18 replies to this topic

[Colakurt]

I got the Peco upswept exhaust on my MPI mini. I really like the looks of the two 2,25" upswept tailpipes, but i do think that the car is too noisy when i drive longer trips.

I have done a little measuring and found that the noise level in the cabin is about 99dB with an almost clean 125Hz tone when i drive about 130km/t. This to me seems like a bad case of resonance.

My question is now, is there any way to remove the resonance? I could add a middle box, but what choices do i have? I can't find anything like a middle box from Peco, the best thing i can find is the RC40 40-014 middle box, but will it fit the rest of my system? or does Peco make a box that fits my muffler?

[Cooperman]

The Peco twin exit box will be causing a loss of power and increased fuel consumption as well as a lot of noise.
Change to a 1.75" bore system such as a twin-box RC40 system for improved performance and less noise.

[racingbob]

twin box will help i put a maniflow twin system but larger

boxes than normal, maniflow fitted it

[Turbo Phil]

As already said the Peco exhaust will be losing you performance, they're rubbish to put it politely. The RC40 is the way to go.

[Cooperman]

As already said the Peco exhaust will be losing you performance, they're rubbish to put it politely. The RC40 is the way to go.

That is being very polite, Phil. Actually they are just junk and to advertise them as a performance exhaust is misleading in the extreme!

[Turbo Phil]

The swear filter wouldn't let me put anything else ! lol

[Cooperman]

How the big Mini parts companies can advertise those 'silly' twin-exit pipes as 'performance improving' is amazing. It's a scientific fact that they reduce performance in terms of power and fuel consumption, yet still they are claimed to 'improve power'. It's not just 'doubtful', it's a downright lie.
If they said that they 'look cool, but reduce power' it would be their opinion of what looks 'cool', but that is not how they are advertised and sold.
B****y disgrace.

[RobWill116]

How the big Mini parts companies can advertise those 'silly' twin-exit pipes as 'performance improving' is amazing. It's a scientific fact that they reduce performance in terms of power and fuel consumption, yet still they are claimed to 'improve power'. It's not just 'doubtful', it's a downright lie.
If they said that they 'look cool, but reduce power' it would be their opinion of what looks 'cool', but that is not how they are advertised and sold.
B****y disgrace.

Sorry to highjack, but is this relevant for all twin exit exhausts? I've got a playmini supersport

[jakejakejake1]

Pretty much,
The optimum diameter is 1.75 inch, (area = pi*r^2 = 2.4 CU In)
So for a twin you would want a diameter around 1.25 inch.
If its much bigger than this then you will probably be losing power.

[Cooperman]

Yes it applies to all twin-pipe exhausts unless the twin pipes have the same total cross sectional area as a single 1.75" pipe. That would make each of the twin pipes 1.25" diameter, i.e. very small.
Crikey, my 2.5 litre BMW only has twin 1.75" pipes and that has about 190 bhp at 6000 rpm, so an engine half that size with about half that power therefore only needs a single 1.75" pipe to perform at its best.
The times this fact has been posted on here I've lost count of..

Edited by Cooperman, 18 May 2012 - 09:16 PM.

[Colakurt]

Thanks, i think i will change the exhaust to RC 40 then.

Just how much noise reduction can i expect when going from a single box system to a two box system?

[Cooperman]

The RC40 twin box system will give around 92 decibels at 5000 rpm measured 45 degrees from the exit at 0.5 metres, if that helps.
I've no idea what decible level the silly Peco system gives, sorry.

[Colakurt]

How is that compared with the RC40 single box?
Just to give me an idea of the difference between twin and single box systems.

I must say that I'm really thinking about changing to RC40, especially if the Peco is as bad as you say.


What about RC40 mounting? I would like to get it as close to the bottom of my car as possible, but still keep it as quiet at possible.

[Ryang556]

The Peco twin exit box will be causing a loss of power and increased fuel consumption as well as a lot of noise.
Change to a 1.75" bore system such as a twin-box RC40 system for improved performance and less noise.

I knew this post was coming!

I remember you telling me this was the best

http://www.maniflow....58&product=1136

[Cooperman]

How is that compared with the RC40 single box?
Just to give me an idea of the difference between twin and single box systems.

I must say that I'm really thinking about changing to RC40, especially if the Peco is as bad as you say.


What about RC40 mounting? I would like to get it as close to the bottom of my car as possible, but still keep it as quiet at possible.

I've never had a single box RC40 on a 1275 so never measured the decibels. I do know the tewin-box RC40 is really excellent in terms of performance and sensible noise. But then, I don't like noisy cars.
With the right mountings, ie.e the original rubber block and 'cotton-reel' types, it fits close to the underside of the floor.

Edited by Cooperman, 20 May 2012 - 11:00 PM.