What's the stock exhaust made of?
 

A friend is getting a Borla stainless-steel exhaust for her 2006 Cooper Convertible. From the advice she's gotten from the vendor, it sounds like the exhaust won't fit perfectly out-of-the-box, because of the extra bracing under the car on the convertibles.

The suggestion she got from the vendor was just to cut the section out of the stock exhaust that has the appropriate bend and splice it into the new exhaust.

I don't have a problem with that idea, but I'd feel better about it if the stock exhaust were stainless steel as well, to avoid the corrosion problems from joining dissimilar metals.

So, does anyone know if the stock exhaust is stainless steel or mild steel?

I don't know if the original is stainless or not riquiscott but there is an easy way to tell. Grab a magnet and see if it will stick to her, or your, exhaust. 300 series SS is not magnetic in the least. 400 series is mildly magnetic. Another indicator would be the presence of rust. Just a suggestion. :) I seriously doubt that the factory exhaust is SS though. It is probably aluminized steel if anything. Stainless is expensive and, in the eyes of most manufacturers, an un-necessary expense.

Thanks -- I'm thinking the same thing - either mild steel or aluminized mild steel. I'll do the magnet check when we actually do the install to make sure.

I'd suggest the Milltek. Less parts and I know the bend is there for the Cabrio. At least the one they sent me did.

The guy at the muffler shop who installed my MyMini touring exhaust told me the factory exhaust was also stainless, but a different type than the 304 stainless in my aftermarket exhaust.

Of course, he could have just taken a guess.:)

The factory exhaust is made with mild stleel.

As someone mentioned, the convetible has a bace underneath, I would suggest selling the Borla and purchasing and exhaust that will fit the convetible perfectly,

Like the Larini or miltek
Victor

I don't know if Milltek makes an exhaust for the Cooper (non-'S'), and she's getting the Borla for only $450 shipped, so if I have to do a little fab work to make it fit, that's okay with me. I already have a tubing cutter and a pipe expander to enlarge the cut ends of the pipe to make slip-joints, so it shouldn't add too much complexity to the job.

Maybe I'm looking at the wrong vendors, but I can't find one that sells a Milltek exhaust for the non-'S' Cooper, cabrio or hardtop, and although I found a place that sells the Larini for the Cooper, they don't list a separate application for the convertible.

Regardless, the Borla is already ordered, and if I have to splice in one section, I'm not too worried about it.

Sorry, I didn't catch the non-S model part. I'm not sure I've seen a MC version.

Gee, everyone else always has all the right tools. :sad: If you're prepared then I'd go for it! I need to rely on others for the more heavy duty activities that may require cutting, welding, etc. I have a hammer and a reasonable toolbox of the usual small tools. The hammer can't do as much as I always hoped it could.

Typically steel with a coating that combines zinc and aluminum. Google galvalume.

Outmotoring has the Milltek in MC (non-S) for $570 but it has too many parts for my taste. http://outmotoring.com/miltek_mini_cooper_exhaust.html Hmmm. The Borla IS a better price. But the Milltek sounds soooo nice.

Fortunately, the chain-type tubing cutters are only about $15, and the wrench-driven tubing expanders are about that much as well. I have a MIG welder, but it's not set up for stainless right now, so we'll just be using clamps where needed.

I have a bunch of single-purpose specialty tools that I've accumulated over the years - if they're inexpensive enough, it's easy to talk myself into getting them, even if I think I'll only need them once. I usually end up needing them over and over again, and it's nice to already have them.

Sounds like my Home Depot trips. Buy a new receptacle, buy a tool. Get some paint, buy a tool. I just need to visit Summit Racing more than Home Depot I guess.

Yep - I saw the Milltek on Outmotoring, but there was no mention of it working with the convertible, so I think it would have put her in the same situation she's looking at with the Borla, for $120 more.

Even Milltek's own website only lists three MINI exhausts - Cooper, 'S', and 'S' cabrio. Either that means the Cooper version fits both the cabrios and tintops, or that they don't make one for the cabrio.

I really like the Milltek, though, and that's the direction I'm leaning for my 'S' cabrio when the time comes.

I'm not sure about MIG welders but with SMAW (stick) welders, you just use a 308, 309 or 316 rod. I can't remember which is which but 2 are for SS to SS and one is for SS to carbon steel. Might just be as simple as snagging a spool of the proper wire and going at it. *shrug* :grin:

Miltek makes a non s exhaust, but availability is not good. Stratmosphere is working on a drop ship from the factory, but no longer stocks them.

Stainless Steel & mild steel
 

Stainless Steel & mild steel are both steel and thus are not disimiliar metals.
For the price you are paying for this exhaust system it should fit without a need for modifications. Buy one that fits!

I would consider them disimilar metals due to the presence of nickel in the stainless steel, but that's just me. *shrug* I know that aboard Navy vessels you can weld the two together but you have to use the proper welding rod so that you get both good fusion and penetration on both the SS and CS. That and so that the weld itself won't rust if the paint flakes off.

I just purchased a Megan Exhasut for mine. It is louder than the Miltek but it sounds so nice. Also it was $350 shipped.


Art

Stainless steel and mild steel are far-enough apart electrochemically that galvanic corrosion is a concern. There's also something called "contact corrosion" that occurs between mild and stainless steels.

As for the fit, the problem is that there are not many (if any) aftermarket options for exhaust systems that are designed specifically to fit the non-'S' convertible. If she had a hardtop Cooper, or a convertible 'S', she'd have a lot more choices, but it's not as simple as "buying one that fits".

I think it would probably be easier and much cheaper to go to Big Al's and have them replace the muffler to the tip with a generic free flowing Magnaflow. They usually carry many sizes. I only suggest this because your not getting a true cat-back anyway by hacking up a Borla to make it fit.

Good point - it hadn't dawned on me that I'll have a hard time splicing the curved section from the factory exhaust into the Borla if the pipe diameters are different.
I've already contacted a local exhaust shop that can mandrel-bend stainless, so if worse comes to worse, I can give him the curved section of the stock exhaust, have him duplicate it in 2-1/4" stainless, and then join it with the rest of the Borla.
As for the price, I agree that she could have gotten off cheaper than $450 having one custom-made at a local shop, except that it would have been mild steel, not stainless. And in that case, just about anyone that's ever put an aftermarket stainless exhaust on their MINI could have probably had it done locally for less - in mild steel.