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Discussion Starter · #1 ·
Hello,

So I'm nearing the end of my rebuild/build. The bottom of the motor is almost completely done, the head is ported just needs a valve job now. I'm going to be running Gt2860-5 turbos on my rb26. I have full aftermarket turbo back exhaust (dumps, downpipe, decat, cat back). All that I have left thats stock on the exhaust is the manifolds. The manifolds have a pretty small outlet flange that doesn't really match the turbos at all (as I'm sure you are all well aware). I asked the guy whos porting the head and he said he would port the manifold too but its gonna be around 210£ to port them, which at that point I told him to forget it as it doesn't seem too hard a job (head porting I can see being what it is as it takes talent/skills/etc....). So I'm wondering should I get the head builder to port the manifolds, or should I port them, or should I leave them alone, or should I get new aftermarket manifolds?

Thanks
Mitch
 

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just port them yourself, get a gasket mark it out and off you go. make sure its smooth and make sure you taper them, don't for get to do the manifold gasket side as well.

if your going to upgrade the manifolds get the tomei ones as they have the least amount of seams, they are very rear to crack unlike the ebay ones which is more of a when.
 

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Discussion Starter · #3 · (Edited)
When you say "don't forget to do the manifold gasket side as well" what do you mean? And also you said to put a taper, should the taper be a along like 2 inches or just a small taper? Along with that question, the Nissan gasket is sligtly larger then the GT2860-5 turbos outlet, so I'm guessing I should just port the turbo's sized outlet, correct?
 

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as long as the turbo housing is larger than the manifold exit bore size
the 2860's will run out of wind before the manifolds start restricting exhaust
I would make them as large as possible without forming a step ...down to the turbo housing, but theres plenty of examples of good power engines on factory unaltered mainfolds.
 

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When you say "don't forget to do the manifold gasket side as well" what do you mean? And also you said to put a taper, should the taper be a along like 2 inches or just a small taper? Along with that question, the Nissan gasket is sligtly larger then the GT2860-5 turbos outlet, so I'm guessing I should just port the turbo's sized outlet, correct?
make sure you do the side that bolts to the engine aswell as the turbo flange.

yes just a smaller tapper dont take out to much meat as they get a little thin in places.

aslong as there is no major steps so the exhuast flow is smooth (so to speak)

i had my turbo's opened up aswell, but you need to disassemble the turbo and have the orintation reset by a turbo specialist once they are done.



 

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... that last part about disassembling the turbos seems like its more trouble than its worth if they'd have to be brought to a specialist.. no? could you just stuff a rag down there and do your best to make certain no dust gets in?

also... should you NOT "port" the gasket itself?... like... do you sand down parts of the gasket... or never?


whats about "porting" the manifold to head side of the exhaust?
 

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Stock manifolds don't break, I haven't ported mine and am quite happy with the power I'm making, and 1.9 bars boost is easy to get if you are crazy enough :)
 

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I'm not so sure that this is worth the effort and expense.:confused:
Sure it smoothes the passage of the exhaust into the turbo and reduces turbulence, but is that your top priority?
If you look at 6Boost's (SAU) manifolds, the collector reduces down to a circular hole through the flange into the turbo which is significantly smaller than the turbo entry.
The idea is to maximise the gas velocity into the turbine.
Also the remaining lip reduces reversion back into the manifold as the exhaust pulses bounce back from the turbine.
All the hard work above seems to produce the opposite result.

Interesting?????
 

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there's nothing like the smell of toluene in the morning....it smells like....serious boost! :D
 

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Discussion Starter · #14 ·
lol, I think I'll do a simple port match from the head to the manifold and leave the turbo inlet and outlet as they are.
 

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Discussion Starter · #16 ·
I can easily see that the smaller outlet of the manifold increase the velocity of the flow but this also volumetrically restricts the flow. I don't know what the correct setup is for this thats whay I made this post. Everyone has different opinions I'm just scared to port the turbo there very little material to port at, definately with the taper you have their rb26r32 on the turbo inlet is very nice, just I'm worried about screwing the turbo up. I'll try to port a bit and see what I come up with, if it gets to thin I'll stop.
 

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I can easily see that the smaller outlet of the manifold increase the velocity of the flow but this also volumetrically restricts the flow. I don't know what the correct setup is for this thats whay I made this post. Everyone has different opinions I'm just scared to port the turbo there very little material to port at, definately with the taper you have their rb26r32 on the turbo inlet is very nice, just I'm worried about screwing the turbo up. I'll try to port a bit and see what I come up with, if it gets to thin I'll stop.

you can leave the turbo alone, there is only abour 2-3mm max that you can take out before its the gasket size. just do the manfold and use the carbon stain as a guide :thumbsup:
 
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