16 replies to this topic

[Adge456]

Hi,
My mini has a straight pipe from when I got it.
I like the look of it, it is the twin pipes at the back.
Only ‘problem’ is that it’s very loud.
Is there a way to reduce the noise a bit withought having a standard side exhaust?
I was looking at the cherry bomb mid muffler but wasn’t entirely sure if this makes it quieter or louder!

Any advice would be great.

Thank you,
Adge

[gazza82]

Cherry bomb? I was waiting for an MOT once and watching the engineers ripping the system off, it had one cherry bomb, to replace with a standard system as it was too loud for the new MOT rules. It wasn't much quieter than having a pipe with no silencers!To pass, it needed a standard system!

Edited by gazza82, 17 July 2019 - 01:41 PM.

[mini13]

RC40 system is always a good bet, twin box ones are pretty quiet, not to pricy either

[Cooperman]

First of all the twin pipes at the exhaust are costing you power and making a lot of noise. The best system for you is an RC40 centre exit twin box system with a single exit pipe.
That system is capable of pasding the noise test for road rallies where max noise is strictly controlled.
An alternative is a Maniflow sysyem with a cherry-bomb as the centre box and a normal rear box leading to a single pipe centre exit.

[unburntfuelinthemorning]

I had a twin box RC40 years ago and it was quiet but efficient so I'd recommend one too.  There are more options available with it now for instance this back box:  http://www.minispare...52.aspx|Back to

[Cooperman]

I had a twin box RC40 years ago and it was quiet but efficient so I'd recommend one too.  There are more options available with it now for instance this back box:  http://www.minispare...52.aspx|Back to

 

That is expensive for a silencer which is going to lose some power and torque whilst not making the car quieter in any way.

[unburntfuelinthemorning]

 

I had a twin box RC40 years ago and it was quiet but efficient so I'd recommend one too.  There are more options available with it now for instance this back box:  http://www.minispare...52.aspx|Back to

 

That is expensive for a silencer which is going to lose some power and torque whilst not making the car quieter in any way.

 

Yes sorry I didn't look at the price.  I take it only the single exit RC40 back box, whether side or centre exit will work as per the original RC40 concept and the twin exit one will not then.

[Cooperman]

To explain again why the boxes with the twin parallel final outlet pipes cause power losses I will refer to what is known as Bernoulli's Theorem.

 

This states that when a fluid passes along a pipe, if the cross-sectional area of the pipe increases, the velocity of the fluid decreases and the pressure of the fluid increases. The increased pressure inside the box increases because the cross-sectional area of the final outlet pipes is greater than the area of the main exhaust pipe. The increased pressure locally combined with decrease in the speed of the molecules making up the exhaust gases causes the required velocity of exhaust gas to reduce from the ideal and the extraction effect is seriously reduced.

 

Hence a loss of power/torque and an increase in fuel consumption. The only way a twin parallel exit can work is if the cross-sectional area of the two pipes is equal to the cross sectional area of the main exhaust pipe. For a 1.75" diameter pipe, the end parallel pipes would need to be around 1.25" diameter to work OK.

[unburntfuelinthemorning]

Even though the RC40 twin exit exhaust is far from being the best for efficiency it must still be an improvement on the standard rear silencers which use strangulation techniques to achieve silencing.

[timmy850]

Any decent exhaust shop can add some extra mufflers to your existing system.

[Adge456]

Thanks guys.
So my back box with the two pipes seems an issue.
My dad has a single pipe at home which I can have, but I remember that being loud too (as it’s still straight through)
So if I got a mid box, would that help and not compromise the torque/ fuel?

[M700FGT]

I have the same problem with mine. My 97 MPI Cooper came with a centre twin DTM which is very loud when i brought it. 

 

I like the look, but i know it's costing my power future costs in hearing aids. 

 

I actually removed the K&N induction and went back to standard filter house with a K&N filter - no difference at all.

 

I was considering swapping to a single centre in stainless, but I'm not sure what the best one would be. 

Attached Files

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[unburntfuelinthemorning]

Thanks guys.
So my back box with the two pipes seems an issue.
My dad has a single pipe at home which I can have, but I remember that being loud too (as it’s still straight through)
So if I got a mid box, would that help and not compromise the torque/ fuel?

Just fit the original standard RC40.  It costs less than £70 and will be quiet and more efficient than your current system.  Bargain really, bends in the right place and everything.  It is a fully straight through system but it is properly designed and works really well.  Hard to improve on for most applications.

 

http://www.minispare...px|Back to shop

[mini-mad-mark]

Just to add my two penn'orth. Not specifically about performance although in theory I can go faster now

 

The twin box RC40 (single side exit pipe) hangs a little bit low in the centre box and round my way we have many speed humps,  and also my drive way goes up to the lip and then down after, so with my car being lowered (slightly - not gangsta!) the box was always getting clipped; not badly, just enough to be annoying and a bit worrying as it sounded worse than it was.

 

I changed to a single box system (still single side exit pipe) I think the noise is slightly higher although I can hardly tell over the engine noise  but if anything it just sounds nicer. Not loud but seems more "rorty" and fixed the main problem: No more issues with speed humps as i can go over without having to slow right down so a net increase in speed (although maybe not power)

 

Not sure what effect on power, single vs twin box RC40? A single box is specified for Mini Spares Stage one kits on commercials/estates.

[riktanius]

I have the same problem with mine. My 97 MPI Cooper came with a centre twin DTM which is very loud when i brought it. 

 

I like the look, but i know it's costing my power future costs in hearing aids. 

 

I actually removed the K&N induction and went back to standard filter house with a K&N filter - no difference at all.

 

I was considering swapping to a single centre in stainless, but I'm not sure what the best one would be. 

The car looks GREAT. Nice job. 

 

Personally... changing the single muffler exhaust to another brand isnt going to do much if they have the same internals. The number of tips or exits doesnt matter as much. 

Modern cars are quiet because they have catalytic converters and multiple silencers before you get to the incredibly restrictive main muffler. I would recommend adding another muffler inline if you want it to be quieter, or even adding a cat.