I cannot find my prior thread so will start anew. I am making a 'ram air' for my Steeda SRI (I enjoy metal working so its a hobby thing). Let me cut to my question. If known or reasonably sure. How much boost (in PSI plz) could a stock 2.0 Duratec take before I run into trouble?
(Stock meaning factory tune, stock injectors and fuel pump).
Thanks.

You'll never get THAT much PSI from running just a ram air intake...
If your car could do 200 MPH, you might get 1.5 or 2 PSI. But every little bit helps, right? And the added benefit of running cooler, denser air from the front of the car instead of from the engine bay will help noticeably...

Things to remember though, is when you restrict the intake tract (increase air velocity) your DECREASING pressure. Think of a carb venturi (it's actually called the Venturi effect)...the carb passageway narrows, speeding up the air flow, cause negative pressure over the metering jet, drawing fuel up the bowl...
So, keep your ram air intake tract constant diameter straight into the engine...
You get pressure from trying to stop the air flow, not speeding it up. The ideal setup would be a large diamter duct, mounted at the very front/center of the car, away from aero effects of the bodywork, travelling straight to a large air box, which then leads to the filter/MAF/engine...
Dumping the air into the air box will pressurize it. The larger the air box, the more pressurized volume is available for the engine. Think of it like this...
You can have a tiny little turbo on your car that produces 30 PSI, but it won't flow enough to feed the engine...cubic feet/minute...the engine might draw more air than the turbo can put out, eliminating all the boost!
PSI is only part of it...like a water tap hooked up to a 3/8" pipe, and a similar sized tap hooked up to a 5" pipe...both give you 80PSI, but which one flows more?
A large airbox will be able to maintain pressure even if the engine is drawing a lot of volume (full throttle, 6000RPM), at least, that's what you want...
G'luck, and post pic's!!

Thanks WuNgUnSVT. I agree with what you said. some detail. I have calculated a 10 sq inch (area) scoop and a "pipe" of 3x4 (12 sq inch (to reduce the 'carry velocity)). This 'dumps' into a box which holds the air filter (I have not calculated the volume of the box yet as I am still building it) . I was having a bugger of a time trying to calculate how much static pressure would be 'apparent' in the box doing 60mph. The reason for my post is this. My brother gave my numbers to a friend (funny car tuner) and he gave me back (for the day in question so he had current air density figures) a calculated 1.77inch of mercury. This equals a (stunning) .86 PSI. WAY more than I thought possible. As temps drop, air density will rise resulting in a potential rise in PSI. What I need to know is where to "draw the line" so to speak so I do not overstep the fuel delivery capabilites (I.E. leaning out during worst case scenarios like a stiff headwind or a big truck passing at speed).

youll b good til about 6 or 7 pis thats what a turbo kit would run so 6 or 7 but like he siad without a power adder good luck getting that much

Wow! 6-7 PSI on the stock tune and fuel delivery? I had know idea it was that capable. Cool! No worries then. After it's installed I will try to take some manometer readings. With those I can finish my spreadsheet.
Thanks again! [:)]

^^^ No Way Without Tune !!!

Wow! 6-7 PSI on the stock tune and fuel delivery? I had know idea it was that capable. Cool! No worries then. After it's installed I will try to take some manometer readings. With those I can finish my spreadsheet.
Thanks again! [:)]


The engine can handle no boost with stock tune and stock injectors. But a SRI isnt adding any boost at all. It is reducing intake restriction ...but no boost is being made at all. Even with ram air...you are funneling cooler air into the filter...and it may be less restrictive than pulling it in on its own...but still no positive pressure past the filter.

^^^ No Way Without Tune !!!

Thats why you get an SVT. They handle alot.

Thats why you get an SVT. They handle alot.

The SVT can also handle no boost without a tune...

With no tune your engine will run like crap and blow with any boost no matter what kind of focus.

Hold plz! I am getting confused. Maybe "boost" is a poor word in this application. Instead, lets use VE (volumetric efficiency). Standard NA focus has maybe 82% VE. With a ram air setup, it is possible to achieve 100% VE. Potentially exceeding that at (rare) times. So my concern is this (and let me use an extreme condition). I drive home to North Dakota in the winter. The air is very dense. So dense that at 60mph I could theoretically attain 2 inches of mercury (~1 PSI at the TB). So my question is very basic. Would this create a problem like running a lean fuel mixture that could harm the engine? Or can the stock tune and fuel system manage this? I am just trying to get a feel for the upper limits. Like I said before, is there a line I should not cross? It's not a performance question, it's a 'potential damage' kinda question.
Thanks!!

simple answer is no, you will not create any problem. the computer can compensate for this amount without a problem since it isnt truly boost, your just letting it breath way better. the ehgine will only draw the air it can use into the cylinder..
now, any form of forced induction (s/c, turbo) will require a tune since the air is being pressurized and forced into the cylinders..

:) lol def need a tune to run boost i found that out the hard way

simple answer is no, you will not create any problem. the computer can compensate for this amount without a problem since it isnt truly boost, your just letting it breath way better. the ehgine will only draw the air it can use into the cylinder..
now, any form of forced induction (s/c, turbo) will require a tune since the air is being pressurized and forced into the cylinders..

That seems to make a lot of sense, and sorry all for the terminology error.
Thanks for the clear answer goinloco1. [clap]

This will do more than just letting the engine breath better...properly done, you will get a ram effect, i.e. boost...just very small amounts.
This is the reason for the large airbox resevior, to keep positive pressure up while the engine is drawing from it...

I've owned Kawi sportbikes, and they've been utilizing ram air for years. Sure, your not going to feel it inthe seat of your pants, but it works...
And I'm pretty sure a 750cc turning 12,000 is drawing more air thru it than any 2.0 Focus could ever dream of, so I think the dimensions he specified for his setup will be ample...

The only concern that I can think of now, is the MAF sensor. It measures air volume, or the amount of air flowing past then pickup sensor. It adjusts the fuel needs by measuring this amount and compensating for temperature (density) and to a lesser extent, the humidity...
Will it be able to 'see' the pressure moving past it as well? Not directly I don't think, but I think it will try to compensate because the air will be denser...

The terminology gets tricky, and there are so many variables it gets hard to pin down a number. One formula I have not been able to find however is 'static CFM' (which is an oxymoron I realize). So if you want to try and answer this one plz be my guest. It is easy to visualize. You have a tube (lets say 3 inch diameter) mounted on the outside of your car, and your traveling 60mph. The tube is open, so you know the linear feet per minute (5280) and can calculate the CFM (110). All well and good. Now, you reach outside and place a cap over the 'back' of the tube (so you have air trying to enter the tube but no where to go due to the cap at the back). Your CFM drops to zero, replaced by some amount of static pressure. If someone can please provide the formula to convert 'potential CFM to static pressure' (I know of know other way to describe it) I would be very appreciative. I cannot find it anywhere on the net and 2 duct engineers could not help either. If your a math whiz, the relevant elements are 'linear feet per minute (LFM)', CFM, and air density.

I think I read somwhere that the MAF can compensate for up to 10-16% more fule correction. Ill deffinetly have to dbl check those # though... but weather its from colder denser air or better flow or even small amounts of boost, like you were saying 0.8 lbs. the MAF will read more air molecules passing it and compensate fule accordingly. This is why you can add an intake and exhaust without a tune and although its not perfect, the MAF compensates with more fule to accomodate the extra air molecules in the cylenders.
GL finding that equation though. I hate math lol

hey im not trying to bring backa dead thread (ok so i am) but i was wondering what youve found out about this litte topic, i have thought about doing this same thing to my 2.0zetec, while the motor is difrent im guessing it will have the same effect on the engine.

so im wondering what youve found out, have you done it? notice a difrence at 60mph? find its not do able? or..... man i want to know. lol.

thanks for any info :)

-levi

Edit: BAH its late and i cant even spell my own name

This is what I have found out.
The math is tricky. I will probably have to submit my specific questions to the applied physics dept at our university and hope someone takes an interest.
Have I done it?
The airbox is 90% complete. The space has a lot of strange angles, plus the fact that it has to split for installation/removal and still be airtight has taken alot of design/development time.
The air pickup (I.E. scoop and pipe) are on paper now. I have a choice between keeping it cheap or making it semi autonomous, which is more expensive but more effective (and more fun in my opinion). >semi autonomous means that the 'scoop' get larger/smaller based on atmospherics and user input<. I will probably build it cheap with the option to add the robotics later.
I have a target date of ~Sept to begin testing. My design goals are.
'Cold' Air supply to the filter.
minimized debris/water pickup
elimination of hydrolock potential.
VE of +100%
Ease of filter service.
All Weather/Geographic location usable.

I have set some tall but I believe achievable goals. I will post some pics when I have something to show other than a box made of aluminum.

wow thats really sweet to hear that your wanting to do it the right way (do the math first :P )

it sounds like a really cool idea, what did you use to design the air box? any CAD or FEA?

and why are you worried about neckinmg it down? im jsut guessing that even with as much flow, i would think the stock motors should be able to handle it (of course we need alll that tricky math to be sure!)

and also how are you planing on reducing debre intake? and water? would like to know cause where i live... theres some pretty heavy rain storms, best of luck and keep me updated

-levi

"what did you use to design the air box?" >> Paper Mockups.
"why are you worried about neckinmg it down?" >> As you accelerate, the additional power is eclipsed by the drag (diminishing returns).
"how are you planing on reducing debre intake?and water? >> control the 'carry velocity' if possible (which is also assisted by having the scoop variable).

well I'm no engineer, but I made a ram air for my SVT and it feels like it's working in the way I want it to... no numbers to back it up, but seat of the pants feel is positive at freeway speeds.

I used the stock airbox and built the ram air ducts to match the inlet (3"). If you figure out how much boost it produces, please let me know.

After much effort, I was able to find the formula and table to calculate the theoretical pressures (From my Dad no less who had them in an architectural book) . I am posting this as it is pertinent to my original question.
Please see the attached table from my spreadsheet. There are 2 'scoops' represented. 12 and 24 sq inches respectively. there is far more potential pressure than I would have attributed to a simple 'ram air'. So now that I have the numbers for you to examine would you please give them some consideration. I have not built the scoop yet (it is next) and would like to have a good estimation before I start the build.
Thanks.

You need to be careful in choosing a place for the scoop, you really dont want to block the radiator... maybe coming out of one of the fender wells?

The 'hardware' in no way impedes or interferes with any existing component (loosely, it follows the path of the stock setup). The scoop BTW mounts underneath, just behind the splash shield. A natural high pressure area.

Ram air is a valid idea... but I would mount the scoop up higher if possible. During the summer the air that low is usually 10-20* hotter than ambiant temps.... after all it is being heated by reflected heat coming up from the asphalt.

The lower edge of the scoop is 6" from the pavement (stock suspension). I did search for a higher position but no solution presented itself unless I wanted to start interfering with normal air flow or start popping holes in the body work. So the location is pretty much fixed. Your point is noted however. I will have to try and rig a differential thermometer. regardless, it still has to be cooler than the air under the hood.

I see you trying to do math here to figure out what kinda pressure you can get at what speeds ect, but your motor creates negative pressure (vacuum) and it kinda throws all your calculations out the window...?

I'm trying to invision the setup here, but I'm having trouble since I've been trying to do something similar, but I have a Zetec with different bodywork to work with. When I was reading this, I learned a whole lotta junk. But one thing I thought of is that on my stock bumper, there are plastic panels that duct air into the radiator. I don't know if these are part of the wheel wells or not, but I just thought it would be easy to cut a hole in that and mount a velocity stack there. The problem is, if you mount it flush, it's angled by around 45 degrees, so I guess it would cut the amount of air picked up roughly in half. I don't feel like thinking about it enough to calculate different cross-sectional areas, much less airflow parameters, so I'm just going by trig here. Maybe you could mount it more toward perpendicular to the front bumper without interfering with airflow to the radiator.

But all this assumes your front bumper is similar to the Zetec in this respect, with an accessible route for a tube.

I see you trying to do math here to figure out what kinda pressure you can get at what speeds ect, but your motor creates negative pressure (vacuum) and it kinda throws all your calculations out the window...?

Simplify the problem as the variables will soon swamp you. Assume 100% VE. Calculate theoretical CFM of engine. Calculate theoretical CFM of scoop (you might want to subtract ~10-15% for losses. hint> watch your velocities). You will find the pressure table in architectural manuals which give PSI at MPH. You can then do some 'ballpark' calculations to get an idea. Accurate measurements are only obtainable with a manometer which you use AFTER its all built.
Can I upload my Excel spreadsheet??? I am building the scoop now. Lots of measure,cut,measure,file,drill,fit,swear,file etc! [eek]

Good luck with this project. I'm an engineering student so this is naturally very fascinating to me. It was a good idea to set your general goals before crunching the numbers and everything.

Dcl2049 >> Once I get it fully built and installed I will take pics and post. It will be an 'aha!' moment. It's worthless to post anything yet as it keeps changing (it is very hard (read impossible) to establish a common measuring point for accurate plans. I have to build prototypes and mount to see where I screwed up then 'rinse and repeat'. But I am close! so close that I am shopping for a new air cleaner! :)

No matter how fast or much volume of air the Manifold unless modified will choke the air charge.

i dont see how the manifold will choke the air?? What if the head outflows what the manifold is capable of giving it, the wouldnt it not choke but maybe help the manifold to flow to the heads standards?