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Old 08-05-2010, 12:34 PM
FireRanger FireRanger is offline
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Exclamation READ ME: All about Intake Air Temperature / CAI / MAF

Here is an air intake lesson for everybody because it really seems like a lot of people don't actually understand how this concept works. This is mostly due to the way gimick products are advertised.

First the science, then the why it matters.

Intake air temperature effects fuel mixture. Air density increases as air temperature decreases. Cooler air has more air molecules than warmer air. The computer will always try to maintain a given air/fuel ratio. So by monitoring the intake air temperature, it knows how to adjust the fuel injectors to apply the right amount of fuel.

As intake air temperature decreases, the air density increases, more air = more fuel needed to maintain the ratio. A side result of more air and more fuel is more power! So, the lower the intake air temperature, the better. However, no matter what you do, you will never get the intake air to be cooler than outside ambient air temperature.

As intake air temperature increases, air density decreases, less air = less fuel needed ot maintain the ratio. A side result of less air and less fuel is less power! This is why when it's 100 degrees in the summer going up hill, it feels like you're dragging a grand piano behind the truck. This is also why an intake that sucks air from under the hood is bad because it can be a crisp 150 degrees under there!

Since your stock intake is plumbed to the outside (in the grill by the right headlight, you are already drawing in outside air, which is as cool/cold/fresh as it is going to get. Adding a new shiney piece of pipe will not change that or make the air be colder. This is why aftermarket CAI kits are a useless waste of money on our trucks. This is PROVEN. If you monitor the intake air temperature sensor, you will see that it matches the outside air temperature exactly. Net gain, nothing.

Now that you know air temperature, you have to know air flow as well. In addition to know the air temperature to regulate fuel flow, it also needs to know how much of that air is flowing. The MAF detects air flow (hence the name...). This combined with the temperature let the computer regulate the fuel flow with precision. If the MAF is dirty, broken, or disconnected, the engine will shit. If due to engine mods that require more air flow, you have to make the intake larger, you will need to buy an aftermarket larger diameter MAF.

The stock intake is more than enough for the stock heads, cylinders, and exhaust. Adding a larger diameter intake will not gain you anything since it is already at peak efficiancy. This is dyno proven. Further reasoning why aftermarket CAI's for our trucks are useless waste of money.
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  #2  
Old 08-05-2010, 12:49 PM
TurdFX4 TurdFX4 is offline
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Default Re: READ ME: All about Intake Air Temperature / CAI / MAF

Hells yeah... I regret getting mine, back before I knew better.

Last edited by TurdFX4; 08-05-2010 at 12:53 PM.
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Old 08-05-2010, 01:14 PM
More_Cowbell More_Cowbell is offline
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Default Re: READ ME: All about Intake Air Temperature / CAI / MAF

great guide should be put under the welcome threads or something
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Old 08-05-2010, 01:24 PM
01_ranger_4x4 01_ranger_4x4 is offline
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Default Re: READ ME: All about Intake Air Temperature / CAI / MAF

As per the request of the OP and since this topic comes up frequently I stickied this thread. Please no bickering about CAI's here.
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Old 08-05-2010, 05:57 PM
supercomet32 supercomet32 is offline
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Default Re: READ ME: All about Intake Air Temperature / CAI / MAF

Two questions

1. If you can FLOW that air more aerodynamicly wil you see increase because of the added air pressures beign forced through the tunnel?

2. if you could some how plumb a cooler of some type be it a freon charge or soemthing would that produce a useful result?
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Old 08-05-2010, 06:19 PM
FireRanger FireRanger is offline
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Default Re: READ ME: All about Intake Air Temperature / CAI / MAF

Quote:
Originally Posted by supercomet32 View Post
Two questions

1. If you can FLOW that air more aerodynamicly wil you see increase because of the added air pressures beign forced through the tunnel?

2. if you could some how plumb a cooler of some type be it a freon charge or soemthing would that produce a useful result?
1: No, the intake is not restricting anything on a stock motor. Dyno testing shows a stock intake vs a pretty looking aftermarket ones yield no improvement, and often reduce performance if anything.

2: Yes. However the resistance of the cooling coils would restrict the air flow so much, it would probably make it worse. An air box and cooling coil large enough to achieve this would be roughly the size of your windshield. Not practical.

On a related note, the intercooler on a turbo does a similar job. The intake air goes through a radiator looking device in the grill that allows ambient ram air to cool the intake air as it passes through the intercooler. Some high performance racing trucks have liquid spray nozzles on the front of the intercooler to increase the effectiveness of the heat exchange. It will still only cool the intake air down to ambient temperature, but it can do it faster. Also impractical for us and only applies to intercooled turbos.
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How to: Aux light wiring, relays, & fuses
Info: 300+ intake threads here on FRF
Info: HID Projectors
How To: NO HEAT Troubleshooting Guide
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  #7  
Old 08-07-2010, 01:46 PM
Yrac Yrac is offline
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Default Re: READ ME: All about Intake Air Temperature / CAI / MAF

Story time! Saw a guy that raced a slant 6 with a 4 barrel. He had copper fuel lines wrapped around a coffee can. He'd fill it up with dry ice on race day and drop a second off his quarter mile time!
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Old 08-07-2010, 02:03 PM
FireRanger FireRanger is offline
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Default Re: READ ME: All about Intake Air Temperature / CAI / MAF

Quote:
Originally Posted by Yrac View Post
Story time! Saw a guy that raced a slant 6 with a 4 barrel. He had copper fuel lines wrapped around a coffee can. He'd fill it up with dry ice on race day and drop a second off his quarter mile time!
Highly unlikely that this is true. Fuel density change with temperature is nothing like air. And cooling gasoline is not going improve combustion.
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How to: Aux light wiring, relays, & fuses
Info: 300+ intake threads here on FRF
Info: HID Projectors
How To: NO HEAT Troubleshooting Guide
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  #9  
Old 08-07-2010, 02:14 PM
Jp7 Jp7 is offline
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Default Re: READ ME: All about Intake Air Temperature / CAI / MAF

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Originally Posted by FireRanger View Post
.... If due to engine mods that require more air flow, you have to make the intake larger, you will need to buy an aftermarket larger diameter MAF......
I scale MAF tables with a single scalar value on Mitsubishi or Subaru. If you have the ford software you can do this also.
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Old 08-07-2010, 02:43 PM
FireRanger FireRanger is offline
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Default Re: READ ME: All about Intake Air Temperature / CAI / MAF

I mean larger in diameter to accomodate the need for more air flow.
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How to: Aux light wiring, relays, & fuses
Info: 300+ intake threads here on FRF
Info: HID Projectors
How To: NO HEAT Troubleshooting Guide
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  #11  
Old 08-08-2010, 08:00 AM
sgtsandman sgtsandman is offline
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Default Re: READ ME: All about Intake Air Temperature / CAI / MAF

One could wrap the intake tube with insualation to prevent the air from heating up while traveling from the head light area to the intake manifold but I imagine the benefit would be marginal.

One could also wrap the exhaust manifold with insulation to bring down engine compartment temperatures though in a moving vehicle, I would think that the resulting benefit would again be marginal on a stock engine.
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Old 08-08-2010, 09:37 AM
Jp7 Jp7 is offline
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Default Re: READ ME: All about Intake Air Temperature / CAI / MAF

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Originally Posted by sgtsandman View Post
One could also wrap the exhaust manifold with insulation to bring down engine compartment temperatures though in a moving vehicle, I would think that the resulting benefit would again be marginal on a stock engine.
You are right for the wrong reasons. Keeping the exhaust hot helps it move faster through the "hot end" of the exhaust.

I do this on Turbo-cars all the time because you want to keep the gasses really hot through the runners on the way to the turbine. That's why I have ceramic coated runners.
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I'm dying to see this at night. Someone go tell the sun to give up already.
Quote:
Originally Posted by beef08 View Post
Your the man, you bring our dreams to a reality within the lighting spectrum
Quote:
Originally Posted by BCobe View Post
Jp7 you always do AMAZING work! Hats off to you sir
Quote:
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People so often confuse "hating" with "knowing better".
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  #13  
Old 08-08-2010, 09:48 AM
sgtsandman sgtsandman is offline
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Default Re: READ ME: All about Intake Air Temperature / CAI / MAF

I was thinking about a normally aspirated engine and the direct correlation to air intake temperatures.

From what I understand, keeping the exhaust temp hotter for better performance also applies to normally aspirated engines as well.
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Old 08-08-2010, 09:51 AM
FireRanger FireRanger is offline
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Default Re: READ ME: All about Intake Air Temperature / CAI / MAF

I'm not sure what benefit keeping the exhaust hotter has in a normally aspirated engine. You want the combustion to be peak but once it leaves the engine, it is just waste.
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2003 Edge 4.0 4wd

How to: Aux light wiring, relays, & fuses
Info: 300+ intake threads here on FRF
Info: HID Projectors
How To: NO HEAT Troubleshooting Guide
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  #15  
Old 08-08-2010, 10:20 AM
sgtsandman sgtsandman is offline
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Default Re: READ ME: All about Intake Air Temperature / CAI / MAF

The thinking is that the longer you can keep the exhaust hot, the faster it will leave the exhaust creating a vacuum of sorts and thus allowing the cylinder to clear better for the next air/fuel charge but this is a digression from your original subject matter...

Edited for word omission
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Last edited by sgtsandman; 08-08-2010 at 11:23 AM.
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