in general, smaller piping with more back pressure will help low end power while sacrificing high end power, and larger piping will help high end power while sacrificing low end power

Here are the pics of the mysterious Y pipe I just took off my car after thinking it was a HR.

Stock DE pipe is on bottom.

Inlet from cat:


Outlet to exhaust:

interesting...

Whoa! Those downpipes are TINY!

guess size does matter

That's a surprise.

Obviously a new direction in flow dynamics design for these engines for Infiniti's engineering... wonder how the power curve maps out for this design...?

I'm pretty sure my inlets holes were bigger than that.

This sedan? Because an article mentions the sedans were a few hp down from the coupes.

So the HR y-pipe diameter does not match the DE pipes coming from the cats? I know we're not looking to gain hp here, but isn't this a bad thing? Sort of bottlenecking.

looks like they were trying to help out the low end power

BigC - What is the ID (inner diameter) of the inlet from the cat? It sure looks like a
G37/370Z Y pipe with the vibration dampeners removed. If it measures somewhere around 1.75" I'd say that's what you've got.

my money is on that being an fx y pipe

My car was noticeably slower across the board after installing that pipe pictured above. I was going to put my stock one back on but decided to just upgrade anyways and get the Motordyne XYZ pipe instead (which is awesome btw!!).

I can measure it tomorrow when I am back at work. 1.75" seems about right.

HR y-pipe from the VQ35HR used in the 07-08 350Z does have the correct inlet diameters to match the DE cats and midpipe. Obviously something changed with the G37 coupe/sedan and possibly the 07-08 G35.