"Cold air intakes move the air filter outside of the engine compartment so that cooler air can be sucked into the engine for combustion."

But from what I know of them, they do just the opposite. Most stock autos bring air in from the outside of the engine compartment, duct through a filter box and into the engine.

Cold air intakes just put a big air cleaner under the hood, next to the hot engine where there's much less air flow and certainly not cold or colder than the outside air.

So what am I missing?

I'm not looking to debate whether or not do they what people claim, just asking about the name and description that both seem backwards to me.

I could be wrong here, cas, but I think the intent is to get the intake further away from the heated mass of the engine (think of the big old round air filter boxes on top of the engines on last-century cars), so as to bring in cooler (more dense) air.

A number of these installations I've seen have had the intake mounted even below the level of the engine, and as far forward as possible. It's still inside the engine box, but away from the mass of hot steel.

Most that I've seen are at the same height and same distance from the engine as the old air box (filter housing), only they're drawing air from under the hood rather than outside air.

In that case, I'll quickly admit that I don't know.

I figure Black92LX will be around shortly to clue us in better.

I agree with OP they are drawing in hotter air than stock intakes in most cases. But they appear to be less restrictive and make nice (to many people) noise on large throttle application.

vthoky had it right the first time.
The air intake usually starts somewhere behind the grille but forward of the radiator and picks up air before it is heated up by the engine.
Plastic components transfer much less heat than older metal parts and the air going through the system changes quickly.

When I see "cold air intake," I think of air being ducted through to the engine from the outside of the car. The outside air is not actually "cold" - unless of course the weather is cold - but is still cool relative to the underhood air. Almost all cars already have external ducting, even if the filter is close to or directly on the engine. Just replacing the existing ducting and hanging a filter off it under the hood, as I have seen so many times, defeats the purpose, IMO.

Originally the cold air intake drew air from outside the engine compartment. Cooler air, greater density, more engine power. Harking back to carbureted days, some engines used bimetalic valves to allow warm air to mix, to reduce carburetor icing. Warm air, by comparison, is generally taken from a plenum that's not just in the engine compartment, but heated air.

Even with carb-mounted filter boxes, the intake. used to traditionally run via a flexible or rigid manifold to the outside of the car, typically adjacent to the radiator, behind the grill. There's been a trend over the years to draw air from inside the engine compartment, in some vehicles, particularly after market installations.

A performance increase will be had by running a manifold from the filter to the outside of the vehicle, rather than simply drafting hot air in the engine compartment.

Just marketing to make you think you're getting something for nothing and getting more power for free, other than the cost of the new intake.

Seriously I've been working in the engine manufacturing business for almost 20 years. And I regularly sit in design reviews with design engineers to help them ensure their designs can be assembled in our plants. The service engineering guys usually get the short end, but they do have a voice too.

If people had any idea the amount of time/engineering/analysis/testing/validation/etc. that goes into producing a modern engine they would give up with all of these stupid quick fixes that promise more power. I can assure you these aftermarket bolt ons do not put nearly as much work into the development process. I really don't think these companies dyno test engines in cells that can simulate very cold weather and high altitudes, along with field testing engines with high speed data loggers with telemetry.

Now, there is a balance to meet emissions regs, fuel economy regs, power, and durability, and a lot of tradeoffs. Everything is extensively electronically controlled so if you change hardware you also need to change the software. So yes, if you want to optimize power at the expense of all the other variables, you can, but it takes more than bolting something on. And once you get into mucking around with the software there's a lot of stuff you can't account for that will affect real world performance in various driving conditions.

Cold air is a relative term really meaning not heated air or outside ambient air temperature.
The original equipment intakes of modern cars are well researched and tested since they have to maximize fuel economy, emissions reduction, and power. The aftermarket stuff is often more concerned with looking cool (hip cool, not cold cool) to sell well. Little actual science goes into many of them and a lot of the end users don't really have a clue.
Selling product is the overriding consideration. Same with aero do-dads, suspension parts and performance wheels and tires.

There are several designs, but the common theme is more filter surface area, and much less restriction between filter and intake manifold (e.g. my old Silverado's 4 in "pipe" flattened down to 1" tall at one point and the cold air intake had a 4 in pipe the whole way).

Some have almost no sealing so air is pretty much the same as under hood.

Mine is the sealed box design by Volant that pulls air from driver's side front fender. Not only does the filter have more surface area, but the box itself is a larger volume than stock. I have it sealed off due to Houston flooding, but there is a 2nd connection that could be piped to a ram air intake under the radiator.

This is a functional aftermarket CAI.



It draws air in from the outside and isolates the filter from the underhood heat.

This CAI does fuck-all.



That is even still the original duct.

I remember the old days when there was a "tube" from exhaust manifold area, not direct connect, up into the air cleaner. Purpose was to help induce warm air into carb so the automatic choke worked properly will keeping the engine running smoothly.

By old days you mean three of the cars in my driveway.

Cool Air Intake (CAI) might be a more accurate description. At least of the products which are nothing more than an open filter on a carburetor or maybe a smooth plastic tube from the fuel injection throttle body to the filter. Many oem intakes are already ducting air from outside the engine compartment. Late model GM trucks/SUV, Camaro and Corvette for instance.

The better intakes are enclosed either by total encapsulation, ducted through the fender similar to oem, or by a partial shroud enclosure to (somewhat) isolate the filter from hot engine compartment and help reduce IAT temperatures.

Most manufacturers will claim gobs of horsepower increases, but few actually have dyno tests to substantiate those claims. Many owners equate more intake noise with more power.

HALLTECH is one of the most regarded high performance late model intake vendors. He does lots of R&D testing to back his claims. That's why his products are so expensive.

So if they were properly named, they'd be called "large volume aftermarket intakes".

Assuming you're talking about a made in the last 35 or so year and that doesn't just have an open air cleaner on the engine, there are two 80's vehicles in my driveway that have "cold air intakes" from the factory, drawing air from the grill. (as do all the "newer" ones)

Actually I'm trying to remember the last thing I / we owned that had an old style non ducted air cleaner. It's been a long time.

A better flowing air filter many times can accomplish just as much as a $300-$600+ CAI. If your 1980s cars are already ducted to the grill, simply replace your filters more often to allow for better filtration and better intake breathing.

Oil gauze filters like K&N used to be the rage. The oil trapped contaminants and the filters were thinner. But oem manufacturers often denied warranty because the light oil on the filters could cause MAF contamination and poor engine performance. It was more often than not the owner failed at re-oiling the filter correctly. I used oil gauze filters for years, serviced them regularly (another owner failure), but learned the correct manner to clean and re-oil. I never had any issues.

Now most after market manufacturers have come out with thinner 'dry' gauze type filters which eliminate the oil contamination issue. They are well pleated for more surface area to trap contaminants but a little thinner to allow for more air flow. It's a trade off.

quote:

Cold air intakes just put a big air cleaner under the hood

Those are just pipes and filters. They may give better airflow but at the cost of warmer air as you pointed out.

True cold air intakes attempt to get you air that has not been heated by the engine. Many do this by piping into a wheel well or toward the lowered end of the car. A good system with clean piping that gets outside air can make some improvement but they are normally minimal on stock cars.

I'll play too.

The cold air kit came out at a time when it was common to put a round filter between two plates and slap them on top of a four barrel. A hood scoop had a minimal increase as it was mostly located at a low pressure area on the car (but looks bitchin'). Cowl induction was a better idea as it not only had cooler air coming in, it was also of a higher pressure as it was higher at the base of the cowl. This worked great until higher speeds (40-50MPH depending on the aero of the car) were achieved and the vortex collapsed. Little pressure when you'd want it most. Taking the high-beam bulbs out and ducting the air into the filter assembly worked great with a four headlight system. Good pressure all the time.

The first example that egregore featured for Roush has two advantages. It gets air from between the fender and fenderwell (a stable and higher pressure area) without the engine bay temperature. It also seals against the hood for more pressurized airflow through a filter with a high surface area.

The $20 intake also pictured looks like garbage and wreaks havoc when the electric fan kicks in.

Most modern vehicles will get the air from the high pressure area inside the fender because it has the most stable pressure and no additional heat. Lefty Sig explained it better than I would. The cold air kit usually reroutes the air from there also.

When I bought my most recent truck, it had a $400+ ram air cold intake kit in it. It took a while for me to find the factory intake duct, but an OEM filter housing made its way back under the hood.

The kit that was in it looked cheap and the housing made it impossible to get to the dipstick to check the oil.

I always love the arguments surrounding CAI's. Most all of them are just silly. Here's a hint. If you live in Florida, Arizona, Texas, New Mexico or some other really hot state, the temp differential between your stock air box picking up superheated air just off the asphalt pavement, or some so called CAI sucking in hot air from the engine compartment is negligible. The CAI isn't going to add any real HP or fuel economy to the equation. The only benefits I can see is 'maybe' slightly less restricted air flow than the stock airbox, and/or a bigger, easier to get at and clean air filter. Short of that CAI's are little more than engine compartment decoration.