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Turbo intake vs. NA intake


Drax240z

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Well I just pulled my turbo intake off my car and compared it to the N42 intake I have. I am not sure what is the source of all the internet rumours about the turbo having bigger runners, but it sure doesn't measure up that way on the bench...... the difference in runner diameter varies from runner to runner, not just intake to intake. Imperfections in the casting causing it.

 

So, I'm curious to know whether I am the only one who has always thought the turbo had bigger runners due to some source on the internet...

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I heard all sorts of (mis)info. I just got one of each and did the comparisons myself. And I found no substantial differences. The N42 seems to have more casting intrusions inside, some of which are hard to grind out. I got most of them, and I'm quite happy with the intake.

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there are myth progenitors out there still repeating the old "22% larger runners" on the turbo manifold.

B.S. they are all the same, except for one L-Intake, and it's not normally talked about in a performance board.

Take a look at the LD intake runners, and you will find a bigger runner.

But big runners are not necessarily what you want. Velocity is just as important as total flow, if not MORE important.

I don't think the size of the runner is that big of an issue on a Turbo motor below say 400HP (maybe 500hp...).

It think it's much ado about nothing.

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Yeah there are a lot of variables to making power with an intake, I think I posted about 3 months ago with some of the things to consider....

 

However I am sure improvements can be made over the stock manifold with a custom manifold, smoother walls, air horns, etc.

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I got a turbo intake, and I figure if nissan went to all the trouble to make it different then the na one, it must be worth having.

 

FWIW, I picked up power and a few PSI going from a tapered NA manifold to the turbo one. I think the tapered one comes on the ZX's.

 

But I did have the EGR cut off, a plate welded over the hole, and I have plates over the other things that stick off the top, and a nice fancy nissan plug where the vent was. POS.

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I got a turbo intake' date=' and I figure if nissan went to all the trouble to make it different then the na one, it must be worth having.

 

FWIW, I picked up power and a few PSI going from a tapered NA manifold to the turbo one. I think the tapered one comes on the ZX's.

 

But I did have the EGR cut off, a plate welded over the hole, and I have plates over the other things that stick off the top, and a nice fancy nissan plug where the vent was. POS.[/quote']

 

Well, there is a big difference between the ZXT and same year ZXs, as you well know. Like you, I would NEVER use one of those old tapered ZX manifolds. Aside from all the AIC and other crap, the older N47 and N42 manifolds really seem no different from the ZXT.

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Tony D., you're right about the LD runner size and it seems that the runner length would help low-end off-boost power as well. Hood clearance issue aside, has anyone out there tried this manifold (with injector bungs added)? DAW

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The LD is not a direct boltup. the runners match the stock gasket size so they are indeed bigger. However, you will have to slot the mounting holes about 1/4" to make it line up with the port on the non-LD head. Also, no provisions for injectors because it is diesel.

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I have a N/A intake witch have been cut in half, ported (all the way, possible when plenum is cut open) to get rid of the bumps and smoothen the runners and I got rid of some of the holes and other "junk".

It was then widend 1/2" to get a bigger plenum, and I put a BMW 63mm trottle on it.

Has worked perfect for me.

 

Here are some pics:

http://speedfreak.nu/modules.php?set_albumName=albuo04&id=aad&op=modload&name=gallery&file=index&include=view_photo.php

http://speedfreak.nu/modules.php?set_albumName=albuo82&id=aau&op=modload&name=gallery&file=index&include=view_photo.php

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wouldn't it depend on where he measures the boost at? like say if he had a 50mm TB and measured before the TB, it would be higher than after the TB, but if you measured it AFTER the restriction, the boost would be lower. so, If he had his boost gauge plumbed into the plenum and measured the boost both before and after installing a 60MM TB, it would show he gained boost. Am I on the right track or am I totally off??

 

on a side note, does ANYONE know where I can find pics of the LD28 intake with injectors plumbed into it for a turbo set-up?? seems to me there were pics of one floating around and either the man ifold or the valve cover was painted/poweder coated red......

 

McAdam

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wouldn't it depend on where he measures the boost at? like say if he had a 50mm TB and measured before the TB, it would be higher than after the TB, but if you measured it AFTER the restriction, the boost would be lower. so, If he had his boost gauge plumbed into the plenum and measured the boost both before and after installing a 60MM TB, it would show he gained boost. Am I on the right track or am I totally off??

 

on a side note, does ANYONE know where I can find pics of the LD28 intake with injectors plumbed into it for a turbo set-up?? seems to me there were pics of one floating around and either the man ifold or the valve cover was painted/poweder coated red......

 

McAdam

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wouldn't it depend on where he measures the boost at? like say if he had a 50mm TB and measured before the TB' date=' it would be higher than after the TB, but if you measured it AFTER the restriction, the boost would be lower. so, If he had his boost gauge plumbed into the plenum and measured the boost both before and after installing a 60MM TB, it would show he gained boost. Am I on the right track or am I totally off??

 

McAdam[/quote']

 

You are right - it depends on a number of factors. Where the boost is measured, where the boost is controlled, and what part changed (the intake, and assuming the throttle body did not). If the boost rises at the manifold (typically where it is measured), the boost must be controlled at the turbo outlet (typical of manual boost controllers), and I would expect that a restriction in the intake runners would be responsible for raising the boost.

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That is the kind of intake I used that I picked up boost switching from.

 

You picked up boost?!!? That implies more restriction.

 

In other words, when I went from the tapered manifold to the turbo one, my boost pressure in the manifold increased, all else being the same. More boost equals more power, so I felt like it was a good thing.

 

Maybe we are looking at it from a different perspective, I likened it to pressure drop across the intercooler decreasing, thus increasing the amount of boost I was seeing in the intake.

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