Muffler shop wouldn't install Magnaflow Resonator on my DD 6V92

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Muffler shop wouldn't install Magnaflow Resonator on my DD 6V92

June 14, 2017, 07:30:46 pm

Not sure if they wouldn't or couldn't. After lots of research on this wonderful forum I ordered a Magnaflow #12771 resonator to install in my DD 6V92.

Amazon.com: MagnaFlow 12771 Exhaust Muffler: Automotive

The muffler shop told me that my DD has 5 inch pipes and that it would be counter productive to step down to 4 inches to install a resonator with 4 inch outlets.

If they are wrong, I'm uncomfortable having it done there.

Any feedback from 6V92 experts would be greatly appreciated. Thank you.

Edited to Add: I am voting for 'didn't feel like doing it'. The largest in/out I see in the MagnaFlow website is 4 inches.

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Re: Muffler shop wouldn't install Magnaflow Resonator on my DD 6V92

Reply #1 – June 14, 2017, 07:37:30 pm

Jeff,
Man I was hoping to hear a great outcome from you on your resonator. I don't know anything about the DD to say about whether it should fit, but if it is a 5" exhaust it makes sense not to choke it down to a 4".

Keep us posted.

Len

Re: Muffler shop wouldn't install Magnaflow Resonator on my DD 6V92

Reply #2 – June 14, 2017, 07:50:17 pm

I wonder what Brett or Pierce will have to say, but 5" resonators readily available

Re: Muffler shop wouldn't install Magnaflow Resonator on my DD 6V92

Reply #3 – June 14, 2017, 07:54:51 pm

Jeff you definitely don't want to go down in size plenty of 5 inch resonators available.Send it back .

Re: Muffler shop wouldn't install Magnaflow Resonator on my DD 6V92

Reply #4 – June 14, 2017, 07:56:39 pm

Thanks Stump.

Re: Muffler shop wouldn't install Magnaflow Resonator on my DD 6V92

Reply #5 – June 14, 2017, 08:01:58 pm

I am not a expert but having the right size pipe is great but more importantly the the item your installing should match the exhaust flow of the engine. In other words in the engine data there is a number for exhaust flow, the item your installing should not restrict that number. Normally the part your buying for your exhaust it will tell you what exhaust flow it is capable of handling.

Usually that can be checked with a manometer for back pressure restriction, not a hard thing to check.

Re: Muffler shop wouldn't install Magnaflow Resonator on my DD 6V92

Reply #6 – June 14, 2017, 08:28:18 pm

Absolutely, do not downsize on ANY engine.

But, I am NOT the DD 2 stroke expert here, so specific DD 2 stroke questions I will leave to others.

Re: Muffler shop wouldn't install Magnaflow Resonator on my DD 6V92

Reply #7 – June 14, 2017, 08:35:30 pm

6v92 flows almost 3000 cubic feet per minute of exhaust, even with the 5" IRRC it's over 250 mph. 5" dia is about 19.6" sqin of cross section, 4" has a cross sectional area of 12.6 sqin. These figures are not exact because exhaust pipe is actually exhaust tube.

Re: Muffler shop wouldn't install Magnaflow Resonator on my DD 6V92

Reply #8 – June 14, 2017, 08:40:31 pm

Quote from: wolfe10 – June 14, 2017, 08:28:18 pm

Absolutely, do not downsize on ANY engine.

But, I am NOT the DD 2 stroke expert here, so specific DD 2 stroke questions I will leave to others.

Thanks Brett, hoping Pierce will see the thread.....

Re: Muffler shop wouldn't install Magnaflow Resonator on my DD 6V92

Reply #9 – June 14, 2017, 08:42:28 pm

Now I am curious if my 8.3 Cummins is 5" or 4". If it is 4", I might just buy that resonator from Jeff.

Len

Re: Muffler shop wouldn't install Magnaflow Resonator on my DD 6V92

Reply #10 – June 14, 2017, 08:44:30 pm

Quote from: lenspeiser – June 14, 2017, 08:42:28 pm

Now I am curious if my 8.3 Cummins is 5" or 4". If it is 4", I might just buy that resonator from Jeff.

Len

Len, the return label is already on the box.

Re: Muffler shop wouldn't install Magnaflow Resonator on my DD 6V92

Reply #11 – June 14, 2017, 09:14:07 pm

My cat 3176 is 4" but steps up to 5" for the muffler and tailpipe. The cummins 8.3 I looked at was 4" all the way thru. If your turbo has a 5" output, i wouldnt restrict it with Anything smaller at all.

Re: Muffler shop wouldn't install Magnaflow Resonator on my DD 6V92

Reply #12 – June 14, 2017, 10:11:11 pm

Don't install a 4" resonator. Andy Wright is a good source of information as he recently did his. He seems very pleased. I think Ken did his too.

The Detroit 2 cycle uses a huge amount of air. You could use the exhaust as a leaf blower. So, it's 5 inches for a reason. Ask Andy the brand he used.

Pierce

Re: Muffler shop wouldn't install Magnaflow Resonator on my DD 6V92

Reply #13 – June 14, 2017, 10:18:09 pm

Quote from: Pierce & Gaylie Stewart – June 14, 2017, 10:11:11 pm

Don't install a 4" resonator. Andy Wright is a good source of information as he recently did his. He seems very pleased. I think Ken did his too.

Nope. I have it on my list but it's no where near the top. Thanks for thinking of me though!

see ya
ken

Re: Muffler shop wouldn't install Magnaflow Resonator on my DD 6V92

Reply #14 – June 14, 2017, 11:09:26 pm

5 inch is what I used, pretty simple couple hours of work. Hardest park was removing the old muffler.

Re: Muffler shop wouldn't install Magnaflow Resonator on my DD 6V92

Reply #15 – June 14, 2017, 11:34:40 pm

Thanks Andy. What resonator did you use?

Re: Muffler shop wouldn't install Magnaflow Resonator on my DD 6V92

Reply #16 – June 14, 2017, 11:46:48 pm

To be honest I can't find the receipt, I'am sure it was just a standard 5 inch in and out resonator. I think I paid 60 bucks for it.

Re: Muffler shop wouldn't install Magnaflow Resonator on my DD 6V92

Reply #17 – June 15, 2017, 02:02:35 am

Our C8.3 Cummins has a 4" pipe from turbo. We found a 5" resonator and installed it with 4 to 5 transition after turbo and another 4 to 5 transition to get through the fiberglass for the chrome tip. We figured we would later widen the fiberglass hole and just bring the 5" out, but never did that so we still have the 4" tip.

Re: Muffler shop wouldn't install Magnaflow Resonator on my DD 6V92

Reply #18 – June 15, 2017, 09:10:55 am

I used a regular one too available at truck places. Walker make.
JohnH

Re: Muffler shop wouldn't install Magnaflow Resonator on my DD 6V92

Reply #19 – June 15, 2017, 09:25:33 am

"tuning" two strokes, like motorcycles uses a restriction to set up a back wave front to "pack" air fuel mix into the cylinder within a predetermined engineered rpm envelope. Doesn't work on DD two strokes with blowers and turbo's. Don't restrict the exhaust. I've got a bus conversion with straight pipe. likely not appropriate for most, but I've gotten away with it so far.

wannabe

Re: Muffler shop wouldn't install Magnaflow Resonator on my DD 6V92

Reply #20 – June 15, 2017, 10:00:26 am

Walker 21835 Resonator Universal 5" Inlet Each | eBay
I used this one.

Re: Muffler shop wouldn't install Magnaflow Resonator on my DD 6V92

Reply #21 – June 15, 2017, 10:05:45 am

Good call, that looks the one I used.

Re: Muffler shop wouldn't install Magnaflow Resonator on my DD 6V92

Reply #22 – June 15, 2017, 10:39:43 am

Before you purchase your resonator, check to see if a stainless version is available. They are usually about double the money but look nice and won't rust.

Don't mistake a 2-cycle motorcycle/chain saw for a 2-cycle diesel. Outside of firing every time the piston comes up, there is almost nothing the same between the two types of engines. No exhaust "tuning" here.

When changing to a resonator, take the time to check your air filter restriction gauge. Since the 2-cycles use so much air, they have a very large air cleaner. Don't try to clean it as that won't work. I tried...and failed. Fairly expensive at about $70 (if you look around) but ours ran much better after installing the new one. Don't even think about modifying the air cleaner or intake tubing. Some have and dusted the engine. Only modification would be to update your U300 to the air cleaner intake up high like the late 1993 models came with (Kent Speers). Otherwise, our air cleaners suck up everything off the rear wheels and will shorten the air cleaner life drastically. I think the U280 of the same vintage have a similar problem. If driving in the rain or damp conditions, your restriction gauge may read higher until the air cleaner dries. Remember, all three manufactures have different limits on the amount of restriction allowed before a filter change is required. Check our old posts for the numbers.

Pierce

Re: Muffler shop wouldn't install Magnaflow Resonator on my DD 6V92

Reply #23 – June 15, 2017, 01:09:51 pm

Jeff:
The Magnaflow 12771 muffler you bought is 4" in and 4" out, SS with satin finish.
The Magnaflow 12774 muffler I installed in my U320 is 5" in and 5" out, SS with satin finish.
They are both available polished for more money, but I covered mine with exhaust wrap.
I used the Magnaflow because it is not as loud as an Aero muffler. The Aero muffler is not as loud as an Aero resonator.
Some Foreforum folks installed Aero resonators and are satisfied with them.
I posted a summary of available mufflers on Foreforums several years ago.

Re: Muffler shop wouldn't install Magnaflow Resonator on my DD 6V92

Reply #24 – June 15, 2017, 01:40:02 pm

Quote from: P. Wyatt Sabourin – June 15, 2017, 01:09:51 pm

I used the Magnaflow because it is not as loud as an Aero muffler. The Aero muffler is not as loud as an Aero resonator.

We started with an Aero and changed to the Magnaflow. No perceived performance change, much less loud.

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