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!

 

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

 

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!

 

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/performance-tuning/331394-mangnaflow-6-x-18-round-muffler.html

 

Yes. That's the larger exhaust trade off. You give up low end pull to get top end power.


Greg

 

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.

 

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.

 

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

 

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?

 

It means that it's legal everywhere except California.

Everything comes down to what you can get away with.


Greg

 

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.

 

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".

 

I think ill stick to stock for now, at least until I become a brain surgeon and can actually afford the supercharger

 

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.

 

Correct, duals attached to an X then at which point split up again at the exit and went out as duals.

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.

 

Yeah. I still believe that 2.25-2.5" is more then adequate for a stock non supercharged Tacoma. 2.5" probably being the better size for it.

 

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....