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Discussion Starter #1
I was wondering if it's possible for an engine to get too cold. I'm fabriating a Ram cold air intake. I am gonna put a dryer machine tube from my front valance and then lead it to my air box, therfore "ramming" cold air into my engine. Is this safe? I don't know if it will be bad in cold weather. Thanks.
 

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You didn't say what year you had. It will not hurt but you will not be "ramming" the air in. I did this on my '93. Superford pics
 

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In order to ram it in the intake the car has to be going faster than the air passing through the TB. I think this is somewhere around 150 mph depending on the TB size.
 

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Discussion Starter #5
Oh..great, I feel stoopid. Well would it still be good if I used the tube for cold air to go in the airbox? Or would that mess my engine up in the winter?
 

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There might be a problem in the winter if there's snow and it might get sucked in because the intake is too low on the ground. You might want to make the lower intake tube detacheable a little past the inner fender well - you can take it on and off before winter and still have a CAI.
 

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When I work it out I get a much lower speed. What am I overlooking?

3.0 Liter engine
3 L = 0.003 m^3

It's a 4 cycle engine so 0.25 of the cylinders are on the intake cycle at any one time. So, the pistons displace 0.00075 m^3 per crank rotation. Assume, WOT and ignore the friction losses so the engine will actually pull in that volume of air.

For the sake of argument, let's discuss 3000 RPM. Thats 50 cycles per second which yields 50 * 0.00075 = 0.0375 m^3/s.

If the TB is 65mm in diameter, the cross section is 0.00332 m^2. That makes the air speed 11.3 m/s. Converting to English units yields 25.2 MPH.
 

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I think your calculation is flawed when you say the pistons displace x amount of air per crank rotation. Air intake only takes half a crank rotation. To be more simplified, just say that 3 liters of air will be displaced for every 2 crank rotations, since a full cycle will have taken place on all cylinders.
 

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Ah, you are right. Half way around pulls the piston down and the rest of the way around pushes it back up. So, we're at 1.5L per rotation for a factor of 2. We're up to about 50 MPH at 3000 RPM. Any more equation bashers out there?
 

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What are you figuring the speed of the air is as it goes through the TB? And just what is your equation?
 

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I was estimating the air speed through the intake as the volume rate of intake (cubic meters per second) divided by the cross section area of the TB opening (square meters.) I didn't write the equation explicitly, since math looks so ugly in ASCII. Instead I listed the steps in text. As was pointed out, I had one factor of two error because I crossed up "Otto cycle" cycles with shaft rotation cycles. Taken all together we'd have:

S = (V/2)*f / A

S ::= intake air speed (m/s)
V ::= displacement (m^3)
f ::= crank rotation frequency (Hz)
A ::= TB cross section (m^2)

Then convert from SI (m/s) to English units (mph)
 

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here is a picture of my CAI with the dryer duct.
 

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Here is a picture of the dirt I banged out of my K&N filter. Put the intake end somewhere it won't act like a vaccuum cleaner.
 

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Originally posted by 3-fords1000@Mar 15 2004, 07:53 AM
here is a picture of my CAI with the dryer duct.
Do I see duct tape in this pic??????
 

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my brother has a cold air intake in his car and it made it fine threw the winter. I don't forsee a problem exept possibly in starting it in the winter. If the air is not coming from the engine compartment it may not be as warm from cranking and failed starts so it could possiblely cause proublems on thoses -40 +++ days.
 

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Here is an interesting article on ram air. Short answer: What matters in increasing the static air pressure. At car speeds air is not compressed at all so no increase in air pressure. So as the speed of the external air exceeds the velocity of the air in the intake, it only change how much air is being forced around the intake, not how much goes into it.

That's what I get for speculating about fluid dynamics, instead of firmware
 

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Your ram air system will have absolutely no (or very little) effect on the operating temperature of your engine. In fact, the colder the air the better off your engine is. When you worry about engine temps, that's when you worry about the cooling system of your car, but for you, go ahead, you will have no problems whatsoever, just make sure you can stop water from getting into your intake. That'd ruin a good day pretty quick.

If you're really interested about engine operating temperatures, here's the nitty gritty. High performance cars in places other than the States like to run a bit cooler (on the order of 75~85*C). Simply put, the colder the engine, the more power you're going to make. There is a trade off, however. Notice how I said "outside of the States." When you run your engine cold, you're also running less efficiently and creating more pollution. That's why some modern cars here have thermostats which OPEN at 85~90*C, which helps to lower emissions greatly.
 
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