Muffler installation with db comparison

[MO MV man]

Hello all,

I installed the Donaldson M070028 muffler following chgofiveo's thread.
EASY install! I haven't reinstalled the shield yet. See pics.
The Donaldson is a far superior muffler, in my opinion, due to it's robust construction (Heavy Duty!) and lack of packing inside (packing WILL soot up and blow out eventually).

The results? Outstanding exhaust noise reduction!
IDLE: the reduction is amazing. Dropped from 93.1db stock to 82.2db!!
CRUISE: Steady state cruise is quieter:
50 MPH, approx. 1950 RPM was 96.4db stock, 92.4 muffled.
HARD THROTTLE: Nail the throttle at 50 and the difference is phenomenal:
102.6 db stock, 95.5 muffled.

What the db readings don't tell and I need to pass along.....
The Exhaust note:
Oh my.....what a colossal improvement....idle still has the C Turbo whistle but no more drone. Cruising on the highway? Incredible.
Deep, "clean" exhaust note AND......it's such a smooth, clean sound that I can actually hear those big XML's growling now!
Seems the faster I go, the more smooth the note.

To those who might look at that and say, "but that's only 11db......only 4 db....".
db readings are interesting.
A 10db reduction, for example, is HALF the previous noise level!
A 5db reduction is quantified as "a clearly noticable change".

AND....
I have a feeling the readings I took in-cab at 50MPH were also reading the usual Deuce in-cab racket (rattles, drivetrain noise, etc.).
BUT the reduction in sound is definitely reduced.

How I did the readings:
Meter: Extech Model 407768 Sound Level Meter
Idle-standing next to the truck in the same spot, extended my arm with meter in hand to outlet of stack.
Cruise-holding meter in my hand in the middle of the cab, both windows open (it was almost 100 degrees yesterday).
Hard acceleration: Same position as cruise.

 

[319]

Looks great. Did you have to bend the mirror brackets?

 

[dozer1]

VERY nice looking install. Thanks for the great pics, the db info and testing.

 

[MO MV man]

Looks great. Did you have to bend the mirror brackets?

Actually no.

But the previous owner bent them from stock (due to tagging a tree or something?) in the past.
That being said, you may have to bend yours.
The tubes do bend pretty easily so no worries there.

 

[MO MV man]

VERY nice looking install. Thanks for the great pics, the db info and testing.

Thanks for the compliment.
I'm glad to return the favor to all those who help me on a daily basis here on SS!

I REALLY wanted to get some sort of audio files together.
But my camera phone produced terrible audio near that stack and the in-cab was a garbled mess with all that driveline noise and rattling metal.

 

[greg burns]

Another db experiment

MO MV man:
I did a muffler installation this week using a Walker RV muffler (21470) from Summit racing. I used a Radio Shack sound meter to measure the levels before and after. It may have a different scale or different sensitivity than the instrument you used. I did measurements at idle (800 rpm) and at 2000 with the meter held on the mirror bracket near the muffler stack. The before and after readings at idle were 101 and 95 db. At 2000 rpm the readings were 117 and 101. There was a third reading in the passenger seat at 2000 rpm with the window closed. The two readings were 105 and 93.

The reduction in exhaust noise was noticeable. The muffler seemed to make all the noise coming through the firewall and the floor much more prominent. Maybe insulation in the cab will be next.

 

[DieselBob]

MO MV man, very nice looking truck. Clean looking install.

 

[gringeltaube]

.................and lack of packing inside (packing WILL soot up and blow out eventually)...................................

Looks to be 7" O.D..... impressive performance for such a short muffler!
Wonder how its built, if you say it has no glass- or rock wool in the outer jacket?

......I haven't reinstalled the shield yet. See pics.....

Any reason you also left out the lower (bent) tube....?


Thanks for taking the time to measure db before and after!

G.

 

[MO MV man]

MO MV man:
I did a muffler installation this week using a Walker RV muffler (21470) from Summit racing. I used a Radio Shack sound meter to measure the levels before and after. It may have a different scale or different sensitivity than the instrument you used. I did measurements at idle (800 rpm) and at 2000 with the meter held on the mirror bracket near the muffler stack. The before and after readings at idle were 101 and 95 db. At 2000 rpm the readings were 117 and 101. There was a third reading in the passenger seat at 2000 rpm with the window closed. The two readings were 105 and 93.

The reduction in exhaust noise was noticeable. The muffler seemed to make all the noise coming through the firewall and the floor much more prominent. Maybe insulation in the cab will be next.

Interesting!
You took your readings in different places than I did, that's where the difference comes in, I imagine.
My idle was VERY near the outlet of the stack.
The 1950/50MPH was in the middle of the cab with me holding it in my hand.

My db meter is from work.
Used by the Safety Dept. to measure in-plant noise levels.
Industrial stuff.

Oh man...you're right about the in-cab noise!
You can sure hear the engine and drivetrain noise now!
Sound deadener would help immensely.

 

[MO MV man]

Looks to be 7" O.D..... impressive performance for such a short muffler!
Wonder how its built, if you say it has no glass- or rock wool in the outer jacket?

Any reason you also left out the lower (bent) tube....?

Thanks for taking the time to measure db before and after!

G.

NO problem on the measurements. I was as curious as everyone else.

The body of the muffler is 7"x14", 3.5" ID inlet and outlet.
I attached a little drawing of how it's constructed internally.
Noise reduction is accomplished by flow re-direction.

When you say "left out lower bent tube", do you mean on the mirror?
I may be missing a mirror bracket......if that's the case.
Who knows what the previous owner did.

 

[5tonpuller]

There are many ways to get it a little quieter. One guy I know moved it to the back by the rear wheels. Here is what I did. There was a lot of others that did it to. These trucks where build with the young and slim in mind. ( I am not that slim ether ) Here is the other tread. http://www.steelsoldiers.com/580271-post29.html

 

[MO MV man]

Trust me, I've thought a LOT about running the exhaust out the back.
And I'll re-use the Donaldson muffler.
I have the whole thing planned in my mind, including exiting behind the passenger rear tire just like modern trucks.

The only thing holding me back is time and a long list of other "to-do's" that are more important.

I bet the interior racket is REAL pronounced with all that exhaust noise at the rear!

 

[gringeltaube]

....................
I attached a little drawing of how it's constructed internally.
Noise reduction is accomplished by flow re-direction....

Wow, that really looks ss (= stupid simple)! Wonder how it would compare to a typical flow-through glass-pack of same outer dimensions, regarding db reduction...?
(Guess its my turn now to do some research...)

When you say "left out lower bent tube", do you mean on the mirror?
I may be missing a mirror bracket......if that's the case.

Yes, I meant the lower support tube, from the vertical post to the bracket on the cowl. The stock one might interfere a bit in your case, but that can be solved in many ways...

G.

 

[MO MV man]

Wow, that really looks ss (= stupid simple)! Wonder how it would compare to a typical flow-through glass-pack of same outer dimensions, regarding db reduction...?
(Guess its my turn now to do some research...)

G.

Hi G.,

I already did the research on the flow-through (bullet) glass packs.
They're rated at 2-4 db reduction, per Walker/Dynomax.
The Donaldson is rated at 10-15.
It passed that test with my idle for sure (almost 11).

The Dynomax bullets are around $60 ($46 and $10-12 "handling" at Summit Racing, for example).
I got my Donaldson locally for $75, tax included.
A LOT more muffler for the money and I'm sure you'd agree that the Donaldson will FAR outlive a bullet.

The bullet was developed as a way for gas engine hot rodders to say, "but officer....I DO have a muffler.....see?....".
As they pointed under their vehicle to a slight bulge in their exhaust tubing that qualifies for a muffler......depending on the mood the officer is in.

 

[Flyingvan911]

If the walker I bought isn't impressive, I'll get a Donaldson.

 

[MO MV man]

If the walker I bought isn't impressive, I'll get a Donaldson.

Which Walker do you have?
The 21470?
If so, that's a nice RV muffler.
Just a LOT bigger than I cared to try and make fit.

 

[TexAndy]

MO MV, do you think you could take some audio recordings for us with yourself or someone else talking in the cab while the engine is idling so we can hear it, please?

I've got a whistler, too... and the big thing keeping me from putting a muffler on the exhaust is that I like hearing the whistle of the turbo.

 

[MO MV man]

MO MV, do you think you could take some audio recordings for us with yourself or someone else talking in the cab while the engine is idling so we can hear it, please?

I've got a whistler, too... and the big thing keeping me from putting a muffler on the exhaust is that I like hearing the whistle of the turbo.

Hey TexAndy,

The only means I have of recording is my cell phone camera.
I tried and in-cab recordings are garbled racket.

I have a whistler, too.
Trust me, the whistle's still there.
Just not as shrill.

 

[Flyingvan911]

Everything I have read in the muffler threads say the whistle gets through the muffler with no change.

Yep. I got the 21470. I've read that it should slide right through the existing mirror bracket. I'll have to see when I get the truck from GL.

 

[greg burns]

Cab noise level with Walker muffler

The idea of an audio recording was mentioned earlier today. I used a Canon digital camera in the movie mode to make a brief recording. It was shot with the passenger window closed and the engine at about 800 rpm. The audio meter is recording the volume level with the Walker RV muffler installed.

The Walker muffler fit within the framework of the mirror bracket. I'm hoping to fab up a more suitable bracket for anchoring the muffler. For now, the 7.25" diameter u-bolt seems to be stable enough.

greg