OK, I see Hot AI and Cold AI. What's the difference? What do they do? what is the impact (how much HP do they buy)

 

One has a heat shield to protect it from engine heat, and the othere allow the hot air of the engine to acess the filter, they are little different in terms of end HP. A good CAI will insulate the intake so when sitting the filter and air a round it stays cool hypothectially giving a little more power off the line, and theoretically give you a litte more power across the borad but nothing significant enough to be more than theory.

 

Thanks. So, what is stock on an MCS? HAI or CAI? Does anybody have photos showing installations of both?

I'm a long ways from doing this, just thinking ahead...

 

The stock would be considered a cold air, completely sealed intake, though not a high-flow system.

Most aftermarket intakes are higher-flowing than the stock box. When you get colder, denser air, and more of it, that translates to more horsepower, because there is simply more oxygen in your engine to combust. A bigger bang means bigger power.

Simple, eh?

 

As a question along the same lines, if a new aftermarket cold air is installed on a MCS adds HP why doesn't an MCS have more HP in cold weather compared to warm weather. I am talking say 32 degrees vs. 80 degrees. At least I have not noticed any difference in HP between those conditions.

 

It would seem the more important aspect of an aftermarket intake is the flowrate of the air. The stock box is pretty restrictive. If you slap on an Alta intake you are going to be getting more air into the engine, hence more HP.

My totally amatuer opinion on the 32 vs 80 degree thing is that once the car is warmed up, even in the cold, the temperature in the engine bay is still hot. This would dimish the difference between outside temps being wintery and springy.

 

It does make more power at cold temps, but the difference is only a couple of HP. And unless you have a really well calibrated butt dyno, you won't notice.

I more noticible difference is going from low altitude to high altitude.

 

The cooler air compared to hot air out of the engine compartment is denser, meaning that there is more oxygen per volume. Fire loves oxygen, burns hotter.

When you are walking on top of a mountain you run out of breath sooner (less oxygen) than when you're walking on the beach (denser air, more oxygen).

 

My butt dyno (which is the super deluxe version with 10x the instrumentation of normal sized ones) can definitely feel a difference in cold vs. warm weather with my Dinan intake... which I would think would be the case for most any aftermarket intake once the "bottleneck" of the stock intake is removed...

More air = good
More colder air = even better

Think about it a minute - if colder air didn't matter, folks wouldn't be adding water sprayers and bigger intercoolers... unless they're just idiots supporting the cause...

I personally think sometimes folks get a little carried away with the metric of horsepower... my butt dyno feels some amalgamated souffle of HP, torque, throttle response, etc.

Just because something (a mod, colder air, etc.) only yields x amount of additional peak horsepower on the dyno, I do NOT personally believe that means it MUST yield a negligible real-road difference. In other words, I really believe some things can have a significant impact on REAL perceivable driving "performance" - but not necessary move the HP curve much...

Am I alone on this?

P.S. I know this is counter to the "show me the numbers" view of performance...

 

Cold air sure does matter. The intercooler's job is to extract heat out of the intake air. When you have a very efficient intercooler, the difference in outlet temps between the HAI and CAI becomes negligable. Its in systems without intercoolers where air intake temp is extremely important.

The theory behind the HAI is that minimizing the pumping losses associated with all that CAI tubing outweighs the small bump in temp compared to a CAI. There has been a lot of testing and research done on this idea since its submission and there are people in both camps. I guess you have to do your own research and decide whats right for you.

 

Agreed - with a perfectly efficient intercooler (which would cool post-intercooler air to outside ambient temp anyway) then CAI vs. HAI is moot. But with the stock intercooler, pumping in air that's significantly cooler (maybe 20+ degrees cooler?) has got to make a difference IMHO.

And with all things being equal (SC, intercooler, intake), colder outside ambient temps will yield colder post-sc air temps methinks - which is a good thing...

 

Thing is though, this is still limited by the ECU's programming. More oxygen, the fuel burns leaner, the O2 sensor will pick up more O2 in the exhaust, which will then compensate by adding more fuel to the mixture, and you're back to the programmed mix. IMO, the biggest impact is with a less restrictive design. CAI helps by keeping the intake temperature more even, but the ECU will still fight to keep the mix "ideal".

 

Have to disagree here. Hotter inlet air to the SC means each rev of the SC pumps fewer O2 molecules. There is a benefit to feeding cool air to the SC, that the IC cannot compensate for.

That said, I am a fan of the HAI. Properly baffled, it runs only a few degrees above ambient, as long as you stop only for short periods (less than about 1 minute). Combined with the low pressure drop, the HAI is a great mod in terms of both cost and performance.

 

Good point. Cold air = good. Even if that cold air is coming from an HAI...

 

More oxygen creats a stronger detonation in the combustion chamber. IE: Nitro fuel carries more oxygen with in the fuel itself than gas. It creates a much stronger detonation, this is why Top fuel motors make way more HP than their blown (supercharged) gas counterparts.
With more oxygen rich air going into the motor the ecu can add more fuel to be burned..More Horsepower!