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Discussion Starter · #1 ·
I know with my NA race engines I am gaining about 1 psi positive airbox pressure at 175mph.

I have also picked up a CONSIDERABLE amount of HP by using ram air into the turbo compressor as apposed to drawing vacuum for inlet air. <I have done a fair amount of testing on this. Ram air has NEVER yielded negative results.

-A: I have ALWAYS thought the air inlet into the fender from the SC airbox was too small. It is as big as toyota could of used without having the dealer/installer cut metal out of the fender. That doesnt mean it couldnt benefit from being larger. I have NOT done any data logging to determine pressure variances in different stages of the intake tract so its completely speculation.

-B: a 'properly' (not just sticking a tube forward and hope it works) designed ram air SHOULD decrease the rotor load and increase hp multiple ways.

ALL THIS BEING SAID!!!!

I am now starting gearing up for the '13 race season so I have limited time to do anything else (and I am being lazy). If anyone that has some smarts is interested please look at the following formula and determine air inlet sizing. This will tell IF toyotas is big enough and what size a ram air will need to be for this engine.

(from my friend and fellow land speed racer Dr. Mayfield....quite possibly the 2nd smartest MFer I know)

The Mayfield Company Homepage - Automotive Analyses

If a determination is made on correct inlet area is made I will design and build a ram air system and post the results.

~JH
 

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Discussion Starter · #2 ·
BTW:

Calculations (IMO) should be made with 1/4m drag racing in mind with this truck. MEANING that a HP advantage should be made at 1/2-3/4 through the 1/4 mile. So whatever (speed) the SC truck should be running in the 1/6th mile?

~JH
 

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Eddy (Supercharged) has a ram air intake on his truck. He used the passenger fog light inlet since his truck didn't come with fog lights. He did a pretty good job on that intake IMO. He should be posting something here once he sees this thread.
 

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I pulled the blower off my Civic to upgrade the injectors. I made a new 4" intake for it to run with the blower off. To my surpise I am actually seeing .2-.5psi positive pressure. From what I have found the guys using velocity stacks(ram air) can see 1-2psi on naturally aspirated engines.

Pretty cool, but I worry about sucking a bug or rock up with a velocity stack.
 

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Hey guys Lizard of the Highways here. Just got a PM from the Brother BS&E inviting me to participate in this thread. We have Sebastian this weekend so not much time to post. After I get him tucked in tonight I will post in detail about my testing of Ram Air Intake Scoops along with pictures and formulas that I have devised over the years from empirical data. I do not race so everything I do is from a MPG standpoint but I am sure some of my findings would be applicable to those who race.
 

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I have been designing, building, and testing Ram Air Intake Scoops on my truck for a little over 100,000 miles. I have made a lot of mistakes and learned a lot from those mistakes. Along the way I have come up with a general set of guidelines based on empirical evidence.

The purpose of a Ram Air Intake Scoop is exactly as the name implies - it scoops air and rams it. The ideal scoop gathers air and force feeds it into the air box. It does this in a perfect world as a straight shot. The perfect world does not exist in my truck and neither does it in yours. There are always bends, turns, and less than ideal routes from the scoop to the air box. The game is in minimizing losses from these deviations.

My first scoop and several subsequent scoops were mounted below the bumper on the passenger side of the truck. A few websites indicated that this location was in an area of negative pressure. I received numerous emails and PM's telling me that this location was actually sucking air out of the intake. More than a few missives called my personal integrity into question. The bottom line is that none of these people or websites actually tested this location on a truck - I did. The location under the passenger side of the front bumper was one of the highest pressure locations tested on the vehicle. As of the time of this writing I am in the process of working out the final details of installing the Ram Air Intake Scoop into the bumper of the truck. There is a little more air pressure in this location and the air will hopefully be a little cleaner too.

There are some fundamental guidelines to basic scoops and some theories that are still in the rather fluid state (pun intended):

  • the larger the face area of the scoop the more air it can gather
  • the walls of the scoop need to converge toward a rear area where the scoop connects to a tube that leads to the air box
  • the angle of the walls must be acute - preferably less than 30 degrees
  • the ratio of wall area (including floor and ceiling) to volume must be as low as possible
  • the scoop must be located in an area of high pressure
  • the depth of the scoop should be more than the width of the scoop (think long and narrow rather than short and fat)
  • the scoop must be the sole source of air for the intake so that it can build pressure and pressure is what gives performance in whatever form you are seeking (HP or mileage)
  • the scoop should gather a minimum of 10 times the amount of air the engine needs at a given RPM and ground speed - this is to provide enough air to build pressure as well as overcome pumping losses from friction
  • curves are always better than right angles - now would be a good time to learn the how's and why's of parabolas
  • tube length from the scoop to the air box must be as short as possible with a minimum amount of bends
  • the tube leading from the scoop to the air box should be as large as possible but this is limited by what it has to go through to get to the air box

There are concepts involving inner directional vanes (often referred to as fences), velocity stacks, and reserve volume but these are still in the research and testing stage so this it something that I will touch on as I learn more about them. Briefly:

  • inner directional vanes (fences) are used for the purposes of aligning air flow in scoops with offset bodies
  • velocity stacks move the end of the intake pipe that leads from the scoop to the air box into the inner volume of the scoop where the fastest moving air can be found in the scoop - air tends to cling to the walls of the scoop and slows down as a result
  • reserve volume refers to the amount of air available in the scoop in relation to the amount of air consumed by the engine at a given speed - this covers both how fast that air can be replenished and the pressure of that air

A few formulas that you can plug into an Excel spreadsheet to help you calculate needed face area at a given speed:

RPMs x Displacement in cubic inches x .5 = Engine Volume in cubic inches per minute

Scoop Height (inches) x Scoop Width (inches) = Scoop face in square inches

MPH/60 x 5280 (feet in a mile) x 12 (inches in a foot) = inches per mile per minute

Inches per mile per minute x scoop face = scoop intake volume per minute (in cubic inches)

Scoop intake volume per minute / Engine Volume in cubic inches per minute = the ratio of scoop intake volume to engine consumption volume​

So there are some beginning basic points to get started with. Ask what questions you have and I will do my best to help you find the answers you seek. I do not know it all but I enjoy what I do.

Some great food for thought can be had in reading and applying Bernoulli's principle - really cool stuff there.
 

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the dealer that installed my SC said you had to use the air box that comes with it. he said i couldnt even use the trd cai. he told me anything else would push too much air to the sc and make the check engine light keep coming on.

i have the apm ram air hood, but never tried the optional air box.
 

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the dealer that installed my SC said you had to use the air box that comes with it. he said i couldnt even use the trd cai. he told me anything else would push too much air to the sc and make the check engine light keep coming on.

i have the apm ram air hood, but never tried the optional air box.
^^^ That is very true. What I did was I added an extra 4" port to the lower portion of the air box, it basically allows double the amount of air entering the box. I have never got a CEL from this mod. Guys that change the intake system that comes with the TRD SC kit get the too much air CEL.
 

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I dont want to hijack this thread but have similar question. Trying to get air into my SC but i cant pull from the bumper or anyplace low. I have glass fenders that directed all the road spray to the air inlet and after installing inner fender liners I was clearly not getting enough air so currently it all pulls from the side of the air box under the hood. I would like to add a snorkel but with the fenders it will have to be all custom. Any thoughts on moddifing the top of the air box with an underhood scoop? Is enough air getting under the hood? Does anyone know of a snorkel kit besides volant that would work?
 

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^^^ That is very true. What I did was I added an extra 4" port to the lower portion of the air box, it basically allows double the amount of air entering the box. I have never got a CEL from this mod. Guys that change the intake system that comes with the TRD SC kit get the too much air CEL.
Your onto something Supercharged... Can you post a pic of your air box?
 
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