Ibanez540r

iTrader: (1)

OK, so after a week of searching various forums and threads, it is still really hard to come up with a solid answer.

What is the sedans OEM exhaust size?
What is the coupes OEM exhaust size?
If they are different throughout the system (reduced etc.) what are the sizes for each (coupe/sedan) for each part of the system. I.E. Cats, Y pipe, Mid-pipe.

Basically, inlet and outlet size of each component would be most useful.

..I think this would be very useful information for a lot of people. Many of the threads I did find, there are numbers tossed around but never state whether it's sedan coupe, after market, OEM. There has not been a clear answer when anyone has asked on other threads.


Reason I ask is, after searching I learned the sedan and coupe share the same design for cats and y-pipe. However, after purchasing a used set of HFCs, I spoke with FI and learned the coupe set is 2 1/2" and the sedan is 2 1/4". They can be used, but in my scenario, putting the coupe HFC on the sedan causes a lip on the matting flanges which is not good for flow and also more then likely cause more rasp. So I am faced with either getting a larger Y-pipe, or selling the coupe HFC and getting sedan. I'm leaning toward the Y-pipe to open everything up, but can't find what the OEM flange/inlet is at the mid pipe?

Also noticed all the cheaper Ebay Y pipes are 2.5" in & 3" out. I know 3" is only for after market systems and would also cause the "lip" issue previously stated. The ONLY 2.5 to 2.5 y pipe so far is from Exhaust Depot. Again though, not sure what OEM is at the mid pipe. Also some mention of some new x-pipes etc., but no one, nor have I, been able to find them listed or for sale on-line.

Wheew...

Opinions & Links accepted

Ibanez540r

iTrader: (1)

Bump - over 40 views and nothing? All these mod happy exhaust guys and no one knows the exhaust diameters?

AZg37

iTrader: (17)

Keep the coupe HFC's, and by a CBE. Problem solved, no measuring needed. After you do the swap, measure whatever you want and post it up on here for future owners with the same question. IMO you are REALLY over complicating things. Companies put a lot of time in R and D to solve all the issues associated with a good exhaust system. Rather than piecing together a system with mixed parts like HFC's mixed with another Y-pipe mixed with stock mid-pipe etc.. just get a proven CBE. It'll save you $$$ and a headache.

surfjax87

Sorry, I meant to get this done earlier.

Sedan OEM exhaust:
2 3/8" at cats
2 3/8" at end of y pipe
1 1/2" at muffler inlet (yes 1.5" )

Steveo47

iTrader: (8)

The inlet for the coupe y pipe is 1.75. That's all I got.

Ibanez540r

iTrader: (1)

^ I don't think that is right. From my understanding there are sections of the Y-pipe that are as small as 1.75", but the flange itself is 2.25 - 2.5"

Awgd8

iTrader: (1)

Sorry to revive the thread.... I just measure this today.

Here are the actual pipe diameter (actual hole not flange) for G37 coupe.

Y-PIPE:

Y-PIPE INLET (x2) : 1 5/8" or 1.625

Y-PIPE OUTLET (x1): 2 3/8" or 2.375

MidPIPE:

MidPIPE INLET (x1) : 2 3/8" or 2.375
MidPIPE OUTLET (X2): 2"

Muffler INLET (x2) : 2 5/16" or 2.313
(Part# 20100 JL01C)

socketz67

This explains why the dyno run Stillen provides for their 2.5 inch diameter cat-back shows the system making a little over 18hp. I think the Invidia Cat-back is also close to 2.5', or maybe a little smaller at 60mm (2.362'?). The Top Speed Pro setup is 60mm back from the Y-Pipe, which appears to also be 60mm, so this is also a good setup as it maintains the same diameter from the outlet of the Y-Pipe to the muffler.

These three seem like one of the better mods available for the 09+ Sedan.

08Gsmith25

Seems like nobody agrees on this. Answers all over the place. I'd like to know as well. I may want to swap my sedan mid for a coupe mid to eliminate rasp IF the coupe mid is bigger diameter than the sedan mid

socketz67

From a manufacturing/cost perspective, it doesn't make sense that the sedan and coupe would utilize different sized mid-pipes as the goal would be to reuse as many of the parts as possible between models.

Ryne

iTrader: (12)

It makes sense if the design was meant to have different exhaust tones for the coupe and sedan. This also is likely where the HP difference between the coupe and sedan comes from.

Edit: I am aware the HP difference is negligible and I don't want to open that can of worms. With that being said, that may explain the theorhetical grounds for Infiniti to claim additional HP in the coupe, whether it be true or not in reality.

08Gsmith25

youd think with the amount of oem exhaust we have laying in around in our garages around the forums we could get a quick answer here. i think the only mystery is the midpipe and possibly the Y pipe exit

socketz67

I wonder if the difference in tone is due to pipe diameter, or just the design differences related to the muffler (dual mufflers vs a single larger one)?

Ryne

iTrader: (12)

It seems more likely that it's the muffler design.

socketz67

I bet that the guys at Stillen would be able to answer these questions about the various ingress/egress exhaust pipe diameters of the stock system, or maybe even Tony at Motordyne or someone on his team. I think those guys spend more time over on the G35driver.com site. Stillen advertises that their catback is 2.5 inches all the way to the mufflers (or at least that's how I interpreted the advertising).