Hey I am just curious with the 04 coupe packages. I think the aero package comes with a rear spoiler and something called a air diffuser? I attached a pic. Is it the parts I circled in the front and rear? If so how can it have the air diffuser if it has no spoiler? I also attached a pic of a G that does not have these parts. It seems rare to find a car without those parts at the lower of the vehicle. Does it mean this car just has aftermarket parts or something.

 

the parts you circled are splash guards. not sure about the diffuser deal with different packages, but the term refers to a piece that goes in between the splash guards on the lower rear bumper.

edit: iirc, the "rear air diffuser" infiniti means is a piece underneath there by the muffler. someone more knowledgeable will have to correct me because my car didn't come with one. the splash guards on my car were added later (as may be the case with some of the g's that have them)

 

I don't know how to post pics, but if you go on ebay and type g35 diffuser you'll see what it is.

 

It looks like the panel piece right underneath the license plate and above the muffler. But it seems that every single car has to have this panel?

 

As far as I know they don't make a model that comes with a rear diffuser...I could be wrong though

 

There is no OEM rear diffuser, but some aero packages have small plastic panels installed under the body.

 

It looks like a panel, but it's actually just part of the bumper. There's just an indent that makes it look somewhat like a diffuser. There are different aftermarket diffusers that you can put on that "panel" to cover it up

 

From the window sticker of my 2003 coupe:

AERO PACKAGE 550.00
Rear Spoiler
Rear side underbody diffusers

The underbody diffusers are two box shaped plastic pieces mounted in front of the rear wheels (directly under the clear vinyl fender protectors).

Unless a car has had the spoiler removed...I don't believe it would be possible to have the side underbody diffusers. They are clearly visible by looking in the front of the rear wheel well. There's no way those pieces could cost 550.00 without factoring in the cost of the rear spoiler.

Just found a couple more plastic pieces behind the rear wheel wells that cover the area from the inner fender liner to the rear bumper cover and side to side from the bottom of the rear fender to the exhaust pipe and include a small fin.

 

Google images is your friend. Just type in "g35 rear diffuser." To answer your question OP, the spoiler and diffuser have no relation to each other.

Here are a few examples. There are many different brands and styles to choose from.

 

The OPS original question was about 04 coupe packages. I think the aero package comes with a rear spoiler and something called a air diffuser? As I stated in my post. Yes, in at least 2003 and 2004 a factory AERO Package which included the spoiler and rear underbody air diffusers was available as a $550.00 option.

Every picture you posted is an aftermarket add on diffuser.

 

Here is one.

https://g35driver.com/forums/exterio...tte-black.html

 

http://lmgtfy.com/?q=rear+diffuser

 

You're right, I posted aftermarket diffusers. But was his question not "what the hell is a rear air diffuser?" even though the ones I posted are not the factory Aero ones, it still gives him an idea what to look for

 

As I understand his question. He was specifically asking about the factory AERO Package. The aftermarket rear diffusers look nothing like the ones that are part of the factory package. It consists of four relatively small finned pieces tucked under the car. One in front of the rear wheel well and one behind the wheel well.

The pictures that you posted are indeed what is generally accepted as rear air diffusers. The good, the bad, and the flat out ugly.

Maybe you know...has the factory ever offered anything that would resemble picture number four of your post?

 

Never mind... I don't feel like arguing. I guess you made more sense of his nooby post than I did. I keep re-reading it and my mind is blown with the general confusion with spoilers and splash guards. I was just trying to help.