Yaaro Dhana

Your equation fails when the fluid velocity is zero because the pressure has to go to infinity in order to satisfy your equation. Whether you mention it or not, your equation has to hold for all velocities. Also, a Pitot tube works by bringing the fluid velocity to zero - which is precisely why I alluded to it.

harddrivin1le

The fluid velocity CAN'T be zero in any case where the mass air flow is greater than zero!

If there is ANY mass air flow then there MUST also be velocity!

The main discussion here is RAM AIR systems and how they "convert" air velocity into increased pressure @ the intake manifold.

You are aware of that, right?

Yaaro Dhana

This blanket statement is false firstly. This is true only for fluid flow under certain conditions and when gravity is neglected.

Secondly, even in the case where it is true, the equation governing it is (p + 1/2 rho*v^2 + rho*g*h) = const.

harddrivin1le

Yes...apparently that's the equation.

How about getting to the core argument:

Can a "ram air" system increase pressure @ the intake manifold in an automobile traveling @, say, 100 MPH?

I say that it can.

Yaaro Dhana

Once again, you are demonstrating your ignorance of fluid mechanics. Equations of fluid motions have to hold true even at stagnation points, i.e., points at which the fluid velocity drops to zero (clue: this can occur anywhere, including an intake manifold). Please go look them up before making further ignorant statements.

harddrivin1le

Premise:

You have a tube.

In order to have any mass flow through the tube, there must be a velocity component (SOMEWHERE in the tube) that is greater than zero.

Is that true or false?

Post your opinions on RAM AIR if you have a doctorate on this topic.

svtmike

Now wait a minute, you guys mean to tell Harddrivin that in addition to V in the Combined Gas Law not being velocity:

V = IR in Ohm's Law doesn't mean the velocity of a speaker is the product of the current and the resistance of the speaker????

and

V = 4/3 * pi * r ^ 3 doesn't refer to the velocity of a sphere?



Mike

harddrivin1le

V in THIS equation equals VELOCITY (flow velocity).

And I have never ONCE reference "the combined gas law.

http://hyperphysics.phy-astr.gsu.edu/hbase/pber.html

"The qualitative behavior that is usually labeled with the term "Bernoulli effect" is the lowering of fluid pressure in regions where the flow velocity is increased."

harddrivin1le

Stagnation POINTS.

You can't have MASS FLOW without also having a VELOCITY component at SOME point(s) in the flow path.

Flanagan

I didn't bring up equipment...

Plastic needs CNC mill and 3D scanner to make a quality mold, as well as an injection molder with either a laser welder or 2-axis movement. It was a nice try, though

harddrivin1le

The plastic is utlimately far cheaper than aluminum for large scale production runs/once the price of the molds are covered.

If it weren't then every production car would be using aluminum intake ducting instead of plastic.

harddrivin1le

The plastic is utlimately far cheaper than aluminum for large scale production runs/once the price of the molds are covered.

If it weren't then every mass produced car would be using aluminum intake ducting instead of plastic.

Aegir

Still at it? My advice is a good bottle of wine and a Kevin Smith film - any of them - for a good laugh. I chose a decent syrah and Dogma tonight. After that, you won't care if V = volume or velocity. A second bottle and you won't care about this thread at all. I'm going for the second right now and suggest you do the same!

Flanagan

I already said that. We're discussing aftermarket intakes, buddy. It's your topic, remember?

Watch Dogma with the commentary on. It's much funnier. :p

harddrivin1le

How many aftermarket intakes are they going to sell? 2?

Those things are advertised all over; they'll sell tens of thousands of them.

harddrivin1le

What's "V" in this equation?:

p + 1/2 rho*v^2 + rho*g*h

and:

http://www.snowgoercanada.com/tech_ram_air.shtml

"Where vehicle speeds are very high, gains from ram air are significant. This was discovered by Rolls-Royce in the late 1920s as the company developed its R Schneider Trophy air racing engine. At speeds above 300 mph, it was noticed that the R’s fuel mixture leaned out enough to cause backfiring. When the mixture was corrected for ram-air pressure gain, the engineers realized they had a "free" source of power. At 350 mph the gain from ram air is almost 15 percent. Similar mixture correction is necessary when ram air is used on drag-race and Bonneville cars and bikes."

Yaaro Dhana

Who said that the velocity was zero everywhere in the flow? You claim was:
which is nonsense. Fluid velocity is not a monolithic quantity. When you have mass flow, the average velocity is non zero, but at different points in the fluid flow, the velocities are typically different and zero at stagnation points.

Once again, your (now retracted) pV = constant was invalid for the simple fact that it does not hold true for points where the fluid velocity drops to zero.

Skeedatl

That page doesn't show the P1*V1 = P2*V2 equation you showed.

A decrease in velocity does result in an increase in sideways pressure, but this is irrelevant in ram air for making power as you aren't going to generate more pressure than that is already present in the atmosphere.

Automotive Ram air is based on the flawed concept that air is RAMMED into the motor, somehow creating a pressure above normal atmospheric pressure.

This does not occur.

Skeedatl

Mathematics says it doesn't.

Yaaro Dhana

Actually, there is no equation below (yes, I am being pedantic).

Skeedatl

Automotive Ram air (per all the bullsh!t articles you've posted) is based on the flawed concept that air is RAMMED into the motor, somehow creating a pressure above normal atmospheric pressure. To deny this is the case is simiply retarded.

And that being the case, it does not occur at automotive speeds; it only STARTS to occur at around Mach .5, speeds FAR higher than automotive applications like the WS6 example you posted.

You don't understand ANY of the applications of the forumlas you're posting. You've confused the two most basic formulas in fludids. You've even confused the definitions of the variables....all this after CLAIMING you took 2 semesters of fluids. Then you come back changed the formula and all your claims as if they didn't happen.

Give it up. You simply don't have the experience to argue this. You don't have the fluids background to support your lunacy. And you don't have the mathematics background to prove your lunacy correct.

AGAIN, I'll say this slowly so you may understand.

At automotive speeds there isn't the compression of the air required to increase static pressure.

Ram air is flawed. In the WS6 example you provided...it's complete B.S. for 2 reasons.

1. The WS6 isn't capable of the speeds needed to compress the air.

2. In order to "slow" the air as you claim, you need a divergent scoop, one that is narrow at the front and wide at the rear. Not a straight or convergent scoop like the WS6 and SS have.

You simply don't know what you're talking about.

Skeedatl

All of the automobiles and bikes in your posted examples including the ZX motorcycle and the WS6 aren't capable to those speeds off a cliff in a hurricane.

You simple can't compare a racing airplane capable with Mach .5 with a car going 100MPH.

There is no ram air effect at only 100MPH.

And in this example you're contradicted yourself yet again.

You first post examples of B.S. experiments trying to prove that Ram Air works by ramming more air into the motor, increasing the pressure above the outside atmospheric pressure; one experiment so flawed that they mildly supercharge the motor to "simulate" increased static pressure (confusing dynamic with static press). This conversion does not happen in street cars, even in fast race cars it doesn't happen.

Strike 1.

Then you screw up all the forumulas and start claiming that Ram Air works by slowing the air, which you still can't generate static pressure higher than the outside pressure, and certainly not higher than through a normal air box. In the WS6 example you posted, the ram air design isn't even built that way. And even if it were, this too doesn't make more power.

Strike 2.

Now you're posting and example, which I've already shown, where at sufficiently high velocities, (Mach .5 and higher), there is enough energy in the dynamic pressure to start converting it to static pressure if restricted...that is at around Mach .5 at STP, you do start getting compression of the air, which is what all these magazine dorks think happens at 50MPH or 100MPH...which is not the case. THEY ARE SIMPLY WRONG AS ARE YOU.

Yer out.

You f-ed up. Face it. This goes to what I've been saying all along. Quite often these magazine guys are just plain wrong. Their theory is wrong, and their "experiments" to try and prove their theories is massively fatally flawed.

You are better off learning from personal experience and talking to racers at the track, rather than relying on the fools writing for Hot Rod, none of which seem to have taken 11th grade chemistry, nevertheless understand more complicated applications of fluids to cars.

Skeedatl

If even after all of this, you still insist on automotive ram air makes additional horsepower, then I must let you live in ignorance. I made the mistake of thinking you would listen and absorb the concepts of fluid mechanics in their most basic forms. I made the mistake to think you would actually question those dorks at Hot Rod and start thining for yourself rather than take everything they say as gospel.

I made the mistake to think you were actually interested in learning something.

I won't make these mistakes again. Next time you pull one of these flying monkeys out of your butt, I'll simply laugh and move on.

If you're actually willing to shut up and learn something, we're all ready to help you.

harddrivin1le

Ram Air provides a quantifiable increase in static presssure (@ the intake manifold) @ speeds that one would normally associate with "racing."

Its effect @ "street speeds" (e.g. 60 MPH) is negligible, though I have never claimed otherwise.

http://www.snowgoercanada.com/tech_ram_air.shtml

"Where vehicle speeds are very high, gains from ram air are significant. This was discovered by Rolls-Royce in the late 1920s as the company developed its R Schneider Trophy air racing engine. At speeds above 300 mph, it was noticed that the R’s fuel mixture leaned out enough to cause backfiring. When the mixture was corrected for ram-air pressure gain, the engineers realized they had a "free" source of power. At 350 mph the gain from ram air is almost 15 percent. Similar mixture correction is necessary when ram air is used on drag-race and Bonneville cars and bikes."

harddrivin1le

An measurable increase (~ 0.18 psig) occurs @ 100 MPH, which is far less than Mach .5.

In fact, that delta P is about equal to the difference between a K&N air filter and a standard paper filter.

Yet, you claim that the K&N filter makes more power, but ram air (@ elevated speeds) doesn't.

harddrivin1le

The conservation of energy for fluid flow, as expressed by the Bernoulli equation, says it:


http://hyperphysics.phy-astr.gsu.edu/hbase/pber.html

and:

http://www.vararam.com/reality_of_ram_air01.html

Skeedatl

Conservation of energy includes a heat component that your example lacks.

The conversion of dynamic pressure into dynamic pressure results in heat. You wouldn't see .176PSI increase in pressure...you would see that energy equivalence given off as heat, and only a tiny amount of heat. Bernoulli's equation makes some non-real world assumptions. Laminar flow and infinate viscocity. Actually READ what you're posting. Bernoulli's equaltion doesn't work in the "real world", just as acceleration formulas don't work in the "real world" because of air resistance.

However, for "math problems" in class, these concepts are difficult if not impossible to fully quantify.

And again, you're confusing static and dynamic pressures so all of this is moot anyway.

You've now switched your argument previously supported with Ram Air articles to one of slowing air increases pressure; failing to realize that you will NEVER achieve a pressure higher than that of the surrounding still air.

With the argument you've laid out, you're better off with a standard air box.

The WHOLE flawed concept behind ram air is that air is rammed into the motor, just as it would with a very fast airplane.

These concepts do not translate to automobiles as air doesn't not compress as automotive speeds like those in your previous examples of the ZX motorcycle and the WS6 Trans Am.

You have to ask yourself, what are you trying to prove. Sure Bernoulli's principle shows that slow air has more "side pressure" than fast air...but that doesn't help your argument for ram air BUILDING HORSEPOWER.

Benoulli's equation shows that you will have a maximum side pressure when the velocity is ZERO. This hardly supports the concept of sticking a scoop on the front of a car.

The concept of Ram Air solely relies on the conversion of dynamic to static pressure...hense RAMMING THE AIR into the motor via overpressure. Bernoulli's equation doesn't not show this relationship. It merely shows differences in static pressures with velocity in a closed space.

The enivronment a car moves through is not a closed space. Bernoulli's principle requires this fixed space, but no other variables.

Basically, you're going to see in a car the air flow into the scoop until atmospheric pressure is reached. At the point, the front of the scoop will become a "solid" just like the rest of the car and the rest of the air will flow over the scoop just like it would anywhere else. Any additional air is not going into the scoop, it OVERFLOWS into the airstream moving aroud the car. Only if the car goes fast enough, Mach .5 or thereabouts will you see pressurization inside the scoop rather that it just being pushed aside with the rest of the air.

Now, the only benefit from ram air at slow speeds, comes not from an increase in pressure, but a filling of the void created by the vacuum of the engine. But even then, you're not conserving enough energy (saving the motor work) to even be measurable given the uncertainies involved.

harddrivin1le

So "ram air" NEVER yields an increase in manfold pressure at ANY speed?

Is that what you're claiming?

Skeedatl

No, and I've never claimed that. Are you actually reading my posts?

Jeez guy...

This is from my post on PAGE ONE OF THIS THREAD!!!!

" Below about Mach 0.5 (or about half the speed of sound), air is considered “incompressible. That is, even if the correct nozzle is selected, and the air is slowed down (the official term is “stagnated”) there will be zero trade. No kinetic energy will be traded in as work capable of compressing the air. The reasons for this are not discussed here; the reader may consult any reputable fluid mechanics textbook for confirmation of this fact. In plain English, a car is just too slow for ram air to work. "

That's when you started posting car and bike article one after another, with flawed logic and experimentation.


DO US ALL A FAVOR AND ACTUALLY READ THE POSTS BEFORE REPLYING TO THEM!!!!!!!!!!!

harddrivin1le

Then you can't make the blanket statement that it's a myth.

A bone stock WS6 will exceed 150 MPH with no problem. That equates a rise in static pressure @ the intake manifold of ~ 2.75%.

http://www.snowgoercanada.com/tech_ram_air.shtml

harddrivin1le

YOUR car might be too slow.

A bone stock WS6 will exceed 150 MPH with no problem. That equates a rise in static pressure @ the intake manifold of ~ 2.75%.

http://www.snowgoercanada.com/tech_ram_air.shtml

Skeedatl

How many times did I say ram air doesn't work below Mach .5 and that the ram air effect doesn't work until around Mach .5? About a zillion.

You just got caught in your own web of bullsh!t and now you're embarrassed. You then molested all the equations trying to support your article postings. Then reversed yourself thinking no one would notice.

Fortunately you can't go reedit your threads. Everyone can see you're full of sh!t to the point your eyes are brown.

Next time don't speak of what you don't understand.

harddrivin1le

It's good for a ~ 2% plus increase in pressure @ the intake manifold @ 150 MPH.

That's Mach ~ 0.2.

Skeedatl

BZZZZZZ, wrong. That energy is conserved in the form of heat, not increased pressure. Less than 2% on paper, even at 150MPH, a speed the WS6 would have trouble attaining, you won't measure it in "reality".

But thanks for playing.

harddrivin1le

Tell that to people who race @ elevated speeds.

You won't measure the difference between a K&N air filter and a paper one "in reality," either, yet you hype the K&N filter.

Skeedatl

Like you? Those WS6 dorks? Those dorks from the ZX article?

You forget everyone can see your previous posts.

harddrivin1le

I forget very little.

And I haven't forgotten your claim that aluminum heads (by default) make more power than iron ones, either.

And you took that argument WAY out of context.

The L-78 aluminum and iron heads were essentially IDENTICAL and ran THE SAME COMPRESSION RATIO.

Yet, the guy was implying that engines equipped with the aluminum head option made SIGNIFICANTLY more power solely due to the difference in material.

They didn't.

And that was the crux of that argument.

Skeedatl

BTW, I run cotton filters cause they stay cleaner and more efficient longer. Not 'cause I'm getting "monster HP".

harddrivin1le

Good.

But you've agrued that they produce more power...

In THEORY they may...but certainly no more than a decent ram air system on a vehicle traveling @ ~ 100 MPH.

Skeedatl

Yeah sure. Nice history revisionism there sport.