Rokk Tech Silent Might Installed!

[betterthanstock]

What makes it more quiet installing it backwards and does that decrease flow from the forward mounting?

It is an asymmetrical design, in that it has some internal openings near one end. Airflow is unaffected, the openings are symmetrical with regards to flow direction, it's just the pipe harmonics due to the length of exhaust pipe before and after the openings, that make it quieter in the range 1800-2500 one way than the other. (In other words, any length of pipe will want to resonate--get loud-- at a certain rpm, and get very quiet at some other rpm, and by placing the muffler in a more optimised position, you can change how it sounds in a certain rpm range)

 

[Forrest Nearing]

By the way, all sound waves are pressure pulses.

but they are not exhaust gas pressure pulses...



when a cranked up 18 wheeler w/ 8" straight stacks on it rolls by me as it's going uphill and the sound gives me goosebumps, oddly enough, my ears don't feel exhaust gas pulses... they just detect the sound waves...



I'm wanting to see quantifiable evidence that this muffler flows better than straight pipe because I'm not buying the exhaust pulse thing, sorry.

 

[Bugracing]

crobertson1;



how close to the cat did you mount the Rokk muffler? Did you shorten the cat-exit pipe? Did you use the stock piping that exits the stock muffer?

Also, do you have any pictures of your installation? Thank you for your help.

 

[crobertson1]

bugracing,



Here are some pictures to answer your questions. The stock pipe was used after and before the Rokk Tech. I think the guy who did it, just cut out the length of pipe/old muffler he needed to put in the new one. This first picture is upside down as I was laying on my creeper looking with the camera. Second picture is the outlet end. Third picture is turned sideways. Sorry.

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[Bugracing]

crobertson1;



Thank you for the pictures. They are great! I have been looking for a completed installation before I perform surgery on my truck. This will make is much easier. Thank you again.

how was the in-cabin sound when you are pulling your big trailer? I am guessing its a little loader than stock but very livable (in otherwords - no/little droning under load)?

 

[crobertson1]

how was the in-cabin sound when you are pulling your big trailer? I am guessing its a little loader than stock but very livable (in otherwords - no/little droning under load)?

It doesn't bother me a bit and I wanted NO drone whatsoever. A little louder than stock, but just right for me. Let us know how you like it.

 

[Matt400]

If I knew for sure that it was more quiet than this muffler I might try one but even that big 51" Donaldson ended up being more noise than I wanted on my 03 so the 05 has remained stock.

 

[betterthanstock]

If I knew for sure that it was more quiet than this muffler I might try one but even that big 51" Donaldson ended up being more noise than I wanted on my 03 so the 05 has remained stock.

Matt, if you look at post #8 on this

https://www.turbodieselregister.com/forums/showthread.php?t=133663



you will see that I tried that muffler. I was not happy with it either, so that's how this design came about. That only shows 13-18 dB reduction. This will be easily 10-12 dB quieter than that, and a lot less back pressure. Give it a try.

Paul

 

[Bugracing]

Paul;



Even though I have not yet installed your muffler, I am most intrigued by it as I am looking for a freeflowing "can" that is tolerable (no or very little droning) when towing a heavy load (8000 lbs closed trailer).

The only question I have is if you offer this muffler with ceramic coating? (to extend the live of the steel). I'd prefer a stainless steel can though.

 

[Matt400]

That only shows 13-18 dB reduction. This will be easily 10-12 dB quieter than that

It's hard to believe that a 41" straight through muffler could cancel noise so well. I see it now has been improved so a Cat or pre muffler is not recommended for additional noise cancellation.



On my 03 I went from stock to a 5" system with a 51" Donaldson Silent Partner muffler which gave me a school bus sound along with a nice drone under steady cruise. At Donaldson's recommendation I went back to a 4" system and their 51" M090544. That change was livable till I sold the truck but every time I heard a stock truck next to mine I missed the OEM quietness.



After that I just figured that OEM will always provide the lowest noise with acceptable flow, after all they do engineer it for the CTD don't they?



At any rate I am concerned about the Cat closing up with added timing & or fueling over time so its removal to preserve it seems inevitable at which time a muffler change would be more easy to do all at once.

 

[Matt400]

Bugracing- will you be installing it in the forward or reverse direction as mentioned earlier and will you be using a cat?

 

[betterthanstock]

The only question I have is if you offer this muffler with ceramic coating? (to extend the live of the steel). I'd prefer a stainless steel can though.

Unfortunately these are custom built for us, and we have a big inventory of aluminized. All last year maybe 1 person asked for stainless. I think based on the fact that this is 1-2 gauges heavier than Donalsdson and other aluminized mufflers, that alone should give it 2-3 years extra life. The welds come pre-painted too, for additional protection. How long do you keep your trucks? Do you do any maintenance of the frame/driveshafts/springs to keep them rust free? If so, then you could do the same to the muffler. (I've seen a 1 year old trade-in at my dealer with rusted frame, so I figure it must have come from the rust belt) The gasses flow thru the inner pipe, so the outer can stays relatively cool for touch-up with regular (non-hi temp) aluminum flake paint.

And with the new ULSD (ultra low sulphur diesel) acid formation inside the exhaust will be a lot less than before, which was never a problem with diesels.

 

[RankRam]

BTS I just put your crank sensor on my truck and I'm really pleased with the results.



Thank you for doing the research and then making this product available for the public.



Now that the Bombing funds are getting low, I'm wondering if you would be willing to start a group purchase for your muffler?

 

[Matt S]

betterthanstock,

Why would you put on two mufflers? Won't that add more restriction? I guess I don't understand what the silent might is. Is it a resonator?

 

[Forrest Nearing]

it's a muffler that flows better than straight pipe between 1900-2600rpm... never mind exhaust volume, it's magical

 

[Sled Dog]

it's a muffler that flows better than straight pipe between 1900-2600rpm... never mind exhaust volume, it's magical

Gonna get some Magic about 10:30 am tomarrow.

 

[Matt400]

Gonna get some Magic about 10:30 am tomarrow.

Let us know how it sounds and which way you install it since it bi-directional.

 

[betterthanstock]

I'm wanting to see quantifiable evidence that this muffler flows better than straight pipe because I'm not buying the exhaust pulse thing, sorry.

OK.

I did some testing. I stuck a water tube gage to the exhaust pipe, about 2 ft down from turbo, just to be able to drill more easily. I put a perpendicular tap to measure pressure, a short piece of aluminum tubing, then a piece of silicone hose to resist the heat, and then clear tubing into the cab.

(I'm positive there were no leaks)



At idle, it's too small to measure.



@ 70-75mph cruise, 2 inches water (0. 07 psi)



@ full blast accelerating 80+mph, 11 inches water (0. 40 psi)

I have about 380 hp at the wheels, a stock truck won't get that high. It is really hard to get this high a number, and it wants to drop right away, but I suppose on a long hill towing, this is what you would get on a bombed truck if your EGT will let you keep it there.



2-4 inches water (. 07-. 14 psi) is typical for medium hard acceleration.



This includes the muffler, and all piping to the tailpiece. I have about six splices, with both welds and stainless clamps from all the mods I've done, and a 12" piece of flex, so this includes all that turbulence as well.

And this really sounds stock quiet inside the cab.



So this is less than just the 51" Donaldson by itself, and about the same as straight pipe, though I have not tested it with straight pipe.

 

[Forrest Nearing]

please post numbers for straight pipe compared to the numbers for the muffler, and please post numbers for engines making over 500rwhp.



thanks

 

[DBond]

If you do a lot of heavy towing, you will get it super quiet around 1800-2500 rpm by reversing the flow direction. SO much quieter, that you don't even need the catalyst, or pre-muffler anymore. Back pressure is still lower than a straight pipe.

So is there a down side to this "reverse" direction? Is it louder outside the 1800-2500 rpm range? Is backpresure higher? Why wouldn't this be considered the normal direction if it is so good?