So I purchased a FI RHFC recently and my goal was to gain a little hp and maybe raise the volume of the exhaust note by a few notches. I wanted to avoid going full cbe for both budget and fear of it being too loud for my tastes. I ask my mechanic to put it on for me and low and behold, after he gets it up on the lift, we see that the whole system was riddled with RUST.

He's telling me that I should probably replace whole catback along with the rhfc at the same time (AND purchase O2 sensors to replace the rusted in ones that look like they will likely break once removed)

I'm still trying to avoid getting a full system and I just started looking at Y pipes. Which brings me to my question. I'm not very educated in the exhaust (and mods in general) dept, but the Y pipes that I've seen (Megan) seem to run 2.5" at the cat and then 3" when it meets the midpipe. Based on some research on the forum, I believe the stock midpipe ( on an 08 coupe) is 2 3/8" at the inlet. I was wondering if this is going to be a problem connecting a 3" outlet to a 2 3/8" inlet. What problems could occur, will I lose much power in the low or high end? Should I even try?

Sorry for the long post and any help is appreciated.

 

"I was wondering if this is going to be a problem connecting a 3" outlet to a 2 3/8" inlet."


My answer would be that it will NOT connect.


To me, that's like asking if you can park your 18 wheeler in a one car garage. lol.... My experience with exhaust is that if you want to match up with stock components, find an exhaust that states it will with the proper size/fitment. From what I have seen, most are unique to their own brand or size so you are forced to buy more. Most common to me for fitting stock would be a catback exhaust (CBE) that's either the same size, or its larger with a tapered exhaust flange to match up. I'm new to the G scene, so I cannot help you with what is out there for your options as far as products. I just bought my first G a month ago (used) and it already had high flow cats and a Tanabe CBE. I'm still learning myself on our setup haha. Hope I helped a little.


Edit: Just thought about adding this....I had an '08 STi hatchback. I bought a 3" Magnaflow CBE that matched up to stock 2.5" downpipe. It was tapered at the last 6 inches to the 2.5" flange. When I got on it, it would whistle. Other than that, sounded great and performed. After I purchased a 3" downpipe, I bought a 3" flange and pipe, took it to a local shop where they made me a new one that slipped into the slip-joint of the axle-back. Whistle gone and 3" all the way back.

 

Ignore that guy, he meant well but none of its correct :/..

Yes it will bolt up just fine to the stock mid-pipe, that's what it was made for. Downside in them being different sizes is it will definitely cause some rasp since its being forced into a smaller area instantly. If it were me, I'd install the RHFC, a Top Speed Y-pipe, a Megan 370z Mid pipe with the little extender to fit the G and an axle back of your choice. It will then all match the sizing all the way through and cost you about $800 total, cheaper than any other name brand exhaust and flow just as well. Should sound damn good too!

Check these out:
Install this: Infinti G35 02-06 Top Speed Pro-1 Performance Mid Y-Pipe - Top Speed Pro 1 Performance

Then get this: 12" Conversion Extension Pipe Kit (Use w/Nissan 370z Performance Exhaust to fit G37 370Z 370GT Z34) - Top Speed Pro 1 Performance

Then this: MIDPIPE-N7Z09-OE - Megan Racing Mid Section Pipes - Lightning Motorsports - Celebrating 20 Years in business ! ! 1996-2016

And finish into these: NISSAN 370Z Z34 BASE & NISMO 09-14, Infiniti G37 VQ37VHR 09-14, 370GT COUPE 09-14, Q60 COUPE 14-16, Dual Axle-back Exhaust System (Bevel Edge Tips)

 

Not trying to argue or come across wrong. I stated I am learning our setup. BUT what I said IS true for other vehicles I have owned (Subaru). Please explain how a 3" pipe matches up to a 2 3/8"? Or am I misreading something?

 

No harm at all man, were all here to learn and share. Our options on the Z platform is a bolt on part and there's no modifications needed. They made it to fit with OEM parts with a very steep and immediate downsize into the smaller piping. Although its not an ideal way to do it, it does work just fine.

 

ok, so correct me if I am wrong. It's similar to what I dealt with with the Magnaflow on my STi, except you are talking about an adapter piece that he needs to purchase? Because the way I read his OP was that the outlet of the Y pipe is 3" that meets right at the midpipe of 2 3/8". Then that adapter might as well be a thin flange.


P.S. I'm all over this because I might look into changing out my Tanabe Medalion exhaust for something with more growl.

 

Yes and no. The adaptor you can get is to fit a 370Z mid-pipe on a G since their exhaust is a bit shorter but it doesn't change the diameter at all, its solely for extending that 3" area. I mentioned this adaptor so it would open the option for the 370z Megan mid pipe and then WOULD match diameters all the way through. Otherwise, there aren't any other options for sale by themselves, only with an entire CB system or take it to a shop for a custom setup.

 

LOL, you basically just said what I said in my first post. The one you said I was all wrong.

 

You said it doesn't fit and they tend to be brand specific and it "will NOT connect", that's completely wrong. I wanted to make it very clear that you absolutely could bolt it on. I did notice your edit though, why not delete the wrong info to avoid confusing people? You still should..

 

You say it will, but I still don't see how....I still stand by it won't until I see how.
This is in my head from OP..... [] = where the pipes meet
HFC 2.5" [] 2.5" Y-pipe 3" [] 2 3/8" midpipe and axleback
Now, how does that second join make sense? To me, it needs to be 3" on the midpipe. All the OP was talking about adding was the Y-pipe and nothing else.

 

And to make my point about Brand specific...My Tanabe bolts together, yet Magnaflow has slip-joints. How are those interchangeable?

 

The Y pipe is what were talking about. Lol Im not sure how else to say it dude... Search ANY 370z/G37 aftermarket y pipe and you'll have proof, they ALL fit man, no mods needed. The 2 bolt flange bolts right up. This is very common knowledge as well as it causing rasp due to the size difference. Search man.

 

I'll sell you my oem ipl setup.

 

LMAO, do you read my post? I have been talking about the Y pipe the whole time. Hey, if it bolts up, then it bolts up. Just sounds retarded to me. maybe they do something with the exhaust that I have never seen before.

 

Y-pipe will bolt up ok, but at least in my situation it added a bunch of rasp (to my TopSpeed Y-back), went back to my OEM Y pipe and am happy again, even though my OEM Y is shredded all to hell