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2Addicts | BMW 2-Series forum Technical Topics N55 (M235i) Engine, Transmission, Exhaust, Tuning M2 exhaust and rear diffuser onto an M235i

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      12-24-2017, 09:18 AM   #1
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M2 exhaust and rear diffuser onto an M235i

After reading the tread by Fasteddy1, where he did this to an M240i, I decided to give it a try. Thanks Fasteddy1 for the inspiration. (Check out this link - http://www.2addicts.com/forums/showthread.php?t=1357273) My objective here is more of a conceptual how-to, with pictures of some major steps along the way. One of Fasteddy1's comments was not to attempt this if you don't have extensive auto body experience, which is probably good advice. Personally, I've prepped and painted a number of cars over the years, molded on fiberglass fender flares, and fabricated a custom chin spoiler and rear spoiler out of sheet metal, but all for myself, not professionally. However, I'll say that a lot of the skills, tools, and techniques I used on this project are the same I've used as a homeowner installing tile, cabinets, paneling, repairing sheetrock, etc. Bottom line, it's more common sense and basic manual skills, and not rocket science.

Parts list and approximate prices, most all bought off of this forum, Ebay, and Amazon: M2 Exhaust - $350; M2 rear diffuser - $100; non M Perf. F22 rear diffuser - $100; 3M 04240 adhesive - $45; 3M 05887 filler - $45; 3M 08571 "caulk gun" for the adhesive and filler cartridges - $55; 3M 05907 adhesion promoter - $35; SEM flexible primer spray, 1 can - $15; SEM flexible bumper paint, 2 spray cans - $35; SEM Bumper Bite flexible glazing putty - $25; Misc. supplies - Denatured Alcohol, sandpaper, masking tape, disposable gloves, etc., $35; Total - $835. On top of that I bought a replacement muffler heat shield in case I want to go back to stock - $50; a spare Exhaust clamp just in case - $35; and Active Autowerke's brushed stainless exhaust tips, because I didn't like the look of the chrome ones - $260. Extras - $345.

Was it worth it, hard to say. My wife and I both like the way it sounds, a bit deeper, more aggressive sounding, but at idle it actually seems quieter. At low speeds, light throttle pressure, (25 MPH limit in our neighborhood), it seems like the engine revs up quicker, and shifts sooner, maybe due to less backpressure? From a looks standpoint, as the last pictures show, the exhaust tips seem too low, and angle down a bit. Not sure if it's individual differences between cars, mufflers, or a difference in the bends and angles between the M2 and M235i exhaust center section, which I did not use. I'll cut the inlet on the muffler, angle it up, and weld it back to fix both those issues. The tips also stick out further than stock, but that's because the non M Perf. rear diffuser is "flat", and doesn't have a kick out of about an inch like the M Perf. one does. I've got a fix in mind for that too. Either trim back the tailpipes and tips some, or, do another version with the M Perf. rear diffuser and an M2 diffuser.

Other looks issues? The "body work" is not perfect. I'm not a professional, I did it in my garage, painted it outside with spray cans, and probably rushed a step or two here and there. There are a few pinholes in the final coat of putty, and a few small "globs" of paint where the spray cans "spit" rather than sprayed. However, it's all down low, you can't see any of it when you're standing up, and certainly not when the car is moving.

Sorry, but no sound clips. I tried, but for some reason my phone would record video, but not sound. I wonder if the initial start up and "bark" of the exhaust overloaded the mic and shut it off? I had it pretty close to the car, and right at exhaust level. It recorded fine when I tested by just talking. I know there are videos and recording of the M2 exhaust on an M235i and 240i out there already.

So here goes the "conceptual" step by step instructions. Obviously a lot of details and "how to" were left out. Overall, I probably spent 25-30 hours on the project over the course of 2 weeks. There was a lot of down time waiting for glues, putty, and paint to dry between coats, set up and clean up time, running out for supplies, etc.

Picture 1 shows the initial cut out on the F22 diffuser, from just outside each of the single exhaust outlets, and just above them. A lot of eyeballing and marking up with a Sharpie before making the first cut. I used an oscillating saw and Dremel tool with a cut off wheel to do cut both the diffusers. Pic. 2 and 3 shows where I cut the small center section off of the M2 diffuser to get it to fit tighter to the F22 diffuser. After the initial cuts, it took a few more trial and error cuts to get them to fit better. Pics. 4 and 5 show a trial fit of the two diffusers just sitting on the floor, from the front and back. Pics. 6 and 7 show how the exhaust heat shield was cut to fit around the tailpipes of the M2 muffler, and a piece of aluminum angle I added to attach the M2 diffuser portion to. Used a jig saw and tin snips to cut the heat shield. Pic 8 is a trial fit on the car, before gluing the two diffusers together with the 3M 04240 adhesive. I tacked it in a number of places first, let it cure, then went back a second time to glue in the entire seam. After doing the front, I took it off the car and did the full seam on the back side as well. In all I probably removed and put back on the original diffuser, and my "new" one a dozen times to make sure it fit and looked the way I wanted. It's actually very easy to do, and I didn't even break one tab on either diffuser. Pics 9, 10, 11 show the diffuser after being filled, puttied, molded, sanded, primed, and painted. I used a 1/4 sheet oscillating sander to do all the rough sanding and molding in, then a hand sanding block and sandpaper wrapped around a piece of 1" PVC pipe for the final contouring. Started with 80 grit and went to 100, 220, 320, and 400 before it was all over. Pics 12 and 13 show it on the car, and you can see there is too much exhaust tip showing, and they are angled down slightly. But, that's all fixable.

If anyone wants more info or details, PM me, I'm also willing to talk and discuss if you'd like. And, if anyone has a F22 / M235i M Performance rear diffuser they are willing to let go of for a reasonable price, PM me, Already have another M2 diffuser to mold onto it.
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      01-03-2018, 08:12 AM   #2
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that is exactly what I need to do.

thanks for sharing.
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      01-03-2018, 09:01 AM   #3
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Quote:
Originally Posted by Hasser View Post
that is exactly what I need to do.

thanks for sharing.
I've ordered another M2 diffuser and F22 M Perf. diffuser to do another version. I want to try and get a better, tighter fit to the exhaust, and hav it not be as flat or plain looking as the standard F22 diffuser. Once I get that done, I might be willing to sell this one, or lend it to someone who could make a mold. If someone could make a copy off of this it might be possible to make an overlay or skin that could be attached to the top of a stock diffuser, or make something with a flange that could be screwed onto the diffuser from the back. That would probably result in a lot less puttying, filling in, and sanding.
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      01-09-2018, 01:40 PM   #4
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is there no way to push the tips further on so they don't stick out as much?
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      01-10-2018, 05:53 AM   #5
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Quote:
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is there no way to push the tips further on so they don't stick out as much?
No, not these, not without cutting off the mounting flange / clamp portion, which is touching the weld seam where the straight exhaust outlet pipe goes into the muffler. I could do that but then I'd have to weld the Active tips on.
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      01-17-2018, 08:40 AM   #6
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Diffuser - one problem fixed, one to go

One of my problems was the exhaust tips angled downward, and sat too far down from the diffuser. Fixed that by cutting the inlet into the muffler, taking out a small "pie slice" and welding it back together. Had to get the inlet about 1/2 an inch higher than it was. The first three pictures show the side view and straight on view after being cut and welded. Outlets are much more level and tighter to the diffuser, but still stick out further than I'd like.

The next three pictures show the 2.0 version of the diffuser, using the M2 diffuser and the F22 M Perf. diffuser molded together. Still needs to be primed and painted.
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      01-17-2018, 09:15 AM   #7
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I've found a company that are doing this now.

ECD in Germany.

will be ready to ship next month.

850 euro
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      01-17-2018, 09:41 AM   #8
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Quote:
Originally Posted by Hasser View Post
I've found a company that are doing this now.

ECD in Germany.

will be ready to ship next month.

850 euro
I saw that in another thread. Looks pretty much the same as what I'm doing with my second version. Wish it was available a few months ago. Would have been simpler and less expensive overall.
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      01-17-2018, 10:40 AM   #9
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Quote:
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Quote:
Originally Posted by Hasser View Post
I've found a company that are doing this now.

ECD in Germany.

will be ready to ship next month.

850 euro
I saw that in another thread. Looks pretty much the same as what I'm doing with my second version. Wish it was available a few months ago. Would have been simpler and less expensive overall.
I'm holding out and will be getting one from them.
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      01-17-2018, 02:07 PM   #10
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Quote:
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I'm holding out and will be getting one from them.
Depending on overall cost, it could end up being a pretty penny when all said and done. 800+ Euro + shipping can hit over 1k easily I think. I would imagine if you aren't comfortable with doing the body work yourself, buying a diffuser and paying a body shop to do the work might still be cheaper, especially if you are already running an Mperf diffuser. Since a brand new M2 diffuser is about $100 bucks.
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      01-17-2018, 02:46 PM   #11
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Quote:
Originally Posted by Luftwaffe1O1 View Post
Depending on overall cost, it could end up being a pretty penny when all said and done. 800+ Euro + shipping can hit over 1k easily I think. I would imagine if you aren't comfortable with doing the body work yourself, buying a diffuser and paying a body shop to do the work might still be cheaper, especially if you are already running an Mperf diffuser. Since a brand new M2 diffuser is about $100 bucks.

I've got right at $500 in this second version I'm working on. Two diffusers (a used M2, and a new F22 M Perf.) and supplies (adhesive, paint) . However, my time and labor is free and I enjoy the challenge of designing it, and being able to say that I made it. Still, in the long run buying 1 would probably have come out cheaper than making 2.
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      01-17-2018, 02:57 PM   #12
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Quote:
Originally Posted by JerryW235 View Post
I've got right at $500 in this second version I'm working on. Two diffusers (a used M2, and a new F22 M Perf.) and supplies (adhesive, paint) . However, my time and labor is free and I enjoy the challenge of designing it, and being able to say that I made it. Still, in the long run buying 1 would probably have come out cheaper than making 2.
Right definitely in that case, but suppose someone is already running the M performance diffuser. Getting the M2 diffuser + paying a pro, will probably come out cheaper than ordering one from Germany.

If you convert 800 euros + shipping to US (I am going to say a conservative estimate of about 120 euros, you are looking at probably close to 1200 all said and done.

You can buy a brand new M2 diffuser and M perf diffuser for about $450. Lets say labor for a shop and painting another $500, and it plants you at about $950 US all said and done.

In your case, you made 2, but I would venture a guess you could probably sell your first proto for a couple hundred to recoup some of the funds I am sure someone in here will snatch it up.
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      01-21-2018, 06:36 AM   #13
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total cost including paint and shipping to the UK is 850 euro.

brand new M perf and M2 diffuser together.

going to be looking good - gloss black and alpine white for me with cyba tips on the M2 exhaust.

i've seen plenty of 2nd hand M2 diffusers for £50 here in the uk on ebay but never seen a M perf one used. new ones run about £350

so say £400 for parts then I know painting would be around £200 form previous work ive had done - so £600 total then the labour to fabricate.

so for me it looks like not to bad.
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      01-22-2018, 01:41 PM   #14
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Quote:
Originally Posted by Hasser View Post
total cost including paint and shipping to the UK is 850 euro.

brand new M perf and M2 diffuser together.

going to be looking good - gloss black and alpine white for me with cyba tips on the M2 exhaust.

i've seen plenty of 2nd hand M2 diffusers for £50 here in the uk on ebay but never seen a M perf one used. new ones run about £350

so say £400 for parts then I know painting would be around £200 form previous work ive had done - so £600 total then the labour to fabricate.

so for me it looks like not to bad.
Within EU its probably a pretty solid option. Shipping to the US for instance it starts to get a bit pricier. Brand new M2 diffuser + M performance diffuser run about $450-500 together. Leaves you an additional 500-600 roughly to get it fabricated. Which will be still cutting it close I suppose.

It is one of those things that will come down to what your situation is. If you have the M performance diffuser already, its much cheaper to just get it fabricated, or if you fund a used one. If you are starting from scratch, ordering it is a pretty good alternative. I think it just comes down to a personal preference. As far as in Europe, the ready to go option is much more lucrative since you wont have to pay higher cost of shipping. Its quite a large package to be shipped international, it is unlikely it will be under $150 US.

I am curious to see if OP has any updated painted pics of his M performance Diffuser + M2 diffuser mounted/painted.
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      01-22-2018, 03:31 PM   #15
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No, none yet, still working on it. I'll certainly post them when I'm finished. It looks very similar to the one in the link Hasser shared, for ECD Performance.
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      01-29-2018, 04:57 PM   #16
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Here's the latest and last version, on the car. The tips are even with the outermost edge of the diffuser, and up tighter to the diffuser than on the first one. Similar in design to the one from ECD.
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      01-29-2018, 05:03 PM   #17
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Man that is looking quite good!
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      01-29-2018, 05:06 PM   #18
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Thanks, I appreciate that. In the end, I think it was worth it, I like the way it looks, and as far as I know, it's one of a kind.
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      02-01-2018, 04:39 AM   #19
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fecking excellent job mate!!

looks spot on - and i'm hoping that's the result I end up with from ECD.

I have asked them to paint it alpine white on the M Performance section and gloss black on the M2 section.

ive gone with the brushed cyba 90mm tips also to add to the exhaust.
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      02-01-2018, 04:40 AM   #20
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Quote:
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Thanks, I appreciate that. In the end, I think it was worth it, I like the way it looks, and as far as I know, it's one of a kind.
until I get mine
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      02-01-2018, 05:48 AM   #21
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When you tightened up the tips to the diffuser it definitely sharpened up the rear end of the car. Looks awesome, heck of a job!

P.s. I hope you are enjoying the sound of that M2 exhaust.
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      02-01-2018, 07:39 AM   #22
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Quote:
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When you tightened up the tips to the diffuser it definitely sharpened up the rear end of the car. Looks awesome, heck of a job!

P.s. I hope you are enjoying the sound of that M2 exhaust.
Thanks, my wife did not like the look previously, and said it looks much better now. I just won't let her know how much it cost to fix it

I am enjoying the sound, find myself turning down the stereo most of the time so I can listen to and enjoy the car more.
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