RB26 N1 Manifolds, any better?

[RB335]

RB26 N1 Manifolds, any better?

Hi Guys.

So in the upgrade path of my GTR, i've had lots of conflicting information, one of them is about Manifolds.

I had been told by one person, he put TOMEI expremes on, and it made the car very laggy.
So I'm wondering, is there any improvements to be felt either low down, mid or top with GT-SS Sized turbos at high boost.

Most say just port match the manifold to the turbo inlet and to the head and don't touch anything, however I have seen some online shops selling
N1 Manifolds, which still appear to be cast, but higher flowing.  I'm wondering surely Nissan would have modified these for a purpose for the N1 models
if they give some sort of improvements.

Has anybody tried the N1 manifolds themselves and noticed any sort of improvement, or could offer any advice.
I don't simply want to hear "stock ones are OK" comment, but some more info and personal experiences.
I remember various articles on Autospeed on porting stock manifolds on RB engines, but did not cover RB26.

Thanks guys.

[JGTC]

 

Tomei shows the difference in ports here - https://www.tomeiusa.com/_2003web-catalogue/000_expreme/each-product/rb26_exhaust-manifold_en.htm

The N1 manifolds are reportedly a 'higher quality' cast with slightly larger ports as standard designed for N1 turbos (old version of Garrett 2860-7s)

Standard RB26 manifolds ported to match the turbine outlets will level out any advantages to be had with N1s or Tomeis.

The one drawback to note with the Tomei manifolds is quite a few owners have had them develop cracks due to being made from a thinner 2.5mm stainless steel rather than cast iron.  This is particularly exasperated when heat wrap is used to dissipate the heat, using exhaust wrap crystallizes the metal ( especially stainless ) and halves its life causing cracks.

Given the difficulty to get to the manifold should they fail, porting N1 or standard manifolds is a much more proven/cost effective method to improve flow.  The money would be better spent on a set of BNR34 dump pipes or Tomei dump pipes if you have the cash.

 

Some good threads to look at;

 

Edited October 3, 2016 by squareznboxez

[r32-25t]

I'm currently making 350kw at the wheels with factory untouched manifolds with -7s, basically with a -7/-9 the turbo will run out of flow before the factory casting of the manifolds.

-5 I'd say is when it's time to open them up

[sucram]

If I was given N1 manifolds I would use them, but I would not pay for them since the difference is so minor and can be done with about 30 mins and a die grinder.

If you go larger in I.D generally you will loose port speed and incur lag. Sometimes with no appreciable top end gain. You can make up some of it with collector design but with low mounts you are limited.