Exhaust Drone

[Agent WD-40]

Terrific.
Is there drone between 1400 - 1800 rpm, low range boom in the 45-75 hz, on deceleration range with the MRT modifications? Also, no drone even when the system is completely warmed up after driving for 10 min?

This solved all the drone I had in the 1400-2000 RPM zone. The 120 Hz sound peaked at 1900 RPM but could hear it rise and fall in the 1400-2000 RPM window. You can see the before & after spectrum analyzer graphs I took. Look at the green peak section - you can see the 120 Hz peak is gone. The green is the "peak hold" taken from idle to ~3k RPM.

Also no drone when the system is completely warm.

It didn't totally mute the 45-75 Hz (you can also see this is still present in my "before" and "after"). What the MRT mufflers did was make it so it is no longer bothersome though. Overall sound is much better managed.

With the stock Borla S-Type I got a very boomy sound at idle when warm as well as some deceleration boom. This was in the 45-75 Hz range you mentioned. My family would plug their ears due to the boom sound at idle as it was so loud at times (worse with roof/windows open). The MRT mufflers knocked this down to a completely tolerable level.

 

[Canadian 392]

This solved all the drone I had in the 1400-2000 RPM zone. The 120 Hz sound peaked at 1900 RPM but could hear it rise and fall in the 1400-2000 RPM window. You can see the before & after spectrum analyzer graphs I took. Look at the green peak section - you can see the 120 Hz peak is gone. The green is the "peak hold" taken from idle to ~3k RPM.

Also no drone when the system is completely warm.

It didn't totally mute the 45-75 Hz (you can also see this is still present in my "before" and "after"). What the MRT mufflers did was make it so it is no longer bothersome though. Overall sound is much better managed.

With the stock Borla S-Type I got a very boomy sound at idle when warm as well as some deceleration boom. This was in the 45-75 Hz range you mentioned. My family would plug their ears due to the boom sound at idle as it was so loud at times (worse with roof/windows open). The MRT mufflers knocked this down to a completely tolerable level

Great!

 

[2024White392]

This solved all the drone I had in the 1400-2000 RPM zone. The 120 Hz sound peaked at 1900 RPM but could hear it rise and fall in the 1400-2000 RPM window. You can see the before & after spectrum analyzer graphs I took. Look at the green peak section - you can see the 120 Hz peak is gone. The green is the "peak hold" taken from idle to ~3k RPM.

Also no drone when the system is completely warm.

It didn't totally mute the 45-75 Hz (you can also see this is still present in my "before" and "after"). What the MRT mufflers did was make it so it is no longer bothersome though. Overall sound is much better managed.

With the stock Borla S-Type I got a very boomy sound at idle when warm as well as some deceleration boom. This was in the 45-75 Hz range you mentioned. My family would plug their ears due to the boom sound at idle as it was so loud at times (worse with roof/windows open). The MRT mufflers knocked this down to a completely tolerable level.

This is good news- any chance you could share sizing of the mufflers you added and/or muffler model numbers? Would like to try adding to stock system as well to see how that goes.

 

[Agent WD-40]

This is good news- any chance you could share sizing of the mufflers you added and/or muffler model numbers? Would like to try adding to stock system as well to see how that goes.

I will ask MRT and share back - didn’t see on their website and don’t have a model number listed on my paperwork. I got the 3” ProSound version.

I believe I was the first person to put this V8 specific version on a vehicle after some initial R&D MRT had completed. Probably why it’s not listed yet.

Dimensions: 3” center inlet / 3” center outlet. Case is an oval ~8” tall, ~5” wide, ~14.5” long.

 

[Canadian 392]

I will ask MRT and share back - didn’t see on their website and don’t have a model number listed on my paperwork. I got the 3” ProSound version.

I believe I was the first person to put this V8 specific version on a vehicle after some initial R&D MRT had completed. Probably why it’s not listed yet.

Dimensions: 3” center inlet / 3” center outlet. Case is an oval 8” tall, 5” wide, 14.5 long.

If MRT could also incorporate either an H or X Pipe to blend the exhaust pulses from the cylinder banks, that would be great too. Perhaps sell this as a unique 392 specific bolt on system

 

[Agent WD-40]

I talked to MRT - these mufflers are not available for sale yet and don't have an ETA. Dave Foxe has been my contact at MRT. He will gladly take the requests and let those people know when they are available. Ask for Dave at [email protected]

Alternatively if you want to send me your email's I'm happy to pass them along to Dave so he can track. He will share the info as soon as this is available.

 

[2024White392]

I will PM you my email. If you are willing to help organize us it may give us a better chance of them making something available to us like what you got. I think there would be a ton of interest in a “392 drone killer” setup from them.

 

[Canadian 392]

I talked to MRT - these mufflers are not available for sale yet and don't have an ETA. Dave Foxe has been my contact at MRT. He will gladly take the requests and let those people know when they are available. Ask for Dave at [email protected]

Alternatively if you want to send me your email's I'm happy to pass them along to Dave so he can track. He will share the info as soon as this is available.

I'll also send you my email for this product.
Agreed. I also agree, "392 Drone Killer" would generate a lot of interest and sales for MRT.

Thanks!

 

[2024White392]

I'll also send you my email for this product.
Agreed. I also agree, "392 Drone Killer" would generate a lot of interest and sales for MRT.

Thanks!

Canadian 392, you have been a leader for us in trying to find a solution here. The more owners that show an interest in a solution from mrt, the better the chance they develop it. Are there other places we should post this information to generate as much interest as possible?

 

[Canadian 392]

Canadian 392, you have been a leader for us in trying to find a solution here. The more owners that show an interest in a solution from mrt, the better the chance they develop it. Are there other places we should post this information to generate as much interest as possible?

Hi 2024White392,
Thank you for the kind words.

I have contributed to the following thread on the other forum. Link is pasted below. I'm sure those on that forum would also enjoy a solution to the 392 Drone problem.

Exhaust boominess

I have an AWE exhaust on my 2022 392 and there is no drone. It sounds stupid in MDS mode, but it isn't a drone. It is loud and obnoxious to people outside the Jeep when it is in performance mode. But it is a good sounding kind of obnoxious, so they can deal with it, LOL. Good luck fixing...

www.jlwranglerforums.com

 

[Spectre]

I'm in to kill the drone

 

[I-10]

I would be interested on what they have to offer.

 

[MRT Performance]

We've been keeping an eye on the great conversation here around the custom exhaust work we did for Agent WD-40 to eliminate drone on his Rubicon 392. It’s awesome to see the interest and feedback from the community!

For those of you who want to stay in the loop as we get ready to launch our newly developed MRT ProSeries Sound—designed with drone elimination in mind—feel free to send an email to [email protected]
with your contact info. We’ll make sure you’re among the first to know when they’re ready to rock.

-Team MRT

 

[Ernesto]

We've been keeping an eye on the great conversation here around the custom exhaust work we did for Agent WD-40 to eliminate drone on his Rubicon 392. It’s awesome to see the interest and feedback from the community!

For those of you who want to stay in the loop as we get ready to launch our newly developed MRT ProSeries Sound—designed with drone elimination in mind—feel free to send an email to [email protected]
with your contact info. We’ll make sure you’re among the first to know when they’re ready to rock.

-Team MRT

I’ve been off the forum for a couple of weeks. Just passed 5000 miles in my 392 problem free. If I can kill the drone issue this might become my favourite car. I’m in for any solution. I represent the UK. Not sure about other European owners.

 

[ruscopin]

I am new here but not new to Jeeps. I had the 2.0JLUR, then JT Mojave, and now back to the Wrangler and without a doubt my favorite. I purchased a new old stock 2024 Final Edition which came with about everything, excluding the fancy roof top, but it did include the drone. I chalked it up as normal. After reading thought this chain, I saw the suggestion about using AI and learned a few things that I need to verify. I hear the drone most when I am off throttle and going through our neighborhood at 25-30 mph. I always drive with the "loud button" on but apparently that doesn't mean the valves are always open. Claude AI is theorizing that there may have been a change to the 2024 model year Active Exhaust Valve Programming. This needs to be verified, but it may be that when the off-throttle condition occurs, the DFCO - (Deceleration Fuel Cut-Off), the exhaust system is under vacuum instead of pressure. This completely changes the acoustic characteristics. If your active exhaust valves close during DFCO (which they might, even in Track Mode), you're creating a resonance chamber at a very specific frequency, ~72 Hz fundamental with strong 129 Hz 2nd harmonic. I am attaching the Claude AI details in a pdf document if anyone is interested.

 

[2024White392]

I am new here but not new to Jeeps. I had the 2.0JLUR, then JT Mojave, and now back to the Wrangler and without a doubt my favorite. I purchased a new old stock 2024 Final Edition which came with about everything, excluding the fancy roof top, but it did include the drone. I chalked it up as normal. After reading thought this chain, I saw the suggestion about using AI and learned a few things that I need to verify. I hear the drone most when I am off throttle and going through our neighborhood at 25-30 mph. I always drive with the "loud button" on but apparently that doesn't mean the valves are always open. Claude AI is theorizing that there may have been a change to the 2024 model year Active Exhaust Valve Programming. This needs to be verified, but it may be that when the off-throttle condition occurs, the DFCO - (Deceleration Fuel Cut-Off), the exhaust system is under vacuum instead of pressure. This completely changes the acoustic characteristics. If your active exhaust valves close during DFCO (which they might, even in Track Mode), you're creating a resonance chamber at a very specific frequency, ~72 Hz fundamental with strong 129 Hz 2nd harmonic. I am attaching the Claude AI details in a pdf document if anyone is interested.

Very very interesting. Want to see what mrt thinks about this given their development of the drone elimination system.

 

[Keithbickford]

I suspect what you’re hearing is the Multi Displacement System (MDS) cylinder deactivation, which turns it into a four cylinder. You might even feel rumble under the driver seat. The Z Automotive No Limitz module disables MDS and that got rid of that annoying rumble and the noticeable lag when you hit the gas before all eight start playing.

 

[ruscopin]

I don't believe it is MDS because I lock MDS out using manual mode. While driving, in traffic, it doesn't bother me but when coasting down hills off throttle, that is when it is the worst, whether in manual mode or normal including MDS.

I'll rig up a gpro this weekend and have a look at the valves. I am trying to stay away from the Z programing to maintain warranty. I just passed 3200 miles. My biggest concern about the vehicle is the transfer case and I don't want to give them any excuses. As for the lag you mention, I have noticed a lag, but I was contributing that to the clutch pack in the T-case. When I feel a lag, the engine still sounds responsive. Is that the lag you are referring to?

 

[Spectre]

I don't believe it is MDS because I lock MDS out using manual mode. While driving, in traffic, it doesn't bother me but when coasting down hills off throttle, that is when it is the worst, whether in manual mode or normal including MDS.

I'll rig up a gpro this weekend and have a look at the valves. I am trying to stay away from the Z programing to maintain warranty. I just passed 3200 miles. My biggest concern about the vehicle is the transfer case and I don't want to give them any excuses. As for the lag you mention, I have noticed a lag, but I was contributing that to the clutch pack in the T-case. When I feel a lag, the engine still sounds responsive. Is that the lag you are referring to?

I find the level of drone is so terrible it sucks the enjoyment out of some of our trucks!! the drone in my wife's 392 has gotten progressively worse over time I am under 6,000 MI!

 

[Canadian 392]

HI All,
I have sent another follow up email to Bob Broderdorf, Jeep CEO about our drone problems, asking for his assistance, and for a telephone call to discuss....