Pacbrake sound

[EZeis]

I installed a Pacbrake PRXB on my 07. I was expecting a ssshhhh noise and instead I get a rumble sound kinda like an engine brake (jake brake). I did have a leak that I fixed and it sounded like a major compressed air leak. So is the rumble normal? You can hear the rumble inside and outside the cab. I haven't towed yet so just an empty truck. At idle kinda sounds like a muscle car exhaust rumble and under load more towards the engine brake sound. BTW, I'm talking when the brake is on (closed). Seems to work great, just want to make sure the noise is normal.





Thanks,

Earl

 

[Prairie Dog]

Thats about what mine sounds like. Personally, I wish it was a bit more Jakey sounding.

 

[AH64ID]

Every exhaust brake I have heard has a constant whistle. Some are quiet and some are louder, based on the exhaust.

 

[EZeis]

Thats about what mine sounds like. Personally, I wish it was a bit more Jakey sounding.

Yeah it's cool sounding, just wasnt sure it was normal. Cant wait to come down the mountain loaded. Miss seeing you on the Wildcat forum.





Earl

 

[EZeis]

Every exhaust brake I have heard has a constant whistle. Some are quiet and some are louder, based on the exhaust.

No whistle, just rumble. Might change once a heavy load is pushing on the brake?? Won't tow till April.





Earl

 

[Prairie Dog]

Yeah it's cool sounding, just wasnt sure it was normal. Cant wait to come down the mountain loaded. Miss seeing you on the Wildcat forum.





Earl

Thanks Earl, I do need check in over there soon.

 

[NIsaacs]

No whistle, just rumble. Might change once a heavy load is pushing on the brake?? Won't tow till April.





Earl

It will sound the same loaded only better since weight will force the rpm up longer. It does sound just like a Jake only quieter. The sound is coming from the air cleaner box not the exhaust. The exhaust will sound like a restriction.



The sound has something to do with the cam profile. Both my 12 valves don't have the cool sound, just the '01 24v.



Nick

 

[AH64ID]

Not sure what Jake's you guys have ever heard but none of the ones I've heard sound like an exhaust brake!



If your near the tail pipe is whistling restriction, some are high pitched some are low pitched. Up near the motor the sound is different, the enigne defenitaly sounds deeper from the increased load at idle. I've never heard anything out the airbox.



If your getting the jake sound of varying intensity I would think the spring in the PXRB isn't evenly regulating, and the valve is going open-closed-open-closed.



I have gone thru 4 different muffler configurations and they all make it sound different. Stock was the quietest. Cat only was same tone as stock just louder. The Donaldson 40" only was unbearable. It was a high pitched whistle, I couldn't drive with the EB on and the windows down, so I added a resonator from a mega-cab and it took the high pitch sound out. Its now deeper and sounds the best out of all the configs.



Each brake will sound a little different, based on how they regulate pressure. I would expect the PXRB and BD to be higher pitched at idle becuase of the increased restriction.



I do like the sound for sure, not knocking it. . but there is a big differnce in an engine brake and an exhaust brake. Exhaust brakes do sound killer when your at 2500 rpms with a load!

 

[NIsaacs]

AH, I can't speak for Earl, but as a 25 year veteran of driving big trucks, Cummins, Mack and Detroit I do know what a Jake engine brake sounds like.



My '01 BD exhaust brake sounds EXACTLY like a Cummins Jake engine brake. My son's '06 with the Jake exhaust brake does not, It sounds more like my two 12 valves. On my '01 the sound IS coming from the intake box. It has to have something to do with the intake/exhaust valve overlap.



Nick

 

[AH64ID]

Very intersting. I have been around a few trucks with BD's and PXRB and like I said never heard one sound like an engine brake, very very different sound to me.



One of the reasons I like my Jake is the lower backpressure at idle, I think the BD and PXRB put too much backpressure on the truck at idle, which could be why you hear it thru the intake box and I don't, even with my cam.

 

[EZeis]

I know what an engine brake is and sounds like. I'm guessing the Pacbrake sounds that way due to the pressure do hicky thingy. Other brakes have a wide open orfice hole and that probably makes the whistle or ssshh noise and why the PRXB doesn't?? I've been around the Mopar Jacob's exhaust brake and they ssshhh so I was expecting that with the PRXB and got a engine brake sound. Since I'm not the only one, than I say it's suppose to be that way.





Earl

 

[AH64ID]

It sounds like the spring that regulates the orifice doesn't settle into one position on the 5. 9 with a PXRB. I know the PXRB on our military trucks with larger Cat's sounds very similar to my Jacobs fixed orifice at idle.