34 replies to this topic

[jeffster06]

Currently I have a single box 1 3/4" maniflow side exit dual tip DTM exhaust (C-ARA340) with a stage 2 LCB (C-AEG376). I know a twin box system will make the exhaust quieter but I am wondering by how much. I love the sound I currently have but the drone cruising around is finally getting to me. I don't think I can add anymore sound deadening to my car, currently I am running butyl rubber sheets just about everywhere along with closed cell foam sheets on top of them.

[MrBounce]

I had a single box RC40 and replaced it with a twin box Maniflow centre exit in the early 2000s - still sounded meaty, but there was no drone and the loud raspiness at start-up disappeared, which my neighbours were eternally grateful for.

[jeffster06]

I've been thinking about reaching out to Maniflow to see if they will sell me just the mid pipe with the resonator, the exhaust is only a couple years old so I don't think I need to replace the whole thing.

[Aly-g]

I've been thinking about reaching out to Maniflow to see if they will sell me just the mid pipe with the resonator, the exhaust is only a couple years old so I don't think I need to replace the whole thing.

I'm sure Maniflow would sell you a mid pipe with the resonator, why wouldn't they ? It's another sale after all.

Allan

[Spherix]

They probably also have decibel readings per setup for you.

[nicklouse]

A twin box center exit is slightly quieter than a single box. A single box side exit is quieter than a single box center exit. The quietest is a side exit twin box. Presuming the same design of system with same silencer dimensions.

 

the bigger the silencers the less noise escapes.

 

the RC40 back box is a twin silencer with a resonator first and a silencer second. This help take out the odd sound pattern the A series head design has.

[minifreek1]

I have Maniflow LCB into a straightpipe and then exiting to a Play Mini rear box. Sounds fine to me and not noisy (I dont think anyway)

[Cooperman]

On my rally cars, which have to meet measured noise limits, the only sure way seems to be a twin-box RC40 system. Rally cars need a centre exit single pipe to reduce risk of damage to the rear box (that is why center exit was originally used).
I have tried a Maniflow with a 'Cherry Bomb' as a centre box, but even with both the noise was right on the limit.
A 998 just needs a good rear box (RC40 is best).

[timmy850]

I have a twin box rc40 side exit. It’s always been too quiet for me, so I’m planning on removing the first muffler

[jeffster06]

A 998 just needs a good rear box (RC40 is best).

 

I guess I forgot to mention I have a 1275 (well really a 1310 now). I used to have a twin box center exit and saw the side dual tip my friend had and liked it so I went with that. This was before I restored my car and put all the sound deadening in, I always felt it was loud before even with the center twin but I was missing quite a bit of the old sound deadening material. 

 

I just feel like the last time I drove it the drone was killing me. I am on the fence though because I don't want to make it super quiet I just want to cut the drone in the car if that's possible. 

[nicklouse]

 

A 998 just needs a good rear box (RC40 is best).

 

I guess I forgot to mention I have a 1275 (well really a 1310 now). I used to have a twin box center exit and saw the side dual tip my friend had and liked it so I went with that. This was before I restored my car and put all the sound deadening in, I always felt it was loud before even with the center twin but I was missing quite a bit of the old sound deadening material. 

 

I just feel like the last time I drove it the drone was killing me. I am on the fence though because I don't want to make it super quiet I just want to cut the drone in the car if that's possible. 

 

Dual tip twice the noise and less power.

[jeffster06]

Dual tip twice the noise and less power.

 

oh really? I figured running the 1 3/4 having dual tip on the one muffler wouldn't make that much of a difference. Hmm maybe I need to change up more then I was initially thinking. 

[fokko]

I see a lot of people talking about the noise outside, but Jeffster is asking to reduce noise inside the cabin. Although there is probably a correlation, in my experience, there are two major components that contribute to drone inside. One is the boot floor that resonates (don't know if you put sound deadening there) and the other one is the LCB. You're saying you have a stage 2 LCB, which is causing significantly more noise than a regular LCB. Even better is a freeflow, but I don't know if that's too restrictive for the power output you're aiming form. Also, most people put sound deadening on the inside, but it makes more sense to put it on the outside, e.g. in the engine compartment. Take a look at modern vehicles. They all have it, for a reason. My first step would be to listen very carefully where the drone comes from. Go driving and look sideways, then you'll probably hear if the drone is coming from the rear (boot floor) or the front (LCB/engine compartment). Then work from there... What might also help is to take a look at the way the exhaust is mounted. If stiff rubbers are used, they'll transmit the noise to the inside cabin. I'm considering modern exhaust hangers for my own Mini (MPI style).

 

Hope this helps!

[jeffster06]

fokko you are correct the drone inside is what I would like to reduce, it can be as loud as it wants outside, I doubt I could ever compete with the noise hell cats and mustangs make around here lol. I recently added closed cell foam to the boot I previously just had just butyl rubber in there. I have covered both side of the rear seat back... which reminds me and maybe this is my biggest issue, I don't have a rear seat, previous owner ditched it and I couldn't justify the cost of one when no one will sit back there. So instead I covered it all with butyl rubber and closed cell foam sound deadener and put carpet over it. I have thought about putting something on the engine side of bulkhead just haven't got around to making or buying something. Maybe my question on the thread should have been how to reduce interior drone? 

Edited by jeffster06, 19 July 2022 - 01:13 PM.

[stoneface]

I have this in my mini to reduce the noise of the SC drops. Worked well, although got rid of the sc drops now.

https://www.nkgroup....dwich-material/