OK..... Here goes... I'm starting my own thread on my journey making a custom SS catback exhaust. Feel free to give me your thoughts. Especially from some of the members on M/A that have a sense of what would look good from the rear bumper. I'm sticking with the dual tip for now. It's always good to have a list of objectives, So here is my initial check list; Needs to attach to the the factory downpipe with the factory clamp. Will include a SS flex joint. Will hang from all of the same factory hangers. Will be made from 2-1/2" OD (63.5mm) T304 SS tubing (factory JCW measures at 2.290" (58mm). Will have a center section with an easily removable resonator / straight pipe with "V" band clamps. The resonator will be able to be repacked with high temperature ceramic insulation or scrabble. The rear muffler will have rebuild-able cores and some acoustical tuning ability (all without needing to be removed from the vehicle). Here is a shot of the factory JCW exhaust tips. They kind of look a little lost don't they?
I counsel against V-band clamps, R&R is easier with two hole flanges. I would take an extra step and replace the factory flange on the downpipe with a two hole; the OE gasket doesn't seal, and the clamp is a hassle to work with. I don't think JCW tips are unattractive, it's the standard bumper cover that lacks flair.
I thought you said business was jumping at your shop and you were up to your ears in work. :frown2: :cornut: Jim
Thanks Keith, Good suggestions.... I'll go with you're suggestion on changing the V-band clamps to two hole flanges. For now, I'm going to stick with factory flange (warranty reasons). I plan to machine a tapered flange to mirror the downpipe flare dimensions. At a later date I can always change it out with something that works better. I may even come up with a split flange with two holes that would eliminate the OEM clamp, yet still preserve the OEM downpipe.
Here's a quick auto cad drawing of the rear view through the twin mufflers. I'll do a quick and dirty cut-out and hold it over the factory tips. I'll snap a pic tonight so you guys can give your impression of 4" outlets. I could also do 3-1/2" outlets but I'm trying the keep the muffler chambers as large as I can to be able to let the sound (gasses expand) in the rear baffles.
Im sure its going to look amazing. 4" is biiiiig, but It all depends on the fit and finish too. On the Stratmosphere i had, the tips were only 3.5 i think, and they looked HUUUGE, but they also stuck out some.
Wish I had the tools, shop and skills you do MM. Why do you want to keep the OEM flange if you are changing the set up? Won't that effect eh warranty regardless. Just asking. Jim
Easy on easy off.... backward compatible..... Stock OEM JCW would get stored here in the shop with only 6-7K miles on it. Someday I may sell the MINI, the original exhaust would go back on. Chuck
Sooo..... Adam Keep them about the same amount of protrusion from the bumper as the stock. Angle cut tips or square cut? This is where I need input from anyone with a bit of styling sense. You will be able to see up inside the tips since the beginning of the baffle will be about a 1/2" back or so. Thanks Chuck
haha, I was about to ask if you would send me the original one. I have to disagree with k-huevo though, I like the v-flanges and I always ended up with having leaks from the 2 hole flanges. One of the things i hated about installing my alta was the flat faced resonator when they could have built it with a tapered entry and exit. Not really sure if it causes any un-needed drag but it always seemed to irritate me for a go fast product.
MM, Let's take a step back What is your intent? To say you can make your own CatBack? (would be very cool and I would be most envious as I paid some serious bucks for my Borlal) Reason I ask is that a Catback with the existing downpipe is not going to really gain you any power (if thats what you want to do, back to intent question). Depending on your design you can make it the sound real bad adz (once again very cool if thats what you want to do) but it's gonna be a very cool sounding noise maker
Excellent question Tim.... I'll try and answer it this way. Every time I'm under the MINI, it strikes me how simple the factory exhaust looks. I'm sure the MINI acoustical engineers put a lot into their tuning of the stock JCW exhaust to get that special sound. I'm really looking at this build as more of developing a tunable exhaust with a little less backpressure. Using the factory downpipe. Then at some point down the road upgrade to more of a performance aftermarket downpipe. All the while being able to adjust the baffles to control the sound. I'm still sort of following some of the aftermarket downpipes, but if I recall correctly, I think they all still throw CEL's. So I'm hoping those issues get resolved. I'm not interested in going catless at all. I realize the exhaust flow is controlled by the narrowest portion of the exhaust. For now I'll assume that's up in the factory downpipe. Chuck
Cool, *figurred* you knew that but wanted to check in, Sounds like a fun project. Should keep you off the streets at night! As far as CEL's my understanding is in the R56 the engines have gotten incrementally more sensitive to after market downpipes. My 07' has only thrown one CEL and that was at MINI's in the Mountains/MTTS and Way of Way Motor Works attributed to change in elevations. Sure enough by the time I hit the Colorado/Kansas border it was gone. In the process of researching downpipes I talked to one exhaust vendor and he was relating that 10's, for example, were very sensitive to downpipes and almost alway threw a CEL How to 'dumb' down the engine? Haven't a clue, maybe in the O2 sensor?
So now for some quick and dirty mockups for the style guys. Here is a quickie with the 4" tubing (outside will be polished on the final version). The center tube would be extended flush with the 4" tube and the baffle plate 1/2" inset. This would be the square cut end (David) OK, same thing but the center tube is flush with the baffle plate. I'm starting to think 4" is just too big. There would be two of these cannons next to each other with about a 1/4" spacing.
I recall talking to Way about exhausts and his recommendation was no more than 2.5" dia on tubing. After that it was detrimental to performance.
I've also read that 2.5" is as much as you need for a MINI's exhaust, it'll flow more than the engine can put out. I like the tip with the extended center tube best. maybe you could paint the baffle plate black. The contrast between the polished outer tube, the black baffle plate and the stainless center tube would look good! Dave
Yeah, I read where 3" is just for bragging rights and the only thing it does is add unnecessary weight. I figured I was pretty safe in only bumping it from 58mm to 63.5mm. That way when the new (future) downpipe goes on that should flow better, the 2-1/2" shouldn't hinder it. The point is I want to maintain the exhaust temperature and flow rate. And going too big defeats that purpose.
Ok, for the style guys.... I made a 1:1 paper template with the 4" tubes and 1/4" space. Sorry about the poor lighting... Here is the template centered over the bumper cutout. If I remember, there is about 3/8"gap on the left and right side and about a 1/4 space at the top. There should be enough clearance where the muffler won't hit the bumper and cause a cabin vibration and still allow some movement of the rubber hanger grommets. Sooooo, is 4" too big or should I go for 3-1/2"? If I go smaller on the muffler tubing it'll reduce the muffler chamber size and that will reduce my ability of adjusting the sound.