The "CAI" is NOT a "performance" modification.

Discussion in 'Fox 5.0 Mustang Tech' started by DMAN302, May 4, 2005.


  1. jb89coupe

    jb89coupe New Member

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    I agree that a mac/bbk fenderwell style cai setup really has no advantage over the stock box with a free flowing filter. The one possibility being the inside of the tube is smooth and rigid whereas the stock tube is ribbed and flexible. However, there is clearly a gain to be had over an open underhood air filter.

    When I bought my car it had the stock air tube/mas going straight to a giant k&n filter. The car would bog once it warmed up and never ran quite right. I picked up a densecharger cai kit cheap and it DEFINATELY made a difference. I'm attributing this entirely to the change in air temperature to the engine. None of you can tell me you don't notice a difference in how your car runs on a cold fall night compared to a 100* summer afternoon. As noted already in this thread the stock airbox ALREADY DOES THIS and the only real reason to switch from the stock setup to an aftermarket cai is for looks. With that said I think a mac cai or powerpipe (which I have now) both look 10x better under the hood than the stock setup, and I have no regrets about buying them or listing it with the rest of my mods.

    Also, I think a lot of times folks will upgrade their mass air sensor and throw a cai kit in the car at the same time, and attribute the gains they feel/see to the cai. Most likely they're noticing the improved response of the sensor.
    #81
  2. dvs bullet

    dvs bullet New Member

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    I totally agree with this comment. The people that make these products will not tell you the whole story either, prime example is "It makes 20 Horse over stock systems" well what they aren't telling you is they are probably still using the intake silencer, with a regular paper filter. Also What engine are they using, like is heavily modified or stock?
    #82
  3. deadlast

    deadlast New Member

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    i only have it in my sig because i dont have any mods :( yet and makes me feel big. however, it did add a nice sucking sound when i step on it
    #83
  4. speed1972

    speed1972 Founding Member

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    And I suppose because I painted my car and included it in my sig that it must have added at least 50 horsepower because it is so smooth now....

    Its a signature block, not a power improvement parts list..

    And for the record, I added one because I like it and if it is worth 2 extra hp then that is 2 more hp than the guy next to me :)
    #84
  5. BLOWN 5.0 FOX

    BLOWN 5.0 FOX Member

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    Bottom line- use good judgement and take the "HP RATING" of most aftermarket and divide it in half. I have found that is a good theory to go on. Obviously companies test their products on a wide variety of engine setups to see what creates the best flow increase over a stock setup. Also there are reputable companies out there that engineer great products and have valid data to back their products up with. After doing a little reasearch you can get a pretty good idea what an actual gain might be.
    Its true,The stock air silencer is restrictive and is a known mod (along with replacing the paper element filter) that benefits the lungs of your mustang. But personally , I prefer forcing air down its throat :crazy:
    #85
  6. Idwitheld-1`

    Idwitheld-1` New Member

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    Each bend or elbow changes the flow characteristics. Bends or elbows are rated for equivalent loss length. For example a 45 degree elbow might represent the equivalent of 6 feet of pipe.
    Sweeping or radius bends are best. Smooth walls are better than "kinked" or ribbed walls.


    The effectiveness of a plumbing system (CAI) could be easily measured with a differential magnehelic.
    #86
  7. 5spd GT

    5spd GT "the 5.0 owns all" Founding Member

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    I have never believed the 45* bend theory equals X amount of feet...I just don't seeing that being feasible. Not 6ft. anyways. Plus their is not "true" 45* bend anyways...it is a sweeping bend...air can contort pretty well believe it or not:nice:
    #87
  8. seijirou

    seijirou Founding Member

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    What you have to understand is CFM is more than a measure of volume, or a measure of rate. It's both, in context of distance. Something that moves 50 CFM over a distance of 3 inches (like a throttle body) isn't moving the same amount of air as moving 50 CFM through somehing 12 inches in lenght, like an intake tube. If that 12 inch pipe can only move the same air as that 3 inch throttle body, the pipe will be more like 45 CFM than 50. That's a loss because of the length of the tubing. It goes that a 12inch pipe with a 45* bend is comperable to a longer pipe without a bend, in the context of CFM over distance.
    Disclaimer: The numbers I use are purely out of my arse and are just there for example, not to be taken literally.
    #88
  9. vristang

    vristang Advanced Member

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    Bends of the proper shape and size will improve flow compared to improper bends. This is by increasing pressure for a change of direction in airflow. The added pressure will help air change direction better than high flow.

    This is, atleast partly, why a bad head job can perform worse than the original ports.

    I don't think it is unreasonable to see gains from the CAI, but there are far too many variables which will influence the outcome to be able to accurately predict hp gains. I am looking for one as I rebuild the motor. Maybe not much power to be found but it will look alot better than what I have now.
    My .02:D
    #89
  10. StangLou

    StangLou Active Member

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    Why cant both sides be right :D.

    Lets take installing JUST a cai on a STOCK '88+ fox body. Say its a fenderwell mount system, and this is your very first mod you are doing to the car. You take off the factory tubing, air box, and silencer. You install the new tubing up to the tb, install the factory mass air meter, and then install you new air filter be it bbk, k&n, whatever. Honestly if you put it on the dyno, you may pick up 3-5hp if your lucky.
    What have you done? You have attached a slightly larger pipe to the stock tb, and stock mass air meter. This may or may not cause your sensor to go whacky. Some it does, some it doesnt. I know a few guys that had to rotate their mam after these install. All things taken into account, you now have a nice free flowing air filter attached to the stock mam which goes to a larger than stock pipe, up to the stock tb. Your "weak" link in this is the tb now. You have increased air flow to it, but its still "bottlenecking" at the stock tb. Also you may have slightly increased the amount of air that can get to the tb, but the velocity of the air will still be very similar to what it was stock.
    Now lets say you have an '88+ fox body with L/T's, Mid pipe, pulley's, h/c/i combo, 70+mm tb, and mam calibrated with 24lb injectors for the heck of it. Hell you may even have a s/c on it. You now have a very free flowing air intake track, and engine work that can make GOOD use of extra air. If your s/c you are also GREATLY increasing the velocity of air going into your engine. In your moddig frenzy you forgot about the ever so popular cai. You run out and buy it!!! You install it and low and behold the adds were close to right, you have picked up maybe 15+ hp.
    Its all in context really. Most companies dont tell you their gains are on s/c cars, or cars that are heavily modded. Is this misleading... yes, but not an inaccurate discription of the "performance" part. On the right combo it may yield those gains. More than likely you will never see gains like that on a stock car.
    Now you have the is chrome really a bad idea for a cai. IMO short answer is no. The air isnt just sitting in the pipe getting all nice and toasty. The air is being pushed through pretty quickly into the engine. The chrome cai would have to blistering hot and you would have to be in VERY dense/slow moving air for it to really affect the performance of your vehicle. I have a chrome bbk piece on my '03. Ive driven it a few hours and felt it, yes its hot, but so is every other part on the engine. Also if you take the car to the track, I have noticed that the chrome ones can really hold cold air as well. I can ice mine down for 30-45+ mins, make several runs back to back, and I can sit my hand right on the cai after I pop my hood, its even still felt a little chilly before.
    Anyways, my book is finished lol. Enjoy!!! Ill be signing autographs at the mall next week!!!
    #90
  11. 300bhp/ton

    300bhp/ton New Member

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    I may be entering this conversation late, and I know I don't have a 5.0

    BUT I think some clarification is needed. And basic engineering prinicples.

    An engine will require an air flow rate of X amount. If the standard airbox setup can supply this amount of air flow then any CAI and filter combo will not help in this area. As an engine will only ever flow as much as is needed. If the stock air box is restrictive (V12 Jaguar XJS for example) then a larger filter/intake path will help as it will allow a greater flow to the engine.

    To visulise, imagine at WOT (wide open throttle) and engine requires 1 pint of water, if the glass is to small it will not be able to hold enough water, if it is bigger than a pint you will not see a benefit as the engine still only wants a pint, the rest of the glass would be empty.

    By changing items such as exhust and cams and better flowing heads and things like throttle bodies you can make an engine require a greater air flow (using the above example it would know need 1.5 pints) so the stock 1 pint class can no longer supply enough. A TB change on its own may offer nothing if the intake can not flow sufficiently for it, OR the engine does not require the extra flow rate due to limitations in cam profile, head flow, timing, etc.

    Some cars will have restrictive airboxes in stock trim, some only once the car is modified. Yet some still maybe ok even for heavily modified engines.

    More proof is 'air flow restrictors' as used in rallying and racing (such as GT racing), this simple item limits how much air can be flowed into the engine, thus limiting how big a bang can be made in the combustion chamber, limiting the amount of HP produced. This is done so that cars like a Ferrari F360 with 3.6 litres can produce the same BHP and compete with larger engined cars like the 5.7 litre Corvette.

    The only way to get more air into an engine is through Forced Induction (FI), this increase the charge densisty, not the flow rate. The engine will still be requireing 1 pint glass of water, BUT that 1 pint glass would contain 2 pints of water due to it being compressed.

    The so called RAM air hood scoopes offer little gains, because as explained above the engine will not increase its flow rate above what it can handle, the only gains a hood scoop will make is at high speed where the air hitting the inside of the scoop will be slightly 'compressed' increasing the charge density, although I doubt you will see any gain this side of 80mph, and only a very small gain at speeds of 150mph+. A hood scoop will also cause drag and make the vehcile less aerodynamic with a greater drag CO.

    Another take on ram air is the ram pipes (bell mouths) inside the intake manifold, if these are harmonically balenced they will aid in air flow causing less turbulance (in the same manor as a note is played from a brass instrument like a trumpet). Again the only benefits you will see is if the stock setup is restrictive to begin with.

    As for the ducting, yes a smoother less turbulent setup should in theory help, but the gains will be so limited and the rest of the system would need to be optimised to take any benefit. The material will probably have little affect either, as the air moves very quickly along it, the only time it may be of concern is on a very hot day with a heavily heat soaked engine bay. BUT once you start moving the air should be cooled down to ambient temperatures anyhow. An as you will not be able to reduce the temp below ambient it will make little to no odds what the tubing is made from.

    The rule about air temperature is simple, cool for power (maximum charge density), hot for economy (minimum charge density to reduce losses due to throttling). With regard to the V12 XJS the standard arrangement is much better than many people think. Sure, the under-bonnet air temperature at idle can easily get up around 70 C but the faster the car goes the lower the air temperature falls - simply because the radiator is passing its heat to a much larger quantity of air per second - so at 80 m.p.h. the engine is breathing air at around 45 C. That's still a bit higher than the ideal but not nearly so bad as many people think. This principle is the same for ALL internal combustion engines.

    As for the shape of the tubing, well the air is being drawn by the engine, not pushed from the out side, so bends (providing they don't reduce the diamter or cause turbulance) should not affect the air flow. To try it out, get your vacuum cleaner with the pipe extension on, switch the unit on. Holding it out straight (no bends at all) then turn it through 180 degree bend in the pipe. It should still be sucking at the same rate, there should be no noticable difference.

    As for the dyno runs, well to be completly impartial you would need to compare a fully functional factory setup (ie not an old dirty filter and a possibly leaking air ducting setup) to a new CAI. If you have a 5.0 it will probably be a good 15 years old by know, so by replacing an old and dirty (blocked) fliter with a new cone setup should see improved performance, but possibly no more of an improvement over replacing the old filter with a new stock one. Tests done on this basis are NO proof that a CAI works on a stock 5.0

    I am not say that a CAI will not yield better numbers, just mearly the possibility that they will not be any better than a stock setup on a stock car. If you want one, I say go for it. If not don't worry and buy something else instead. Because even if it does make a difference it will only be a small amount over good (ie clean/new filter) stock setup.

    Hope this helps.
    #91
  12. willys1

    willys1 Banned

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    Ive been away for a few days.I'LL check my mail and clean out my PM box :D
    #92
  13. willys1

    willys1 Banned

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    Holy cow,those are Daves thoughts :hail2: Can you define "Bling"? or is it "Bling" "Bling" :shrug: You are so F@cking Amazing :hail2:
    #93
  14. Venom351R

    Venom351R Founding Member

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    Power pipes N/A= :nice:

    CAI Mac, BBK, exc.... :notnice:
    #94
  15. oz

    oz Founding Member

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    The reason some CAI's mess up the MAF is because they promote turbulent air flow and dissimilar air speed in a given cross section. Air comes in at a rate roughly equal across the opening, when it gets to a corner, the air on the outside of the corner speeds up while the air on the inside slows down. This causes some turbulence. Depending on where the hot wire is located in the MAF, how close to the elbow it is, and how sharp a turn the elbow has predicts how much of a problem it will be.

    While I don't believe the 20 hp hype, I do beleive the Ford air box with silencer could be improved. I also beleive that a properly executed CAI flows better than the stock box. If you still think the stock box is great, for example just look at all the compromises Ford put into the headers. Ford has to worry about packaging and ergonimics. Both of which restrict performance.

    As for 'cold air' I think there is a slight advantage to getting air from the fender well (vs the space just outside of the radiator up front) but dynamic heating of the air in the intake is not the reason this is better. At highway speeds the inlet air is closer to ambient temperature than that close to the radiator (and certainly colder than the air under hood).

    Plastic CAI's are more effective than metal ones assuming the inside of them is smooth. Plastic does not transfer the under hood heat into the air as easily (plastic is a better insulator than metal and therefore does not easily transfer heat). Another example of this is insulating the upper intake from the engine with a spacer... helps keep the intake air charge cooler, longer.

    Signatures are for 'modifications'... "big a$$ wing", "fart tips", "window stickers", "knobby off road tires" can all be listed... not particularly tasteful mods but mods just the same. :D
    #95
  16. 5spd GT

    5spd GT "the 5.0 owns all" Founding Member

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    Holy Cow...those are willys1 free post...can you define "free post" or is it "free post" "free post":shrug: :D
    #96
  17. seijirou

    seijirou Founding Member

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    Thanks 300 for describing airflow, and oz for better discribing the turbulance than I could

    :rlaugh: @ 5speed
    #97
  18. Grandmaster

    Grandmaster New Member

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    I got a CAI because i needed a new air filter anyways, and it looks better than the stock box. As far as difference...what difference? Maybe as much as changing spark plugs when the old ones were very slightly dirty.
    #98
  19. darthcual

    darthcual Member

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    It is a well known fact that the 302 is starved for more air whether it is stock or not so i dont agree w/ the "theory" that it is getting all the air it needs. Ford must take other things into account besides making maximum hp. Like having reliability and a quite ride.
    #99
  20. willys1

    willys1 Banned

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    Thats gotta be one of the biggest mod lists Ive seen!!! What do you run? 12.1,,12.2 ?

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