talskinyguy
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- DeKalb, IL
I had 2 goals when adding a muffler
1. As quiet as possible.
2. Not choking the engine so much that I burn something up.
The first step was figuring out the CFM of the exhaust.
I used this from donaldson's website to figure that out.
http://www.asia.donaldson.com/en/exhaust/support/datalibrary/1053747.pdf
I came up with an intake CFM of 540 using a VE of 1.5, but the stock air filter is only rated for 410 CFM from what I can find, so I'll just work with both numbers.
This gives me an exhaust CFM at 1000 degrees of 1108 if I assume 410CFM intake, and 1460 if I assume 540CFM intake.
At this point I decided to use the numbers that went with 410CFM intake since that is what the intake filter is rated for. This seems to assume a VE of 1.12 for the math to work out, which seems low for a turbo engine, but the intake is going to restrict flow at this point anyways.
The form from donaldson also said to not exceed 3 In HG of exhaust pressure, so I am looking for a muffler that flows 1108 cfm at 3 In of HG.
I found this Donaldson muffler M090146 with the following specs.
And this is where my compromise came in.This muffler has the most sound reduction rating by nearly 10dBA that I could find. And how often am I sitting at 2600 RPM and running full throttle? In my experience never. 2400 RPM gets me back down to a flow rate that causes less than 3 In HG and I am rarely ever full throttle in that scenario either.
This math is based on my own assumptions of how I drive and my fuel pump not turned up at all. I will be getting an EGT gauge in the future to make sure that I don't burn anything up, because this amount of back pressure will definitely make my EGT's raise faster, but I don't think they will get to any dangerous amount with the way I drive the truck.
Then again maybe all this math is garbage on this engine because the head doesn't flow worth a **** or something. Because it is generally agreed upon that its 1.5 cfm intake to each hp and 2.2-2.3 cfm exhaust per hp. If that is true then I'm below even the 1 In HG number for this muffler at max hp of the engine.
1. As quiet as possible.
2. Not choking the engine so much that I burn something up.
The first step was figuring out the CFM of the exhaust.
I used this from donaldson's website to figure that out.
http://www.asia.donaldson.com/en/exhaust/support/datalibrary/1053747.pdf
I came up with an intake CFM of 540 using a VE of 1.5, but the stock air filter is only rated for 410 CFM from what I can find, so I'll just work with both numbers.
This gives me an exhaust CFM at 1000 degrees of 1108 if I assume 410CFM intake, and 1460 if I assume 540CFM intake.
At this point I decided to use the numbers that went with 410CFM intake since that is what the intake filter is rated for. This seems to assume a VE of 1.12 for the math to work out, which seems low for a turbo engine, but the intake is going to restrict flow at this point anyways.
The form from donaldson also said to not exceed 3 In HG of exhaust pressure, so I am looking for a muffler that flows 1108 cfm at 3 In of HG.
I found this Donaldson muffler M090146 with the following specs.
| Inlet Diameter: | 3.50 Inches (88.90 MM) |
| Outlet Diameter: | 3.50 Inches (88.90 MM) |
| Body Diameter: | 9.00 Inches (228.60 MM) |
| Body Length: | 44.50 Inches (1130.30 MM) |
| Overall Length: | 51.00 Inches (1295.40 MM) |
| Rated Flow LR: | 578.00 CFM (16.3574 CMM) |
| Rated Flow MR: | 817.00 CFM (23.1211 CMM) |
| Rated Flow HR: | 1010.0 CFM (28.583 CMM) |
| Back Press LR: | 1.00 In Hg (25.40 MM Hg) |
| Back Press MR: | 2.00 In Hg (50.80 MM Hg) |
| Back Press HR: | 3.00 In Hg (76.20 MM Hg) |
| Attenuation: | 19-25 dBA |
And this is where my compromise came in.This muffler has the most sound reduction rating by nearly 10dBA that I could find. And how often am I sitting at 2600 RPM and running full throttle? In my experience never. 2400 RPM gets me back down to a flow rate that causes less than 3 In HG and I am rarely ever full throttle in that scenario either.
This math is based on my own assumptions of how I drive and my fuel pump not turned up at all. I will be getting an EGT gauge in the future to make sure that I don't burn anything up, because this amount of back pressure will definitely make my EGT's raise faster, but I don't think they will get to any dangerous amount with the way I drive the truck.
Then again maybe all this math is garbage on this engine because the head doesn't flow worth a **** or something. Because it is generally agreed upon that its 1.5 cfm intake to each hp and 2.2-2.3 cfm exhaust per hp. If that is true then I'm below even the 1 In HG number for this muffler at max hp of the engine.
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... insulate your cab and hood. that will help a lot.