Cold Air Intake - anyone using one?

Discussion in 'Toyota Prius Family' started by zm15, Apr 6, 2012.

  1. zm15

    zm15 Member

    I'm looking at the Injen Cold Air Intake, part #SP2090, to increase horespower and MPG.

    Has anyone installed a aftermarket air filter in their Prius? And if so, did you see any MPG improvements??
  2. RedylC94

    RedylC94 Well-Known Member

    A cold air intake system will hurt MPG, especially in winter.

    I don't have a Prius, but believe an aftermarket air filter is very unlikely to help MPG of any modern car.
  3. JusBringIt

    JusBringIt Be Inspired

    I don't think it will hurt your mpg, as I have one on my eclipse. I can't state for sure however, but I wasn't about to complain about 48mpg in a car rated 23mpg combined. The cold air intake will not increase your mpg however.
  4. herm

    herm Well-Known Member

    coal air intake increases air density, thus more oxygen, more fuel and more power.. if you want that stuff.. hot air intake means lower density and lower pumping losses .. higher MPG since the engine will act like its smaller.

    You will also get pinging if the timing does not self adjust.
  5. PaleMelanesian

    PaleMelanesian Beat the System Staff Member

  6. JusBringIt

    JusBringIt Be Inspired

    It's really not that simple. You have to take into account engine loading efficiency, driving conditions, driving techniques, etc.
  7. herm

    herm Well-Known Member

    I like to simplify things..
  8. JusBringIt

    JusBringIt Be Inspired

    Paper filters are used to reduce noise. Some cars have a MAF sensor, others have a MAP sensor and this alone changes results in some cars.

    Simple is good, but sometimes will leave out plenty of details that could in particular sway the impending decision one way or the other.
  9. herm

    herm Well-Known Member

    a little plainer then, all things being equal:

    1. cold air intake = more power

    2. hot air intake = better economy
  10. JusBringIt

    JusBringIt Be Inspired

    There we go :D
  11. phoebeisis

    phoebeisis Well-Known Member

    There isn't any reason a cold air intake would improve part throttle FE in a modern spark motor car .(even if it actually worked- brought in cold air,and didn't foul up any intake tuning the OEM engineers did)

    If it actually did what it was supposed to it would improve volumetric efficiency at full throttle-more full throttle HP
    But no reason it would improve part throttle FE-
    If it lowered resistance before resistance before the throttle plate- the throttle plate would just be closed a bit- because you only "need" a given a fixed amount of air for a fixed RPM and load.
    If you don't shut the throttle plate-then you get more air and fuel-and you accelerate-which you don't want.

    Now if you had infinite gearing-and no lugging considerations-maybe it would help
    But lugging and gearing are always

    Besides if the Prius engineers could get another .25 mpg by a simple filter intake change

    The OEM engineers are better-and have better testing equipment-than the after market engineers(better in respect to FE MPG)
  12. JusBringIt

    JusBringIt Be Inspired


    The reason for the lower flowing filters lies in the fact that they are much quieter than aftermarket filters. For increased flow, you could simply increase the surface area of the paper filter and still have quietness. That said, I believe the engineers tested this and balanced cost with efficiency.

    I'm basically saying they didn't add anything they need to that wasn't economically feasible. In WOT conditions, an aftermarket filter MIGHT improve gas mileage, but only if there are other modifications that assist on the back end. The restriction posed by the filter prevents the intake manifold from reaching a higher relatively pressurized state. This limits power output by limiting the amount of fuel that gets into the cylinders. Less fuel into the cylinders at WOT means a "leaner" mixture. A lower resistance filter has an even leaner mixture, but as you improve the flow capacity of your paper filter, that resistance gap narrows.

    If you just go out there and buy a K and N filter and drop it in your box, no mpg increase, marginal power increase at WOT depending on results from the cost benefit analysis of the paper filter the manufacturer used.
  13. I didn't think a k&n filter swap was a "cold air intake".

    For example, for my truck yes, k&n makes a replacement filter. But a few companies make a cold air intake with a scoop that sucks air from under the bumper.

    "cold air intake" not the same as a k&n filter swap.
  14. RedylC94

    RedylC94 Well-Known Member

    True, but ZM15 asked about cold air intakes AND about filter swaps (without naming any particular brand).

    Not to name names, but some low restriction filters have been known to allow too much dirt through, which will wear out an engine before its time.
  15. worthywads

    worthywads Don't Feel Like Satan, I am to AAA

    CAI is most often a misnomer, most are just a short tube with heat drawn from engine compartment or more of a WAI. Both my Tacoma and wife's Element are more CAI than these CAI. None of these hold an air tight seal from the engine compartment.

    From K&N

    "We certainly understand why it is theoretically possible for a consumer to experience a mileage increase after installing a K&N air filter or intake system, however, we do not go so far as to make a general claim that our air filters and intake systems will provide an increase in mileage."

    This report is very convincing to me that even the dirtiest air cleaner will not hurt the driver looking for max mpg. I've decide 60K intervals on my air filter! :eek:
    Last edited: Apr 6, 2012
  16. Wonder if they did the diesel filter test.
  17. Rackster

    Rackster Well-Known Member

    I'm a CAI skeptic. There was a time when such designs would support improved performance (HPs and MPGs), but unless you are driving a very old carbureted vehicle (with a scoop perhaps), then sticking with the OEM designed solution is the best bet.

    The interesting thing about K&N is that they are very careful in their wording; dancing on the fringe of making a claim, but not making it. Given that they aren't in a regulated environment, it's almost commendable. They leverage the consumer testimonials with precision; they make the claims the manufacturer will not. The issue here though is that finding credible objective evidence to support the testimonials. K&N publishes plenty of test verification data but browsing the internet doesn't yield much in the way of credible corroborating verification data. And validation data...none that I could find so far. Some interesting attempts out there, some are pretty decent, but aren't very scientific.

    From my perspective, folks are better off enjoying their vehicles as designed by the OEM manufacturers. Even with the manufacturer's verification data, the increases are so marginal, I think most folks wouldn't justify the expense.
  18. RedylC94

    RedylC94 Well-Known Member

    I'm skeptical that CAI would improve fuel consumption even with a carburetor, in most cases. Thermodynamics are against it. It really will increase power.

    worthywads: Some OE intake systems draw air from a fender instead of using hot under-hood air. However, the plumbing between the fender and the engine may not be insulated, so ...
  19. worthywads

    worthywads Don't Feel Like Satan, I am to AAA

    I see a 2-3 F difference between ambient temp and the intake air temp on my scangauge. I'd prefer a WAI.
  20. Rackster

    Rackster Well-Known Member

    You are probably right. Thinking back to the cars of the 50s and 60s, often times the ram air ducts were insulated; the colder the better. And back then, at a dime or two a gallon, FE was not a concern.


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