Firewall intake???
01-30-2009, 12:22 AM
#1
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Firewall intake???
I have been thinking about where to route my intake pipe and i was wondering if the cold air from the firewall is a adequate "cold air intake" spot. I would like to find cold air without having to cut up the fender/wheel well. I have a single side intercooler (both hot and cold side pipes come from the same side) so there are pipes in crossing the front of the engine.
Could i route the intake pipe to grab air just below the radiator fan behind the sway bar? would i have to worry about dust/moisture?
Just trying to find some clean cold air thanks in advance
Could i route the intake pipe to grab air just below the radiator fan behind the sway bar? would i have to worry about dust/moisture?
Just trying to find some clean cold air thanks in advance
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01-30-2009, 12:33 AM
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ganked from this thread
MX-5 Miata Forum - My home-made cowl / cold air intake - Aircraft Spruce ducting
MX-5 Miata Forum - My home-made cowl / cold air intake - Aircraft Spruce ducting
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01-30-2009, 02:44 AM
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I had a home made intake for about 3 months on my car like that when it was N/A.
Rain is no problem, unless your drian there is clogged and it like fills with water lol.
Did it make an effect? Well, it sounded cool...
Rain is no problem, unless your drian there is clogged and it like fills with water lol.
Did it make an effect? Well, it sounded cool...
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01-30-2009, 09:45 AM
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Cowl induction is a proven successful mod on thousands of performance cars over the last forty years. It has been a factory performance feature on many cars over the years as well.
The area at the base of the windshield is at a slightly higher pressure than the air underhood, so it helps to feed air to your engine just a little bit better. It has been proven in the wind tunnel to be a superior design to most low stock hood scoops (like the ones on my GTO). The scoops don't outperform cowl induction until they get over 2 inches or so above the hood surface. This is due to boundary layer stagnation.
The second benefit is, of course, the air is much cooler than underhood air. That is actually the greatest benefit.
Thirdly, some of the factory and racer cold-air mods were bad about sucking up water and road debris ('66 Olds 442 for instance) from in front of the radiator, below the front bumper, or in the fenderwell. For brake ducting it isn't an issue because water or debris and dirt aren't quite as harmful to the brakes (minus warpage). The cowl area is as high out of the debris as you can go to easily find clean, cool, higher pressure air.
These are some of the same reasons that Trans-Am and NASCAR and many American Le Mons Series race cars take advantage of cowl induction. And that Aircraft Spruce and Specialty kit looks sharp, but I would DIY.
The area at the base of the windshield is at a slightly higher pressure than the air underhood, so it helps to feed air to your engine just a little bit better. It has been proven in the wind tunnel to be a superior design to most low stock hood scoops (like the ones on my GTO). The scoops don't outperform cowl induction until they get over 2 inches or so above the hood surface. This is due to boundary layer stagnation.
The second benefit is, of course, the air is much cooler than underhood air. That is actually the greatest benefit.
Thirdly, some of the factory and racer cold-air mods were bad about sucking up water and road debris ('66 Olds 442 for instance) from in front of the radiator, below the front bumper, or in the fenderwell. For brake ducting it isn't an issue because water or debris and dirt aren't quite as harmful to the brakes (minus warpage). The cowl area is as high out of the debris as you can go to easily find clean, cool, higher pressure air.
These are some of the same reasons that Trans-Am and NASCAR and many American Le Mons Series race cars take advantage of cowl induction. And that Aircraft Spruce and Specialty kit looks sharp, but I would DIY.
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01-30-2009, 10:15 AM
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It sounds DIY until you start checking prices, though. Spruce is very high on everything.
I'm a cheap bastard. I would find/build the flange for a couple of bucks from the U-Pull-It junkyard, used machinery parts from where I work, or Home Depot.
I'm a cheap bastard. I would find/build the flange for a couple of bucks from the U-Pull-It junkyard, used machinery parts from where I work, or Home Depot.
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01-30-2009, 11:12 AM
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Yeah that is definitely not a cowl intake kit.
Don't buy the tubing from Spruce. Shop around. I just bought 5' of that same Aeroduct tubing, for the same purpose, from another source, for ~$30 with shipping. You only need about 3 feet. I used this stuff because the materials are good and the interior wall is smooth (for reduced pressure drop) compared to that plastic accordion tubing stuff sold at Pep Boys and the like.
This setup works well; this is what I am using. In my case though I am placing an air filter in the cowl area. I an using a 3.5" dia by 6" length cylindrical K&N filter, two of them in series.
The only thing is that this cowl setup is considerably louder than an under the hood intake. I have used both so I know. During cruise it is fine, but at WOT you can definitely hear it. In fact, if you have the vent on 'fresh air' instead of 'recirculate' it is a little louder since the air intake for the vent is in the cowl area. This setup IMO is not unbearably loud, but definitely not stealthy. It sounds like you have a shop vac under your hood. The high pitch compressor whine is somewhat suppressed by the tubing's resonant frequency.
Don't buy the tubing from Spruce. Shop around. I just bought 5' of that same Aeroduct tubing, for the same purpose, from another source, for ~$30 with shipping. You only need about 3 feet. I used this stuff because the materials are good and the interior wall is smooth (for reduced pressure drop) compared to that plastic accordion tubing stuff sold at Pep Boys and the like.
This setup works well; this is what I am using. In my case though I am placing an air filter in the cowl area. I an using a 3.5" dia by 6" length cylindrical K&N filter, two of them in series.
The only thing is that this cowl setup is considerably louder than an under the hood intake. I have used both so I know. During cruise it is fine, but at WOT you can definitely hear it. In fact, if you have the vent on 'fresh air' instead of 'recirculate' it is a little louder since the air intake for the vent is in the cowl area. This setup IMO is not unbearably loud, but definitely not stealthy. It sounds like you have a shop vac under your hood. The high pitch compressor whine is somewhat suppressed by the tubing's resonant frequency.
Last edited by ZX-Tex; 01-30-2009 at 11:25 AM.
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01-30-2009, 05:38 PM
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I'd take that bag off before you try to drive that car anywhere. 
I need to figure out some kind of CAI. I have a charge pipe running right where most put their intakes. This cowl idea might just work, I just have to buy a filter that will fit. Too bad about it being louder though. Mine is already a little louder than I like at WOT.
I need to figure out some kind of CAI. I have a charge pipe running right where most put their intakes. This cowl idea might just work, I just have to buy a filter that will fit. Too bad about it being louder though. Mine is already a little louder than I like at WOT.
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01-30-2009, 06:03 PM
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Yeah it is louder, just wanted to get that in there before someone does this and then bitches about the noise. But it works well, and it sounds sweet IMO. It is good for a few 'WTF is that' head turns too if that is your thing.
SV650 no offense but I am not sure I like that setup as shown with your stock airbox removed. It would rely on the cowl always being at a higher pressure than the hood area, otherwise it will not work properly. I like the sealed approach better for that reason, like the ones in the other pictures above. Are you going to fabricate a box to enclose the filter?
SV650 no offense but I am not sure I like that setup as shown with your stock airbox removed. It would rely on the cowl always being at a higher pressure than the hood area, otherwise it will not work properly. I like the sealed approach better for that reason, like the ones in the other pictures above. Are you going to fabricate a box to enclose the filter?
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