Custom Flowmaster exhaust DIY for 2001 330ci 5-spd

[707BimmerBum]

Custom exhaust DIY for my 2001 330ci 5-spd

They are a few options out there for e46’s when it comes to bolt-on cat back exhaust systems. None of which would give me the sound I was looking for on my ‘01 325cic Manual! Aggressive Sound level with little to No interior resonance! I had already successfully set-up my ’88 e28 535iS with a Flowmaster DBX muffler and custom compression-bent cat-back system. But it was time I figured out the M54 engines for exhaust. So this sparked my interest and research into a custom exhaust for my e46!

Most of us know what Straight piping an M54 gets you…. No Bottom End power, interior drone, and a car that sounds like absolute garbage(IMO!)! To operate efficiently the M50/M52/S52/M54 engines want a high pressure exhaust. That high pressure exhaust in our BMW’s keeps the exhaust velocity up. Exhaust velocity is very important with BMW and all combustion engines for that matter!

Why ruin the interior cabin of your luxury sports car with resonance (aka Drone) by an aggressive or straight pipe exhaust? It’s not worth it!
So since I started at Flowmaster in December 2015 I felt I needed to do some R&D of my own with some of our product and compare to what my friends have on their cars!

After a few months of research, I sold my 325cic and acquired a well maintained 150k mile 330ci Manual that was 100% factory under the hood. Perfect test bed for my exhaust development! So this thread will document my exhaust journey as I test products on my M54 powered e46!
When selecting exhaust you need to assess what exactly you want from the system. For example my small list below:

1. Clean Aggressive Exhaust Sound throughout the RPM Range that sounds like BMW!
2. Deep Exhaust Tone at Idle!
3. POWER! HP AND Torque!
4. Quality Parts
5. Cost effective
6. Good Looks

Noticed that it is ranked for good reason! What is most important to you!?

First off I knew I had a challenge ahead of me: creating a “Free Flow” exhaust without killing the very important Back Pressure the M54 needs to operate! That Challenge was only lightened when I found Flowmaster’s Laminar Flow muffler line up. A muffler line started when its big brother was originally designed to quiet it down the Apache Helicopter for covert-ops. The Laminar Flow muffler is Not a true straight through design, but they are capable of handling some serious horsepower. These mufflers actually provide a small amount of back pressure at lower RPM’s and will progressively decrease back pressure as the pressure in the exhaust increases across the RPM range. After reading a lot about the muffler’s design, I realized the Laminar flow mufflers were alone in their market. You can find the Pro Series, DBX, and Super HP2’s on the Flowmaster website. All single in/out mufflers! Ranging to fit 2” pipe all the way up to 5”. So no matter if you have an M10 4-cyl or a Big Cummins 6bt Turbo Diesel… Flowmaster has a Laminar flow muffler for your application!
IMG_3852.JPG

Let’s start with the stock system. As seen in the pictures, it is a Dual System that runs 2” Pipe, a secondary muffler, a resonator, and the primary muffler under the rear bumper that has a Vacuum operated flapper valve. That Valve closes and opens to increase and decrease backpressure respectively! All of this stock equipment, in my mind…. Had to go!

For the 3.0L I had some options:

1. Stock Style System 2x 2” running back to a Dual In/Out muffler
2. Single Pipe System 2.5” running back to a Single In/Out muffler
3. Stock Style System 2x 2.25” running back to a Dual In/Out muffler
4. Single Pipe System 3” running back to a Single In/Out muffler

IMG_3857.jpg

Options A & B are very close in internal pressure. As are options C & D. If you are lowered, You may want to go the dual pipe route to keep the clearances under the car. If you have a 2.3L or 2.5L, options A and B would be your only options due to the low power output in stock form.

For stock application 3.0L’s: 2.5” Single or 2” Dual will work best. Since I knew I was going to be doing quite a few more upgrades to the power. I figured going with the larger diameter system would give me the most room for gains later. For ease of finding parts and fabrication, I went with the 3” Single system.

I also decided that I was going to tech myself how to weld and do my own exhaust! This definitely complicated the process a lot! Granted a muffler shop would have charged me at least $200-$300 to have it all welded in. But lack of $ and a deadline(Before Bimmerfest) forced me to do it myself!

So I started ordering parts!

Flowmaster Parts:
#815937 – 3” Universal Fit Dual Exhaust Kit
#Y214300s – 2x 2.25” to 1x 3” Scavenger Y-Pipe
#13014310 – 3” DBX Muffler
Prototype Sample Tip – 2x 3” to fit 3” pipe

Other Parts needed:
(2) Factory 2-bolt Flange Exhaust Gaskets (Pelican Parts)
(1) 18” length of 2”Diameter Pipe (O’Reilly’s)
(2) 2” to 2.25” Pipe Adapter (O’Reilly’s)
(2) Shock Bushing Set (O’Reilly’s)
(2) L- Bracket for Cabinetry (Local Hardware Store)
(1) Flat Bar Bracket for Cabinetry (Local Hardware Store)
(4) 8mm x 1.25 x 35MM Bolts (Local Hardware Store)
(4) Flat washers for the 8mm bolts
(4) Fender Washers (Local Hardware Store)

Parts Needed from stock exhaust:
Both 2-bolt flanges cut off with roughly 6-8” of pipe each
Both rear Hanger Brackets cut off
Both Rear Rubber Hangers and hardware
Both Cradle Mounted Rubber Hangers with Cradle

Tools Needed(If DIY):
Measuring Tape
Welder and equipment(MIG preferably)
Chop Saw
Angle Grinder
½” Drive Socket
15mm Socket 6” Extension(Flange hardware)
13mm Socket with 12” Extension(Hanger hardware)
Jack
(4-6) Jack Stands for car and exhaust

Once I had everything(so I thought) I needed it was time to remove the stock exhaust and start the Mock-Up process.

Removal of Stock system:
I jacked up the car enough for me to get underneath with plenty of room. Set my jack stands and was ready to remove the stock system. Place the Jack under the center resonator and apply a small amount of pressure. (4) 15mm nuts hold on the flanges. (4) 13mm Nuts hold on the rear hangers. (1) 13mm on the Exhaust to Transmission brace. (8) 13mm holding the Exhaust Cradle’s in place. Remove all of the hanger nuts and bolts. Unplug the vacuum line from exhaust flapper valve. Your stock stuff is now ready to be removed. Grab the jack and tailpipe and in one movement: lower the jack and pull back on the exhaust and jack at the same time. The exhaust is roughly 130-150 lbs so it is Heavy and awkward. It may take some wiggling and side to side movement to get the exhaust off of the Flange Studs. Once removed, you will then cut the rear hanger brackets off. Chop off the front flanges. Unbolt the cradle from the stock system! Now that stock system is scrap metal!

Mock-Up:
Once removed you are ready to start Mock-UP! A process I did numerous times to get it just right. This process does take some patience! I just wanted to get it in and start welding, but there is Lots to do first.
You will need to lay out the Flowmaster exhaust kit to figure out what pieces you will use. Find every piece you need using the diagram. I used 4 pieces from the kit of 16 pieces (Listed Below). This gives you plenty of extra (a complete set of spares for all 4 pieces) if you mess up. Or an exhaust system for your friend’s car as well and split the costs! But having a bunch of left over 409 Stainless 3” Mandrel Bent pipes around the shop is NOT a bad thing! Trust me it can come in handy!

Parts Needed from #815937 kit:
26033s - #1(Cut at Bend for straight Pipe #6)
26036s - #2(NO CUT)
- #3 Flared Straight piece cut from 26035s26035s - #4(Cut at Bend giving you a SMALL straight pipe with flare for #3)
26067s - #5(S-bend NO CUT)
- #6 Straight Piece cut from 26033s
Diagram.PNGIMG_3757.JPG


Mock up:
Now placing the muffler in the desired location(stock resonator location) with a jack or jack stand under it: STARTS your mock-up process. All of the pipes used will Slip fit together. Limiting the amount of butt welds and keeping the hard welding to a minimum. So I took all the above parts and put them together in the order listed, placing lengths of 2x4 or jack stands underneath the pieces to support the exhaust. Make sure you leave the most rearward cradle in the car, so you can use it as a support. You will see the exhaust systems bends taking shape under the car and utilizing the factory exhaust pathway and heat shielding!

Once all those pieces are in place it is time to mock up the Y-Pipe to the downpipes. Not an easy task. The left side downpipe is not at the same angle at the right side until it travels almost 18” before making a bend. You want to utilize as much of that 2” pipe as possible coming off the flanges. The y-pipe slips over 2.25” pipes. So I used the 2”-2.25” adapters and placed them inside the Y-pipe. Then I angle cut the left side 2” existing factory pipe attached to the flange to the odd angle (as seen in the photos) on the Y-pipe. This will take a bunch of cuts and patience to get right, so take your time! I then bolted up the flanges TIGHT and tack welded the Y-Pipe parts in the proper position to work with the down pipes. All this work is done to bring the 2x 2” exhaust pipes together to flow through one 3” pipe.

*****At this point please use a 10mm Socket and disconnect the battery to prevent any issues with the ECU while welding****************

Now that you have the muffler and Y-Pipe in the proper location along with the proper pieces in between, you are ready to tack weld up the system! I started with the muffler and the #5 piece(Part# 26067s). Making sure the S-Bend is angled up in the proper position I tack welded the muffler to #5 and #5 to #6, #6 to the Tip. Solidifying the Tail Pipes and muffler. I also welded on one of the rear hangers to prevent any further movement of the rear of the system. The Drivers Side Rear hanger utilizes the factory hanger rubber and small piece of bracket that was cut off the stock muffler assembly. That will be welded to one of the L-brackets(cabinet bracket) from the hardware store. See the picture of the hanger below. The next part is kind of tricky, cause you will need to cut #3(from the #4 – 26035s) with as much straight material as possible. Next I tack welded the #3 piece to the muffler with the unflared end of the pipe going into the muffler. Now place #1 into the flare of the #2. These two pipes will take some spinning and adjusting to get #2 piece to meet up with the Flare of #3 and the #1 lined up to the Y-pipe to be butt-welded. Those two pieces will need to be adjusted to not only for the pipes to line up, but for the under car clearances to be at a maximum with the exhaust touching any part of the body. Once you have these pieces in place you are ready to tack weld everything that has not been. Once tack welded to prevent the system from changing shape, you are ready to finish all the welds. Using the jack, remove the system and finish all the welds out of the car.
IMG_4031.JPG

Hanger Fabrication:
Once the welds are done and the system is in one piece, you are ready for install and hanger fabrication. Install the system and tighten the flange Nuts all the way. Bolt up the rear hanger that is already welded to the tailpipe. With the Jack: Apply a “small” amount of pressure taking the sag out of the rubber in the rear hanger. You will then mock up the passenger side rear hanger, weld the second L-bracket to the other hanger piece removed from the stock muffler assembly. Bolt that hanger rubber and newly fabricated bracket into place and mock it up to the tailpipe and weld into place. Now it’s time to fabricate the exhaust cradle-hanger at the middle of the exhaust. Next you will need to insulate the cradle with shock bushings and fender washers(as seen in the picture) to make sure you get absolutely no vibrations from the exhaust. Use the longer bolts to utilize the shock bushings between the cradle and floorboard, with the fender washers insulating between the metal washer and the cradle. The factory cradle has two rubber hangers that were unbolted from the stock exhaust. You will need to cut the flat bar bracket to fit between the hanger stud’s and the pipe. So bolt cradle into place and mock up the flat brackets on either side. The drivers bracket should angle under the pipe cradling the movement of the pipe, with the passenger side bracket you will cradle the pipe a little less and should attach to the side of the pipe instead of the bottom of the pipe like the driver’s side. Before tack welding the hanger brackets in place, apply pressure on the rubber hangers towards the pipe. This will allow the rubber to be sprung and not just sagging under the exhaust’s weight. Once Tack welded in place, you can work on the front hanger. The front hanger is a flat bracket that comes off the transmission and over to the exhaust. Bend the flat bracket closer to the engine. Using the clamp on the end of the bar attach it to one of the 2” pipes coming off the manifold flanges by tightening down the bolt and pinching the pipe.

Now that the hangers are mocked up and done. You will need to remove the exhaust once again! This time making sure the welds on the hangers are nice and solid! Once you have finished the welds on the hangers. You are ready for final install!

Final Install:
Using the jack, install the finished exhaust system and double check all bolts to make sure they are tight. Don’t forget the (2) OE Flange Gaskets like I did!
You are ready to lower the car back to the ground, hook up the negative terminal on the battery…. And then… The moment you have been working towards!

Fire that bad boy up!

[bo vice]

you're going to have to post a video/sound clip..

[707BimmerBum]

you're going to have to post a video/sound clip..

Im posting a couple video clips of my exhaust tomorrow. Ill try to get my buddies e36 M3 this weekend!

[707BimmerBum]

you're going to have to post a video/sound clip..

Sorry It Took me 23 videos to get it to sound alright. Here are my YouTube clips.

A bit of idle, a few 4K-4500rpm revs, and a 6000 rpm rev. 25% throttle launch. 50-60% throttle 1st. 30% throttle 2nd gear.
https://youtu.be/CbcLErtCx_w

3rd Gear ~4500 at Fly-By 60-75% throttle.
https://youtu.be/fLuVxwRiSeA

Hope you enjoy it as much as I do. The car sounds amazing multiple drivers of different car brands have ask me at traffic lights what exhaust I have cause it sounds good.

The power gain speaks for itself.

Let me know if you have any questions.

Brandon

[Feenx]

It's been over a year. How are you living with the exhaust?