So I've been doing some reading tonight, and I hope someone will be able to answer. While trying to figure out how much CFM our engine sucks in (465 if my math is right) I was curious as to why an electric turbo wouldn't work. Here's what I came up with.

So if my engine sucks in 465 CFM, wouldn't a fan producing 600 CFM result in an increase in horsepower? No, because it's not pressurized. MAP sensors read PSI not CFM. So, basically the idea of a supercharger is forcing compressed air into the engine and keeping that compressed air constant throughout the air intake, TB, intake, and heads. So when the valve opens to have air "shoved in" the compressed air shoves a lot more in than your engine would be able to produce naturally. Thus increasing the amount of gasoline you would use and still maintaining the perfect air to fuel ratio. More gas and air, bigger explosion, more horsepower. Bear with me here, so say our engine naturally sucked in 2 PSI of air into the cylinder and used a teaspoon of gasoline, which created the perfect mixture. Add the compressed air, it shoves in 10 psi and now uses 5 teaspoons of gasoline, and once again, more fuel, more air, bigger explosion, more power. And on top of that, compressed air is naturally cooler, which obviously cools your engine as well, resulting in even more power.

I hope I've explained this how I see it working out in my head, and it makes sense to everyone. But this leads me to my next question.

If the MAP sensor reads PSI and not CFM, why does an aftermarket CAI produce more HP? Here's the answer I worked out in my head.

It produces more HP because with the stock CAI assembly it's restricting the airflow by a considerably, thusly reducing the amount of air your engine is allowed to breathe in. By adding an aftermarket setup and greatly reducing restrictions in the pipe and filter itself, your allowing more air, which once again results in greater horsepower.

I know this is long, I was just reading and had to make sure I was right if I was to ever be asked this question. Any inputs would be great, thanks!

 

At Moparmadness a couple of years ago I spoke with a design engineer at one of the booths. He explained the stock filter and muffler are super restrictive because the average soccer mom doesn't want' to hear air sucking in the intake and exhasut rumbling out the back.

They pretty much choke the engines in new cars to make them quiet.

 

What about my supercharger question? Does that make sense?

 

Just testing my understanding of how a supercharger works. Is that right? So basically it's like an air tank, hooked into your CAI tubing, blocking off the end and keeping it pressurized.

 

CFM is a measurement of air flow, where PSI is a real time pressure measurement. At 3 -4 CFM per real Horse Power at 90 PSI. Air flows at Cubic Feet per Minute to be compressed into Pounds Per Square Inch.

An ordinary four-stroke engine dedicates one stroke to the process of air intake. There are three steps in this process:

1. The piston moves down.
2. This creates a vacuum.
3. Air at atmospheric pressure is sucked into the combustion chamber.

Lets start with the MAP Sensor. It works kind of like a vacuum gauge that sends signals to PCM sending air pressure data. A na engine will use am1-Bar MAP sensor from 0 to 14.7 (one atmosphere) psi of vacuum. A 2-Bar sensor works from 14.7psi lbs of boost up to 30 lbs of boost.

The PCM receives signal input from temp, pressure, crank, cam, etc and begins meeting fuel maps for the demands. Based on this, the PCM will signal the fuel injectors to perform as demanded by the sensors. The PCM controls the fuel maps by sending the appropriate message to control fuel flow rate, spark timing, and idle speed.

The blower increase intake by compressing air above atmospheric pressure (14.7psi). By forcing more air into the engine it provides "boost." Now that the air charge is delivered, the PCM will create a fuel map to add more fuel to the charge. If not, the cylinders run the risk of running lean (below 11.5 A/F).

 

Awesome thanks man. That was my basic understanding, but not worded as elegantly. So it turns a system based of off free air flow into a pressurized system.

 

My pleasure.

Yes and the PCM signals everything to compensate for the boost.

 

Just trying to wrap my head around this. Much appreciated.

 

I like the idea of a CAI, but was worried that it might make the truck less resistant to splashes when driving through big puddles.