Lets see if anyone can give some input on this....about exhaust piping diameter, which size would be the best for the g35 coupes? 2.5 or 2.75?

 

different setups will require different diameter exhausts - i.e. and f/i application is going to want a larger diameter exhaust than that of an n/a car. need to be more specific with your questions.

 

well i'm all n/a i know that turbo applications will need large piping for freer flowing but i have n/a set up and don't wanna lose much back pressure...i just ordered the greddy evo 2 and it's about 2.75 diameter and i see the hks tru dual high power is about 2.5 so wondering which would give better gains and blah blah you know what i'm trying to say...lol...and plus i don't think anyone uses 2.75 on turbo applications i think they all go with 3 inch and bigger

 

2.5" is perfect for n/a

3" for FI

 

the greddy evo 2 is 2.75 so i'm guessing thats bad if 2.5 is perfect?

 

+1

You can get some good power out of dual 2.5" but not much past ~450whp. 3" will go well beyond that.

 

so anything wrong with 2.75 on n/a?

 

There is nothing wrong with 2.75" diameter exhausts. What makes a bigger difference is the diameter or testpipes or headers.

 

The whole back pressure bs everyone talks about is a myth.. Back pressure is your enemy....

Look at this thread then let's see what you think of back pressure..

https://g35driver.com/forums/v36-eng...r-stillen.html

 

Full exhaust? Best from what I've heard is a single 3". Another option would be full dual 2.25". This is for an N/A setup though.

 

Wider piping will get a deeper tone. Generally.

 

Does anyone know the diameter on the outlet of stock headers for a de?

 

Single 3" works pretty well as mentioned above. Why not share your mod list tho? Just saying NA isn't enough info to be accurate. While a lot of the information above is good, a bone stock block and a dammed up monster are going to have different needs even tho both are NA. Of course, when in doubt just buy a Motordyne TDX2.

 

Didnt realize how old this thread was.. no clue on stock header outlet size. Would be able measure tomorrow if I remember, have a set in the garage somewhere.

 

mods I have in order I purchased
K&N drop in filter
Borla cat back exhaust
MRev2 lower plenum
Kinetix V+ upper plenum
Motordyne ART test pipes
NWP engineering 75mm throttle body/spacer
75mm intake tube
I think my H pipe in the borla is restricting air flow, ART diameter is 2.6 in and borla is 2.25. I bought the borla cause I was new to the platform and that company is highly praised and build exhausts for some top cars. But if the headers outlet is less then 2.6 I don't see a reason to replace it.
One of the main reasons I bought the borla was because they didn't make hp gain claims but factual benefits of it ex. 20lbs lighter, 45% increase in airlow. Its a damn good exhaust but I think the H pipe needs to go.