Internal exhaust stingers

[anthony_marquart]

In a previous thread I asked about exhaust stinger mufflers. A few people have suggested adding an internal stinger. I want to make a few comments and questions about that.

I have done this before,.. but I don't remember having much noise level decrease. Has anyone ever taken DB reduction data on this?

-I should ream out the pipe ID one brass tube size and JB weld into place. Everyone agree on this way of installation?

Some say the tube length should be 10x the diameter. Some say run the tube exactly to the beginning of the convergent cone. (typically the seam) sounds like those might be about exactly the same thing.. thoughts?

- How does this really effect the function of a tuned pipe? now the exhaust flow path is very much changed. seems to me that the gas in the exhaust side is now somewhat compressed. Increasing pipe pressure to the tank.

- How does this flow path change the way the pipe pushes gas back into the engine?

maybe over thinking it.,. it worked well for me in .12 engines.. 45s?

Anyone have experience doing this specifically with the macs 45 pipe?

thanks

 

[Blackout]

An internal stinger will get you to around 89 dbA so they work quite well to reduce the noise to a legal IMPBA level. But, they will not be enough by themselves to keep noise-sensitive neighbors happy. Sadly, I have been dealing with this for a couple years now....

 

[DickJones]

In a previous thread I asked about exhaust stinger mufflers. A few people have suggested adding an internal stinger. I want to make a few comments and questions about that.

I have done this before,.. but I don't remember having much noise level decrease. Has anyone ever taken DB reduction data on this?

-I should ream out the pipe ID one brass tube size and JB weld into place. Everyone agree on this way of installation?

Some say the tube length should be 10x the diameter. Some say run the tube exactly to the beginning of the convergent cone. (typically the seam) sounds like those might be about exactly the same thing.. thoughts?

- How does this really effect the function of a tuned pipe? now the exhaust flow path is very much changed. seems to me that the gas in the exhaust side is now somewhat compressed. Increasing pipe pressure to the tank.

- How does this flow path change the way the pipe pushes gas back into the engine?

maybe over thinking it.,. it worked well for me in .12 engines.. 45s?

Anyone have experience doing this specifically with the macs 45 pipe?

thanks

Anthony, I have done extensive testing of DB" levels going back to 1998 and continuing up thru summer months of 2013, I tested hundreds of ad on mufflers, and lots of stinger tubes added to the exhaust stingers, I never found one stinger add on that came even close to the IMPBA DB" levels, and 3 ad on mufflers that were in the mid 90 DB"S levels, and 2 ad on mufflers that registered in the high 80 DB"S. What I believe has happened as far as IMPBA and NAMBA is that IMPBA clubs do not enforce these levels, they simply require each boat to have some sort of so called muffling device even if it does not bring the noise DB"S down at all, even though they are in the IMPBA rules because to many boaters are against trying to bring there boats into compliance and NAMBA rules simply mandates having some type of muffling device. By adding the smaller diameter tubing U will increase the back pressure and how long the tube is, "how far it stick"s in side the pipe will determine the amount of back pressure. There will also be a disruption in the wave flow as part of the design of the rear cone as it normally follows the wall of the rear cone down to the exhaust stinger where part is returned into the engine exhaust port and some out the rear stinger.

mobydickk

 

[anthony_marquart]

That is what I thought Dick. Was hoping someone would confirm my thoughts. I have add on from rum racing. Haven't been able to test it's yet.

 

[lohring]

Below are the results of a pipe test on a CMB 35 with the same stinger in a "normal" and inverted position. The pipe was made with a screw in stinger so we could test different diameters. It was just as easy to screw it in in either position. The length was about as long as the baffle cone. The test also shows the power boost at lower rpm with water injection into the header. Water injection is the purple graph. The blue and orange graphs are the two stinger positions. As you can see, the power is the same for either stinger position within the precision of our dyno.

Lohring Miller

 

[Blackout]

That is what I thought Dick. Was hoping someone would confirm my thoughts. I have add on from rum racing. Haven't been able to test it's yet.

If that muffler is not quiet enough, let me know, I have been working on some designs over the past couple years and plan to build and sell some this winter or next spring.