[royevans]

Forgive the newbie question...but what causes this? I love it, just curious!

[beken]

MCS is supercharged. When accelerating, you get boost. The intake air is compressed into the cylinders. When decelerating, you get a bit of vacuum, which causes what seems to be a bit of backfiring. Hence the popping noise.

It's quite normal.

[royevans]

Thanks!!

[Kaelaria]

OMG what body cavity did you pull that answer out of! LOL!

The popping is 100% from the design of the exhaust system and it's backpressure.

[jon vital]

Yeah, especially as it does it at very low revs too.

[Restyle]

...and it never did it on the previous Cooper S`s prior to the 2004 makeover

[Lee Bradshaw]

Quote: Originally Posted by Restyle

...and it never did it on the previous Cooper S`s prior to the 2004 makeover

Mine does.... Maybe the exhaust is blowing!

Not getting it checked though, it sounds lovely.

It is a prefacelift March 04' though???

[laura f]

Quote: Originally Posted by Restyle

...and it never did it on the previous Cooper S`s prior to the 2004 makeover

i thought it was an 05 model year thing I am willing to be wrong on the timing.... but it sounds fantastic

[Lee Bradshaw]

Quote: Originally Posted by villa mini

i thought it was an 05 model year thing I am willing to be wrong on the timing.... but it sounds fantastic

You're welcome to come and have a listen to mine! Everyone round these parts is forced to listen to it anyway!!!!

[kapps]

The earlier models do it, just not nearly as much. You'd have to rev up to 3k rpm (or very close to it) and quickly let off. Anything more or less than 500 rpm off 3k and it won't do it. I took a test drive in an '05 and I could hear it on every shift...even as low as 2k rpm. It sounds sweet. Aftermarket exhausts increase it's presence.

[laura f]

http://www.mini2.com/forum/showthread.php?t=84809

this thread makes me grin

[RenaultF1]

Quote: Originally Posted by Kaelaria

OMG what body cavity did you pull that answer out of! LOL!

The popping is 100% from the design of the exhaust system and it's backpressure.

LOL...what a great response...

[Parc77]

Was going to say both my 2002 S and 2004 S have always made the noise, but I know it happens alot more with the 05 cars since the slight power increase/mild makeover, wonder if the next model will have flames coming from the exhaust

[djbohne]

Quote: Originally Posted by Parc77

Was going to say both my 2002 S and 2004 S have always made the noise, but I know it happens alot more with the 05 cars since the slight power increase/mild makeover, wonder if the next model will have flames coming from the exhaust

I'd trade my 05 in for a 06 in a heartbeat if it ever did that... how friggin cool would that be...haha..

[beken]

Quote: Originally Posted by Kaelaria

OMG what body cavity did you pull that answer out of! LOL!

The popping is 100% from the design of the exhaust system and it's backpressure.

Nice response....and back pressure is cause by ....?

I remember lots of popping sounds from Mazda's RX-7s as well as other turbocharged cars. All engines internal combustion engines have back pressure when decelerating. However, you get a lot more of it in boosted engines. Of course I agree with you that the MINI's probably tuned to exaggerate the noise and I rather like it.

I pulled the information from some cavity where I worked on a thesis on fuel additives for increasing the speed for flame expansion in various forms of fuels.

[Restyle]

I dont think they altered the exhaust system on the facelift models from that of the original MCS, so I think its down to something else..
Isnt this Popping Phenomena actually due to Deceleration Fuelling
..This is when after the throttle is closed suddenly and the engine is being overdriven, unburnt fuel ignites in the exhaust system producing this characteristic popping noise.
This is normally corrected by the Engine Management System which usually reduces the fuel to the engine on overrun, or in some cases cutting it off all together.

As the extra 7bhp on the facelifts basically comes from an engine remap, isnt it more logical that it was purposely built into the remap

Hey, I`m not complaining, It just adds more Character to the Car

[jon vital]

So do some of the MCS remap upgrades take away the popping?

[retired00]

I think modern engineering lets them tune the sound of the exhaust, not just the decibels. I recall when the Miata first arrived the articles in Road & Track about the degree to which they worked to replicate the sound of a British sports car--MGB I believe, prior to production. With emissions police being what they are, I doubt any unburned fuel is making it to the exhaust or cat converter on a factory job. Gas there usually means a new one at the next emissions test.

[kapps]

I also think it's because a slight amount of fuel is being injected into the cylinders on overrrun. Most cars cut the fuel but some don't completely do it.

It's like comparing a Viper and Corvette exhaust. Both are huge displacement open exhaust but the Corvette doesn't burble while the Viper does it all the time. Have you ever noticed that on the MINI when you let off the throttle, it doesn't instantly start engine braking. I think the ECU keeps some fuel flowing (actually for emmisions reasons) for a 1/4 second or so. At the right rpm, that might be what's causing the burbling.

[EBW_170]

Sorry but you are all wrong!
The popping sound is made by a small speaker system built in to the rear silencer