I have a NISMO
Stock exhaust w/ AAM HFCs
It was tuned and there is only a slight amount of rasp left.
I want to replace the Y-Pipe with a resonated XYZ pipe and see what that does.
My only concern is, the 3 inch outlet of the XYZ pipe will be mating against a 2.25 inch inlet of the mid pipe.

Would it be acceptable to replace the midpipe with one that reduces down to 2.25 inch from 3 inch? Like more of a gradual reduction than the sudden XYZ 3 to the mid pipe 2.25?

I'm trying to keep the stock muffler because I want it to look stock, and not be THAT much louder than stock.

 

The 0.25 inch difference is minor. Effect on exhaust volume and speed is inconsequential.

 

Another option is to get a Borla exhaust.

True Dual, so you don't need a Y-pipe at all.

It's resonated (no rasp or drone), is not much louder than stock, and looks close to stock.

 

It's a .75 inch difference actually. I was thinking the XYZ pipe was 2.5 out but it's actually 3. I was thinking of maybe a custom mid-pipe with a gradual 3-2.25 reducer in it. Not sure if that would cost a lot or not... :/

I was thinking about borla... but it wouldn't look stock on a nismo. The nismo is open enough to see the muffler from behind, and it has big 4.5" tips on it.

 

Motordyne exits at 3 inch, stock midpipe is 2.75. It is really no problem.

 

The XYZ pipe with the resonator will kill off your rasp, almost guaranteed, it's a good pipe, mine is bolted to the stock mid section, don't worry about the size difference, it's minimal and as i said, the res will kill off the rasp you have.

 

Oh the story changes. 0.75 inches is a significant drop. Think about what this looks like inside the piping. Do not like this restrictive choke point.

 

Yeah, if it's really .75", that's huge. Going from a 2.25" diameter to 3" is almost double the area!

2.25" = ~4sq inches
3.0" = ~7sq inches

 

If you want the OEM look and no rasp, go with Nismo S-Tune OR Fujitsubo Legalis-R:

https://my350z.com/forum/nismo-350z/...the-nismo.html

Other good OEM-ish exhausts are DC Sports, Invidia Gemini, Tanabe....

https://my350z.com/forum/nismo-350z/...-exhausts.html

If I were you, I wouldn't waste my time spending the $415 on a resonated XYZ pipe, just to eliminate some rasp. I'd spend $800 or so on a full cat-back system that sounds good, improves performance, and has that OEM-style look. Last year, I was in this same boat (see Fujitsubo link above) and will be purchasing the Invidia Gemini this Summer, as it is a combination of all three areas (looks, sound quality, performance) at an affordable price.

 

OK, first off, the Y-pipe is the second most restrictive part of the exhaust system, with the cats being primary.

Secondly, the exit of the stock Y pipe is 2.5 inches, not 2.25.

There is no problem with the difference between 2.5 and 3.0, i'm not sure on the actual inlet of the stock mid pipe, just the exit of the stock y-pipe.

The XYZ pipe has been setup with the merge point at the optimum position for most power and torque, so you gain, not lose.

A full cat back will not gain you the power/restriction removal that the XYZ pipe will give you.

 

hr y pipe /thread

 

The HR pipe would work, but it's not great, it's the lesser of two evils, it's just not *as* bad as the earlier 350 y-pipe.

 

So wait, the stock Y-pipe inlet is 2.75 inches? If so, I did not know that... In that case it would be fine.

 

Yup, and just for completions sake, i measured the inlet to the mid section over the weekend. The Gasket for the XYZ pipe was barely a quarter inch larger, if not a smaller amount.

 

Meaning it would work?

 

Yes, exactly

 

Cool. There is hope. I hope.