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The hood of my '83 turbo has a NACA style scoop, which I _think_ is there to bring in air to keep the brake master cylinder cool. I'm replacing the engine in the next few months, and I'm going to have to re-route the intake to accommodate the intercooler and larger turbo. While I'm at it, I'm planning to seal up gaps around the radiator and intercooler, and doing a bit of tweaking of the airflow into and out of the engine compartment for better cooling and less lift. Anyway, I'm wondering if I can use that naca scoop for the air intake (I'd need to fabricate a filter box), since it's directly above the turbo, and I'm thinking that all the air coming into the engine compartment really should be doing so from the front. Using that naca scoop as the air intake seems like an obvious improvement to me, but the fact that I haven't seen it done this way before by people who actually know what they're doing makes me wonder what I'm missing. Is this a laughably awful idea for some obvious reason that I'm not seeing?


Along the same lines, would it be possible to open up the front of the power bulge and use that for the intake? The plumbing would be more complicated for that route, maybe using the hood itself for most of the ducting, but it just looks like that would be the obvious place to put the intake. Or would that also be unworkable? Thanks. 

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It's also there to help cool the turbo.


I don't see how you will be able to run the turbo inlet, along with the AFM and the compressor piping all in the same area, while fighting the intake directly above the turbo. 


Most people run a silicone fitting into the turbo and rig it up to sit right behind the radiator (get rid of the clutch fan and go with some electric fans on the radiator)


What is the front of the power bulge?

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I neglected to mention a few things, my bad. The incoming engine management system doesn't use an airflow meter, so that should simplify the plumbing a bit (hopefully enough to make a straight-ish shot down from the naca duct feasible). The turbo itself is water-cooled, and the exhaust side of the turbo and the exhaust manifold are coated with this silver ceramic stuff that should help keep their exterior temp down. I'm definitely getting rid of the stock fan, and I've got a couple of electric ones to take over its job. I've seen setups where the intake is behind the radiator, but it just doesn't seem right to use pre-heated air like that for a turbo intake, which is my main reason for wanting to have the intake coming from outside the engine compartment and have the path to the turbo be as short and direct as possible. (And maybe a bit of positive pressure there won't hurt, either) 


The power bulge is the raised portion of the hood that runs down the middle, and the front of it is a trapezoid that looks like it could be opened up to serve as the air intake. A raised bit of the hood, right out in front like that, I don't see why it hasn't been used as the intake all along- it just looks like it ought to be, IMHO. If I were to do this, I'd probably see about using the bulge itself as the air duct to get the air back to the turbo, but that would mean going around the intake manifold on the way down, which might be too complicated to be practical. Of course, I don't really know what I'm talking about here, so my reasoning may well be flawed, which is why I'm wanting to run this by some people who actually know about this stuff.

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  • 2 weeks later...

That hood scoop's main purpose is to allow the column of super hot air off the turbo to escape the confinement of the engine compartment.............after you've parked the car.


Same goes for the scoop in the pre 1987 300zx.......which was done away with once they went to dual feed injectors.


It's there mainly to combat vapor lock though I guess it does help keep the master cylinder cooler while driving.

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