Do Stock Mufflers Restrict Flow
 

I have a TTP intake, headers and 100-cell cats going to a stock muffler on my 2.7L Boxster. I tried a Gemballa muffler with that rig, but it was way too loud for my tastes. My current exhaust setup sounds fine, but I am wondering if the stock muffler is acting as a bottle neck for the exhaust gas in my system.

If the stock muffler is not restricting gas flow, I am fine with keeping it. If it is restricting flow and effecting efficiency or performance, I would consider getting a Dansk port muffler if it allowed the car to breath better. The reason I would consider a Dansk is that my sense is that they are not too loud and they give good exhaust flow. In the best of worlds I would like a muffler that provides good flow and is not very loud (oxymoron?). Any ideas, thanks,

Ed
:cheers:

Here's a drive-by video of my 01 2.7L with the Dansk sports exhaust with super sound tips. It's throatier above 4K rpms, but not super loud. No other exhaust mods...just the muffler-

http://video.tinypic.com/player.php?v=21ctwex

Sound of Dansk Muffler
 

Muffler sounds very cool.


Ed :cheers:

100 cell CAT
 

Hi, Ed. I am planning to do exactly the same as what you have done. Intake, header and 100cell Cat to the stock muffler.
Here is the question. Did you get a CEL? If you did, what is the proper fix for it?
I have some idea for that. See what you think.
I am thinking to extend O2 sensor wiring to reach front side of CAT and rear of CAT. I might have to install O2 sensor eliminator (that is what they call it, about 10 bucks) to have system thnk it still have good CAT. Let me know what you think. Thanks. :)

______________
2001 Boxster S triple black
16000 mi

Mufflers and Exhaust Gass Flow
 

"I have a TTP intake, headers and 100-cell cats going to a stock muffler on my 2.7L Boxster. I tried a Gemballa muffler with that rig, but it was way too loud for my tastes. My current exhaust setup sounds fine, but I am wondering if the stock muffler is acting as a bottle neck for the exhaust gas in my system.
Ed
"

Originally Posted by edevlin

"Hi, Ed. I am planning to do exactly the same as what you have done. Intake, header and 100cell Cat to the stock muffler.
Here is the question. Did you get a CEL? If you did, what is the proper fix for it?
I have some idea for that. See what you think.
I am thinking to extend O2 sensor wiring to reach front side of CAT and rear of CAT. I might have to install O2 sensor eliminator (that is what they call it, about 10 bucks) to have system thnk it still have good CAT. Let me know what you think. Thanks. "



Well in answer to my question about the stock muffler restricting the flow of my 2000 2.7L boxster with TTP headers and high-flow cats, the answer is that it does not appear to, at least not based on a couple dyno runs. The first dyno run with TTP headers/100-cell/stock muffler was 201 hp. By adding a Dansk Sport muffler to my system the car dynos at 201 hp, and maybe a few ft/lbs less torque, so little or no difference, at least at its current state of ECU tune.

In response to the question about CEL with header and 100 cell cat, yes I am getting a 1275 CEL code. In my setup I put on the TTP headers which have no cats on them or bungs for O2 sensors. The 100-cell cats I use are located downstream near the muffler and have bungs for O2 sensors right in front of and behind the cat. I put on 4 new O2 sensors (with longer cables to reach) to the sensor bungs in front of and behind the cat.

I think the problem in my case is that the cat and the O2 sensors are located too far downstream in the exhaust flow. Because of that the first set of O2 sensors which is normally right at the base of the headers is too far away and is not heating up enough.

I am in the experimental sorta mode so next week I am going to put a O2 sensor bung for the first set of cats at the base of the TTP header, where it is found in stock cars and see if that helps get rid of the CEL.

BTW, as I said previously when I put on a Gemballa muffler, the car was loud.... too loud for my tastes, so I put the stock muffler back on. Last week I installed a Dansk Sport muffler and it is also loud, not as loud as the Gemballa, but still loud. The Dansk also has a 2-3K resonsance that is annoying when cruising at highway speeds.

The reason I tried the Dansk muffler in the first place was to see if I could squeek a little more performance out of the exhaust, not more sound. I will try this setup for a while and decide if I will keep it or go back to the stock muffler. The only plus so far for the Dansk muffler is that it sounds nice outside of its annoying low-rpm resonance range. Also, it's lighter than the stock muffler. How do you say "live and learn" or it it " I know just enough about this stuff to be dangerous....".

Ed

:cheers:

100 cel CAT
 

Thanks, Ed for very informative research/ trial. I will also pursue what you have done.
I was talking to a dude in FVD. He said that I will get a CEL using 100cel CAT. He was saying that ECU needs to be reprogrammed to have engine recognize as if it has normal/ properly functioned CAT(400cel). Another words, 100cel is not enough to emulate normally functioned CAT. He didn't say that 100cel would not pass emission test. I don't think he can say that knowing that 100cel CAT would require mod on ECU.

Anyway, I think you are right. Header that I got from Che has a bung on the end of header. So I will install the front sensor like you recommended and I will plan to install O2 sensor with O2 sensor eliminator at the rear of 100cel CAT. By the way what kind of wires did you use to extend the wire to the back side of the engne? Do you know where to find temperature rated wire? Or you know where I can find extension wire for Bosch O2 sensor? Please advise. Thanks. :) PS. Good luck on your experiment. I hope that works.

Adventures with Exhaust
 

"Anyway, I think you are right. Header that I got from Che has a bung on the end of header. So I will install the front sensor like you recommended and I will plan to install O2 sensor with O2 sensor eliminator at the rear of 100cel CAT. By the way what kind of wires did you use to extend the wire to the back side of the engne? Do you know where to find temperature rated wire? Or you know where I can find extension wire for Bosch O2 sensor? Please advise. Thanks. PS. Good luck on your experiment. I hope that works."

We used wire from old O2 sensors to extend the wire. BTW, if you are extending the wires, be careful that you match up the wires properly. They did not seem to be marked that well. I think two of them were marked the same, I suspect they were just heater wires. When you get a CEL after an mod like this, we end up second-guessing what may have gone wrong. If you get the wiring right, that will eliminate one of the variables, have fun,

Ed

:cheers:

Well in answer to my question about the stock muffler restricting the flow of my 2000 2.7L boxster with TTP headers and high-flow cats, the answer is that it does not appear to, at least not based on a couple dyno runs. The first dyno run with TTP headers/100-cell/stock muffler was 201 hp. By adding a Dansk Sport muffler to my system the car dynos at 201 hp, and maybe a few ft/lbs less torque, so little or no difference, at least at its current state of ECU tune.

In response to the question about CEL with header and 100 cell cat, yes I am getting a 1275 CEL code. In my setup I put on the TTP headers which have no cats on them or bungs for O2 sensors. The 100-cell cats I use are located downstream near the muffler and have bungs for O2 sensors right in front of and behind the cat. I put on 4 new O2 sensors (with longer cables to reach) to the sensor bungs in front of and behind the cat.

I think the problem in my case is that the cat and the O2 sensors are located too far downstream in the exhaust flow. Because of that the first set of O2 sensors which is normally right at the base of the headers is too far away and is not heating up enough.

I am in the experimental sorta mode so next week I am going to put a O2 sensor bung for the first set of cats at the base of the TTP header, where it is found in stock cars and see if that helps get rid of the CEL.

BTW, as I said previously when I put on a Gemballa muffler, the car was loud.... too loud for my tastes, so I put the stock muffler back on. Last week I installed a Dansk Sport muffler and it is also loud, not as loud as the Gemballa, but still loud. The Dansk also has a 2-3K resonsance that is annoying when cruising at highway speeds.

The reason I tried the Dansk muffler in the first place was to see if I could squeek a little more performance out of the exhaust, not more sound. I will try this setup for a while and decide if I will keep it or go back to the stock muffler. The only plus so far for the Dansk muffler is that it sounds nice outside of its annoying low-rpm resonance range. Also, it's lighter than the stock muffler. How do you say "live and learn" or it it " I know just enough about this stuff to be dangerous....".

Ed

:cheers:[/QUOTE]

Ed, did you buy the Dansk exhaust with the "super sound tips" shown below, or the one that looks like a hot dog shape? I have the super sound tip version, and since the muffler itself is shaped exactly like the OEM muffler, there is no resonance at all, just a throatier exhaust note due to the different baffles inside. The hot dog muffler from Dansk does exhibit resonance in the range you speak of.

http://www.pcars.us/albums/5267.jpg

"Ed, did you buy the Dansk exhaust with the "super sound tips" shown below, or the one that looks like a hot dog shape? I have the super sound tip version, and since the muffler itself is shaped exactly like the OEM muffler, there is no resonance at all, just a throatier exhaust note due to the different baffles inside. The hot dog muffler from Dansk does exhibit resonance in the range you speak of."

I got the hot-dog shaped Dansk muffler, which I thought did not have the resonance I am getting. Do you know if there are any differences in the performance or flow-rate characteristics of the two mufflers?

Ed

:cheers:

Both versions are advertised to supposedly give the same 10-15hp gains over the OEM muffler (take that with a grain of salt of course), but I'm not sure about the flow rate differences. I took a look at the inside of my Dansk before putting it on, and compared it to the OEM muffler, and noticed that the baffles were different. I suppose that is what gives the louder and more throaty sound. I havn't dyno'd my car with the Dansk on, but my butt-o-meter indicates quicker throttle response and a bit more oomph at full wail, although that could be due to the louder sound.

I would ask the place you bought the hot dog dansk if you could exchange it for the super sound version. Good luck.

Oh..and not to mention, it looks so dang good on the car once installed! ;)

http://i13.tinypic.com/2hwfd04.jpg