Ram air Vs short air Vs cold air

[wilson4]

all things being equal what will give the best performace increase?

Ram air (assumeing no turbo) - rerout air intake to face incomming air possbily behind grill

Short air - add a high flow air filter to a very short tube and connect it to throttle body

Cold air - rerout air intake to get air elsewhere in engine compartment

basically im asking is it more important to have more pressure but hotter air, less pressure and colder air or less restrictive intake and hotter air?

[chevcamaro_86]

i personally like the short ram intake were you use the short tube and then i used an adapter to the filter and ran a tube to the front of the car to give it its cold air the best way to do it in my opinion is to run a low resistance tube to the front of the car in front of the radiator the only problem i see with that is water for rain or car wash.

[wilson4]

Originally Posted by chevcamaro_86

i personally like the short ram intake were you use the short tube and then i used an adapter to the filter and ran a tube to the front of the car to give it its cold air the best way to do it in my opinion is to run a low resistance tube to the front of the car in front of the radiator the only problem i see with that is water for rain or car wash.

so its basically like a short air intake filter incased in a big tube that goes to front of car?

[KiwiBacon]

Cold air is going to give you the best improvement.
The miniscule pressure rise you get from ram air does not make up for the number of insects and leaves you collect.

The standard filter box in most cars is very good. Simply directing the intake for that to a cold air zone will give you best results for the lowest cost.

Many factory systems are tuned for resonance at certain frequencies to pulse charge the air into the engine, picking up a few percent in areas the engineers decided it needed it. If you replace the factory air system with something simpler, you may lose out in certains parts of your engines rev range.

[UncleBob]

ram air is quite effective, but not until very high speeds. Under 120mph its doing very little.

motorcycles have been using ram air for many years, and at 150+mph, its good for 10+% increase in power. Thats a notable improvement.

As for cold vs ram, ram IS cold since in order to have ram, the incoming air must be 100% sealed from engine air.

The large vs short, is mostly a question of volume to the "air box". Done properly (large amount of volume at the right places) it would be the most effective, but thats a level of engineering that is difficult to calculate all the parameters necessary

[curtis73]

Uncle bob is spot on. My first choice is a combination of all three; cowl induction. Its short, cold, and as effective as any other ram air (which is very minimal.)

[CivicSpoon]

I know it's not listed in the options you gave, but a cold air box is the best IMO. Short ram intake with a box around the filter to keep away engine heat, and a tube ducted to the other side or bottom of the box helps bring cold air to the filter. So you get the high rpm/mph power of a short ram, while still getting an increase in power at lower rpms/mph (instead of just losing it like a short ram will). Very similar idea, if not the same, as what chevcamaro_86 said. But honestly, unless you want power in a certain part of your power band over another, for a specific reason; an intake is an intake. Do you want it for a daily driver, weekend warrior, drag racing, SCCA, race car? That is what will really help you determine what one is best for you.

[KiwiBacon]

Originally Posted by UncleBob

ram air is quite effective, but not until very high speeds. Under 120mph its doing very little.

IMO It's completely useless unless you're going for land speed records.

Stagnation pressure (max possible gain from ram air)= 1/2density*velocity^2.

At 50 km/h stagnation pressure = 117 pascals
At 100 km/h stagnation pressre = 470 Pascals
at 200 km/h stagnation pressure = 1880 Pascals (almost 2% of atmospheric pressure)
at 300 km/h stagnation pressure = 4200 Pascals (almost 4% of atmospheric.

To get 10% requires a speed of approx 130 m/s which is 460 km/h.

[GreyGoose006]

but theres nothing wrong with a cooler engine

[UncleBob]

I don't know the exact math, just basing my numbers off of real-world experiments bike magazines have done. IE, measure actual intake pressure at speed, then apply said pressure to the intake on a dyno.

Not all ram air has the same effect, due to pressure changes over different spots on the frontal area. Its quite interesting to see the pressure curve vs speed for several different models, because they can be quite different between them

[UncleBob]

here's one tech article on it, using a kawasaki ZX9

http://www.sportrider.com/tech/146_9508_ram/

[KiwiBacon]

Originally Posted by UncleBob

here's one tech article on it, using a kawasaki ZX9

http://www.sportrider.com/tech/146_9508_ram/

Quite a well done article for a magazine. But I think the plumbing of their manometer has given them false readings.

In this picture http://www.sportrider.com/tech/146_9.../photo_07.html
you can see the tail end of it hanging down and back, this means the air stream is sucking on the other end as well as blowing on the end hooked up to the air box.

To get a true reading the tail end which measures the static air pressure has to be at 90 deg to the air stream.
If the tail end faces into the flow, the measurement will be lower than it should be, if the tail end faces away from the flow, the measurement will be higher than it should be.

This fits with their measurements being higher than they should.

Their manometer read 20mb (2kpa) at 120 mph (approx 54 m/s)
The maximum possible stagnation pressure at that speed = 1/2*1.2*53.5*53.5
= 1.7 kpa.

Which proves their readings were distorted.

[UncleBob]

here's a much more precise article, using an actual datalogger over 6 different bike models (the last one being a non-ram-air bike, amusingly, a ZRX1100, which is the bike I own. But mine is turbo'd and running 18psi ) Note that one of the bikes tested was the hayabusa, which is the fastest mass produced bike in the world, (before the self-introduced speed restriction was applied by all manufacturers of 300 km/h) with a top speed of 191mph or so (depending on who you ask)....but it had some of the less impressive pressure readings, interestingly

http://www.sportrider.com/tech/146_9910_ram/

[KiwiBacon]

Originally Posted by UncleBob

here's a much more precise article, using an actual datalogger over 6 different bike models (the last one being a non-ram-air bike, amusingly, a ZRX1100, which is the bike I own. But mine is turbo'd and running 18psi ) Note that one of the bikes tested was the hayabusa, which is the fastest mass produced bike in the world, (before the self-introduced speed restriction was applied by all manufacturers of 300 km/h) with a top speed of 191mph or so (depending on who you ask)....but it had some of the less impressive pressure readings, interestingly

http://www.sportrider.com/tech/146_9910_ram/

Excellent article.