"porting" Gtr Turbine Housings

[Antimatter]

G'day guys

I know in may cases people will port there standard manifold to there match larger turbos housings, but I am wondering if anyone has had experience with porting the .48 housing on standard GTR Turbos when they rebuild them. I have seen some turbo shops do it - but I wonder if it is done because it "looks" like it would be a good idea or if the have proven that it does.

I have seen this done on turbos when they are mated to previosly ported manifolds - or when mated to after market manifolds (i.e. tomei or HKS).

This is not something I had done before as I have little understanding of A/R's and what effects changing the size of the "hole" will have on the turbo. One would think "bigger hole - better flow"...... but is it that simple?

I will get some pics up shortly to better illustrate what I mean (pics added).

As usual.. value your thoughts.

Cheers

Edited February 29, 2008 by Antimatter

[R31Nismoid]

bigger hole = less responsive.

I get what your getting at, but all its going to do is incite less response... without much increase in top end because it'll be the compressor running out before the rear.

[Adriano]

Depending on which part of the ex housing you are talking about enlarging, if its from the throat in, then i have found gains in boost control on highflow turbos especially when you aid the flow to the w/g flap. however if you are talking about enlarging the diameter-ie the clearance between the ex wheel and the housing, its an old school highflow technique, and whist preventing overboosting, it also causes lag city.

[Antimatter]

Depending on which part of the ex housing you are talking about enlarging, if its from the throat in, then i have found gains in boost control on highflow turbos especially when you aid the flow to the w/g flap. however if you are talking about enlarging the diameter-ie the clearance between the ex wheel and the housing, its an old school highflow technique, and whist preventing overboosting, it also causes lag city.

Yeah - talking about the "throat in". I could be convinced this may help with hi-flows as you mention. I have also seen the w/g hole enlarged to assist with flow and / or boost control. I am wondering then at which point it may be advantageous - probably not at all with standard comp wheels - but maybe of value on the next size up (comp wheel)?

I can see credit in your point too Nismoid - as stock (unmodified) .48 GTR housing give fantastic spool up. I cant see that getting any better.

[full house]

my advice is, if you're not sure, just simply don't do it!

[Cubes]

Port match it.

[discopotato03]

Sorry if this sounds like a silly question but are the GTR's std manifold outlets actually that much wider than the turbine housing inlet or is that mark merely a carbon stain from where the gasket doesn't cover the housing flange .

I've had very little to do with RB26's but I do know they use a more compact and I think slightly differently angled turbine housing that your run of the mill T28/GT28 one .

My best guess would be that Nissan was concerned with gas speed into the two turbine housings (vs one) and so the housings inlet was made smaller to keep the velocity up . If the std manifold is the same dimensions as the housings inlet I reckon I'd make sure there were no steps in the wrong direction and call it day - I don't speak through experience though .

Cheers A .

[juggernaut1]

Definately port match the turbo to your manifold to reduce any turbulence at the flange as it enters the housing which would reduce gas speed, particularly on low boost and transition to boost (i.e. offboost conditions).

Refer following comment from Kyle (6boost) on a recent discussion article on this forum re aftermarket manifolds. I realise your car isn't a 700 evo engine but the same principles apply. After that there's always extrude honing your manifold and turbine housing.

"(we were testing outlet shapes and sizes, and for a 700+hp car, the small hole was just too restrictive), and the red line was after 40min work with the die grinder to port match the manifold from a round hole to the same rectangle as the turbo. The results?? 380rpm faster spool, 40hp at all 4 wheels on the same boost,"