Question relating to air charge density and forced induction

[Camarorulz]

I just read that forced induction does not actually increase the air flow through an engine, it actually just increases the air charge density. I'm confused by this: I thought the whole point of increasing the compresssion of the air is to be able to increase the amount of air/fuel mixture going into the cylinders. I'm confused someone please help me out with this one.

[ February 14, 2003: Message edited by: Camarorulz ]</p>

[daWhoady]

Ambient air is around 14.7psi. In Forced Induction, you are mearly increasing the psi. So if you are getting 6psi from a supercharger, your engine is taking in 14.7+6 psi at that given time. So what you are basically doing is compressing more air molecules into a given area.

[Cole]

Ram air is forcing the air into the engine, there for creating a high fuel/air mix meaning hp.the Horse power gain depends on how fast you are going at what rpm. in a 98+ T/A the ram air adds 17 moving hp. it is like a "natural" (but very week) super charger.

[John_D.]

<blockquote>quote:</font><hr>Originally posted by Camarorulz:
I just read that forced induction does not actually increase the air flow through an engine, it actually just increases the air charge density. I'm confused by this: I thought the whole point of increasing the compresssion of the air is to be able to increase the amount of air/fuel mixture going into the cylinders.<hr></blockquote>

They were probably talking about air flow in terms of cubic feet (or equivalent). The engine won't flow more cubic feet. Same volume.

But.... A cubic foot will contain more air... Denser air, since it's compressed. So in terms of mass, there is more air going in. Which does exactly what you said, lets more fuel be ignited...

That's the only distinction I can think of.

[Camarorulz]

I know what RAM air is, and I don't consider that a true form of forced induction, but that didn't address the question at all. What I was asking about is this: this book I read said that the AMOUNT of air flow is not actually increased, meaning that the amount of air molecules is no more (am I wrong?) and I thought the point of compressing air was so more could be forced into the engine.

EDIT: John_D I saw your post after I wrote this response. What you said pretty much clears is up for me, I understand now, thanks [img]graemlins/thumbsup.gif[/img]

[ February 14, 2003: Message edited by: Camarorulz ]</p>

[John_D.]

<blockquote>quote:</font><hr>Originally posted by Camarorulz:
EDIT: John_D I saw your post after I wrote this response. What you said pretty much clears is up for me, I understand now, thanks [img]graemlins/thumbsup.gif[/img]
<hr></blockquote>

Cool. I saw where we had posted at nearly the same moment... :)

[pvtschultz]

That is very true about the flow. There are two measures of flow, volumetric and mass. Mass flow rates are always conserved, meaning what goes in must come out. While volumetric flow is not conserved. Vloumetric flow rate, Q, is equal to VA. Mass flow rate is equal to the volumetric flow rate times the density of the air.

<blockquote>quote:</font><hr> Ram air is forcing the air into the engine, there for creating a high fuel/air mix meaning hp.the Horse power gain depends on how fast you are going at what rpm. in a 98+ T/A the ram air adds 17 moving hp. it is like a "natural" (but very week) super charger. <hr></blockquote>

Ram air is not forcing any air into you engine. The design for the T/As ram airr allows for a larger, straighter, slower (less velocity), flow path. This all means less flow losses. Flow losses result in a pressure drop of the flow stream. Ram air at 100 MPH will result in a pressure gain "ramming affect" of all of 0.3 psi, which will be lost in flow losses. The true effect of the raim air system is merely cold air induction, which increases the intake charge density, increasing the power output.

[Camarorulz]

RAM air actually increases you VE, isn't that right? RAM air supposedly creates a mild supercharging effect because it increases the pressure of the air entering your engine. Thus, more air molecules are contained in a cubic foot volume of air.