Air & Exhaust Article - BHAF Muffler Uhh??

[Tractorman]

 

A BHAF Muffler  - Uhh??

 

I like the Cummins engine, but I try to do anything I can to make the engine quieter.  The BHAF air filter flows lots of air, but it also allows a lot of engine air intake noise to be heard in the cab – more noise than the factory air box and the factory air filter.   This inspired the idea to experiment with a BHAF muffler on a big honkin’ air filter –  in this case, a NAPA 2790.

A BHAF muffler is not for everybody.  If you like air intake sounds, turbo sounds, and amplified exhaust brake sounds inside your cab, then this project may not be for you.

For my first muffler I used a length of ribbed plastic drain pipe inserted into the filter.  I decided to measure the pressure drop through the pipe on a road test.  I hooked up an analog water manometer  gauge (mounted inside the cab) at connection port “B” for the test. 

All of the following tests were done driving the truck in fifth gear at wide open throttle approaching 2500 rpm.  The pressure drop measurements are recorded below:

Port “B” connection

  4” H2O  @ 27 psi boost @ 2500 rpm WOT – BHAF with NO muffler
20” H2O  @ 27 psi boost @ 2500 rpm WOT – BHAF with plastic ribbed muffler
  9” H2O  @ 27 psi boost @ 2500 rpm WOT – BHAF with steel muffler

Port “A” connection

  1” H2O  @ 27 psi boost @ 2500 rpm WOT – BHAF with or without mufflers

The plastic pipe muffler failed in terms of pressure drop (20” H2O) probably due to the restrictive 3” inside diameter and ribbed internal surface.  The steel pipe muffler is the winner.  It is still effective as a muffler, but at a pressure drop of only 9” H2O under the same test conditions.  The improved pressure drop is likely due to the increased inside diameter (from 3” to over 3 5/8”) and from a smooth inside wall compared to the ribbed plastic pipe.

So, I scrapped the ribbed plastic muffler (although I ran it for 40,000 miles) and made a steel one.  This muffler consists of one part – an 8” length of thin-walled steel exhaust pipe with an outside diameter of 3 13/16” and an inside diameter of 3 11/16” (wall thickness approximately 1/16”)  These diameters could vary slightly – in my case the NAPA 2790 BHAF connection has been deformed to a slightly smaller diameter over time because when the filter was new there was nothing in place to support the tension of the intake hose clamp.  For more BHAF information, IBMobile wrote an article regarding dimensions and specifications of the  most popular BHAF’s – thank you IBMobile!

Check your local muffler/exhaust shops in the area for a piece of exhaust pipe to meet these dimensions.  If you can’t find an exact match, select a pipe that is slightly larger in diameter and then modify the pipe as described below.

I made the thin-walled steel muffler piece from a slightly larger diameter exhaust pipe with a wall thickness of approximately 1/16”.  After cutting it to the 8” length, I cut out and discarded a piece of the wall and reshaped the remaining pipe to the proper outer diameter with the aid of a vise. I stress relieved the pipe so the cut edges touched each other and then I  soldered them together.  I made sure that the seam joint was flush and smooth for an airtight seal.  I inserted the muffler into the air filter leaving a small edge visible.  This will allow for at least 3 inches of air space between the inside back wall of the air filter and the end of the pipe.

I hope that you will enjoy a quieter ride in the cab without the sacrifice of performance.

- John

 

 

 

View full Cummins article

[dripley]

Well i might be in search of a piece of pipe. Did you not add a clamp for the BHAF to the pipe? 

[NIsaacs]

Have you tried this one at all (6469)? It is what I use on my Ford conversion. It might be quieter than the 2790.

https://www.napaonline.com/en/search?text=6469&q=N%3D1000015700%26Nty%3D1%26Ntk%3DKeyword%26Ntt%3D6469&isProduct=true&indices=PIA

[dripley]

Never have. But at $108 it would be hard consider for noise reduction.

[NIsaacs]

45 minutes ago, dripley said:

Never have. But at $108 it would be hard consider for noise reduction.

 

The thread is about the BHAF 2790, not exactly cheap either. I figure anyone wanting the 2790 might consider the 6469, if noise was an issue....

[dripley]

 

2 hours ago, NIsaacs said:

 

The thread is about the BHAF 2790, not exactly cheap either. I figure anyone wanting the 2790 might consider the 6469, if noise was an issue....

How much do you pay for a 2790?

Just looked it up wow thats pricey too. They are about half that much at Vulcan.

http://www.vulcanperformance.com/Big-Honkin-Air-Filter-BHAF-p/bhaf.htm

[NIsaacs]

10 hours ago, dripley said:

 

How much do you pay for a 2790?

Just looked it up wow thats pricey too. They are about half that much at Vulcan.

http://www.vulcanperformance.com/Big-Honkin-Air-Filter-BHAF-p/bhaf.htm

 

I use FleetFilter and always order $200+, that gives me another 20% off. I do have to pay shipping but no tax, so it is a wash.

2790/$40....6469/$44

[dripley]

1 hour ago, NIsaacs said:

 

I use FleetFilter and always order $200+, that gives me another 20% off. I do have to pay shipping but no tax, so it is a wash.

2790/$40....6469/$44

60% off Napa's list price would make it a viable option, though I know nothing about the other filter.

[Dieselfuture]

2 hours ago, NIsaacs said:

 

I use FleetFilter and always order $200+, that gives me another 20% off. I do have to pay shipping but no tax, so it is a wash.

2790/$40....6469/$44

Does 6469 have steel mesh inside. My next filter I'd like to get with the mash inside, and if a muffled 6469 does, I might just give it a shot. 

[NIsaacs]

54 minutes ago, Dieselfuture said:

Does 6469 have steel mesh inside. My next filter I'd like to get with the mash inside, and if a muffled 6469 does, I might just give it a shot. 

 

The picture don't show the mesh.

[Dieselfuture]

26 minutes ago, NIsaacs said:

 

The picture don't show the mesh.

Some pictures are deceiving, wasn't sure if you used one before. 

[NIsaacs]

5 minutes ago, Dieselfuture said:

Some pictures are deceiving, wasn't sure if you used one before. 

 

When it gets light I will look at my Ford, it has the 6469.

[NIsaacs]

No mesh, at least on the inside of the outside. I did not pull the intake off to look at that part, but I will if you want me to.

 

[Dieselfuture]

27 minutes ago, NIsaacs said:

No mesh, at least on the inside of the outside. I did not pull the intake off to look at that part, but I will if you want me to.

You don't have to, next time you have it out maybe. 

I went to local car qwest and they have a wix one for 110 bucks, ran it through my city account and it came up to 36 bucks lol. But they won't sell it to me for that price because it's some special government cheese discount we get. Anyway the part number is 46469 for Napa and 88469 for wix or whatever they get.