[enne]

My V6 Camaro has a 2.5" Magnaflow exhaust on it from headers to tips. 3" on an Accord is a little much, though I don't know the stock diameter. Did they tell you that you would probably lose low end torque by putting such a large exhaust on?

https://www.carthrottle.com/post/wg3b6r9/

An exhaust system’s purpose is to evacuate gasses from the cylinder, and logic would say that a bigger pipe would evacuate more of those gasses. This “bigger is better” idea doesn’t always ring true, however, and there can actually be power loss at lower rpms when the exhaust diameter is increased. This is due to a decrease in exhaust velocity which leads to the presence of turbulence. This turbulence can hurt performance, and that leads people to believe that less back pressure causes a loss in torque.

To better understand this, you should understand what these terms mean:

Back pressure is basically the pressure that opposes the desired exhaust flow.

Exhaust velocity is how fast the exhaust is moving through the pipe. (To an extent, a smaller diameter pipe will increase velocity, and a larger diameter pipe will decrease velocity).

Turbulence is the inefficient tumbling of exhaust flow cause by a lack of velocity.

Basically, the optimum exhaust system balances between having low back pressure and high velocity while avoiding turbulence. It’s good to reduce the restriction on flow, but if too much velocity is lost, that’s not good either.

Exhaust scavenging
Another important aspect that ties into good velocity is what’s called exhaust scavenging. Exhaust pulse scavenging works on the concept of the idea that exhaust comes in “pulses” which exit each of the cylinders on the exhaust stroke. A 4 cylinder engine will have 4 pulses per 2 revolutions, while a 6 cylinder will have 6, and so on. Behind these “pulses” exists a small vacuum which helps to pull the next pulse along. The higher the speed of these pulses, the more effective the effect of the scavenging effect is, and the better the exhaust gasses will be pulled through the exhaust system.

 

[enne]

I don't know an answer for the 2.5 piping to a 2.25 muffler. Sorry. I assume it will work fine.

It's only a quarter inch, they can probably just use adapters.

 

[enne]

If you would've come here before putting on a random exhaust setup, you would have learned that a new exhaust would do nothing for it, and you could have saved your money for something else. Not a shot in the dark really.

I did weeks of research before purchasing and having my Camaro's exhaust installed. And I am happy with it because I got what I paid for and knew what exactly I was getting:
I stuck with 2.5" because 3" would've been obnoxiously loud, and would've been harder to mate with the other components that weren't 3". I bought Pace Setter shortie headers that would actually fit, because mid- and long-tube headers don't typically fit on the stock V6. I found exhaust tips I really liked. I went with a Magnaflow muffler because IMO Flowmaster doesn't sound as good (I listened to other people's setups online to find the sound I wanted), and Magnaflow also makes a specific muffler for my make/model/year of Camaro. And it all cost me less than $1k with parts and labor included. Didn't need any custom piping done. I learned all of this from going online and reading about what other people have done to their cars.

So... yeah. Little bit of research goes a long way. I could now get the car tuned to run a little better, but since it's not a race car and the exhaust is stock diameter, I don't have to.

 

[enne]

Originally I thought the shop would put 2.5" on.

the guy there told me he would put 2.5 piping on it, that's when I left. When I got back, he said he put 3 inch on it. So I had to simply drive it a bit and see.

So, you were told you were getting 2.5 but were given 3? That's not how you worded it in your first post. It seemed like you just dropped the car off without discussing pipe diameter and that's what they went with. If they told you one thing and did another, you need to talk to them about that.

 

[enne]

Uh-huh.

Putting a (wide pipe) catback on a car is the equivalent of screaming to get your point across instead of articulating your argument.