Exhaust diameter

Fhjkalfhu · 01-08-2018, 10:19 PM

So I have searched for awhile now and can’t find an answer. Wanted to see if anyone could help.

I have had beluga test pipes on for about 4 months now, and I’m getting tired of the fumes. So I decided to get HFCs, but noticed the z1’s are 2.5” outlet. I know my catback exhaust has a 2.25” diameter and I started thinking maybe I’m having more fumes or a leak because my test pipes are also 2.5” and found out they were.

So my question is, is it bad to hookup a 2.25” catback to a 2.5” hfc/tp? Does it cause any problems at all?

Just1nfj · 01-08-2018, 11:18 PM

The stock exhaust is 2.25, not sure about the stock cat. If the exhaust smell is present in the cabin i would for sure check for leaks.

To answer your question check that video, i think he put it in a way better way than i could explain it
https://youtu.be/jjPeP_Nn2B4
-FJ

Fhjkalfhu · 01-09-2018, 08:50 AM

Thanks. I understand the importance of exhaust velocity and all that good stuff. I’m just asking if bolting a 2.5” outlet cat to a 2.25” y-pipe is bad.

2011 Nismo#91 · 01-09-2018, 12:14 PM

The only time you should smell fumes is standing outside at the back of your car. I have test pipes and the only time I smelled them were during the initial period.

To your question, "bad", not in the sense your going to harm your car or see a noticeable change in power. But it's not good either.

Fhjkalfhu · 01-09-2018, 12:23 PM

Yea maybe I have a leak at the manifold or something, but I doubt it. Other members say they’ve had similar exp when they’re running their climate control but I have only noticed it this season since it’s the only time I run my climate control. Z1 responded to my inquiry and said there shouldn’t be any issues. I guess it’ll give me a reason to get a better exhaust soon!

01-08-2018, 10:19 PM	#1 (permalink)
Fhjkalfhu Base Member Join Date: Feb 2017 Location: Somewhere Posts: 114 Drives: 2009 base white 7AT Rep Power: 8	Exhaust diameter So I have searched for awhile now and can’t find an answer. Wanted to see if anyone could help. I have had beluga test pipes on for about 4 months now, and I’m getting tired of the fumes. So I decided to get HFCs, but noticed the z1’s are 2.5” outlet. I know my catback exhaust has a 2.25” diameter and I started thinking maybe I’m having more fumes or a leak because my test pipes are also 2.5” and found out they were. So my question is, is it bad to hookup a 2.25” catback to a 2.5” hfc/tp? Does it cause any problems at all? Not_Z_but_G likes this.

01-09-2018, 12:14 PM	#4 (permalink)
2011 Nismo#91 A True Z Fanatic Join Date: Mar 2011 Location: NJ Posts: 2,381 Drives: slowly Rep Power: 33858	The only time you should smell fumes is standing outside at the back of your car. I have test pipes and the only time I smelled them were during the initial period. To your question, "bad", not in the sense your going to harm your car or see a noticeable change in power. But it's not good either. __________________ GTR TT 493Whp/431lbft, Ecutek, Southbend 6puck,Quaife, RPM RollBar 4Point, R888R, JRZ RSPro F(10R/10C) R(10R/6C) 1000f500r inlbs+150inlbs Tender, SPL everywhere.Full Specs

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01-08-2018, 11:18 PM	#2 (permalink)
Just1nfj Base Member Join Date: Nov 2017 Location: Edmonton, AB, Canada Posts: 18 Drives: Nissan 370z 2017 Rep Power: 7	The stock exhaust is 2.25, not sure about the stock cat. If the exhaust smell is present in the cabin i would for sure check for leaks. To answer your question check that video, i think he put it in a way better way than i could explain it https://youtu.be/jjPeP_Nn2B4 -FJ

01-09-2018, 08:50 AM	#3 (permalink)
Fhjkalfhu Base Member Join Date: Feb 2017 Location: Somewhere Posts: 114 Drives: 2009 base white 7AT Rep Power: 8	Thanks. I understand the importance of exhaust velocity and all that good stuff. I’m just asking if bolting a 2.5” outlet cat to a 2.25” y-pipe is bad.

01-09-2018, 12:23 PM	#5 (permalink)
Fhjkalfhu Base Member Join Date: Feb 2017 Location: Somewhere Posts: 114 Drives: 2009 base white 7AT Rep Power: 8	Yea maybe I have a leak at the manifold or something, but I doubt it. Other members say they’ve had similar exp when they’re running their climate control but I have only noticed it this season since it’s the only time I run my climate control. Z1 responded to my inquiry and said there shouldn’t be any issues. I guess it’ll give me a reason to get a better exhaust soon!