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Pros & Cons From Enlarging or Downsizing Your Exhaust Pipe Diameter

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Old 09-01-2014, 04:59 PM   #1
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Pros & Cons From Enlarging or Downsizing Your Exhaust Pipe Diameter

I'm interested to hear what people have to say. First post by the way...

HAVE FUN!
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Old 09-01-2014, 07:27 PM   #2
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Welcome to TW, Tacomas...

I run an aftermarket header so I went with a slightly smaller 2 1/4" OD tailpipe from the factory stock 2 3/8" OD exhaust. It helps the exhaust gases to retain their velocity, because velocity enhances scavenging.

Greg
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Old 09-01-2014, 07:35 PM   #3
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I went to a 3" with headers and y pipe..... Had no low end tq. It was like driving a civic. Don't open it up too much!
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Old 09-01-2014, 08:26 PM   #4
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I put on a 2 1/2" cat back and can say it hurts low end but cranks over 3500rpm. I had to put on the intake spacer to regain low end and they work great together. To do it again I would just change the muffler and use the stock exhaust. Here is my thread with more details...

http://www.tacomaworld.com/forum/per...d-muffler.html
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Old 09-02-2014, 11:12 AM   #5
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Quote:
Originally Posted by shr133 View Post
I put on a 2 1/2" cat back and can say it hurts low end but cranks over 3500rpm.
Yes. That's the larger exhaust trade off. You give up low end pull to get top end power.


Greg
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Old 09-02-2014, 10:22 PM   #6
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Over 30 years ago I did a little drag racing. There was calculation we used for how much pipe was needed after the headers to get correct backpressure. After that the pipe does nothing but move exhaust away from passengerrs. Not much point to this story except to confirm that all the magic happens within a few feet of the heads.
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Old 09-02-2014, 11:34 PM   #7
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Quote:

Over 30 years ago I did a little drag racing. There was calculation we used
for how much pipe was needed after the headers to get correct backpressure.
For racing, for hp the length is determined where the bluing stops or use a yellow crayon draw a line on the pipe and where it stops melting is the proper length.
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Old 09-03-2014, 01:27 AM   #8
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Quote:
Originally Posted by steelhd View Post
Over 30 years ago I did a little drag racing. There was calculation we used for how much pipe was needed after the headers to get correct backpressure. After that the pipe does nothing but move exhaust away from passengerrs. Not much point to this story except to confirm that all the magic happens within a few feet of the heads.
It's more than backpressure alone. It's also the timing of the reflected exhaust pulses travelling back to the exhaust ports which creates the scavenging effect. The greater the exhaust gas velocity, the more powerful the scavenging effect. Larger pipe diameters slow down the flow, and reduce the scavenging effect.

Greg
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Old 09-06-2014, 11:56 PM   #9
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Very interesting... I'm going to make another thread on this but since I have the question in my head, what's 49 states legal? Or does it come down to what can you get away with?
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Old 09-07-2014, 12:43 AM   #10
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Quote:
Originally Posted by Ihatetacomas View Post
Very interesting... I'm going to make another thread on this but since I have the question in my head, what's 49 states legal?
It means that it's legal everywhere except California.

Quote:
Or does it come down to what can you get away with?
Everything comes down to what you can get away with.


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Old 09-10-2014, 04:00 PM   #11
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Stock Diameter?

Ok so I just measured my tacoma's exhaust and I measured a 2 1/2 inch diameter with a 3 inch tip. Is this normal? I bought this preowned from a dealership and it only had 28,XXX miles on it, I don't think whoever had it would spend that much on an exhaust and only keep it for 2 years... By the way there's no logo anywhere on the exhaust...looks pretty stock to me.
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Old 09-11-2014, 06:31 AM   #12
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Later year Tacomas (at least the 6 luggers) are reportedly getting 2.5 exhaust piping stock. Not sure what year they changed, but I know my 09 is 2.25. So updating one of these 2.5 stockers makes even less sense then on the earlier models. Just get a new muffler welded on if you want more sound, or if you do want more high end at the expense of low end, move up to a 3".
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Old 09-15-2014, 12:22 PM   #13
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I think ill stick to stock for now, at least until I become a brain surgeon and can actually afford the supercharger
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Old 09-15-2014, 12:31 PM   #14
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It's kind of like inhaling air through a super thick straw. If it's too thick, you aren't going to get a whole lot of airflow going through it. If it's too thin it will be more difficult to move air and you will essentially choke yourself. Exhaust piping should be setup according to the horsepower/torque that the engine is capable of putting out. Anything over and you aren't helping anything.

Matter of fact, with our given HP/TQ #'s 2.25" piping is more then adequate. Hell My 440HP/425TQ 2005 GTO ran 2.5" piping and that size was more then plenty to satisfy it's power needs.
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Old 09-15-2014, 12:36 PM   #15
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Quote:
Originally Posted by 12TRDTacoma View Post
It's kind of like inhaling air through a super thick straw. If it's too thick, you aren't going to get a whole lot of airflow going through it. If it's too thin it will be more difficult to move air and you will essentially choke yourself. Exhaust piping should be setup according to the horsepower/torque that the engine is capable of putting out. Anything over and you aren't helping anything.

Matter of fact, with our given HP/TQ #'s 2.25" piping is more then adequate. Hell My 440HP/425TQ 2005 GTO ran 2.5" piping and that size was more then plenty to satisfy it's power needs.
2.5" duals on the GTO though, not a single out, right.
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Old 09-15-2014, 12:57 PM   #17
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Quote:
Originally Posted by 12TRDTacoma View Post
Oh I forgot, we don't run duals. Lol.
Yup, that's my point. But for the close to stock Tacoma, the point is still valid 2.25-2.5 is adequate, while 3" starts moving the flow characteristics to a higher rpm.
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Old 09-15-2014, 01:17 PM   #19
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I would suggest talking to a proctologist before getting your exhaust pipe enlarged OR downsized. Just to be sure it was safe to do so.
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Old 09-15-2014, 01:21 PM   #20
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Quote:
Originally Posted by BamaToy1997 View Post
I would suggest talking to a proctologist before getting your exhaust pipe enlarged OR downsized. Just to be sure it was safe to do so.
Not downsized,,, rejuvenated....
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