BIG question: ram air side effects

I installed a poor man's ram air intake on my 82 POS pickup. It consists of a hole cut in the front of the body of the truck below the bumper. This hole is about 4 or 5 inch in diameter. A slim, long plastic funnel is jammed into this hole and cut flush to the body. This funnel is pushed directly into the corrogated intake hose that runs to the intake/airfilter box. The edges around this funnel piece is sealed against the contacting hose surfaces so that all air rammed into the funnel must go into the airbox. This should create pressure in the intake system. This BIG question is this: What is the effect on the vacuum powered systems that rely on the vacuum created by the intake? I assume that this vacuum is not there when I run the truck at high speed. Are there vital vacuum powered systems that will deteriorate that might end up causing major damage to the engine? BTW, I drive mostly on the interstate = I drive over 70 MPH most of the time. Thanks.

Reply to
Thater
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Reply to
Craig Williams

Put a boost gauge on your intake manifold and post the speed(MPH) needed to get 1 psi of boost pressure!

Reply to
Woodchuck

Give us of the dimensions of the funnel and hose and I can do some friction and force calculations. But, I seriously doubt if the force at

70 mph is enough to generate a positive pressure.

Woodchuck wrote:

Reply to
John A. Stephens

You aren't going to get anything. NACA the predecessor of NASA, did similar testing and created the NACA airduct. Used widely on aircraft. One that actually worked, its design was very technical, and it looks cool. it was a simple design which came out of wind tunnel testing,and only worked at speed way above the automobile speeds in question. But in construction if the angles of the different sides of the duct varied as little as one degree, its effects were negated completely. Generally speaking the interior drag of the duct counteracted any gains in pressure if manufacturing tolerances were altered at all. It was not cost effective and only used in aerospace. Part of the secret speed of the P51 fighters of WW2 was the design of the radiator duct which actually produced thrust in certain flight conditions. But remember they go over 400 mph. and have much more air flow or pressure to harness. And were also supercharged. So what's that tell you....There's no shortcut...Also a similar principal was used for thrust augmentation on radial engine aircraft of the time and they were turbo, AND supercharged.. Even aerospace today alters the design , and uses them to direct airflow only. Its nonfunctional counterpart is seen on automobiles in some hood designs from the sixties. It looks fast but didn't work, its seen around in different areas, on different cars, and looks like a wedge with extended out sidewalls. On another note, if you remember bournellis principal which stated for an increase in velocity you get a decrease of pressure and visa versa, This is how you get a vacuum in a venturi. If you squeeze the hole size down you get an increase of velocity and a decrease {vacuum} of pressure. This works both ways . If you widen the hole you lose velocity but increase pressure, can be applied to an automobile in your case and has been....The air flowing over the top of the hood of your car passes the area by the bottom of the windshield before going over the roof. This creates an increase of pressure and a decrease of velocity. A sort of widening or reverse venturi effect, of the air from the front of the car , passing over the roof is created. Chevrolet or Pontiac at one time, I believe the camaro, but not what year, installed a reverse hood scoop. {Not like the fake 79 trans am scoop design.) that actually worked and had a butterfly actuated flapper that opened when stepping on the gas pedal. It actually gained pressure but was only negligible and was dropped for cost I imagine. I also don't think this works with the hoods with the gap between the window, either. But if you figure how to rig the opening at the base of your windshield , and your interior duct drag is low enough , it should work.I doubt you will ever know it , and when I speak of a pressure increase , I mean its real small. There is no shortcut to turbo, or supercharging, or pumps of any design would become obsolete. Sorry,

"John A. Stephens" wrote in message news:5qhXb.1830$ snipped-for-privacy@monger.newsread.com...

Reply to
verndog

What you all forgot is the horsepower gains from water injection. That scoop works great for filling the air filter up with water. Nothing like a few cylinders full of water after hitting some good puddles.

I thought the 1969 Z28 cowl >You aren't going to get anything. NACA the predecessor of NASA, did similar

Jim B.

Reply to
jimbehning

I understand that the performance from such a device is negligable, except for the simple COLD air aspect. My concern is the effect on the vacuum systems. Yes this is on an 82 VW pickup. Will this cause any damage due to loss of vacuum. As I understand it, vacuum is created from the air intake, straight from the intake manifold. Thanks.

Reply to
Thater

Reply to
Randolph

augmentation on

Reply to
verndog

|Vacuum is taken at the manifold, after the throttle valve. At small |openings of the throttle valve you will have as much vacuum as you had |before. Even without your mod, if you are running wide open throttle at |low RPM you do not have significant vacuum. That is why brake boosters |(and the ventilation controls on A2 Golfs / Jettas) have their own |vacuum reservoirs and check valves. Your ram intake is not going to |cause any harm at all. One might speculate that the cruise control |(vacuum operated) would be railed a little earlier than before, but I |doubt even that would happen.

I think he is referring to clean air taps into the intake tract preceding the throttle body, such as the PCV clean air tube. There would be no negative consequences to these from any positive pressure generated by the scoop. Rex in Fort Worth

Reply to
Rex B

My software says that at standard sea level conditions the "total pressure" (ram air pressure) at 80 mph is 1.0078 times ambient pressure. Say, 30.15 inches of mercury when ambient pressure is 29.92 inches. That assumes perfect conversion from velocity to pressure. In practice, a ram air induction system will not deliver that much pressure rise.

Although perfect ram intake efficiency gives a .78% pressure increase at 80 mph, *power* increase is less because ram compression heats the air too. The temperature rise is just 1 degree F, resulting in the ram air density being .55% more than ambient.

To show what can happen at oval racing speed, 100% pressure recovery at 230 mph gives 31.88 inches of ram pressure at 29.92 inches ambient pressure. Temperature rise is 9.5 F. Taking the pressure and temperature into account, ram air density is 4.6% more than ambient.

Reply to
Paul Hirose

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