Hi there,
I was wondering what would be the best, cold air intake or a short ram. At first I was think doing a custom job but after reading a lot on both, I decided to go with either one of those. What do you think would be the best choice ??If your car is NA, cold air intakes will always be much more effective than short rams.
not always, but in most cases… yes…
if your cold air is so far down and has so much piping that it makes it hard to get that air to the engine, then your screwed. High quality (term used lightly) cold airs will do a better job than ram airs.
but you can get ram airs on ebay dirt cheap that do the same thing. the colder the air the better, so why not get a short ram and plumb some flexible piping from a front vent up to the air intake area, you get cooler air getting to it in the first place, and it only costs a few bucks…
I will probably go for a custom cold air instead of buying a brand like everyone does. It will be has or more efficient then those brand. Thx guys
piping doesn’t matter, your enigne creats a low pressure area internally, high pressure air will naturally flow to it, the ONLY draw back to a long intake is that it inevidable has more bends then a shorter piping… THIS will cause flow to decrease… but were talking .5% to 2% depending on the curve … if you can reach clean flowing air , say from under the car, then the losses due to the bends are superceeded by the gains from having a cooler , denser air flowing into the engine.
the concept of ram air on a passenger car is laughable,
also , pet peeve #5… the term ’ ram air’ is two things , a) used sucsessfully by the SR71 black bird to go mach 3.5 or a GM firebird sales gimmick that only proves how poor flowing the original air intake was on the car. A ‘Ram Air’ system in it’s best form for a EFI car, ( straight into the TB , shortest tub lenght possible… at 100kph, provided you had clean flowing air and the intake was dead on the very leading edge of your nose, you’d make @ .028lbs extra of air pressure… of course that all goes to pot as soon as a car or anything passes infront of the air stream…
While I am aware that the terms minor and major head loss don’t actually imply that the major head loss will be greater, the major head loss is still a factor that you’re not considering. Minor head loss being provided by any change in diameter, bend or valve, and major head loss being provided by fluid viscosity inside the actual piping. Considering how major head loss works, having a longer pipe will definitely have an effect on the mass flow rate. You could argue that intake piping can’t be very long anyway, but considering the diameter of the intake there will be significant head loss even at those lengths.
Theoretically speaking, the short ram with cold air being ducted to the area surrounding it, by a duct with a sufficiently large mass flow such that it can deliver enough cold air for a cold air reservoir to exist, and some sort of insulation to prevent the hot air from mixing in would be best.
The head loss from a reservoir flowing into a pipe is quite large, but in the case of an intake has to occur at one point, so it would make sense to minimize any further head loss by placing the reservoir as close as possible.
This can be easily represented by a pipe sucking water from a lake. When the pipe is long, it’s a bitch to suck in the water. If you dig a bit, and make a smaller lake near the pipe, you can have a shorter pipe, and the smaller lake will be fed by the bigger lake at a far greater rate than the straw could ever suck.
Or you could apply the 2 most desirable principles, short ducting with cold air venting… Formulate an idea, design it, and then proceed to build it… Rather then just identify the problems of both systems, make a better alternative that reduces the factors of both.
Don’t over analyze, apply theories, and build it…
your application of fluid dynamics has validity no doubt, but the water to pipe scenario is not quite right, first water is much heavier then air, next vacuume pressure draws the air at much faster rater then the heavier water… that being said… your all missing one key factor, that i was going to leave out, the throttle plate, it designates how much air will be allowed to ingrees to the plenum chamber… it’s useless to have X thousands of a percenatage more air pressure if the throttle is only 1/4 open. not to mention the turbulence it creates destroys any flow characteristics you had to that point… plus if you wan to get technical in a 2.5" intake pipe, a simple 1/16" lip or drop ( say at a coupling ) will caused low pressure areas that will again destroy any gains you had with sort lenght intake…
also your pipe theory works but you forgot to include that while sucking on that pipe from a lake gravity is applying -9.8m/s^2 to 1kg/L of that water… gravity is so minor on the volume of air your working with here that it’s not applicable… therefore the pump doing the work to pull the smae ammount of air is having to work that much harder to do it…
Easy Roto,
The question was which is best, not why it is so…
If you don’t want to cut out your battery tray, go short ram…
Thanks…
There is a significant difference in the density of water and air, and gravity effects would be present if we’re sucking in water from a higher altitude, so that was a bad analogy to use. A far better one would be breathing through a drinking straw, and then cutting the same straw in half, and then in half, etc…
In the scenario I proposed, an air ram effect would not be used, as I’m well aware that it does a whole lot of nothing on a street car. It would merely provide cold air to the intake, shielded from the hot air, in the same manner that you would get it if you ran the intake to the bumper. However two very large benefits exist from doing the ducting & heat shield vs. running the intake itself to an area down low on the car where there is cold air to begin with. The first would be what I already said about head loss from the actual pipe length, turns, etc. The second would be that water can get into your intake if it’s in such a position, and while it is still possible with the duct and shield idea, it is far less likely.
I will admit some serious deficiencies with my duct and shield idea. The biggest is the fact that I’ve not looked into finding a suitable path for a duct, nor suitable room to construct a heatshield in the car. This is because I haven’t really looked, since I can’t know exactly what space is taken up by the SR20. I only know where the KA is right now. The SR may free up space, or take up more, or both at the same time in different locations in the engine bay. I also don’t know where the intake on an SR is located.
Oh, and the 1/16" lip or coupling you were talking about wouldn’t be any different on a short intake or a long one. Regardless of how efficient or inefficient the coupling method used is, it will exist on both the short intake and the long intake, harming both equally.
Another idea that hit me as I was typing this, could be having a hood that is vented right over the intake and constructing a small heatshield around that. It would work in the same way as the ducting from the bumper would, but it would require a lot less effort to set up.
In both of the heatshield ideas, the shield would only be from the front and sides and not the back. Not having the shielding in the back would prevent additional turbulance inside the heatshield itself, and would have a nice effect of cooling the rest of your engine bay. Hot air wouldn’t be able to get in from there anyway, as the cold air would be blowing out there.
I’d draw a diagram, but I don’t gots photoshop right now 
If you run a bypass valve, you don’t need to worry about the motor drawing in water as it automatically opens under a preloaded pressure value …
You are also forgetting about heat soak from the engine bay on the piping as well. While it may be minimal, so is your idea of heat sheilding it.
At speed, under hood is an extreme high pressure area relative to on top of it. A vent will not draw air in but rather expel air out, which is why they’re used for cooling.
The only purpose that the shielding serves is to direct the cold air to where the intake is, as opposed to scattering it and mixing it in with the hot engine bay air. When it flows past the intake, it will do that anyway and cool the rest of the bay a bit, but atleast it goes to the intake first.
spd-demon - scrap the hood idea then 
you’d think that , but it’s the exact opposite… the pressure wave hitting the leading edge of the car ( bumper) will push the air up and away from the hood creating a low pressure area over it, the steeper the attack angle/rake of the hood the less effect this wave has. ( the hood of the 240 is pretty flat like most FF/FR cars on the road.), the wave does not settle back to the hood until somewhere back towards the windscreen ( where it promptly gets lifted again… ) , this occours in any vehicle moving through air( in this case ) , at the extreme end when a fighter is breaking the sound barrier you can see this pressure wave condese infrom of the nose , ( ral world proof for all ou people who dont’ beleive in physics ) … this of couse is not a car but the same properties and effects apply. the ONLY way to create a venting surface say at the nose of the hood for a V mount IC, would be when the high pressure air is forced into the air stream. ( high pressure moving to low pressure… )… as seen in examples from the C TII and the WRX/STI top mount IC’s are placed as far back o the hood as possible to catch the air stream drawing back down to the hood…
under hood is very low pressure, otherwise no air would ennter that space to begin with and you’d have a big stagnant bubble there, the under hood is very low pressure in comparison to the air moving under the car, very often ( eg: FC3S ) a diffuser plate is added under the car to increase the low pressuer effect and draw in even MORE air.
At speed, under hood is an extreme high pressure area relative to on top of it. A vent will not draw air in but rather expel air out, which is why they’re used for cooling.[/quote]
your using a worst case scenario ( al la AEM long civic intake riceness )
persnonally i’d never build one like that if you paied me, I actually run bumper ducted air into a boxed area ( heat shield ) so I can’t disagree with your design idea… water/heat soak/velocity loss… can all be overcome with good engineering. though.
Wow… You’re my new favourite person. Knowledgeable and nice at the same time