No, they're not morons but I think they could have at least put an inlet radius on the 2.5" flow through. It would make a huge difference on the discharge coefficent. That same muffler could flow a lot more with it.

BTW what other inefficiencies are you referring to? Upstream of the muffler I don't see any design defficencies. Mabey little tweaks could be made but everything seems reasonable and within practical limitations. Certaintly nothing worth bothering with. Looks good to me.

I can't see what's going on inside the resonators but I assume it's straight through with no sudden expansions or contractions in the flow path. Nor any miter turns or turbulators either.

If you know of some funny business going on upstream of the muffler let me know. Mabey there could be an easy fix. Otherwise it all looks first class.

In Theory, practice and theory are the same.
In Practice, practice and theory are not the same.

2004 G35 6MT Blk/Blk Sedan Stillen Air, Stillen Exhaust

 

Hydrazine,

You're correct, there are no inefficiencies from the X-pipe to the inlet to the muffler, as far as I know.

The company that builds Stillen's exhaust systems also builds systems/components for other companies. I was surprised as to which ones. Unfortunately, I was asked not to talk about the details of the commercial system's design or their other customers, so I guess you're pretty much on your own.


DaveO
03 G35 AT Sedan / DP / Willow / Premium / Sport / Aero / Mods / 262 & 260.7

 

OK,

Here is what I made today. Flanges with 3" long stubs of 2.5" tubing. I spoke with a performance muffler shop today and he explained all his 2.5" mufflers have expanded tubing ready to slide fit on to 2.5" tubing. So this is why I made the flange parts. I will go to the muffler shop tomorrow to see what he has. Hopefully he will let me try out a few high flow mufflers before making a purchase. I am keeping my fingers crossed. Anyways, I won't purchase anything unless it sounds dramatically better than the Stillen. No need to toss away $$$ for little change in sound or performance.

For uncompromised performance, I can simply hook up the straight pipes. They will be punishingly loud but that will be OK once in a while for special occasions. They ought to sound much better and offer much bigger gains on a TT.


In Theory, practice and theory are the same.
In Practice, practice and theory are not the same.

2004 G35 6MT Blk/Blk Sedan Stillen Air, Stillen Exhaust

340115-flange.jpg

 

These are the straight pipes I cut today. I still need to expand the end of the inlet side so it can slide fit onto the flange stubs.

I should be able to try them out tomorrow afternoon. LOUD LOUD LOUD. Mabey I will make a few rips through the neighborhood just to let everyone hear it. >=)



In Theory, practice and theory are the same.
In Practice, practice and theory are not the same.

2004 G35 6MT Blk/Blk Sedan Stillen Air, Stillen Exhaust

340119-Straight Pipes.jpg

 

Dave,

When you say there is additional power to be had, how much is still left to squeez out from what you have seen?

BTW how can I post a short MPEG video. I will take a small video of the straight pipes with sound.

In Theory, practice and theory are the same.
In Practice, practice and theory are not the same.

2004 G35 6MT Blk/Blk Sedan Stillen Air, Stillen Exhaust

 

Hydra

- when you make an mpeg, i'll let you ftp it to my seerver, i'll serve it up.

- I am planning to do this very same thing tomorrow morning (friday)

- I was at Mike's muffler here in L.A. (godd shop, mandrel bends, etc.). Looked at some magnaflows. Now I am torn b/w getting a dual 2.5 in and single 3.5 out with a nice big (4" diam) tip, or dual 2.5 in/out with two smaller tips (both 4x11 oval). Any suggestions (I know it's subjective, but still). The dual/single one had a very nice design for this kind of muffler. The duals ran the length of the muffler in a v type pattern, converging pretty smoothly into a large opening. Advice here please!

- I think there will be a sizeable gain for me with replacing the muffler, as the single 2.5" diameter is restrictive, not to mention the design (transition) flaw, as well as the restriction mentioned by Dave.

- The mufflers were both in the $130-150 range...

- as far as those flanges are concerned... if I were to go with that, how do we know if the rotation of those flanges would be the same as we weld it on, so as to make the mufflers interchangeable...

G

 

Hydrazine,

How much additional power... I really don't know, I'm not good at crystal *****.

I recommend you check out the following link.

https://g35driver.com/forums/showflat.php?Cat=&Board=1&Number=132596&page=&view =&sb=&vc=1

A few of us worked on Sedan Exhaust System designs starting about a year ago. Jim C built his own.


DaveO
03 G35 AT Sedan / DP / Willow / Premium / Sport / Aero / Mods / 262 & 260.7

 

Only an enthusiast like Dave would search for a post that is 10 months old[img]/w3timages/icons/wink.gif[/img]

2003.5 Black 5AT Sedan
z-tube/ jwt popcharger/crawford plenum/crawford cats/
stillen exhaust/grounding kit/e-fans
technosquare ecu /350z thermostat/double din

 

Gurgen,

"- I was at Mike's muffler here in L.A. (godd shop, mandrel bends, etc.). Looked at some magnaflows. Now I am torn b/w getting a dual 2.5 in and single 3.5 out with a nice big (4" diam) tip, or dual 2.5 in/out with two smaller tips (both 4x11 oval). Any suggestions (I know it's subjective, but still). The dual/single one had a very nice design for this kind of muffler. The duals ran the length of the muffler in a v type pattern, converging pretty smoothly into a large opening. Advice here please! "

Sounds all good. But I'm thinking the single large tip will look more agressive. The muffler shop near my place has lots of Magnaflows too. I may even see the muffler you're referring to. I'll have to check it out.

"- I think there will be a sizeable gain for me with replacing the muffler, as the single 2.5" diameter is restrictive, not to mention the design (transition) flaw, as well as the restriction mentioned by Dave. "

I definitly have to agree with that. If it makes a difference NA it will make even more for TT.

"- as far as those flanges are concerned... if I were to go with that, how do we know if the rotation of those flanges would be the same as we weld it on, so as to make the mufflers interchangeable... "

I started thinking about that yesterday too. If your muffler inlet has expanded tubing ready to slip fit onto 2.5" tubing (like my muffler shop explained to me) you will need the flanges if you ever want to reinstall the Stillen muffler but if you make additional flanges with stub tubes like I show in my prior post, changing from one muffler to the next will be as simple as a slip fit.
My straight pipes, for example, should be able to slip right onto your stub tubes. We could even try glass packs or just about anything.

In Theory, practice and theory are the same.
In Practice, practice and theory are not the same.

2004 G35 6MT Blk/Blk Sedan Stillen Air, Stillen Exhaust

 

Hydra...

I will drop by Midas this morning and get my self a pair of those flanges with the 2.5" stubs...

My cell is 323-578-0587. Call me if you can when you see this message, will be faster to coordinate things that way.

Gurgen

 

Good stuff in here, guys!!

I'm in a similar state. I just barely finished with the install of a custom 3" exhaust. Basically, it's resonated test pipes, a Y pipe w/ flex sections that collects into a straight 3" pipe. No mufflers for now so, yeah, it's loud. The plan is to add one or two resonators as needed to cut down on the loud noise at 2400 rpms.

--Steve

 

Steve,

Aren't you running the PE TT now? I bet that helps with the sound a lot.

Have you got your TT all dialed in and dynoed?

In Theory, practice and theory are the same.
In Practice, practice and theory are not the same.

2004 G35 6MT Blk/Blk Sedan Stillen Air, Stillen Exhaust

 

Today I spent so much time at the muffler shop I couldn't get much done. But I did get a good download on muffler tips. To make it real short, Flowmasters are completely out of the question on our cars. The muffler guy said flowmasters and other similar chambered/baffled mufflers sound great on American muscle cars but sound completely ricey on imports. Not that we don't already know, but it is good to hear a third party confirmation, he also said that straight through designs like Borla and Magnaflow are the only way to go for our type of engines.

He did say that both Magnaflow and Borla are good mufflers of the same quality, but when you purchase Borla, you pay extra for the name. He also suggested visiting the Magnaflow website and then calling their 800 number for suggestions. He said the typical price for a Magnaflow muffler would be anywhere between $60-$100 dollars. Sounds low, but I will get a more firm quote when I know the actual part number. He also said I could try a few mufflers before purchasing! Now I just hope the muffler I want to try is one he has in stock.


In Theory, practice and theory are the same.
In Practice, practice and theory are not the same.

2004 G35 6MT Blk/Blk Sedan Stillen Air, Stillen Exhaust

 

Hydrazine, yep I'm running the PE kit. I'm still working on getting everything in place so I can boost to 15psi.

With the exception of a *very* loud resonance at about 2200-2400rpms, my current exhaust (with the turbos and the test pipes being the only muffling influence) isn't any louder than the Stillen.

--Steve

 

Steve,

"my current exhaust (with the turbos and the test pipes being the only muffling influence) isn't any louder than the Stillen. "

Well I guess I'm not too surprised to hear this. I just tried out the straight pipes today and the results were a somewhat of a surprise to me. The straight pipes weren't nearly as loud as I expected. I was waiting to hear something completely off the charts but it wasn't too much louder than the Stillen. Don't get me wrong, it's loud, it's just not what I expected.

I must say the quality of sound is much more interesting with the straight pipes. The very low frequency tones completely come to life. Almost like they weren't present at all with the Stillen they are definitely there now. Fortunately, I really like the low frequencies. They aren't fatiguing or overbearing at all.

The midrange loudness is unchanged from the Stillen level until about 3000 to maybe *3500 RPM. *(At this point you can hear the rice coming in.) The rice peaks out at about 4000 RPM and fades again at about 4500 to 5000 RPM. Beyond 5000 RPM the sound is broad band thunder. All frequencies are in full effect. It is very loud, but the quality of sound is good. It is also much more revealing of the engine load and throttle position.

Because the quality of sound changes so clearly with throttle position it gives a good audible feedback to the driver. Conversely, the Stillen is always loud but it seems to have the same type of sound no matter what the load or throttle position. For me, the Stillen muffler sound is not too pleasant to listen to. The straight pipe sound is much more interesting and much more informative. The revealing sound provides a feedback that would be desirable on the track.

I also did some freeway cruising at 2500 RPM. No problem at all. Nearly unchanged from the Stillen level of loudness. I took a few stabs at the pedal while at 2500 RPM and the loudness is not much different from the Stillen but the detail of sound is clearer. The Stillen muffler seems to screen out much of the engines attitude but not so much of its overall loudness.

While on the freeway I opened it up to WOT at high RPM to get a feel for the sound and any effect on the engine. When you open it up it clearly projects an aggressive sound to all surrounding cars. I came up on a later model black Prelude. There were three skinhead vatos giving me the Skunk eye as I accelerated past them. Because I was experimenting with the different throttle positions at high RPM they must have taken it as a challenge because they tried to jump on the gas. ...when I saw what they were up to I hit the gas and left them real quick.

Is it streetable? It's marginal. You could probably do it but with a level of risk. I took a drive on various surface streets, the freeway, to the market and the autopart store. If you drive like a normal person it's acceptable and you won't draw attention to yourself. If you are driving hard when passing a cop, expect to get nailed. I drove by three squad cars with no problems. I stopped at a red light only to have a motorbike CHP with Terminator glasses pull up next to me. I saw he was looking at me but he didn't do anything. When the light turned green I turned left with my foot very light on the gas. I was sweating it but I got away.

Whew! NO MUFFLERS right next to a CHiPr and I didn't get spanked!!!


In Theory, practice and theory are the same.
In Practice, practice and theory are not the same.

2004 G35 6MT Blk/Blk Sedan Stillen Air, Stillen Exhaust

341473-Straight pipes 1.jpg