"cold air kits?" ha!

Further, most of the aftermarket "cold air" cone filter setups merely suck hot air from under the hood.  If the filter is not enclosed (like the stock filter), it is definitely NOT a "cold air kit."  These open filters average 20-40 degrees hotter in intake temps than the stock filter box.  There is reliable dyno data which prove that such systems cause a loss of power.  But more importantly, although the intercooler will remove most of the extra heat, a few degrees hotter IATs might be the difference between detonating or not.

Fortunately, there are some true "cold air" filter systems on the market.  The first is Powersurge Performance's "FASTAir" system ($200 + $175 for cone filter).  The second cold air kit (to the left) is from Johnny Lightning Performance ($275 with filter).  JLP has recently upgraded its filter kits to include the cool perforated filter top shown below.  Volant also makes a fully enclosed filter box, but many people have reported poor results or other dissatisfaction with it.

A true cold air kit can show a dramatic difference in intake air temperatures.  As reported by soap from F150 Online:

Was helping a friend this weekend work on his L.  He has the full PSP Fast Air kit.  I wanted to check out how it worked so when work was done we took a ride up to the local parts store and I did a little data logging.  We drove 3 minutes to the store and parked.  In the 12 minutes we idled in the parking lot the IAT rose from 82* to 146*.  11 seconds after pulling out on the main road (45mph) the IAT dropped to 82* . . . 1* warmer than the outside temp reading of 81*.

FYI . . . I logged another friend's L the same day. All he has is a open element cone filter, no ram air or fresh air kit.  On the freeway cruising at 70MPH his IAT never got below 92*. The outside temp at that time was 78*.

"Ltnbolt" from the F150 Online boards reports on the PSP FASTAir kit:

"had DealerJim's Autotap hooked up to my truck last night. The air inlet temp started at 109 degrees while idling for about 15 minutes while we setup the laptop.

As I drove down the street in the rain at about 40 mph the temp started dropping. After about a mile it was in the high 80's when I stopped to make a turn. In another 1/2 mile it was down to the same temp my overhead thermometer was reading which was 73 degrees.

It would start climbing every time I stopped for a light and drop quickly to outside temp when I started moving again."

"Silver 2000" reports:

"I'm recording just 2 to 10 degrees over ambient in the same temps w/ the stock airbox. . . . w/ the modified stock airbox [holes drilled in the stock airbox] I'm seeing anywhere up to 50 over ambient in traffic and low speed cruising. When on the highway or interstate I'm getting +20 over around 55 to 60 and about +10 over at 80."

On the other hand, Silver 2000 found that a cone-style filter added .2 to the mass air voltage (4.9 versus 4.7), so the cone filter definitely appears to flow more air with a modified engine.

"Wydopnthrtl" reports:
 

"It takes a steady 30 mph to "flush" the hot air from the face of an "open" filter.  I'm not nearly finished yet, but I can tell you already I'm definitely going to end up with an enclosed/fresh air setup.  So far I'm seeing temp differences of up to 50 degrees F (at filter face)."

"Camcojb" collected some excellent data in May 2004:

I had the Swanson $300. open air filter setup with nice billet aluminum MAF adapter and anodized aluminum brackets and air diverter. Very nice quality. I always wondered about the IAT though. So I did some datalogging yesterday and since I thought I knew what was going to happen I had ordered an Airaid system to replace it.

It was 83 degrees yesterday and today when I tested. I drove the exact same 40 mile round trip with a mix of in-town and rural 55-65 mph open roads.

Yesterday I had the Swanson 4" by 9" open K&N filter and their brackets and panels which supposedly block and divert hot fan air from the filter on the truck. Once going and up to temp the IAT1 temps (at the MAF) were at least 17-18 degrees above ambient. The IAT2 temps (after the intercooler) were between 25 and 30 degrees above that. So for a cruise on an 83 degree day the IAT1 temps were at about 100 degrees with the IAT2 temps between 125-130 degrees. This was the best case while at a steady cruise of at least 55 mph and no stop lights. Swanson told me they stay within 10 degrees of ambient.

When you got into traffic the temps rose quickly. Averaged 30-40 degrees above ambient with the below 45 mph heavy traffic and occasional red lights. Saw a high of 130 degrees (47 degrees above ambient!) sitting at a couple of lights. The IAT's stayed about 25-30 above this which put them over 150 degrees at points, and we're not under any boost yet. What surprised me the most was that the IAT1 temps took so long to drop even when moving in traffic. I mean literally miles to get 4-6 degrees of drop. I had to run at 55 mph without stopping for about 10 miles to get them back to 17 to 20 degrees above ambient again.

Today I installed the Airaid. I've heard good and bad, but figured it had the exact same filter as the Swanson and was basically enclosed, drawing air through the (probably) too small factory hole in the fender well. I am planning on adding a fresh air hose to the box for additional cool air, but decided to go ahead and try it just to see if there was a difference.

Same exact route and same temp today so it was a very even comparison. On the open road section my IAT1 temps were within 3-4 degrees of ambient for an improvement of 13-14 degrees. The IAT2 temps were the same 25-30 degrees higher, but of course were lower than the open filter due to the IAT1 temps being so much lower.

In town traffic and stop lights saw the same temp rise as before, but never exceeded 22 degrees over ambient, versus up to 47 degrees over with the open filter. Most of the time they remained 12-15 degrees over ambient. But the biggest difference was in how fast the temps dropped when you pulled away from the light. Before it took miles (literally) to see a 6 degree drop in temps at the IAT1. With the enclosed unit they dropped 10 degrees within a 1/4 mile tops, and dropped the rest of the way to 3-4 above ambient within 1/2 to 3/4 of a mile. HUGE difference as the IAT2 temps are so much improved due to the lowered IAT1 temps.

It's basically like jumping on your truck on a 65 degree day versus jumping on it on a 85-90 degree day. There's (on my truck) a 20-25 degree reduction on the in-town slower speed stuff and 14-15 degree reduction out on the open road.
 

Finally, as well said by Kenne Bell:

"Right there on the list [of most ridiculous products] has to be those "underhood exposed filters" that suck in 200° underhood air instead of ambient (70°-100° air from the fenderwell). 10° air temp rise is -1% HP. That's how dynos are calibrated for temperature changes. Does anyone really believe that all those OEM manufacturers designed expensive plastic inlet systems - for the last 20 years - that pull cool air from the fenderwell, hood or grill because they didn't have anything else to spend their money on?"

The moral of the story:  If it ain't broke, don't fix it.  For stock engines, the stock airbox is fine.  For modified engines, the PSP or JLP kits are the ticket.  All other cone filter setups are suboptimal.

For those who say that it doesn't matter, ask them why Ford's own performance filter kits (like the 05-06 Mustang kit to the left) have heat shields.

Before I decided to go with the Johnny Lightning filter--not for performance, but just because it looks good, increases the delightful blower whine, and is easier to clean with the optional "Outerwear" filter cover.

Another option is to add a simple cold air duct to feed the stock airbox (with stock paper filter or K&N).  The flange pictured is a header flange with a piece of 3" pipe welded to it.  Parts are available here.  One Lightning owner who added a home brew cold air reported a before-and-after times of 13.64 @ 99 versus 13.53 @ 102!
 

The ultimate cool air intake has to be the Keystone Restyling shaker hood shown below.  The Keystone shaker ducts air from the scoop through a series of channels, which then opens just above the air filter.  Cool.

My shaker hood airbox is shown here.