Good work, Bill! As I am fond of quoting: "Without the data, you're just another guy with an opinion."
6" H2O is ~ 1.5% pressure gain, since one atmosphere is ~ 407".
To improve accuracy when I ran a similar test, instead of having the reference as cabin pressure, which can vary with windows open/closed, HVAC blower speed, etc., I made a 1/8" 'static tube' with the forward facing end blocked and bullet-nosed, and small holes drilled in the sides 120° apart. I taped this to the top of the radio antenna to keep it clear of body-induced turbulence and connected it to the manometer.

 

Exactly, the reference pressure is just as important as what you're measuring. I am curious which way and how much cabin pressure would change at speed though. I've felt my ears pop on the highway before with the windows up.

 

Interesting thread. We were discussing similar context in the Corvette forum. I linked the guys over to this thread.

 

Are you talking about the Pitot tube??

If so, that tube is not meant to compress air at all ... actually it wants to keep the air exactly as it is, so the pressure can be used to deduce airspeed.

example ...
measurement from the pitot tube = pt - ps

pt = total pressure
ps = static pressure

The instrument can then use that to determine the planes velocity with Bernoulli's equation ....

V^2 = 2 * {pt - ps} / r

V = sqrt [2 * {pt - ps} / r ]

Exactly. This is the reason ram-air doesn't work until relatively high speeds. As soon as the air pressure in the intake track reaches a critical positive value (dependant on the velocity & density of the incoming air), the air approaching the intake will be pushed away by the higher pressure inside the intake itself ... therefore naturally negating any "ram-air" effect... On the contrary, a supercharger works because it is forcing air into a sealed space (the intake manifold), where the air can not escape and therefore is forced to gain positive air pressure, while being unable to effect the air entering the intake system. On a street car, the power gain of a 'ram-air' system (if any) is most likely from a cooler intake charge, as J-Rod and other have said.



P.S. I just wanted to add that I am consistently amazed with how much great info 300bhp/ton learns via reading through the internet ... whew.

 

Is that an insult??

 

Of course not.

 

If one leg of the manometer was connected to the above static tube and the other left open in the cabin, it wolud be easy to check the effects of blower and road speed, window opening, etc. Smokey Yunick mentioned a related issue with the Rochester FI system in a '57 Chev; I'll see if I can find it...

 

Soooo, who has really done a test of Ram Air for drag racing? What would the perimeters be for the test to be valid?
Like three passes without ram air and three with ram air on the same car??

All the "FACTS" that have been posted are facinating but I don't see a test for the cars we drive or drag race, to prove it one way or the other.

I guess the next time I race I will take all these facts and tell all the guys drag racing to remove their ram air systems because it has been proven they don't work. I know they will listen to all these facts - then run my *** out of the pits

I have an idea for ram air on the car I am setting up for drag race only, so I am going to run it with and without ram air to see if their is a difference.

 

I am going to write to Mythbusters and see if we can get a scientific test done.

 

I love your sarcasm about everyone else’s "facts", but your ingenious idea won't work at all. There are far too many variables to just "run three passes with the ram-air on and then run 3 with the ram air off ".... Even if the ram-air does work, the speeds you would need to be running for it to be significantly effective would be tough to reach on a 1/4 mile track, and even then you would only be above those speeds for a small fraction of the complete run ... therefore the gains would be small, and easily mistaken for driver inconsistencies, a hotter/cooler engine, tire condition, changes in air temperature, track conditions, wind speed, etc, etc, etc.

 

That would be a pretty cool episode.

 

Best of luck on Myth Busters. It would make an interesting episode.

On a different note, although I am not active as a pilot, I do have a commercial/instrument/single and multi-engine pilot's license. I also used have my single/multi-engine and instrument flight instructor's license and instructed back in the 1980's. I can tell you that during takeoff, you do not see any rise in manifold pressure or torque until approaching 100 knots (115 MPH). Even then, it isn't dramatic, like maybe a few percent (things are pretty busy on takeoff).

Steve

 

It is not so much the ram air effect (which many have proven is non existant) as it can only get to about what ~.3 psi. It is the idea of unchoking the engine and not causing it to have to suck and not causing a vacuum inside of the lid.

"Ram air" intakes work not by compressing air but by lessing the vacuum inside the intake (lid) along with supplying cold air.

 

The "ram-air effect" does actually work just fine ... it is just relatively non-existant at the speeds our cars will normally drive (not to mentioned designed incorrectly, as others have said). Take a look at scram-jet engines, they work off this principle ... shove a large volume of air into a space, compress it by forcing it through a small opening, then ignite it. However, it takes mach 3+ or so for these engines to compress enough air to function.

The fact that the Ram-Air supplies colder air has been stated numerous times, and seems to be the best arguement as to why any power at all could be gained from a 'ram-air' type system on a street car.

 

well how much do you think da helps a run about every 800 ft is 1tenth is that safe to say on a N/a car

 

You have to think of air as a fluid. Think of water in your pool as the air in the atmosphere ...

Take a big bucket, with a small hole at the end (your intake system) .... now dunk it in ur pool, and move it under the surface of the water at a given speed. Then move it faster next time. If you could measure the amount of water that escapes the back end each time, it would be essentially identical since you cannot generate enough force to trap and Compress the water. Basically the water that is trapped inside the bucket and cannot get through the hole is forming positive pressure in the bucket that is keeping other water from entering. This is exactly how your intake track is acting when you have a big lid with small tubing ... only a certain amount of air can get past that opening.

Now, if you were able to move that same bucket through the water at a very fast speed, you might see a noticeable difference in the amount of water that is forced through, simply because the force of the oncoming water can overcome a greater pressure differential as speeds increase.

As far as DA ... you just have more air in a given volume, it is denser (hence the name, density altitude). Just as if you were to go to 100 feet underwater.... the water is the same, just denser.

 

you didn't answer what i asked a tenth is a good estamite for about 800 ft Da right well the only difference between two weekends was 60lbs lighter, and a da difference of 1600 i went on an average of 111.8 one weekend and 115.4 the next weekend, Da difference 2mph and weight 0.6mph that is 2.6mph but my total was 115.4-111.8 = 3.6 so i gained ~1mph from my new intake over the FTRA, so obviously the engine is not working as hard to get air in as it did on the first day at the track.

I am not agruing with you that air is hard to compress at the speeds we travel in the 1/4 but it does compress slightly, and the intake is designed to unchoke the engine, ie why it works over the FTRA, larger hole, fills up the air box faster after an intake suction from each cyclinder, basically keeps it filled with atmosphere pressure(slightly above at the traps) thoughout the whole run. lowering or eliminating the vacuum.

Chris

 

Sorry, I didn't realize that was a question .... I'm also not really sure what you're talking about, is it a Ram-air system you have on your car, or what??

As it has been said numerous times, and what I just said 2 posts ago ... one of the reasons that you could see a gain from a "ram-air" system, would be due to the colder air it is pulling in from Outside of your engine bay. Colder air is denser, and therefore you will naturally go faster. This is the same as if you were to run the car on a colder day.

I would guarantee that if you took your "ram-air" system off, and went to the track on a day it was 30 degrees cooler outside, you would see a similar gain.

 

I would like to offer my 2 cents on this ram air thing. I've read all the posts in this thread as well have just completed my own "Sux2bu intake" design, which can be seen at https://ls1tech.com/forums/generation-iii-external-engine/474888-homemade-camaro-ram-air-pics.html . Before I installed the ram air intake I had the FRA mod. At the track, the IAT's would climb to 150 degrees while in the staging lanes. At launch I would be pulling timing due to the high IAT's. By the end of the quarter mile I would only be at 85 degrees IAT. Well above ambient. So based on my oberservation, the FRA mod was inhaling a lot of hot air. Now when I was on the highway, I would always end up at ambient due to the air constantly flowing.

My hptuners got stolen so I cannot log IAT's currently. However, I created my intake design out of 100% plastic parts because I didn't want the air to even have an excuse to get heated up at idle or any other time. Before my ram air design, I went 12.77 at 110.25 with a DA of 100ft. with a 60' of 1.99. After the addition of skinnies and ram air, I went 12.67 at 110.25 with a DA of -100ft with a 60' of 1.93. I then took the ram air off and went 12.67 at 110.25 with the same 60'. I should really bracket race this car!

Now without HPTuners I can't tell what the pcm is doing. I don't know if its pulling timing from KR or another source. Hell it might not be doing anything. So I won't comment on whether or not ram air works until I can make back to back runs on the same night while EFILive is monitoring things.

So...based on my observations, if the pcm is not controlling certain power making functions(timing, fuel, etc) then my results support that ram air, in fact, is a myth at 1/4 mile speeds just like this thread says it is. And that any gains should be attributed to decreased intake temps or other pcm functions that have not been monitored.

 

You are most certainly correct.

For the "ram-air" concept to work, you would need to be able to physically COMPRESS the incoming air entering the intake ... much like a supercharger does. Since air will not compress unless a significant amount of force is added to it, having that happen at the speeds normally obtained on a highway or a 1/4 mile track, is extremely unlikely.

As you said, however, the colder air an intake like yours pulls into the engine WILL be denser, and will therefore produce more power than the same volume of hotter air would. So even though the same AMOUNT of air is going through your intake, that air is denser, and will therefore produce a gain in power.

This is the same concept as DA, the higher you go the less dense the air is and the less power your N/A car makes. This applies when you look at Outside Air Temps as well .... your car produces more power when you’re driving in 40 degree weather than it does when it's 100 degrees.