Cai

[Jet321]

Will a cold air intake boost MPG's? I've been thinking about getting one but haven't been sure, I know chromeintakes on ebay has a nice one, opinions, thoughts?

[charlieb]

you dont normally get any better mpg with a cai.most people use them to increase(minimal at best)horse power but it has to be matched up with a proper exhaust to make any difference at all.keeping a vehicle properly tuned and maintained and staying off the skinny peddle on the right is the only way to save mpg.

[ArizonaAVEO]

I purchased a CAI for my Hemi Ram a month ago in hopes to get my MPG to a level where I could stomach driving 90 miles/day with it. It brought me from about 15.5 average to 16.5 average. Which is why I'm purchasing an Aveo next week. My experience is that CAIs increase performance but not so much MPG. Maybe because your foot gets a little heavier knowing there's extra horses under it, but even with cruise control I couldn't squeeze as much MPGs out of it as I would have liked. And that is also with a high performance exhaust. I agree that keeping it maintained and tuned as well as proper air pressure in the tires is your best bet. It will take a very long time for the CAI to pay for itself with fuel savings.

[charlieb]

I purchased a CAI for my Hemi Ram a month ago in hopes to get my MPG to a level where I could stomach driving 90 miles/day with it. It brought me from about 15.5 average to 16.5 average. Which is why I'm purchasing an Aveo next week. My experience is that CAIs increase performance but not so much MPG. Maybe because your foot gets a little heavier knowing there's extra horses under it, but even with cruise control I couldn't squeeze as much MPGs out of it as I would have liked. And that is also with a high performance exhaust. I agree that keeping it maintained and tuned as well as proper air pressure in the tires is your best bet. It will take a very long time for the CAI to pay for itself with fuel savings.

if u want hard core gas savings dont go with the aveo get a vw tdi (3x mpg over the aveo)

[JPD]

The new Aveo (non-sedan version) is sold in the UK with a 1.3 VDCi diesel managing 95g/km and 78.5 mpg but isn't available in the US. I have the old Aveo (1.4 sedan) and a simple drop-in K&N replacement filter (33-2320) improved the economy from 33mpg to 35mpg, thus paying for itself ($40) quite quickly.

[jriggs87]

I agree with JDP, it is minimal but since your engine works more efficiently and uses more dense air, you dont have to use as much "skinny pedal" (charlieb )

[wylee]

If a CAI works as the name implies, MPG will go down. Cold air is more dense and requires more fuel to maintain the air/fuel ratio. Some hypermilers like SRI's since they pull warmer less dense air from under the hood.

[jriggs87]

I forget who spoke about it, and it has been talked about in alot of other car forums, but alot of people have been able to use less throttle with cai to go the same speeds as you would normally with stock filters. Colder air doesnt mean more air, just better air. I may be wrong, i would think an SRI would need more fuel because as that name would imply, you are 'ramming' the air into the engine instead of letting it flow in. take for example forced induction, if you supercharge, you will need to up the fuel amount being produced. with a cai, you dont need to improve fuel sending, because you are getting the same amount of air, just cooler air. of course with a better filter, more air can be let in, but not enough to need to change fuel amount sent to the engine.

[Daox]

Ram air is for all intents essentially bogus for street cars. At the speeds our cars travel you don't get a significant pressure build up in an area to force air into the engine. At most you might see a fraction of a psi (1/2 psi would show a ~3% increase in power woohoo). To get this pressure build up you would have to place your intake right at the front of the vehicle pretty much in the bumper at the stagnation point (the point where air flow seperates to go above/below the vehicle, its the highest point of pressure on the vehicle).

Wylee is pretty much correct. While it does have to do with air density, it doesn't really have to do with more air = more fuel to maintain a/f ratio. If you get more air your engine will compensate with more fuel, but that means you'll be making more power and that also means you'll be accelerating. In that case, you'll simply close the throttle a little to maintain speed.

In general, warm air intakes are usually good for mileage and bad for power. The warmer air is less dense, this means to get the same amount of power out of the engine, you need to open the throttle farther than you would if the air was colder. When the throttle is open further, the engine doesn't have to work as hard (think of trying to drink through a straw vs a straw that is partially blocked) and this makes it run more efficiently. Warmer intake air also helps increase flame speed inside the combustion chamber which also increases efficiency.

Cold air essentially does the opposite. In general, CAIs are good for power, and bad for mileage. The intake air is more dense and therefore increases the maximum output of the engine. For every 5 degrees F lower temperature you gain roughly 1% more air (read ~1% more maximum power). More air in the engine means more power.

Ideally, cars would have two intake tracks so you could have the best of both worlds. One would suck air from the front of your vehicle and one would suck air heated by your exhaust or coolant. You would have a computer controlled actuator to choose hot/cold depending on how far down you're pressing on the gas pedal. I think Volvo even did this back in the day. However, the additional cost must not have been worth the trouble as I don't believe they still have these systems. Now a days, all car makers plumb their intakes to cold air (there are a few exceptions) to inrease engine output as much as possible.

[jriggs87]

interesting... how would you explain how people say when they installed a CAI that at the same speed as they would a stock filter set-up, they are able to use less of the gas pedal, giving them better mpgs. I just feel like, for example the late model pontiac firebird with the big hood scoop and ram air induction, would need more fuel to be able to balance the A/F ratio, where if the induction was not forced, would not need to compensate with more gas.