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Discussion Starter · #1 ·
I have a R33GTR.

I have the 2530s and Tomei 260/260 9.15mm cams.

All things being equal, what difference in whp, response and torque should I expect if I have my stock exhaust manifold ported and add Tomei turbo outlets aka elbows?

Anyone with first hand experience?

Would you do one or the other or both mods or neither?

Thanks in advance.
 

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You will improve both response and power - win-win really! Don`t be tempted to open the turbine flange on the manifold too much though, just match it to the turbine inlet......
 

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Discussion Starter · #3 ·
Thanks Ex.

I thought I read somewhere here that the stock exhaust manifold already matches up to the 2530s?

How much bigger is the 2530s over the stocks?
 

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legalr,

The outlet of the stock manif is somewhat smaller than the turbine inlet even on the stock turbos. You can see the outline of the turbine inlet size if you can get ahold of a manif pic...there is a definite restriction. The N1 manif are the full size ones. I saw a pair side by side once and I'd say the N1 was about ~30% larger. And it matched up to the N1 turbine inlet pretty well which I believe is the same size as the oem one.
 

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just get aftermarket manifolds. even if you port your stock ones it's still not going to match up right. one other thing, are you just going to upgrade turbos and cams? how about fuel system? you must consider fuel system or else the motor it's going to blow.
 

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huracan0613 said:
just get aftermarket manifolds. even if you port your stock ones it's still not going to match up right. one other thing, are you just going to upgrade turbos and cams? how about fuel system? you must consider fuel system or else the motor it's going to blow.
The problem with aftermarket ones are that they crack. Even the best most expensive HKS ones leak and crack on the street.

The stock cast ones do not. With ANY turbo you can fit undermanifold, for a street car, I recommend highly to stay with a stock or N1 exhaust manifold.
 

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Discussion Starter · #7 ·
Thanks guys.

Huran, yeah, i'm doing fuel upgrades too. just didn't want to pile too much detail in this thread. wanted to get right to the meat of the topic. thanks for the heads up though.

I was told that the n1 exhaust manifold requires alot less porting than the stock non-n1s. If I had the extra dough, I'd probably upgrade to the n1 exhaust manifolds.

Looks like I'll be porting my stocks afterall.
 

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i believe tomei makes cast iron manifolds, but if you can get a hold of the n1's those will work too. a friend of mine has that setup that you're about to do and he has the hks manifolds. so far he hasn't had any problems with them, but stick to cast iron though.
 

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The outlet of the stock manif is somewhat smaller than the turbine inlet even on the stock turbos. You can see the outline of the turbine inlet size if you can get ahold of a manif pic...there is a definite restriction
absolutely , contrast between before and after .
and made a big difference , although that is with Trust T517z



With ANY turbo you can fit undermanifold, for a street car, I recommend highly to stay with a stock or N1 exhaust manifold
But at what point does it become a restriction ?????

So far ive managed [email protected] on origional ex manifods (ported) will they cope with much more ?
Any experience on this sean ??
 

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Discussion Starter · #10 ·
Nice pic Jay.
 

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The std manifold are very good, both design and manufacture. They do overlap the exhaust ports by lots! Grinding is easy, you don`t need special tools.

Don`t open the manifold to turbine flange too much - in the picture above, unless the turbine housing has been opened out as well, the housing will now overlap the manifold. This is worse than doing nothing as now you have a sharp lip in the gas-flow.
 

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Nice pic Jay
Cheers mate :) , i done this over 2 years ago to match my trust turbo's & just knew the pics would come in handy eventually .

Don`t open the manifold to turbine flange too much - in the picture above, unless the turbine housing has been opened out as well, the housing will now overlap the manifold. This is worse than doing nothing as now you have a sharp lip in the gas-flow.
Maybe i should have said that i only opened mine out this much so it identically matches the turbine housing :) (the T517z's are fairly large)
 

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For those of you who have matched your exhaust manifolds to your ports and turbo inlets, how much did this actually make in terms of power and boost threshold?
 

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JAY-R32 said:
But at what point does it become a restriction ?????
So far ive managed [email protected] on origional ex manifods (ported) will they cope with much more ?
Any experience on this sean ??
Justins car had the full HKS manifolds with the crossover tube. 2530s with small cams and a "normal" type setup were about 500 hp at the wheels.

Same turbos and maifolds, on a car with no cams we did around 480 at the wheels.

When we were tuning for nitrous, we did off nitrous run, around 1.5 bar and did 477 at the wheels. Thats with ported stock manifolds. On the bottle 612 rwhp. 2540's and nitrous 654 rwhp. 137 mph in the quarter on the 2530's , nitrous, and stock manifolds.


Going from my special source, they say the ported N1 manifolds are good up to 600 wheels, not worth changing.
 

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Discussion Starter · #15 ·
Justin's car on what kind of gas and boost?
 
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