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Guest Message by DevFuse

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A VIN, and the reason why a muffler is an emissions device...

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8 replies to this topic

#1 WJM



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Posted 14 November 2003 - 10:52 AM

Ok, lets have a look at this VIN as see whats up...


And now for the muffler.
Im getting 21.7 MPG now. I HATE it. I was getting 29MPG!!

Reason: I installed a factory 4wd exhaust system to pass emissions.

Now, usually, the max allowed CO readin is 220, and the last time i got it inspected, the reading was way up there (sometihng like 218 or so), and I had a straight thru muffler. IE no backpressure. 29 MPG.

Now...BIG backpressure, stock muffler, quietness, and pass emissions with 81 CO reading, and LOW LOW MPG now. So, Back pressure, low CO, and the sence came to me.

The muffler restricts the air from flowing out so quickly, that way the air stays in the cats for longer, giving the honeycomb and the exhaust gases more time to interact, much longer, therefore the air comming out of the cats, are cleaner than before.

Thats my spin on it. I'd still rather get more MPG tho. I AM switching to a 3 way cat on the GL-10 when I get some more $. The RX will get a 3way, as its sitting here waiting to be installed.

#2 Holmes


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Posted 14 November 2003 - 11:26 AM

More backpressure keeps the cat hotter too right? I knew there had to be a good reason why they would put such a restrictive muffler on our rides. I need to keep that in mind when I'm buying a new muffler.

#3 Dante


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Posted 14 November 2003 - 12:07 PM

Hmm... That's another reason to consider a Supertrapp disk-only muffler. Here's what the manufacturer claims:

Remove discs to decrease the exhaust opening and increase back pressure.

-This decreases the powerband to give you more low-end torque.
-Decreases the exhaust tone.
-Enriches the carburetion.

Add discs to increase the exhaust opening and reduce back pressure.

-This increases the powerband to give you more top- end.
-Increases the exhaust tone.
-Leans out the carburetion.

I learned about them at www.subarubrat.com

You could also remove disks to pass emissions and then add them for actual driving ;)

#4 Holmes


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Posted 14 November 2003 - 12:53 PM

Those look pretty nice, but I wonder how they would stick the sniffer up the tailpipe if it has a cap on the end?

#5 RallyKeith


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Posted 14 November 2003 - 01:05 PM

I've run a supertrapp on my autocross car for years. I just took it off and converted the car back to normal since I've bought an STi. The muffler has rusted off of my RX however, so I think the supertrapp has found it's new home.


#6 Hodaka Rider

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Posted 14 November 2003 - 01:50 PM

Use header wrap on the y-pipe and the cat. Keeps the heat in, allowing the cat to do it's job better while keeping the flow up. Speaking of flow, retaining heat in the Y will increase the flow, too. All good. Keep your mpg and whatever muffler setup you had before.

#7 Flowmastered87GL


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Posted 15 November 2003 - 03:36 AM

Well... stock system is 2 cats and small pipe... non stock is usally 2 inches ID or bigger and only 1 cat... that CAn explain alot (mine is 2.0 to cat 2.25 muffler to 2.5 to exhaust

#8 GeneralDisorder


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Posted 15 November 2003 - 03:41 AM

Flo - not all stock exhaust hs 2 cats - my 84 4WD exhaust has just one. the 2WD had two tho.


#9 Flowmastered87GL


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Posted 15 November 2003 - 04:05 AM

Hmmm fascinating...

My education is based on stock EA82's.... so I guess it varies.

You learn something new every day.

Now I will I be sober enough to actually retain this?? :D

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