........In the cowl setup you have to remember we are talking about atmospheric pressure. Moving air creates low pressure, still air, high pressure. Low pressure air can be utilized more efficiantly by a naturally aspirated engine. Low pressure air does not mean less air. It's guided by high pressure and in a cowl setup the engine as an air pump will suck more air more efficiantly. In a ram air setup, think of it this way. The car is moving forward into still air, high pressure. The air is channelled into the ram and sucked by the engine causing faster moving air, low pressure. Higher atmospheric pressure will force more air into a low pressure, therefore, a ram will create more power as does a cowl. Both utilize cool air and we all know what that does for power........Zapr.

 

Hold your hand out the window of the car in a vertical position. Is there less pressure against your hand while you're still, or while you're moving?

 

There's plenty of good information here, but it's unbased. "Ram Air" never meant compressed air into the engine. It gives you more horsepower because the air is cooler, allowing for slightly denser air/fuel mixture.

 

Sounds very sensible to me. This has been a very interesting read as I had no idea there were so many conflicting views on Ram Air. I have no new scientific input but I have some first hand experience as I run a Ram Air system on my car. When it makes the most difference is on hot days adding consistency more than anything else which supports TraviZ view of merely the cold air being the improvement not so much the "Ram" effect. But in my case it also makes the highway roll on throttle response much better than a plain open element does. I have not however noticed any improvement in trap times or speed but... One of my good friends is a Mopar guy and his Road Runner gets a 3 tenth improvement with the Ram Air system he fabbed up over open element or even no cleaner at all. He runs deep into the 11's mind you so perhaps the high MPH he reaches could be giving him the extra push at the big end and his system uses large dual six inch piping into a HUGE breather he made. Interesting differences between us but this is merely my experience perhaps others with first hand results/improvements may chime in.

Impressive knowledge guys

 

Have you ever seen a piece of trash or paper in the back of a pickup at freeway speed. The object (if it is light enough) will follow a circular pattern in the back of the truck (up right behind the cab, back some, then down, then towards cab along bed, then back up) The same effect happens behind the cowl scoop. The only difference is there is a low pressure area under the scoop, so the air on it's way back forward is pushed into the carb. BTW, my physics teacher would never let us say "sucks" (e.g. This Sucks, She Sucks) He would always correct us with a smile and "Creates a low pressure area"

 

ok, so cowl induction uses the vacuum created behind the scoop to help it "suck" more air in to the throttle body / carb. That is understandable. It's also understandable that they would put it close to the window, to help direct the air.

What i think this thread is all about though is that all these naturally aspirated induction types fall within the marginal difference catagory. As long as the flow is direct and short the different kinds dont really make any meaningful difference in performance.

Why that is is due to all types of variables. For one, your air induction would have to be the weakest point. Two, your intake would need to be insulated from the engine bay to give the "cold air" any chance to remain cold ...otherwise you might as well just open the back of the hood by removing the rubber strip and do an open air filter setup. etc etc.

 

Yall are to smart for me.......But did yall notice that travisz put this up for discussion and hasn't been back?

 

I noticed that too... YOO HOO!! Travis??

 

.......Again, we're talking about atmospheric pressure. Not wind!......Zapr.

 

So a car traveling at 60 MPH in a 80MPH head wind with gust up to 100MPH isnt gonna see or feel any performance gains???

 

Explain how moving air magically has lower pressure then?

 

I think hes talking about Bernoulli's effect or force. Thats a little different in this case and is not entirely true or on base.

 

take it from an aerospace engineer who does airflow analysis for a living-- cowl induction and ram air both operate under the same principle. Recovery of total pressure from the free stream.

regardless of how fast you are going the static pressure of the free stream is always 14.7 psi (or thereabouts). when you are traveling along in your car the theoretical maximum TOTAL pressure you can recover if you STAGNATE the air going by against some surface (windshield or into a ram air box) increases. Now of course you are going to have losses in your intake tract but if you make the pressure at the entrance to the tract HIGHER by stagnating (slowing) the flow relative to the free stream you will increase static pressure throughout the system as long as some part of it isnt choked (mach one).

So to sum up, cowl induction functions as an increase in static pressure against the windshield due to turning and the cowl is designed to draw from this area; ram air ducts are designed to capture the free stream and allow it to be slowed at some point WITHIN your intake tract, this acts as an improvement over an intake point within the engine bay where freestream pressure has already presumably undergone losses getting in.

Again as my numbers show above you have to be going VERY fast to get multiple percent increase in pressure so I agree with the above people who say that the decrease in temperature would be more important because it could be more than 10 degrees (big gains).

 

Ok, I work at a Pontiac/'Cadillac dealership, and let me ask this then if Ram Air is not effective. Why do the air filters become clogged after only 12,000 miles while a regular air intake is still nearly spotless? That obviously tells me more air is getting through. Insight anyone?

 

Its because its exposed to more outside contamination. The other filters draw cleaner air from within the engine bay. Ever notice how the outside of your car is dirty will the engine bay is not.

 

[QUOTE]Originally posted by Apeiron
Explain how moving air magically has lower pressure then? [/ QUOTE] ........Ok. Putting your hand out the window in a moving car, as you used for example, your hand is forced back. Remember, you're moving, the air isn't. As the air moves around your hand it creates a low pressure behind your hand and the air in front ( still air, high pressure ) pushes your hand back. Cowl setup? Air coming over the cowl will spin at the base of the windshield causing low pressure and the engine can draw in more air. That's how it was designed to work........Zapr.

 

That was some interesting sh*t. They dont teach you that in school. But I dought anyone really buys cowl-hoods and ram airs thinking 10hp gains. For most its a fashion statement.

 

A true cold air / ram air setup. where the engine feeds directly from out side colder / fresher air. Will have gains over a car that sucks hot dirty air from under the hood.

 

[QUOTE]Originally posted by zapr

Quote:

Originally posted by Apeiron
Explain how moving air magically has lower pressure then? [/ QUOTE] ........Ok. Putting your hand out the window in a moving car, as you used for example, your hand is forced back. Remember, you're moving, the air isn't. As the air moves around your hand it creates a low pressure behind your hand and the air in front ( still air, high pressure ) pushes your hand back. Cowl setup? Air coming over the cowl will spin at the base of the windshield causing low pressure and the engine can draw in more air. That's how it was designed to work........Zapr.

Your understanding is not entirely true and is incomplete.

 

The "warm air" intake would only suck hot air when the car isn't moving. That's not all that important. As soon as the car is moving, the air is being replaced in the engine bay quite rapidly, not giving much time to heat up. In fact, it probably gives you the same amount of time to heat up as if you were running a metal intake pipe through the engine bay to the outside to pick up cold air, where the tube has been heated up by the engine and now all the air must travel through that to the intake.

Remove the black rubber strip on the firewall side of the hood and the performance of a warm air intake and a cold air intake will become just about the same because they will be taking in air that is just about the same temp. Even if you use insulation, it only really makes a difference to the air intake temp when you're not moving compared to a warm air intake temp.

So much air is moving through the engine bay when the car is in motion (and leaves directly if you remove that strip) that I'd be surprised if the temp was raised from ambient outside temp by more than 2 degrees. That's not even close to the kind of temp difference you need to make any measurable performance gain.
And the only time the temp difference is not negligable is when you're stopped. And who cares what your performance is when you're not moving.

I've yet to really see anyone with a temp sensor properly positioned near the map/maf sensor and having that positioned near the throttle body (to reduce error due to the air warming up after those things as it enters the carb/TB) show me that cold air intake produces a performance gaining charge over just an open element filter with that strip removed at the back of the hood to let air escape.

Something that is not so negligable is something called "the pulse effect". Supposedly exhaust and air intake have an ideal volume they like to breath out and in into. This volume is usually provided by a tube so we'll say they have an ideal radius. This is because for any given rpm range, the engine is breathing in and out a certain amount of air and if it's doing this through a tube, than you want that radius to be such that the last time it breathed in or out causes a force that pushes the air away or sucks in towards and before the air settles the next "pulse" occurs. This means that the air is already moving towards the TB or carb by the time it opens to breath in more air due to the last time it opened and removed some air. The same for exhaust, the exhaust is still moving away by the time the valves open for the next cycle this makes it easier on the engine to pump air and since it's an air pump it performs better. This is the idea i believe behind the fact that open headers causes a loss in low end power, due to the fact that the exhaust is just entetring open air, not producing any sort of pulse effect to help suck the exhaust out of the engine at low rpms. The lower the rpms, the smaller tube the exhaust must travel through in order to have a pulse effect. The higher the rpms the wider the tube should be. Hence open headers is optimal at high rpms, but not low...Same true for intake.
Now if this is what really happens and produces such a noticable effect, it is much more important than choosing between cai and wai.


heh, sorry for ranting. off to the junkyard now.

 

What about staging and the launch? Not moving much there after a long standstill. Perhaps thats why I notice such an improvement when its hot. hmmm

 

staging and the launch... I'd think most people on this board and in reality, aren't building their cars to race. 9/10ths of the people probably have never taken their cars to a track that has the ability to measure such things. Far more likely is that most people are building up their car to perform well while at the same time, remaining a daily driver .... If the staging and the launch have become your bottleneck ...then you're probably not driving a daily driver anymore. And you'd be obviously outside of my statement about not caring about performance when stopped, since when you've crossed over from daily driver to race car, you're in an entirely different mindset about what your car should be. To those types of people, 1 hp / ft lb increases matter, and they'll spend the money to get them.

You could always run the coolant fan for a while before you go ahead and launch though to bring in fresh air ....turn it off before the actual launch and probably bring that performance difference back down to negligable.

Either way, were talking about performance gains that can really only be noticed after you've dumped all kinds of money fixing all of the other weakpoints in third gen cars.

I mean, to be real, unless you're at a track and you've timed yourself more than 3 times with your cai on and immediately switched over to your wai and tried that while the ambient air outside was unchanged, ... unless you've done that and seen a measurable difference, any difference you do feel is likely all in your head. And not all cai's are created equal, just like not all wai setups are equal. My favorite cai's are the ones that try sucking the air close to the ground down the fender. On a track or on the road, whenever it's sunny out the road surface and air close to it is much hotter than the ambient air, so the name is really ironic.

And this is probably off topic by now since it's supposed to be about ramair.
ramair is just a direct cai. It performs better than a stock air box because anything performs better than a stock airbox setup. They are usually very short intake tubes directly to the TB / carb so they probably even do a little better than other cai's and other wai setups. Does it have anything to do with true ram air effect, no. Can you make wai's perform just about as good if not better, sure and without much work too. Is colder air better than warmer air, yes until you get to extreme cold air. Is a wai letting the engine breath warmer air than a cai, depends but even if it was, it's in racing land and i'm not even sure it would be big enough of a difference to matter there either.

People spend way too much time on air intake setups because it's cheap and easy to do ...but it's a waste of time to debate performance gains unless you've fixed some of the much more important and performance effecting problems with your stock engine. Worrying about your intake while running a stock intake manifold is like trying to help someone having an asthma attack by moving them outdoors. And getting an exhaust put on without moving to tubular headers is equally as pointless. And eventually you'll probably want to bore the block out etc etc. The restrictions are inside and they're much more integral to how well the engine performs than what's going on at the ends. If you're someone not out for that kind of performance from a daily driver, than this discussion probably doesn't matter to you either as performance probably wasn't the primary reason for you choosing whatever you ended up choosing.

Really, we can debate fluid dynamics all day about how each and every air induction setup works and which is more efficient but in reality, modifying the nose of the car to be more aerodynamic would probably have a greater effect than switching from ram air to cold air.

 

Wrong side of the bed this morning?

 

The "you" i was referring to wasn't you in particular, just people who seem to always get into intake debates between wai/cai/ram air etc...in an area where almost everyone is using the cars as a daily driver and doesn't have the engine built up to the point where 1-2 hp is the difference between winning and losing.

 

So, we have come to the decision that RAM AIR is so negligible at the speeds our cars attain, it is hardly a HP booster. However, it seems that we are also debating the effectiveness of CAI. I recently read that you can lose 2% of your HP per 10 degrees that your air intake raises. On an engine yielding high HP, this can be a noticeable amount of power, esp. if you are able to lower intake temperature by 20-30 degrees or more. As for how hot underhood temp is while cruising, I am not sure, but I guarantee it is warmer under that hood than it is at the grille, in the fender, or at ground level. This would be true at any speed. I don't think turning on the radiator fan while staging is comparable to CAI, b/c you are drawing air through the radiator, (120-190 degrees). I am sure it isn't btwn 120 and 190 outside of the hood.
My ..... I get 4 cents b/c I am young and unwise.

 

your radiator is maybe an inch or two deep. The air is coming through it at stop via the fan at over 1000 cfm. The air wont heat up more than a degree or two if that. Air is a horrible heat conductor, that's why fans have to shove so much of it by something so hot as a radiator to conduct the heat away from it. So the heat it does conduct from something is spread over a huge amount of air, so you really barely heat any given volume up. If your hood has that rubber strip removed, the air can easily pass from the radiator through the back without remaining stagnant in the engine bay. The fan is not a replacement for cai, but then again, if your launch intake air temp is your biggest concern, or even a meaningful concern, you probably aren't concerned with anything mentioned in here as you already know everything about how to make your car perform at it's peak.

people who get cold air intake dont want to put insulation around their shiny chrome tube to keep that "cold" air at temp as it travels through the "much hotter" engine bay. A cai and a wai while the car is moving (with the rubber strip gone) are the exact same thing, since without insulation, the tube is at the same temp as the engine bay ambient air. The cai forces air to go in a direct route, not allowing the engine to suck air that's been stagnant around the engine. If you make it so that the air isn't stagnant, then there is no reason to go cai. If you disagree that the air doesn't warm up in the short time it passes by the radiator or through the engine bay that's ventilated, then you have to agree that the cai's air is equally warmed up as it passes through it's tube that sits at the very same temp you think the wai would be taking in, closing that difference - a difference that was already not that large to begin with.

If you're someone who can notice that kind of hp gain / loss than you'd feel it whenever you drive through a shadow like under a bridge or behind a building, since the temp difference there is around 20 degrees from direct sun.

A noticable amount of power is made from cai that's supercooled. That is, beyond the negligable difference of ambient air outside the car and under the hood when movin. Real CAI basically has a large intake tube that gets cooled by any number of methods to some crazy low temp, so that by the time it reaches the tb, it's still much colder than ambient.

 

To put it simply. "Ram Air" at highway speeds is ineffective as far as increasing intake charge density. You can, however, see a significant HP increase due to a cooler intake charge.

Now " Ram Air" at speeds over appoximately 100MPH is an entirely different matter. There you can start to achieve significant increases in intake charge density with the use air intake scoops.

This is a proven engineering principle. Look at any modern road racing car ( Normally aspirated ) from the 1970's on-ward. All use some form of high mounted, forward facing air scoop. F1 cars, ALMS cars and Pro Stock cars all utilise " Ram Air " intakes. And they are very effective.

The article at Vette.Guru is so full of incorrect assumptions and statements, that he is trying to call " Fact's", that it is laughable. Who is this guy? No credentials of any sort...just some more unsubstantiated " Theories" concocted up out of his head and presented as fact.

Air is not compressable till about .5Mach? Give your freakin' head a shake. That one statement is so completely wrong ...it's just pathetic. That is the whole premise on how air boxes, plenums and high mount scoops work.

You could compress air at 20MPH given the correct circumstances. IE: A huge airbox and plenum and a teeny tiny engine. It wouldn't be much of course...but you could get an increase. All that matters is the the volume of air being collected at the mouth of the inlet and driven into the intake Plenum is greater than what can be consumed or moved by the engine itself or move through the throttle butterflies in the same time period.

Given current engine regulations and air box size restrictions , it generally takes about 100MPH before you see any significant increase in charge density ( IE supercharging or compressing of air in the inlet chamber) with the use of airboxes. Once you get above 150 mph or so the affect is considerable. Bear in mind that F1 cars and ALMS cars often excede 200 mph, and you can see the benefits of using high mount air scoop, air boxes and " Ram Air"


There are many, many technical articles written by Racing car engineers over the last 30 to 35 years showing how a properly designed " Ram Air " system can provide significant supercharging affects on race engines at higher speeds. Start reading magazines such as Race Car Engineering or Race Tech. You will find much more accurate information there than by some " unnamed " Guru at some "Vette sight.


Formula One teams, Lemans prototype cars and other series invest THOUSANDS of hours in the wind tunnel and MILLIONS of dollars in designing air boxes and high mount scoops. If it didn't work...do you really think that they would be wasting all that time and money on it?

Edit: Spelling

 

Here is a site for Motorcyles that has a calibrated air blower to simulate the affects of a vehicle travelling at high speeds, while the bike is attached to a stationary dyno.

A simple device that clearly shows that " Ram Air " does work:

http://www.soft-engine.com/pagine.we...ese/airbox.htm

 

Nobody said ram air doesn't work, or if they did, they were wrong. They said that it's gains are so small as to be negligable in cars at the speeds they regularly attain. Even the bike only attained a 4hp gain and it's a much smaller engine and it runs at a much higher rpm band so you'd figure such an engine would be much more reactive to changes in various fuel variables. On a bike, 4hp probably means something more than a number on a piece of paper, it really doesn't to a car that weighs a ton. I highly doubt such even such small gains would be seen in a car, and it's definitely not something you're going to be able to notice.

 

Though I started this topic, and have yet to post since then, I have concluded that ram air is a myth in the term of the word, air is not really being 'ramed' (forced) into the engine, though it does provide the outside air which is much colder then air from the engine bay. and theirfor, is denser which does create some power.

 

I don't know how you can say that, we have already proved air is rammed into the intake, if it is made properly. F1, indy cars .... use ram air very effectively.

 

The last 2 posts sum it up pretty well. Total pressure recovery only becomes relevant to engine power at over 100MPH but the cooler charge gives benefits that are noticable at 0MPH.

 

I too have seen tests similar to that motorcycle one with a Kawasaki bike that had ram air. At about 160mph, there was a few % HP gain. I don't recall the numbers off the top of my head, but the link above speaks for itself. 117HP/113HP = 3.5% on a 250HP motor would yield 8HP or so. I'd say that's a decent amount. However, this is at 160MPH, and most of our cars won't be seeing these kinds of speeds, or at least not regularly.

Nevertheless, ram air's main advantage, as mentioned is a shorter pipe to bring cold air to the engine.

Now the part I disagree on is that a fender-mounted CAI won't give any advantage. My engine used to have manifold air temps of around 122-126*F. Once I installed my CAI (using the stock tubing from TB to MAF and then 3.5" PVC piping to the K&N), my manifold air temps dropped to 94-98*F. Still, its not the same as the ambient air temps, but it is a solid 25-30*F drop in temps, even at speed. And that was over a slightly modified intake in the first place. I had ground out the little tab in the bottom of the air box and removed the plastic intake tube taht was about 2" long and rotated the box to suck air from right in front of the radiator (removed A/C). Don't know how much this affected intake temps, but I would assume this did a little bit since it was coming in from in front of the radiator then.

As for the assumption that the radiator may only increase the temp of air passing through by 1-2*F, are you nuts? Have you ever felt the air that comes out the back of the fan on the radiator? I'd say it makes quite a big difference, and air does not move freely through the engine bay as much as you'd like to think.

I've been meaning to make and calibrate a thermocouple one of these days but haven't gotten around to it. Maybe I'll make one later tonight and calibrate it over the next few days and get some temps on the outside air vs. the temps behind teh radiator, and then again the fender temps compared to the stock air intake location temps..