Here's a mini-read [pasted below] with more info on the magnetic properties of stainless steel than most of us would care to know. It doesn't really go into 200 series [used in things like cheap flatware and appliances] or 400 series ferritic stainless [usually magnetic and used in things like expensive knives, as 440C, and production exhaust systems], but covers the interesting property of 300 series SS that can go either way. In summary, if you try to use a magnet to see if steel is stainless steel: if the magnet sticks if may or may not be stainless; if it doesn't stick, then it's stainless for sure. -B

...snippage...
Austenitic Grades
All austenitic grades have very low magnetic permeabilities and hence show almost no response to a magnet when in the annealed condition; the situation is, however, far less clear when these steels have been cold worked by wire drawing, rolling or even centreless grinding, shot blasting or heavy polishing. After substantial cold working Grade 304 may exhibit quite strong response to a magnet, whereas Grades 310 and 316 will in most instances still be almost totally non-responsive.
The change in magnetic response is due to atomic lattice straining and formation of martensite. In general, the higher the nickel to chromium ratio the more stable is the austenitic structure and the less magnetic response that will be induced by cold work. Magnetic response can therefore be used as a method for sorting grades of stainless steel, but considerable caution needs to be exercised.

Stress Relieving
Any austenitic (300 series) stainless steel which has developed magnetic response due to cold work can be returned to a non-magnetic condition by stress relieving. In general this can be readily achieved by briefly heating to approximately 700 - 800°C (this can be conveniently carried out by careful use of an oxy-acetylene torch). Note, however, unless the steel is a stabilised grade it could become sensitised to carbide precipitation. Full solution treatment at 1000 - 1150°C will remove all magnetic response without danger of reduced corrosion resistance due to carbides.
...snip...

Cold Working
Many cold drawn and/or polished bars have a noticeable amount of magnetism as a result of the previous cold work. This is particularly the case with grades 304 and 303, and much less so for the higher nickel grades such as 310 and 316. Even within the chemical limitations of a single standard analysis range there can be a pronounced variation in the rate of inducement of magnetic response from cold work.

Magnetically Soft Stainless Steels
In some applications there is a requirement for a steel to be "magnetically soft". This is often required for solenoid shafts, where it is necessary for the plunger to respond efficiently to the magnetic field from the surrounding coil when the current is switched on, but when the current is switched off the magnetic field induced in the steel must quickly collapse, allowing the plunger to return to its original position. Steels which behave in this way are said to be magnetically soft. For corrosion resisting applications there are ferritic stainless steels which are magnetically soft, usually variants of a grade "18/2" (18% chromium and 2% molybdenum) but with very tightly controlled additions of silicon and often with sulphur added ...snippage...

 

Can anyone post some pics of what the Mini looks like after the 1-Ball in the back? I'm wondering if it will look strange to be a eunuch....



Ryan

 

Ryan,

Everything will look the same, assuming your exhaust man centered the tips, except the right muffler/resonator will not be visible. From the back, at the eye level of a following MINI, only the bottom inch or two of the muffler/resonator is visible. If you know what to look for, you can spot it instantly. However, most people don't look and/or notice. Hopefully someone will post a picture or do a Photoshop conversion for you...

-B

 

Muy,
Did you have the guys at the muffler shop fabricate the entire wider tube (from behind the cat) and the bend, or did you buy the bend seperate and just have them remove the thinner pipe and weld them together.
How much did the wider pipe cost?
Did you have to weld it to the cat, or is there some sort if clamp?


Ryan

 

I ask, becasue I'm planning on doing the 1-ball mod, and I'm trying to crunch prices to see what the cost to power benefits there are to widening the pipe behind the cat to the new bend in the 1-ball. I'm also looking for "descriptor" words to use when I ask the muffler shop abotu what kind of pipping i need to purchase.
I suppose I will by the by-pass bend from onr of the mini sites out there, unless you know of a cheaper way to get it!

Thanks in advance Muy!

Ryan

 

TrippleBeem...I took in the before & after pictures from one of the one-ball threads on here and explained basically how it works. The exhaust guy put it on a hoist, cut on the straight pipe before the curve with a sawsall, then cut after the 1st muffler. He grabbed a pipe about 2 feet long of the right diameter to go outside the factory pipes, bent it on a mandrel bender to about the right angle, brought it back and tested for fit, then did a final bend. He cut off the excess pipe, tack welded both ends of the joint, lowered the pipe and welded around both ends, then remounted the exhaust. Removed the passenger side muffler during the process.
I sometimes get a little rattle when the car is cold, it goes away once the exhaust heats up.
Oh yeah, I was charged $40 for this and to weld the exhaust for my classic back together (it was shipped cut in half). I was back at my desk in under an hour.

 

I understand the basics of the mod, but in reading the entire thread, I noticed that some people replaced not just the part of the tube that was the new bend, but also all the piping from the cat to the new bend, and I'm wondering how much it cost to get the new 2.5" tubing (from the cat to the new bend), and wether the increased diameter will make any difference to exhaust flow.


Ryan

 

Ryan,

Hard to add much to the posts below, but perhaps this will help...
My Exhaust Man's Plan-A was to just cut off the right side muffler and install the mandrel bent 90-deg bend. However, once he got into the work, he showed me that to do it right, there would have to be another little bend added in the straight run pipe to line things up properly. So, if the section of pipe behind the cat needs to be removed and tweaked, then our thought was to just go ahead and replace it with 2.5" tubing. This added section of pipe was cheap [$8-$15?]. My total cost out the door was something like $85. Sorry, no dyno runs to prove the benefit... But if you believe it's faster, then it is...
-B

 

Thanks for the info, I'm talking to a trustworithy muffler shop in Chicago about the mod today, and the they are pretty excited about the job. I'm going to photograph the entire job and post it on this thread, so I'll let you all know what happens!


Thanks again to everyone on this Thread for so much good info!


Ryan

 

I had mine done at the same place Barry had his done, price had gone up only $10 to $95 on a year, not bad. Basicly he cut of the pipe at the cat leaving about 1.5" of 2.25" pipe, bent the 2.5" new length from the cat and slipped it over the stub of the old pipe and welded it on. Then the passenger side was removed and the elbow welded on in place. I don't have any dyno info available but I can say that it is easier to start off in 1st while the AC is on than it was before, it does feel stronger through the range so I don't think there was any loss. I like the sound as well as any I have heard, no neg stuff that I can see, it's been modified about a month now. Originally this was to be until I had enough money saved to get a real catback, but now I think that if I do get that $800-$1,000 it takes, the money will go for a new wire-feed welder to add to my collection. I might also mention that the other day I recieved a nice card from the A-Real Mufffler signed by the family thanking me for the business, can't ask for better than that.

 

So I can get Stainless steel 90 degree mandrel bend for about $25, what does it require to install that? If possible I'd like to be able to do it DIY, assuming I decide to go this route for now.

 

I had mine done for $75. On the road and out the door. I didn't even get my hands dirty.

 

Note that cutting out the one resonator, you're going from one size pipe to a different size. I think it's 2 1/4" -> 2 1/2". And I can't remember if that's inside or outside diameter. But assuming you get all of the right piping, it's hella easy to DIY. Get one of those saw-type exhaust cutter things ($10-20). Fit it together, then clamp or weld.

Most people get a shop to do it, usually <$100, and no fuss. I really wonder if everyone's shops are using SS tho.

Easiest DIY is to get the MyMini clamp-on bit. It's the right size, right diameter. 1/2 hour job at most.