Cold air intakes

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Making a CAI, or a shortram intake
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When I think of Cold Air Intakes, the first car that I think of is the 1964 Ford Fairlane THUNDERBOLT. Detroit Steel Tubing, known as DST purpose built these cars for drag racing for Ford. The engines that they were using were 425 HP 427 Cu. In. How do you feed cold air to a engine of this size? BIG PIPES! How big? About 6 inch diameter. When you need to get cold air from the frontal area to the gigantic carb intake you take the most direct route. Kick out the inner headlights (who needs four headlights on a drag strip), add some grills to keep out large debris, run the expansion pipe up to the aluminum intake box and you have it. Check out the pictures on how they did it back in 1964.
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==Introduction==
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Cold air induction can add (or maintain) power by feeding the engine colder outside air rather than the engine ingesting the preheated underhood air. The difference can be fairly significant, especially with high output/high performance engines.
  
[[Image:Headlight_intake_grill.jpg]]
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Cold air induction can allow for richer carburetion  tuning with an increase in power. It can also reduce the tendency for detonation.
  
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==Ford Thunderbolt==
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When the subject of cold air induction comes up, the first car some may think of is the 1964 Ford Fairlane Thunderbolt.
  
[[Image:Side_view_of_cold_air_intakes.jpg]]
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Dearborn Steel Tubing (known as DST) purpose built these cars for NHRA Super Stock drag racing for Ford. The engines that they used were the (very underrated) 425 HP, 427 cid high riser side oiler.  
  
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To feed cold air to a engine of this size required large (~6" diameter) tubing connected to a large aluminum air plenum box atop the dual 4 barrel carbs. The large air box required a bulge in the hood, and to get cold air from the frontal area to the large intake box, the designers used the area where the inner headlights normally resided for the intake. They added grills to keep out large debris, and ran the ducting up to the intake box (seen below). The result was the iconic look of the Ford Thunderbolt.
  
[[Image:Dual_intake_pipes.jpg]]
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[[Image:Headlight_intake_grill.jpg|thumb|center|400px|Cold air intake]]
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{|
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|[[Image:Side_view_of_cold_air_intakes.jpg|thumb|center|370px|]]
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|[[Image:Dual_intake_pipes.jpg|thumb|center|370px|]]
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|}
  
Of course, other people have their own views on what cold air intakes should be, and they're entitled to them. '''BIG IS BETTER'''
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==Fabricating a cold air induction system==
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This is really quite simple; a great project for the budding automotive enthusiast. A homemade cold air intake can be built using nothing more complicated than coffee cans and dryer duct, the can can be pop riveted to the air cleaner sides after cutting a hole the shape and size desired. Then route the dryer ducting to a source of outside air. On older vehicles, this was usually from the grill area or under the bumper. This isn't the prettiest or most efficient set-up, but illustrates the basic concept can be adapted using low-tech methods and materials.
  
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==Design considerations==
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Generally speaking, bigger is better because it is less restrictive. However, packaging the system under the hood has to be a consideration.
  
This is really quite simple; a great project for the budding automotive enthusiast.
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First you need to know the diameter of the stock intake tubing (if it is to be used/reused) or the size and shape of the air cleaner snorkel if it's to be used. If using a remote filter like a cone type reusable gauze filter, the location needs to be selected based on available space and a suitable carb "hat" needs to be bought or fabricated.
  
First you need to know the diameter of the stock intake tubing, and where you want your filter- usually a cone type reusable gauze filter.
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==Late model production vehicles==
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In most cases, the late model passenger car/light trucks on the road today are using some sort of cold air intake. If the air filter housing/box is located on one side or the other of the engine compartment, and has ducting that goes through the inner fender, this duct work is pulling in outside air. Most aftermarket cold air intake kits include ducting that is smooth, not ribbed or corrugated. This allows for less disruption of the airflow, which is also beneficial in combination with the cold air intake.
  
Then you look under the hood...
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A high flow air filter in a stock intake box/housing with smooth ducts can work well on late model applications, sometimes as well as the high dollar kits sold in the aftermarket. In these cases the only "advantage" to the aftermarket kit is the looks.
It probably looks something like this
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[[Image:http://www.ayocee.com/cmine/albums/oilchhowtwo/normal_Oil%20Change%20Howto%20002.jpg]]
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It's a stock 1.9L Saturn engine, of the SOHC (single over head cam) variety.  Notice the stock intake tubing on the right side of the picture. It's designed to be cheap to make, reduce noise, and be easy for the guy on the production line to install, with minimal care for performance, especially in a non-sports car (think Corvette or Porsche).
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Take the measurements of the throttle body outside diameter (OD) and head to the parts store. Since the throttle body is horizontal (if it were a carb, it'd be a sidedraft), you'll need a 90-degree elbow to follow the general path of the stock stuff that has . Make sure it's heat and oil resistant, and then get some tubing with the same inside diameter (ID) as the throttle body. The intake tubing (some people use pvc pipe, I prefer metal such as aluminum) needs to have the OD the same as the ID of the 90* elbow.  Using various parts, being creative and inventive, piece these together ensuring you have enough room for the air filter at the end!
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==Potential gains==
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A law of physics states that for each 10º drop in air temperature going into the motor, power will pick up by 1%. This is because when the air is colder, it is more dense and therefore contains more oxygen. So potentially, a 100º drop in air temperature would equate to a 10% increase in power. On a 400 hp motor, this would equal a 40 hp power increase.
  
Lastly, make sure you have provisions for crankcase lines (or a crankcase breather filter) and have enough hose clamps for all joints in the system. The picture below is of a Saturn 1.9L engine (the twin cam variety) with a shortram intake.  It's not a true cold air intake since the air going into the engine is from the engine compartment.
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Of course, a tuner would have to compensate for more oxygen by jetting richer to correct the air/fuel mixture. The later model EFI systems sense more oxygen and automatically richen the mixture.  
[[Image:http://hotrodders.com/gallery/data/3121/IM000157.JPG]]
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Normally a shortram/warm air intake is a better idea if your car sees snow and other wet, inclement weather.  A CAI is better suited for track use or for a car which rarely (if ever) sees bad weather.  If your car pulls water up in the intake then you'll hydrolock it and if you're lucky you can pull the spark plugs out, crank the engine a few times, reinstall plugs, and be on your way.  Lots of times you'll ruin the internals of the engine since water will not compress.  The engine parts will bend before water will compress!
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[[Category:Engine]]
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[[Category:Carburetors]]

Latest revision as of 07:06, 31 March 2012

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