I'm at it again - fixing drone on a brand new MBRP

[rc328]

Thanks a lot ,the drone is driving me crazy at 3200 rpm. I'm gonna look in amazon for the vibrant, I want to archive the drone reduction you got in the second video.
Thanks again.

 

[Clint Beastwood]

Thanks a lot ,the drone is driving me crazy at 3200 rpm. I'm gonna look in amazon for the vibrant, I want to archive the drone reduction you got in the second video.
Thanks again.

What exhaust do you have?

 

[Clint Beastwood]

Thanks a lot ,the drone is driving me crazy at 3200 rpm. I'm gonna look in amazon for the vibrant, I want to archive the drone reduction you got in the second video.
Thanks again.

I'm just trying to clarify - it's not the vibrant that reduced the drone, even after the vibrant I had the boomy peaking at 3200RPM, what fixed the drone was the loop of pipe that looks like a trombone. Let me know what exhaust you have and I can take a look to see if you're likely to have enough room to do the quarter wave tube. The Vibrant only mitigates the high frequencies (some crackling, the high pitched turbine noise). The deep noise (at ~3200rpm) has a wave length of 10.5 *feet* so the vibrant is way too short. That's why I math-nerded it out and came up with the looped section. You can copy the exact same length I reference in my initial post, and show an exhaust shop the picture of how mine is looped, but it's only going to work if you have no rear muffler or a really tiny one (like the vibrant). I bought an MBRP to test, it's the drone-iest exhaust I have ever seen, and just the looped portion completely resolved the drone and quieted it down.

 

[wetwea33]

I just put a vibrant 1142 right where you did and im catless resonator deleted and it honestly killed alot of the drone and quieted down alot. Im happy with the results its now live-able.

 

[Clint Beastwood]

I just put a vibrant 1142 right where you did and im catless resonator deleted and it honestly killed alot of the drone and quieted down alot. Im happy with the results its now live-able.

Right on. If that deep pressure feeling around 3200 gets to you, this thread is exactly to target that frequency, around 107hz.

For me, adding the vibrant just made the 107hz "crush" more obvious, but I am extremely sound sensitive. I even wear earplugs at the movies (you can still hear the movie fine, just less loud - and you can't hear people talk or babies crying!)

 

[rc328]

I have no exhaust , I removed the muffler when I got the car,

 

[The_Ryan]

This is all very interesting. My Maperformance exhaust drones like crazy right at 3200rpm, despite all of the reviews saying otherwise. Maybe I'm just sensitive to sound as well?

I may just make the full switch to a different system. I can't even enjoy the exhaust sounds because of the boomyness at 3200rpm

 

[Turbo9922]

This is all very interesting. My Maperformance exhaust drones like crazy right at 3200rpm, despite all of the reviews saying otherwise. Maybe I'm just sensitive to sound as well?

I may just make the full switch to a different system. I can't even enjoy the exhaust sounds because of the boomyness at 3200rpm

Thermal all the way. I love the way it looks and the way it sounds.

 

[Clint Beastwood]

This is all very interesting. My Maperformance exhaust drones like crazy right at 3200rpm, despite all of the reviews saying otherwise. Maybe I'm just sensitive to sound as well?

I may just make the full switch to a different system. I can't even enjoy the exhaust sounds because of the boomyness at 3200rpm

If you decide to keep it, you can use the same expansion tube design I used (quarter wave resonator) to totally kill that 3200rpm drone. That's literally what I built that rear loop for - just find an exhaust shop that can fit a loop in the rear muffler cavity (if the MAPerformance exhaust leaves enough room) of the appropriate size and you should be drone-free almost instantly. Just find the RPM drone range and target the middle of it, or target the rpm where the drone is the absolute worst, and work from there.

 

[HalfBaked]

I have an mbrp as well, should i have an exhaust shop make the same piece to your specifications? Or would it be different since I dont have the vibrant muffler?

 

[Clint Beastwood]

I have an mbrp as well, should i have an exhaust shop make the same piece to your specifications? Or would it be different since I dont have the vibrant muffler?

The vibrant pic is just a shot of one of my custom exhausts, I've made a few.

The current is just an MBRP aluminized with the custom rear resonator - I just included the pic so you could show a shop what you wanted, but if you have what I have (mbrp) then the length I used should work for you. It needs to be teed in at a 90 degree angle to work, a forward or rearward lean to the angle will not work.

 

[HalfBaked]

The vibrant pic is just a shot of one of my custom exhausts, I've made a few.

The current is just an MBRP aluminized with the custom rear resonator - I just included the pic so you could show a shop what you wanted, but if you have what I have (mbrp) then the length I used should work for you. It needs to be teed in at a 90 degree angle to work, a forward or rearward lean to the angle will not work.

Noted. Any performance loss with the resonator or would it be a source of restriction if i go big turbo down the line? Not sure if I have the stainless or aluminized since I bought the car with exhaust.

 

[Clint Beastwood]

As long as it’s a 90 degree tee, no - it’s leveraging the same effect as blowing across a bottle to make the hoooooooo noise. Once the chamber is pressurized there’s no turbulence because there’s no flow. The catch is the quality of the welding - if they booger a chunk of weld into the pipe it could add turbulence, but I’m guessing it would take an *extremely* bad weld to make a difference. Remember if your exhaust is stainless to get stainless resonator as well. My
Mbrp is aluminized but I had the chamber made in stainless so I could reuse it if I want.

 

[JNLimon]

As long as it’s a 90 degree tee, no - it’s leveraging the same effect as blowing across a bottle to make the hoooooooo noise. Once the chamber is pressurized there’s no turbulence because there’s no flow. The catch is the quality of the welding - if they booger a chunk of weld into the pipe it could add turbulence, but I’m guessing it would take an *extremely* bad weld to make a difference. Remember if your exhaust is stainless to get stainless resonator as well. My
Mbrp is aluminized but I had the chamber made in stainless so I could reuse it if I want.

Hey there, been reading all this post and just installed one for the MBRP in T409, yes it droned a lot. I used the same 107Hz without any calculations to see how it would perform. It removed lots of drone but know I did the "maths" and found that the real frequency is at about 85Hz, same as the phone app says. I will add the remaining 8" if possible for my specific application. Thanks a lot for your guidance this really does make a significant improvement.

Something else, do you know how can you mitigate the drone between gear changes when pushing it hard? It drones a tiny bit between gearshifts, probably due to downpipe.

 

[Clint Beastwood]

Hey there, been reading all this post and just installed one for the MBRP in T409, yes it droned a lot. I used the same 107Hz without any calculations to see how it would perform. It removed lots of drone but know I did the "maths" and found that the real frequency is at about 85Hz, same as the phone app says. I will add the remaining 8" if possible for my specific application. Thanks a lot for your guidance this really does make a significant improvement.

Something else, do you know how can you mitigate the drone between gear changes when pushing it hard? It drones a tiny bit between gearshifts, probably due to downpipe.

yeah if you have a down pipe it’s gonna be a little noisy before you mod your exhaust more, make sure the mbrp isn’t resting on the mid chassis brace. When my mbrp rested on the brace I was getting some 90ish hz oscillations. New hangers and adding a few washers to the mid chassis brace (and like 4000 hours of adjusting clamps) and it went away. You can increase the delta if your resonator by packing some steel wool into it, it wont cut the droning as much but it’ll increase the affected frequency range.

remember too that the temperature outside will affect your “tuning”, so try to set your length based on results for your average outside temperature. I think I might just sell or cut up all my custom exhausts to reuse the tubing and buy a thermal because I have another project to dump time into now.

I really recommend doing the math of rpm of max droning to get the actual frequency, 85hz reeeeeally sounds like your exhaust is vibrating on the frame somewhere (if you’re getting 85hz on your meter at 3000-3200 rpm). if you’re getting more droning at lower rpm it might be the downpipe, I haven’t done a downpipe (ca smog woo) so I don’t know how it affects the droning. Also make sure whatever sound meter/mic you are using can actually capture 85hz or your data could be off a bit.

As a side note. Depending on how your chamber is angled you can accumulate a bit of moisture in the resonator. I make mine out of t304 so it won’t rust, but have thought about adding a pinhole. If I had more time and better functioning hands I wanted to “sleeve” the end of the resonator so I could adjust the length and clamp it to fine tune.

 

[Clint Beastwood]

I also had issues with the mbrp sliding back and forth on the rear section and touching the valance by the tips which added noise, I got some screw on collars and added them to the hangers to prevent lateral movement. I have given up on getting the mbrp tips to line up that’s a whole other enchilada.

 

[JNLimon]

yeah if you have a down pipe it’s gonna be a little noisy before you mod your exhaust more, make sure the mbrp isn’t resting on the mid chassis brace. When my mbrp rested on the brace I was getting some 90ish hz oscillations. New hangers and adding a few washers to the mid chassis brace (and like 4000 hours of adjusting clamps) and it went away. You can increase the delta if your resonator by packing some steel wool into it, it wont cut the droning as much but it’ll increase the affected frequency range.

remember too that the temperature outside will affect your “tuning”, so try to set your length based on results for your average outside temperature. I think I might just sell or cut up all my custom exhausts to reuse the tubing and buy a thermal because I have another project to dump time into now.

I really recommend doing the math of rpm of max droning to get the actual frequency, 85hz reeeeeally sounds like your exhaust is vibrating on the frame somewhere (if you’re getting 85hz on your meter at 3000-3200 rpm). if you’re getting more droning at lower rpm it might be the downpipe, I haven’t done a downpipe (ca smog woo) so I don’t know how it affects the droning. Also make sure whatever sound meter/mic you are using can actually capture 85hz or your data could be off a bit.

As a side note. Depending on how your chamber is angled you can accumulate a bit of moisture in the resonator. I make mine out of t304 so it won’t rust, but have thought about adding a pinhole. If I had more time and better functioning hands I wanted to “sleeve” the end of the resonator so I could adjust the length and clamp it to fine tune.

Actually the drone is at about 2600 rpm so it might be the Mishimoto downpipe as you said. I made extra sure that the exhaust isn't hitting that center brace and it doesn't show signs of friction. Perhaps adding some less stiff hangers would help and extra bit. I'll keep doing tests.

 

[JNLimon]

I also had issues with the mbrp sliding back and forth on the rear section and touching the valance by the tips which added noise, I got some screw on collars and added them to the hangers to prevent lateral movement. I have given up on getting the mbrp tips to line up that’s a whole other enchilada.

Haha I actually like the different tips... Temperature should be ambient temperature? Do you have any estimate on the temp yo used if it is exhaust temperature?

 

[Clint Beastwood]

Actually the drone is at about 2600 rpm so it might be the Mishimoto downpipe as you said. I made extra sure that the exhaust isn't hitting that center brace and it doesn't show signs of friction. Perhaps adding some less stiff hangers would help and extra bit. I'll keep doing tests.

I did find the mbrp hangers cracking after just a few weeks of use. My best results were whoosh hanger at the downpipe, next one back torque solutions, the other two whoosh. The whoosh hangers are an absolute delight but did allow the exhaust to slide around a bit on the metal hangers so I used the collars.
It should be safe to pop the mid brace off and go for a drive just to be sure, I know some mention taking it off and leaving it. I’m hoping Ron makes a new brace, or I’ll just fab one myself eventually.

 

[The_Ryan]

I've recently thought about looking into making a particle damper. It works at a much wider range of frequencies than a J pipe, and isn't as sensitive to temperature changes. Though to be honest, this exhaust bangs around enough, I'd rather not add any more weight the thing to make that problem worse. I'd think it'd take a good amount of filler to make that particle damper work too. Maybe someone can give that a try? From what I can find, particle damping tuning is more of a guess-and-check process than a calculation to find the right masses, but there are white papers out there that will lead you the right direction