DIY - Modified NISMO Exhaust - better sound, better power

nismolife

I've seen a lot of threads out there asking if a Nismo exhaust could be modified to at least make it louder and possibly improve it. I couldn't find any real attempts to mod a 09 Nismo can, so I decided to try it. My fall back plan would be to just buy a FI setup, but I wanted to try my hand at it first just to satisfy my curiosity. Note that stock non-Nismo muffler cans may be a bit different, but I'm betting that they are all similar enough to do this mod.

I finished the project and I really like the results. The sound is quiet at idle, but livens up quickly as you get on it. There is *no* drone or nasty rasp whatsoever. I didn't dyno it, but the Nismo is doing some things I'm not used to - like breaking loose on dry pavement at 40mph (2nd gear, throttle only), or 70mph in the wet. Definitely no loss of torque, and the butt-dyno says maybe a small increase was found.

Update: I attempted to record some videos and found out my new phone (HTC HD7) actually has noise cancelling, which does a great job of eliminating the exhaust sound from the video! I'll break out my GoPro cameras & see if I can do better.

The 09 Nismo muffler can has 3 internal chambers. The main exhaust dumps into the center section, mixes, and then exits back out side sections. There are two 2.5" ports in each side section to allow for this flow. There are also a number of other smaller ports dumping into the center section, presumably for tuning the sound(?)

In this mod, I decided I would create a better flowing crossover pipe that joins the two sections, hopefully getting better sound without a loss of torque. The crossover pipe is made of 14 g stainless exhaust tubing from Summit Racing, in 3" and 1.5" sizes Summit Racing SUM-640130 - Summit Racing® Stainless Steel Exhaust Tubing - Overview - SummitRacing.com. I'm a novice welder, so this was my chance to go buy some stainless mig wire & get some practice welding stainless. You need (1) of the 3" and (1) 1.5" piece of the stainless tubing.

First, a tip on removing the axle-back muffler can section - crack all four exhaust flange bolts loose first, before taking them off. I did them right-to-left and by the time I got to the last one, there was enough force pulling against it that the nut stripped and I ended up having to cut the welded bolt off the flange in order to remove it. Shoot some penetrating oil on them as well before attempting to take them off. I couldn't reach these bolts with an impact, so I had to reef on them with my socket wrench, which probably contributed.

After loosening the four main flange bolts, find the bolts holding the mounting brackets to the body - on my car, there were 3 bolts on each side holding triangular steel flanges. Careful with these too, because as they come out, the weight of the muffler section starts to put stress on them - you could end up having trouble with these also - especially take care when replacing them. The idea is to remove the mounting plates - not to try to pull the brackets out of their rubber vibration-isolators. The mounting plates and rubber isolators will just hang off the muffler pieces until you mount it all back up again.

Assuming you aren't still busting your knuckles to get the muffler section out, have a look at the surface of the steel - note tack weld marks running the circumference of the oval shaped can - there are two inner rows outlining the center section, dividing the can into thirds roughly.

I started the project with a sheet metal saw (like a small sawzall), but found later that a thin metal cutoff wheel on a handheld grinder worked way better. Pick a line to the *inside* of the line of tack welds and cut the can in half. I chose to cut close to the tack welds on both sides, sectioning the entire center section out in two cuts.



At the half-way mark, I dug out all the fiberglass and steel wool - it will make a huge mess when you work around it, and mind you don't breathe the dust that clouds up when you pull it outta there.



Cut and trim the edges until you have cleaned up the sectioned can, creating two separate smaller muffler cans. These still have muffle material in them, so they will still quiet your exhaust down a bit. You can see it in the two "top" 1.5" ports. The other two ports are mainline dumps from the engine-side. One of these gets covered up and the other (closer to the center) gets cross-connected with the 1.5" tubing.



The perforated pieces simply keeps the fiberglass material from blowing out your exhaust tips, so get out that grinder and cut the welds. This will reveal the two large 2.5" ports, along with a tiny one in between. Sorry I couldn't find a clean pic of this stage.

At this point, I chose to weld the entire seam at the point where the newly cut shell and the inner section wall come together. This looked like a place for exhaust to leak out or vibration to occur. This pic shows the crossover already in place, but you can see the outer seam is welded. You can also see the patch I welded over one of the smaller 1.5" ports - I re-used some stainless sheet from the center section for this.



Next Post: making up the center section & test fitting, measuring, test fitting, measuring, test fitting...

hazzazi

wow, good job... i'm interested to see videos on this.

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delorean

Awesome, can't wait to hear this! post vid

nismolife

I used (3) 3" stainless pieces to make the crossover pipe. Since all the ports just dumped into the center section, I figured I could tie them all together with exhaust tube, so long as the exhaust pressure could mix efficiently.

IMPORTANT: take the two seperated exhaust cans and mount them back on the car first. Use all the mounting bolts as if it was final install. Make sure the exhaust tips are aligned, and everything looks good. Now measure the width between the two cans - this is the only way to be sure you'll get a final product that aligns those tips.

Mine measured out to 8" even - and I noticed that there was some spring tension that caused the back half of the cans to measure slightly wider than 8", and I could see that in the alignment of the exhaust tips. By making the x-pipe 8", it would pull everything back into straight alignment. Please don't just use my measurement - who knows how your car may differ!


In order to achieve a free-flowing x-pipe, I cut baffles into the two outside tubes (shown is first side). I sectioned the center tube lengthwise to help size the baffles, but eventually I just cut the other side of this center tube as well, producing two rounded center pieces to tie it all together.

Before cutting into the tubing, and in order to make sure the x-pipe ended up wide enough to cover the two 2.5" ports, I stood the two outside tubes on the garage floor, and then stacked the center tube on top. This let me shift things around until I had the width measurement I needed - about 7.5".


Here's the x-pipe before welding all seams.

Now, take the x-pipe back to the car. Loosen mounting bolts enough to be able to slip the x-pipe up in-between the two cans, then go back through the process of tightening and aligning the exhaust tips - this is your last chance to get the alignment correct - once its welded in, you get to look at your handiwork every time you walk out to the car, so take your time, get help, get it right.

Use Sharpie to make alignment marks on the side of the can & x-pipe. I chose not to tack weld the x-pipe in, because I wanted to make sure the fit was flush to the can. Once you have your alignment marks, you can take the cans and the x-pipe down to the bench & weld 'em up.

The final step was to measure and cut a piece of the 1.5" tubing to cross connect one of the smaller engine-side ports (these are the ports that don't have muffle material visible, and are closest to the flange). I chose the port closest to the x-pipe, because it looked like I'd be able to weld it all up without leaks. I had to grind off the lip of the port in order to fit the tubing between the cans. I chose to just patch over the remaining 1.5" port, mostly because I couldn't see how to do a decent job welding the seams. I can't speak to the outcome, but I imagine I could have just patched both these holes and let the extra pressure go to the x-connect section, but I didn't want to create too much back pressure.


Another look at the patched port. The 1.5" tube is just out of view.


Here's the whole unit, before doing the smaller cross connect. Note: I *did* run it this way for a few days, but it was too loud in my opinion - good for a bit of fun, but not what I was looking for. Plus, the low-mid torque felt very mushy with the engine-side ports still open. The two "top" ports (you can see the fiberglass material) will be left uncovered - the material has stayed put so far .

That's pretty much it - mine bolted right up with no fuss and the tips look aligned. Firing it up was much quieter than running around with the engine-side ports opened, and after driving it a bit that torque was back big time. The exhaust isn't crazy loud, but is notably louder than the stock Nismo. Its not raspy, there's no drone and I still hear that off-throttle between gears stumble-kinda-misfire sound that I've really come to like.

Hopefully if you try this mod you'll like the results as much as I do. At this point, I don't plan to upgrade the exhaust - though I may get some high-flow cats for even more flow.

hazzazi

do you have any video of the setup, u could share??

Thank you for making this post

Sent from my Galaxy Nexus using Tapatalk

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vividracing

I'd be concerned about moisture and/or debris getting inside the muffler.

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HArturo319

This was an interesting read... what ever happened to the final product?

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Me And Zoloft Get Along Just Fine

JARblue

I'm pretty sure that last picture was the final product.

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HArturo319

OK but where's the soundclip? Did it work? How did it hold up?

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Me And Zoloft Get Along Just Fine

JARblue

I would like to hear a sound clip as well, but I can't imagine I'd ever do this to my muffler. My guess is it held up just fine unless vivid was right about his comment. But it would be good to know either way

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MR.nismo

Bump bump. Nismolife can you post a video when starting up and a drive by? Also, tell us the pros and cons you encountered. Is it much louder inside as you drive it? Thanks. I won't be doing that to my muffler, but is very inetresting what you have done. Well done sir!

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DEpointfive0

Considering this thread was last touched by nismolife over a year ago, and since he hasn't logged on in over 9 months... Consider it like Justin Timberlake says,
"Dead and gone"

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Slowfashow

Some say he got married and he was never seen or heard from again.

Cvzg77r

^lmao yeah that could of definitely happened

Vbp6US

Sad