1st Gen R53 Cooper S Free Flowing Quiet exhaust

It won't.

 

Straight free flow and quiet should not be used in the same sentence. :lol:

 

This. Been there, went back to split cans. If you run 3 inch from front to rear, you'll have to do something about the battery box. With 2.5 and a bend, you can clear it.

Seriously, if this is a street car, I'd split the exhaust and go with two cans.

 

It's not that I think it's better; I'd rather run a straight pipe. But with it straight, with a cat, and a big magnaflow muffler in front and back, it was too loud on throttle. Car was making "only" 250WHP, and the drone and noise at high speed was too much. At civilized speeds it's was ok. I still have the magnaflow up front, and JCW cans in back, this works well. I'd rather go the Milltek route for the cans and keep it 2.5 the whole length, but it's not a big deal.

Didn't try a resonator, I'm not sure anyone has had much luck with one at high HP, but it would be worth a try. Not sure with what you're running how well it'd work. Spiral cone insert may be the way to go for the loudness, but it's the drone that's going to kill you. You're going Rotrex, right? If you're going to try a straight pipe, please, please talk to Jan and Colin. There are ways to do it, but it's not easy. Coastfab is the way to go if you're dead set on this route. But it's much easier to split the cans in the back--it makes all the difference in the world. I may try a straight pipe again, I'd really like to put on a rear diffuser, but after my first foray into that, I might not.


Engine is done, or very close to being done and back in. Car is in Irvine; all the work is being done there. I'm just a spectator...opcorn:

 

The straight-back works under the batt box with a 2.5" pipe, and that's PLENTY of flow area for about any streetable 1.6L Mini motor, even at full chat on a pulley.

I was determined to make this configuration work. In so doing, I ran, extensively, over a DOZEN different muffler configurations in the straight-back configuration on my R53 (15% pulley, Alta CAI). All were crazy loud, even with a spiral "muffler", not glasspack, upstream. Crazy loud.

And resonant: that length pipe has a resonance about 2800-3200RPM, right AT the 68-73MPH range, not that anyone spends a lot of time there. And it doesn't matter the mufflers, I've tried Magnaflows in various lengths and diameters, Summit aluminized glasspacks in various lengths in both 2.5 and 2.25" diameters, Summit stainless glasspacks, a memorable RedHot glasspack (insane loud, basically hollow), along with two variations of spiral core mufflers, one of which held too much heat under my shifter box and about melted the bottom off it - even with heat shielding there! You should small fresh exhaust-roasted nylon. Mmmmm), and I ran many in several combinations, long muffler upstream, long muffler downstream, change out one muffler for another, re-run.

Even my exhaust hangers are tired! Two of those 6 bolts that hold the chassis brace on (keep it on, BTW), had to be replaced once!

At least most of my exhaust bolts are well anti-seized.

Lessons:
- Loud. Power, but loud. Mainly from resonance at the above ROPM range, and it's nearly impossible to cure unless you go with a Heimholtz Resonator, basically a capped specific-length "T" off the exhaust that wraps around the battery box and cancels the resonance - a bit - at the desired rev range. Difficult to calculate the length and diameter, heavy, and little performance gain.
- Put the higher-restriction muffler upstream of the lower-restriction one (you need a pressure differential to make them work).
- Exhausts get HOT - either relocate the battery box (difficult) or use some heat shielding on the bottom (easy), and a heat-shielded batt box works fine with even a 2.5" on a somewhat-lowered car (I'm down about 1/2", you can go up to about 1", but measure). You can also flatten one side of the aft pipe (or ovalize) for some additional clearance.
- Exhausts get HOT (2): Don't put a nice, dense, spiral muffler beneath your battery box. It's fine while running, but the retained heat will eventually toast the bottom of the shifter box, making it fall off. It'll then heat your cupholders such that a hot cup of coffee will be waiting about 10 minutes afer you buy the iced frappucino. And if you've already installed the short shifter with the shifter box bottom missing, just plan on heat.
- Resonance is a BEAST to get rid of. Putting the ac on recirculate made a difference, opening a window made a difference, but in winter with neither of these options available, I still had to open a window. You know that feeling when your ears need to pop? That. Plus noise.

The quietest least-uncivilized system I ran in this config was a 2.25" system fabbed from a stock front pipe into (2) Summit stainless glasspacks. Found a bunch of horsepower (~10 using some calculations on acceleration rate on a known long straight hill, same weather conditions, passenger load and gas), but it'd still drone a bit at highway speeds, MUCH noisier than the Borla Race system I'd been running, and I can't compare it to the JCW I currently run because, well, the JCW is relatively silent (and honestly doesn't provide much if anything in the way of horsepower gains).



I had a total of 14 different configurations on, including the stockie and the Borla Race (easily the sweetest aggressive-sound system out there). I miss them. They made POWAH. They sounded awesome in tunnels and under bridges and in parking structures.

But I like my hearing, and my Harmon Kardon, more.

Hope this helps!

 

One of the best designs I've had on a car was on my WRX. 4" collector at the turbo tapered down to 3" race cat then to the back to taper to 2.5" for the Prodrive muffler. It made power and was reasonable on volume. Has any one tried a tapering approach to MINIs?

 

There's some good info above. I'd add that we have never seen more than about a 5 horsepower increase with exhausts--custom or canned. We played with straight-through, unmuffled 2.5" exhausts for a track car that did little more than make noise. Net effect: -4whp.

 

That's exactly what Jan has said as well.. After reading through all of this I'm just sticking with twin cans. I was going to give it another try eventually, but if Dixon couldn't get rid of all the drown with everything he tried, there is no way I'm going to bother at this point.

 

Yeah just get a nice Milltek and call it a day. I just have the custom straight back as a noise maker which is good for scaring the crap out of people. :lol:

 

Wow - people read stuff! Thanks for the shout, and yeah, I can officially say I've "been there done that". The power was wonderful (we really did find a bunch with ju-ust a touch of restriction, but not enough), the sound and popopopop during downshifts are addicting, and those cliffside-corner rev-matched downshifts on Hellbender are devine, but I really ended up missing my Harmon Kardon, and my friends on the 2-way radio, and my hearing... and giving up 5-10hp was WELL worth the investment in the long run.

 

I just put my FUN and LOUD straight pipe exhaust on for the Dragon this past weekend.

Yup that sound is so good it's addicting. It's makes my Milltek sound like a JUSTA.

 

Sound Off 2012 - FRODO - 2005: [ame="http://youtu.be/j_rdluCO7bo"]Sound Off 2012 - PAUL - 2005 - YouTube[/ame]

 

Yup that's my exhaust on Frodo's MINI back in the day.

It sounds much better and deeper now since it is broken in.
(Full of Carbon and not bare SS)

 

I have been playing around with stock r56 resonator. So far I have got the sound down but it still drons on the high way. I am sure there is a way to have a good straight throw exhaust but that gole is beyound my means

I really want to try a stock r56 exhaust. That might be the ticket. The flow descent and the res/muffler are really quite.

 

QUITE ? What's the point or fun of that. :lol:

 

Because on a r53 it my be livable. Just trying to find a solution to this problem.