[spool twice]

Bumping an old thread I know, but I didn't want to create a new one since I dont have an M2, but have an S55. I'm getting pretty close with my custom exhaust set-up inching closer and closer to the N54/N55/B58 sound. I'll do a full post about it on here and also my section (S55 M4 section) on what I did. Since our chassis is basically the same with the same suspension mounting points/rear subframe points, it should work as well.

Stock turbos, stock downpipes, stock mid-pipes, stock rear muffler. Only change is the resonator-to-rear muffler area and I can post what changes are made on my final version soon. There is an inherit imbalance to the S55's exhaust piping because the engineers went for a symmetrical twin turbo layout (as opposed to the N54's asymmetrical layout). The imbalance of it throws a traditional inline 6's naturally balanced exhaust pulses out of balance (I can get more into it later once I finish everything, its more to help others out who want to go a custom route).

Here is a video of "version 1" the first prototype using an H-pipe. "version" 2 will use an x-pipe (to capture more of the howl up top).

[Moflow]

Well, if you're going to bump a super old thread, i'm going to respond to a super old post.

Originally Posted by MrOhnoez

I mean how many production cars have an air to liquid intercooler as stock?

The...ahem...1988 Toyota Celica All-Trac had an air to water intercooler.



The following generation (5th gen, hood scoop celica) went to air-to-air before the generation after (6th, four headlights) went back to air-to-liquid. None of them had heat exchangers connected to the intercooler coolant, so they'd heatsoak pretty bad after a while.

[DriverDaily]

Originally Posted by Lukeni

Since you have basically two times an inline three cylinder in the s55 (two manifolds, each with one turbo) it will never sound like the n54. Iirc n54 is one manifold with two turbos.

Another problem is cylinders two and five are much closer to the turbos than the other cylinders.

Then, the turbo outlets are different distances from the crossover. If everything was equal length it would sound much better.

[spool twice]

Originally Posted by DriverDaily

Another problem is cylinders two and five are much closer to the turbos than the other cylinders.

Then, the turbo outlets are different distances from the crossover. If everything was equal length it would sound much better.

A small handful of us started this on the M3/M4 section with success (or at least 90%) equalizing the pipe lengths between driver/passegner sides using the rear section and then merging them with an H or X pipe, since there is limited room to accomplish this in the midpipe

Heres a guy who did it with an x-pipe

https://youtu.be/hMbj6-9B1zU

Then here is a before/after with this guy with catless downpipes (so raspier naturally), but you can here a change in pitch, he used an H pipe

https://youtu.be/GVlPXfXI8nw

[DriverDaily]

Originally Posted by spool twice

A small handful of us started this on the M3/M4 section with success (or at least 90%) equalizing the pipe lengths between driver/passegner sides using the rear section and then merging them with an H or X pipe, since there is limited room to accomplish this in the midpipe

Heres a guy who did it with an x-pipe

Then here is a before/after with this guy with catless downpipes (so raspier naturally), but you can here a change in pitch, he used an H pipe

I believe the stock midpipe muffler has a merge, just not a very good one. The AA midpipe seems to be a big help.

Also, fixing the crossover between the 1-2-3 and 4-5-6 cylinders helps, but you still have the problem at the manifolds.

[spool twice]

The issue with the OE merge pipe is its merging unequally spaced exhaust pulses, the same goes for the AA mid-pipe to a certain degree, which is why none sound like the videos above. All of which is created by the unequal-length downpipes (difference is over a foot) so it gets tricky and wont be 100% perfect. We had to eliminated the OE H-pipe and kept the pipes independent until the new merge pipe.

Yeah the manifold is still the issue, but thankfully we have turbos that cancel that somewhat.

I can post pics of what we did soon, just posting while on the road currently.

I'll get more video's soon as my external mic is finally here with a proper wind sock to minimize the wind noise/buffeting.

[spool twice]

This is basically what I did to mine (others may have a variation of this):



My drawing skills are terrible (obviously the curves are smoother in execution). The red lines represent what was done. The top pipes are the passenger side, and the bottom pipes are the drivers side. You'll need to add length to the passenger side to get it more equal in length to the drivers side, and then merge them. Don't worry about the U-shaped curve, there is plenty of space in that area where it isn't the lowest point in the exhaust (the secondary cats still are)

Here is a small sound bite (16 second audio only), of my exhaust where the microphone isn't clipping the sound due to how loud the exhaust gets at wide open and the relationship of where the microphone is mounted.

Its part-throttle revving up to about 4,500rpm, sounds decent in SPORT mode, especially for it being rather in-expensive for my exhaust shop to fabricate, keeping the engine in the 4,000-4,500rpm range daily sounds glorious now:

[doughboy]

spool twice..

I can see now that you've hit the nail on the head here.

Of course, now i see it after looking at all sorts of other things - the N54 had opposing direction turbos leading to same length DPs and exhaust route. So pulses remained true to firing timing between both 123 and 456 routes all the way to the tail pipes where it pops out and we here it as 1 5 3 6 2 4. If they're not evenly spaced then it sounds a bit er well S55 ish..




You design should be pretty low cost as it is only plain tubing.

On the new bend section does it lose the hanger that currently sits next to the diff?

Do you have an exact extension figure or just approx a foot?

[doughboy]

Originally Posted by Lukeni

Since you have basically two times an inline three cylinder in the s55 (two manifolds, each with one turbo) it will never sound like the n54. Iirc n54 is one manifold with two turbos.

Please look at the engine design..

N54 and S55 are both twin turbo twin manifold.

One for 123 and one for 456.

[Vulpe]

I'm really intrigued as to how this sound is the result of the exhaust layout.

I immediately thought of the WRX/STI but those sound completely different. So I was thinking it was because the unequal part happens before the turbo and not after. But the FRS/BRZ has a similar sound with no turbo. Is the unequal portion changing between the headers and exhaust that much of a difference?

[doughboy]

Originally Posted by Vulpe

I'm really intrigued as to how this sound is the result of the exhaust layout.

I immediately thought of the WRX/STI but those sound completely different. So I was thinking it was because the unequal part happens before the turbo and not after. But the FRS/BRZ has a similar sound with no turbo. Is the unequal portion changing between the headers and exhaust that much of a difference?

It doesn't really matter where the unequal part happens, it is the total length from exhaust port to exhaust tip.

Exhaust pulses travel at the speed of sound (roughly) so for them to emerge from the exhaust pipe where we hear them in equal spacing and in Inline 6 firing order (1 pulse every 120degrees of crank rotation) the pipe lengths must be pretty much the same for all cylinders.

But S55 design has both turbos rear facing, so the 456 (rear) turbo exhaust exit is a good foot further rearward than the 123 (front) turbo exit and no attempt is made to cater for this in the exhaust system.

So the pulses from 456 will clash with 123 pulses further back and will not give equally spaced "smooth" 120deg separated 153624 pulses.

The N54 had opposing turbos so that made the gas flow routes symmetrical as spool twice says.

[spool twice]

Yep, the rear banks are simply shorter in overall length as compared to the front banks. Equalize the length before they crossover is key to getting a different sound

And you are correct, it wasnt expensive at all. Just $350 in tubing and labor and a pre-fab Flowmaster x-pipe for $75.

Only downside thus far is removing the center resonator which has a crossover pipe (had to do it to remove that crossover), there is more of those "farts" and "pops" upon releasing the throttle thats raspier, I still have to source some small resonators or reuse the OE one, but somehow stick pipes inside the inlets to block the crossover piece but retain the resonated portion.

Limitations is still the lower note the oe exhaust tends to steer towards. People on the M3/M4 forums have custom mufflers that actually sound more 2jz/RB26, all from equalizing the pipe lengths and then crossing them over. Simple concept right?

A few small clips:

1st gear fly-by

2nd gear directly behind

1st gear part-throttle to 4,500rpm

[doughboy]

Hah very simple concept lol.

Bingo - sounds like my old N54!

I was also thinking that two small single resonators in place of the combined centre resonator would soften the rasp and keep the gas streams separate.

[doughboy]

Look here:

N54 DPs are same length each with opposing turbo connection from the centre of the motor.

S55 DP are very unequal length from turbo flange back. Head port to turbo flange is the same for 123 and 456. So this DP length difference is the overall pipe length difference.

[spool twice]

There is approximately 16-18" in pipe length difference by the time you get to OE crossover section, pretty crazy right? It's no wonder most (pretty much all) S55's sound so monotonous.

The solutions on the market isn't their, no matter how many single mid-pipes or resonators you add, the monotonous sound is still there, albeit with less rasp. Resolve the difference in pipe length, cross them over after resolving this, and you'll get a sound that mixes an N54/N55 with some harder-edge S55-ness in there, and cheaper than most mid-pipes to boot.

[doughboy]

I'd like to see some pictures of your system, even just development shots would be cool...

[spool twice]

Sure, heres prototype #2, I used more of a "chambered" crossover where is a greater chance of pulses collect into that one area to blend vs a traditional H-pipe or X-pipe

Ignore the ugly look, the final version will look normal. Unfortunately the space constraints will not allow it to be clamped on, it'll be a weld-on

Prototype #2 picture

You can see the U-bend added underneath the passenger side rear subframe. Its a good length added in a compact manner...almost 22-24", then subtract the length where the inlet/outlet bend occurs, which is almost 8", effective overall added length 14-16" on my system.

I don't know where the shorten distance in the exhaust occurs in the M2c though as compared to the M3/M4, im assuming its just a shorter mid-section?

[doughboy]

Looks pretty good for a protoype. Is it just mild steel at this stage or stainless?

[spool twice]

Aluminum for now, it will be stainless on the final.


Did a small stationary rev before heading home tonight

and a comparison between a stock ZCP, ZCP w/ single midpipe (deletes secondary cat), and an S55 M4 with equal-length exhaust pipe

[doughboy]

I like your approach, you've applied some simple physics to a problem and not been swayed by the hype that "oh you must be a multi million dollar manufacturer to do this kind of thing"..

and got good results..

It suprises me none of the aftermarket manufacturers have picked this up - but I think this idea is kind of too "outside the box" for them.

[Faikius]

Originally Posted by spool twice

Aluminum for now, it will be stainless on the final.


Did a small stationary rev before heading home tonight

and a comparison between a stock ZCP, ZCP w/ single midpipe (deletes secondary cat), and an S55 M4 with equal-length exhaust pipe

Great content here. Appreciate the methodical approach.

I've already had an exhaust shop fab up a muffler delete that came out great however the stock middle resonator remains in place. Based on what I've read here I'm going to have that removed / replaced with straight pipe, extend the passenger side a bit as you've illustrated, then add an x-pipe.

Will report back once done.

[spool twice]

Yes passenger side is the key. You have a it more room without the muffler so you have a bit of an advantage for space.

You could probably use any universal x-pipe because of the room you have. I had to use a compact flowmaster 815953 which is more of a chamber/collector crossover than a traditional x or h pipe.

The change in tone is pretty drastic, it just sounds more "full" yet refined at the same time, likely because there is a bigger range of sounds coming through and not just added volume.

I'd like to hear this set-up sometime with catless downpipes and midpipes.