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Aftermarket intakes for 1.8 - worth it?

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I'm still on the fence about the Miata's intake.


Every aftermarket intake claims to boost power, provide a smooth path for air, colder charge, etc... but dyno plots are very scarce, and rarely show a fair comparison between the OEM and the aftermarket (they're always skewed to provide better testing conditions for the replacement parts.)


The OEM intake is apparently very well thought out and not really a source of restriction... the LAST thing I want to do is spend a point on an intake and have it drop the HP output!


What are ya'lls experiences with NA / NB Miata intakes? I know I've seen everything out there... from expensive imported carbon fiber shinies to PVC and dryer duct. Spending the TT point on intake means I can go all out, add a scoop, etc. But if the stock one is functional but ugly, I'll keep it and spend the point on something else!


Thanks in advance!

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I custom built my intake for $40 but I lazily slapped it together. I need to custom build it either to (1) place the filter on the intake manifold side behind the headlight or (2) run piping under the driver's side headlight for cooler air. I haven't done #1 yet since the coolant reroute is partially in the way. Here's mine...



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Objective is gaining power / cutting lap times. Intake is just a single point in TT, but that point could go weight reduction or another more beneficial modification. I would just go for it, but I've happened across several instances recounted on forums where people actually lost power by messing with the intake.


I'll likely build one regardless, and keep the stock setup on hand if I want to reallocate the point. :) I'm guessing the most beneficial thing I can do is get it cooler air and get it away from the exhaust manifold.

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something I've seen people do as a result of learning is having a long straight pipe on the intake to allow the air to stabilize. Fake a look at the ddm works stage 2 intake for the NB...it's a pitcrew knock off...


On an NA you should be able to rig something up like chris has on his NB...put a filter behind the headlight and build a heat shield. I did something similar for my turbo setup and it fits a-ok :)

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I'll e-mail you a photo tonight. But I removed the pop-up light.

Yo AJ, pls post (another) image of yours. Ok, you have to move the MAF wires and figure out what to do with a headlight cover, but it's in an awesome position for good air - cold side and NOT behind the radiator flow. I'm actually thinking about a wire mesh cover for the headlight. I still think SamUK should market his work.

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Alright! From my build thread, here is my intake solution. I have a lot more pictures if you guys are interested, but here are the highlights.


For the intake tube, I recycled a performance intake/velocity stack from my VW GTI. I used the plastic autozone bits and silicone couplers to hold it all together. I had to dremel in a bung for the idle air tube, which I don't like and will be finding a better solution for (probably get a nice metal one like Andy's.) The MAF fits perfectly in to the Spectre tubes though, which is nice. I had to lengthen the MAF wires to reach the new location.




For an air box, I faked a template together using foam board, then cut the it out in black HDPE plastic. It is held together with corner braces, and it's mounted to one of the headlight mounting holes (the one behind the overflow tank) and a few sheet metal screws. I plan to further seal it off with some sort of rubber boot around the intake tube, and put a gasket between it and the headlight door.


For the headlight door I busted out the mad fiberglass skills!



I covered the OEM door with aluminum foil, and applied fiberglass cloth on top. The hardened result peels away from the door, and the foil peels away from the fiberglass. I did two layers of cloth as smooth as I could for the top surface.


A NACA is supposed to provide an air inlet from an aerodynamic surface without disrupting the airflow over the surface. I wasn't impressed by any of the offerings on ebay, they don't have sharp edges like they are supposed to or are missing the airfoil at the top back of the inlet. Plus they're all pretty expensive.


So I set about making my own. To calculate the shape I used this spreadsheet: http://www.vansairfo...ead.php?t=41754


This gave me the horizontal and vertical profiles of the duct that I wanted based on specified height and width. I used Inkscape to make a vector drawing of the profiles, placing nodes at each point from the spreadsheet then smoothing the curve. I printed a bunch of copies, then taped the copies to 1/2" insulating foam that I had laying around. I cut the vertical profiles out of the foam and superglued them together, then used the horizontal profile to cut the solid block.


I wrapped the foam in foil and applied a patchwork of fiberglass cloth strips over it, leaving a lip on the top facing edge. for attachment.



You can see the pink foam template inside the hardened fiberglass shape.


I removed the template and positioned it where I wanted on the headlight, checking fitment with the filter for enough clearance. When it was where I wanted, I applied a thick patchwork of fiberglass strips to attach it to my headlight door, doing the same with some corner braces to provide attachment points for the finished product.



After it set up, I used a rotary tool to cut the duct hole out and went for a test fit:




Then came the body filler. Mix a small amount, apply, shape, wait for it to set up, then sand. It was a pain getting the filler smoothed out inside the duct due to confined space.



I got it mostly smooth then hit it with paint. It's not perfect, but I planned to vinyl wrap it, so small blemishes and scratches won't show through.



It came out very nicely. Now we'll see if it works!

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I'm starting to look at coolant reroute as well. Now that I've got a proper temp gauge I'll be able to see where it goes after a hard driving session. It does seem necessary, given the way the coolant inlet and outlet is set up.

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I was looking at that, it seems like without the light there there's a straight shot to the intake from the front, but I'll try it with the light installed first to avoid messing with the pressure differential between the engine compartment and the nose of the car. I might put a cheap thermocouple (read: remote BBQ thermometer) in there to see IATs with and without. :)

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LOL, not really. I'm not running a belly pan, so that probably is much more detrimental anyway!


In other news, the intake performed wonderfully at Putnam Park. It makes cool noises and the butt dyno says the intake and exhaust make a HUGE difference. I was pulling other Miatas on straights that I've been dead even with in the past.

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In other news, the intake performed wonderfully at Putnam Park. It makes cool noises and the butt dyno says the intake and exhaust make a HUGE difference. I was pulling other Miatas on straights that I've been dead even with in the past.


Nice. If the butt dyno is happy, that's a good thing.



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Pressure differential? Really?


Novel! A Miata that generates enough forward momentum to worry about pressure differential.

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The pressure differential would be for cooling effect, not for an aerodynamic advantage. facepalm.gif If you've got higher pressure on the engine compartment side, less air flows through the radiator.


A spec miata builder commented on my lack of a belly pan while admiring my hood latches, and said it would lead to heat problems. A missing turn signal probably wouldn't matter compared to that.

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