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How to Mod your stock airbox to flow better

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Old 05-03-13, 02:47 PM
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Originally Posted by GuiltySoul
Yea I just replaced my intake snorkel and put a hks drop in filter.



It's definitely a lil louder and has pretty good response but we won't really know without real testing

You aren't getting any air into the snorkel with that cover there.
Old 05-03-13, 04:34 PM
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I really dont understand why folks want to just throw on a cone filter and say done. If you do this, it needs to be isolated and getting a fresh cold air source.

Unless you are asking for 400 HP, why not just modify the stock airbox? It has plenty of room if you remove the damn baffles.
Old 05-03-13, 04:39 PM
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GuiltySoul doesnt the cooling pannel block the cool air from your snorkel. Im just wondering because I was thinking about getting one, but have never seen one used with factory intake setup.
Old 05-03-13, 06:31 PM
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Cold air comes up from below the snorkel. S5's have additional ducting in front of the snorkel's entrance for that purpose. So the cooling panel is certainly not helping.

Also, the S5 snorkel is larger ducting than an S4. So putting an S5 snorkel on an S4 is an upgrade all by itself, but could make R&R of the radiator cap a little more difficult if your running an S4 radiator.

To the OP, to clarify aren't you just talking about smoothing out the inside of the bottom and top of the airbox. Grinding down the little squares to make a smooth top and bottom interior surface, correct?
Old 05-03-13, 07:04 PM
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Originally Posted by pistolgrip
Also, the S5 snorkel is larger ducting than an S4. So putting an S5 snorkel on an S4 is an upgrade all by itself
But the intake port on the airbox top is the same size for S4 and S5, so why would the increased snorkel size matter?
Old 05-03-13, 08:08 PM
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Originally Posted by jjwalker
I really dont understand why folks want to just throw on a cone filter and say done. If you do this, it needs to be isolated and getting a fresh cold air source.

Unless you are asking for 400 HP, why not just modify the stock airbox? It has plenty of room if you remove the damn baffles.


Coolness over function.
Old 05-03-13, 08:59 PM
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As a guess, perhaps kind of like going to a higher amperage alternator. The devices are still only going to draw what amps they can use. But more amps available means less chance any of those devices will be starved.

So perhaps Mazda engineers reasoned that more air available at the junction is a better thing?
Old 05-03-13, 09:01 PM
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I don't see how this is really gaining any power? It is still restricted to the snorkle's size. This took a few hours of fabbing with minimal tools when I was living in an apartment. Theres a duct that comes from in the bumper area, passed beside the rad. I've had bugs splattered on the bottom side of the duct, and the bottom of the filter so it does draw fresh air and, plus any that is shoved in through the still in place oem snorkle.

This is not dyno proven on my TII, but I originally had it on my Na with a 2 1/4" exhaust and rb header and it put down 134hp and 132 ftlb to the wheels on a mustang dyno.
Attached Thumbnails How to Mod your stock airbox to flow better-image-2452350048.jpg   How to Mod your stock airbox to flow better-image-736263881.jpg  
Old 05-04-13, 06:50 AM
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Originally Posted by Doc Holaday
I don't see how this is really gaining any power? It is still restricted to the snorkle's size. This took a few hours of fabbing with minimal tools when I was living in an apartment. Theres a duct that comes from in the bumper area, passed beside the rad. I've had bugs splattered on the bottom side of the duct, and the bottom of the filter so it does draw fresh air and, plus any that is shoved in through the still in place oem snorkle.

This is not dyno proven on my TII, but I originally had it on my Na with a 2 1/4" exhaust and rb header and it put down 134hp and 132 ftlb to the wheels on a mustang dyno.
Mustang dyno give low readings, you really had around 150 @ the wheels, was this an s4 or s5?

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Old 05-04-13, 05:05 PM
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Originally Posted by Doc Holaday
I don't see how this is really gaining any power? It is still restricted to the snorkle's size. This took a few hours of fabbing with minimal tools when I was living in an apartment. Theres a duct that comes from in the bumper area, passed beside the rad. I've had bugs splattered on the bottom side of the duct, and the bottom of the filter so it does draw fresh air and, plus any that is shoved in through the still in place oem snorkle.

This is not dyno proven on my TII, but I originally had it on my Na with a 2 1/4" exhaust and rb header and it put down 134hp and 132 ftlb to the wheels on a mustang dyno.

I believe I remember reading your post when you did that. I like it.

I posted this in case people didn't want to go as far as you did and just modify the stock box.
Old 05-04-13, 05:08 PM
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Originally Posted by pistolgrip
Cold air comes up from below the snorkel. S5's have additional ducting in front of the snorkel's entrance for that purpose. So the cooling panel is certainly not helping.

Also, the S5 snorkel is larger ducting than an S4. So putting an S5 snorkel on an S4 is an upgrade all by itself, but could make R&R of the radiator cap a little more difficult if your running an S4 radiator.

To the OP, to clarify aren't you just talking about smoothing out the inside of the bottom and top of the airbox. Grinding down the little squares to make a smooth top and bottom interior surface, correct?
No, to get rid of the 2 air silencer baffles.

I suggested possibly smothing out the inside of the box, although I haven't done it myself. I want to do this though.
Old 05-04-13, 06:43 PM
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Originally Posted by wthdidusay82

Mustang dyno give low readings, you really had around 150 @ the wheels, was this an s4 or s5?

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S4, it was a fun little beast, now it will be powering a sweet vw beetle.

And yes I see that some people wouldn't want to get rid of the stock box, but this really wasn't any more difficult to do that cutting out plastic. I just can't see much of an actual hp gain with the trimming.
Old 05-06-13, 09:34 PM
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It looked like you made it out of aluminum. Looks good, you fooled me. :p

My point of this post was to educate people how to open up the stock airbox system if they wanted to keep it, instead of relegating themselves to sucking hot air through an unsealed cone filter. Cone filters are wonderfull, if your keep them away from engine bay temperature air.
Old 05-06-13, 09:59 PM
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Originally Posted by jjwalker
It looked like you made it out of aluminum. Looks good, you fooled me. :p

My point of this post was to educate people how to open up the stock airbox system if they wanted to keep it, instead of relegating themselves to sucking hot air through an unsealed cone filter. Cone filters are wonderfull, if your keep them away from engine bay temperature air.
+1 putting a vent on the headlight to breathe some air into the location of the cone air filter would aid in ensuring you are getting cold air

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Old 05-06-13, 10:31 PM
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I think JohnV pretty much defined where the flow restriction is in the stock S5 n/a intake track and noted his findings and his solution:

https://www.rx7club.com/2nd-generati.../#post10601567

https://www.rx7club.com/2nd-generati.../#post10626094

The first picture is an older shoot of the engine bay of my car with that same CAI when it was first installed. The second photo is from last weekend.
Attached Thumbnails How to Mod your stock airbox to flow better-dcp_2024-640x427-.jpg   How to Mod your stock airbox to flow better-dsc00939-640x480-.jpg  

Last edited by DeaconBlue; 05-06-13 at 10:36 PM.
Old 05-06-13, 11:43 PM
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Originally Posted by DeaconBlue
I think JohnV pretty much defined where the flow restriction is in the stock S5 n/a intake track and noted his findings and his solution:

https://www.rx7club.com/2nd-generati.../#post10601567

https://www.rx7club.com/2nd-generati.../#post10626094

The first picture is an older shoot of the engine bay of my car with that same CAI when it was first installed. The second photo is from last weekend.
Where do you get a metal intake tube
Old 05-07-13, 04:57 AM
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John V's looks like custom made, the one pictured a few posts up is from Corksport.
Old 05-07-13, 08:21 AM
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Originally Posted by wthdidusay82
+1 putting a vent on the headlight to breathe some air into the location of the cone air filter would aid in ensuring you are getting cold air

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I've always wondered if those did any good. I really don't think those work very well at all. But routing the filter so that it sits in front of the radiator, or under the headlight seems to work. I don't see how those vented headlights do anything except for aesthetics, there's too much blocking the path. Like the headlight itself, and its housing.
Old 05-07-13, 09:04 AM
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This is true, you'd probably need a decent sized scoop for it to really catch any air and even with that it will give diminishing returns (depending on your speed) , with the possibility of air eventually completely passing over it once a certain speed is reached.

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Old 05-07-13, 09:05 AM
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Originally Posted by texFCturboII
I've always wondered if those did any good. I really don't think those work very well at all. But routing the filter so that it sits in front of the radiator, or under the headlight seems to work. I don't see how those vented headlights do anything except for aesthetics, there's too much blocking the path. Like the headlight itself, and its housing.
Not to mention, "What happens to the vent (and the air it supplies) when the lights are up?"
Old 05-07-13, 09:22 AM
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Originally Posted by clokker
Not to mention, "What happens to the vent (and the air it supplies) when the lights are up?"
*searches unsuccessfully for picture of that guy who ran dryer vent tubing from intake to empty headlight housing.

Old 05-07-13, 09:36 AM
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Originally Posted by texFCturboII
*searches unsuccessfully for picture of that guy who ran dryer vent tubing from intake to empty headlight housing.

I remember that!

Didn't mazdatrix or racingbeat do the same in one of their race cars?
Old 05-07-13, 10:35 AM
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i had a cone filter on my 3 rotor, and i removed the little rubber shield on the hood. with the headlights up, intake temps would drop a couple degrees
Old 05-07-13, 04:34 PM
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Just take off the headlight assembly on that side when you go to the drag strip. Lol

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Old 05-07-13, 04:40 PM
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Originally Posted by wthdidusay82
Just take off the headlight assembly on that side when you go to the drag strip. Lol

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what if i don't go to the dragstrip?

actually i should say i never did any testing to see if my intake temps were high with a cone filter, i just noticed they would be lower with the headlights up


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