I've read many threads about the Cold Air Intake system (CAI) on many website and there seems to be almost as many different understandings, beliefs or discriptions of the definition or understanding of this as there are members writing about it. Am I correct or not … Cold Air Intakes (CAI) draws air taken from a source of the locally ambient air of the region and stays taking air from this ambient source during the engine operations, and is constant to this local environment, which is non-changing except by atmospheric changes. If so, then inside the engine compartment, where the temperature is constantly changing as the engine builds heat while running and preforming it's function … is not the local ambient source of cooler air.If this thought is correct, then there are limited true CAI's on the market for our trucks. From what I have read and understand:a) the original vehicles air filter system which 'only' draws air from the fender well and not from the engine compartment is the first true CAI system.b) the next system developed (it looks like in marketing dates) would be the Banks designed system with the filter housing drawing intake air from the fender well and from below the front bumper and nothing from the engine compartment.c) the next system appears (it looks like in marketing dates) developed and put on the market would be the S&B system with the similar design as the Banks and nothing from the engine compartment.d) somewhere between the 'a' and this point will be the Home Depot style system, since I can not find the oldest time frame someone design / installed one with no air from inside the engine compartment.Anything else would seem to be considered an 'air intake system' or I guess would be labeled as (AIS). Taking the source of air from inside the engine compartment AND with outside the engine compartment air swirling in it's enviroment. Restrictions to these system would be:1) Blockage to the opening of the air box, like the opening to the fender well to the air box, and if an extension is added, to that.2) A dirty or restricted filter.3) Blockage to or in the tube from the air box to the closest intake portion of the engine, turbo, carburetor or injection intake, ect.If I'm even somewhat correct on this, it confuses me on the many argument / discussion to this topic in so many websites. If I'm not even somewhat correct in this, them I'm just as confused as the rest. I'm old, bare .. with me ... Your opinion / thoughts ?(I forgot to mention the Volant CAI system. It appears they do not sell many since most truck owners do not want to loose their passenger driving light with their fender intake tube).

But there is missed problem with cold air intakes...In any case cold air intake do bring in cold air to the engine but how cold do you really need it? Like I'm up here in Idaho and can pull my manifold temp well into the +20*F bracket on a -25*F day. I find that temps below 100*F (or 60*F weather) in the maniold tend to hurt MPG. Colder the air becomes the harder and later the fuel ignities hence why on the VP44 truck the engine rattle heavily in the cold morning because the ECM kick the advancement way up to compensate for the cold and latency of ignition.Like I found out after 2 years of studying the IAT sensor and its function... You want warmer air to promote ignition of the fuel for better MPG's. Also if you running a box like Edge or Quadzilla you'll get more timing with warmer manifold temps hence better MPG's (Confirmed from Quadzilla Techs).Like myself my IAT is permanently fixed 143*F and my MPG's are roughly 20 MPG even with winterized fuels, temps as low as 0*F to 10*F above. Also I'm running a winter front trapping warm engine heat under the hood for the BHAF to draw in. Give about a +10*F gain on the IAT temps in the manifold vs. without a winter front.Winter weather no longer has a effect on my MPG number any longer...

Not arguing your findings, it seems you have documented proof and is accepted. You don't need or want a CAI in your terrain. It benefits me in my environment. There are more terrains then the north 40.After reading many articles / threads on this, here and other sites, there seems to be a confusion on a true CAI, it's benefits and restrictions.

It more of finding what makes the better MPG than the most HP/TQ... I know with each and every truck seem to be a bit different in what it likes. So it more of a matter of monitoring the IAT temps and seeing which temp nets you the highest MPG value. Since we know you truck most likely is not going to run 1/4 miles track it going to be a daily driver right? So MPG value is going to the number to chase not the HP/TQ number. As for the rest of the system of the tube, filter, etc... There is a lot of claims of flow and such but once again you not running track so your air flows will be much less and short burst for WOT. Like my typically driving I see about 2-5 PSI of boost. I'm capable of 35 PSI but rarely need it even towing.

Ok, I'll accept it, I'm not on a track, haven't been on one in 35+ years, and now don't want to be.As in the beginning of the thread, wanting one or not, is this the correct understanding of a cold air intake system ?

I can see what the issue is with what.people call a CAI. You are correct on all your thoughts. People who ditch the stock box for a BHAF are now sucking in warmer air, definitely not a cold air intake. I think the origin began with rice burners putting pvc pipe up to a void in the engine compartment that happens to be on the front end in a spot that cold air blows directly on it. On our trucks there is a space like that between the headlight and radiator. It is small but you can see what they are trying to aim for. Most cars these days come stock with true CAI's. They have a pipe run straight to somewhere on the front that inconspicuously draws cold air and even has a RAM air effect. My moms camry has this, stock. Now drawing from the fender isn't exactly a CAI. The fender can get slightly warmed up and heat the air or the fender could be drawing air from a hot source. This would all be negligable heat vs. a true CAI. On our trucks, it is pointless. I have a sensor on my BHAF and the most I see is 20F over ambient going uphill with a trailer, most times it is 0-10* difference. That little difference is quickly diminished by the turbo compressing/heating the air. Then the intercooler takes it back down to ambient. Nothing is gained from a CAI in the end. Scientifically, colder air in and hotter air out is the key to efficiency. I didn't run a winter front at 10* and the mpgs were the same but the power was definitely higher. It is the intercooler that does all the magic, not the intake. The intake might matter if it was 50* or more than the ambient, and even then I have doubts, the intercooler does its job very well.

Actually your right, I didn't factor in the possible heat migration from the engine compartment to the inner fender well. But it seems if there is an increase it would be insignificant at most. This being the fact that with movement, the air should cool sightly. Though the sunlight shining on the fender will warm it some also. Once stopped, say at an intersection, it should increase quickly on a hot summer day with a hot engine. So even the original factory install is not even classed as a true CAI ... close but not a true CAI system.

I have had CAIs on Performance Cars (gas) & even trucks got into the act in 60s & 70s. Not sure it did anything on the street but it did in race cars. The problem is that these vehicles are naturally aspirated gas engines. Diesels fire from the heat of compression, & a whole lot more pressure. Super-chargers & turbo-chargers are a whole different ball game where even more heat (of pressure) is added to the air mix prior to entrance into the cylinders. Enter the Inter-cooled, turbo-charged diesel. The intercooler gets rid of most of the heat prior to entering the intake. Lessons learned from gas engine, naturally aspirated race cars of the past really no longer apply. Guys keep buying CAIs because they don't understand our diesels. I am also running an IAT (sensor) fooler on a switch. In cooler temperatures it's worth about 1 mpg to me.

Guys keep buying CAIs because they don't understand our diesels. I am also running an IAT (sensor) fooler on a switch. In cooler temperatures it's worth about 1 mpg to me.

All those 1 MPG gains add up quick...