it rich or lean?

The additional back pressure to the tank will make the engine run richer.

If the muffled pipe in fact had more back pressure. Some of my muffled pipes had more back pressure than the non muffled version, but some had the same or less.

If I remember correctly, we made a small batch of AB 45 nitro pipes. Then on the first batch of AB 45 muffled pipes, the pipe builder made a mistake and made the stinger bore too small. They had way too much back pressure. Those were the silver pipes. The next batch was made correctly. They are the black AB 45 pipes with the AB logo. I think the back pressure was about the same as the original nitro pipe. Again, just be prepare to make some mixture adjustment.

CMB now sells the original AB nitro pipe as their own.

 

[mtruex]

A muffler wont make a bad pipe good or a good pipe bad. It could cause problems if its too restrictive and builds too much heat. But for the most part its not a big deal.

 

[Andy Brown]

A muffler wont make a bad pipe good or a good pipe bad. It could cause problems if its too restrictive and builds too much heat. But for the most part its not a big deal.

The correct muffler will make a good pipe better.

 

[LohringMiller]

It's all about adjusting the back pressure just like with stinger diameters and lengths. Terry's excellent pictures show what I was talking about. You can test this most easily on a dyno, but I have a spread sheet from a series of on the water tests done on a gas mono in 2003. We ran it by a dB meter a fixed distance from the shore and measured the peak rpm. We increased the performance from 17360 rpm with the standard M&D pipe to 17500 rpm with the best added on muffler. The sound level dropped from 97dB to 85.3 dB using the muffler plus water injection.

Lohring Miller

 

[StephenLilly]

Ok thank you everyone for your help, I wound up getting a muffled novarossi pipe from Ron Shaw. He helped point me in the right direction with length and what to expect from the increased back pressure. Hopefully get some laps on it this weekend or sooner!

 

[mtruex]

A muffler wont make a bad pipe good or a good pipe bad. It could cause problems if its too restrictive and builds too much heat. But for the most part its not a big deal.

The correct muffler will make a good pipe better.

Na

 

[Terry Keeley]

We found running an internal stinger with a "through" after muffler quieted things down a bunch and didn't effect performance in the least.

It's a little different tuning by ear but you get used to it.