[gravelled]

The ads for K&N, Poweraid intakes, etc. state I can get better gas mileage and HP by installing their products and letting "cooler air" / "more dense air" into my intake.

The "cooler air" angle must be a promotion gimmick. I understand how increased performance occurs when your engine breathes better which will happen with these products. This is common sense.

But if cooler/more dense air is a plus, then shouldn't I get more MPG and HP when driving in the cold winter air without changing anything? Are you guys getting better mileage and HP in the winter?

JP

[horatio102]

The gas is different in the winter... different formula, etc. Usually my economy goes down.

[bcompton]

My apologies if this posts twice - it hung up after I pressed the submit button before...

Yes and no.

Colder air is more dense. More dense air means the engine increases fuel flow to maintain air/fuel ratio. More air and fuel means more HP, if everything else is the same.

More air and fuel doesn't necessarily make your engine more efficient, so there is no guarantee about MPG. Most likely, you will drive like you have more HP (i.e. more aggressively, because it's fun all of a sudden) and your MPG will decrease.

K&N setups, along with all free-flow intakes and exhausts, do decrease the amount of work the engine performs to breathe. From that there is a minor increase in MPG and a noticeable increase in HP. Their new cold air setup is designed to draw more from the outside and less from the engine compartment, and that's where they are getting cooler air. Hot rodders have been doing that for years and it does work. Just remember, you are giving up the water trap of the factory air box when you go to a cone filter....

[GW]

Cold air does actually increase power somewhat. An old drag racers trick is to place a bag of ice on the intake manifold before 1/4 miles runs to cool the fuel air mixture. I had a Mustang GT that I added a psuedo ram air kit (open air box) and the car always ran a little stronger in the colder days than the hot humid days. I don't have a technical explanation, but colder air does work better than warmer air for producing power.

As for K&N, take their claims with a grain of salt. Adding a K&N filter alone will in no way lead to a significant increase in hp. You may realize 3-5 hp at high rpms at the very most. The only real benefit to adding just a K&N is that its washable and last for a very long time. If you do a lot of dusty off roading, it will save you some money in the long run.

For real hp, you will need to add a K&N and an open air box. That way you will see some more hp. The key is to make sure the open air intake is shielded from the hot engine air. If it isn't, when the motor gets up to operating temp, it will just be sucking in hot air from under the hood which really defeats the purpose. It needs to be routed as far away from the engine or shielded on one side. Remember the old muscle cars with the hood scoops, and air cleaners than sealed to the hood when closed. That was a great system since its always cold air, not hot engine compartment air.

As to how much hp increase, who knows. What you do get is more noise on acceleration. A lot of guys make this mod, hear the noise and think their cars much faster - the seat-of-the-pants-o'meter! There is some minor hp improvement, less that 10 I would guess, but nothing dramatic.