MAF Sensor and Aftermarket Intakes

[blueroadster]

In the stock configuration, there is a hose going from the valve cover and to the intake plumbing before the MAF. The air going through the intake creates a constant vacuum that helps to escape gasses from the valve cover back into the intake. The interesting thing though, is that I looked at a lot of aftermarket intakes available for the 06-07 Si and every PIC that I saw had the hose that went from the valve cover routed to the intake track after the MAF sensor. This would allow for vacuum to still exist in the hose going to the valve cover whenever the car is running, but the MAF sensor would not have a chance to register the air (even though it is a minute additional amount in the grand scheme of things). Any comments or thoughts? I would have thought that aftermarket intakes would still allow for the MAF sensor to read as in the stock configuration.

[blueroadster]

All the ones that I could locate had the connections after the MAF unlike the way it is stock. Here are PICs:

AEM SRI

Fujita SRI:



Ingen CAI

Ingen MR SRI

Ingen SP SRI:



K&N Typhoon

[chilipepper]

subscribed

[blueroadster]

<<< Waiting for those in the know to chime in.

[DirtKurt]

The hose that is run off of the sri is the intake for the pcv system. The air enters the motor through the tube off of the sri, passes through the head and block exhausting hydrocarbons and whatnot, and is then passed into the actual intake manifold where it is burned. The pcv system is not inhaling air from some other source and then dumping it into the intake un-metered, it is taking metered air and passing it through the motor and burning it.

[blueroadster]

It makes sense that the air at some point is registered. It comes in the intake, registers at the MAF, travels through the system where some air is bled out (like through the valve cover) so it should not need to be registered a second time. That seems logical but in the stock configuration, the hose is plumbed into the intake pipe before the MAF.

[bluetroll]

i'm sure there's some logical reason for this... i'm sure injen spent their time and money designing it.

[chilipepper]

Does anyone have an engine schematic that can be posted or linked that provides details on the PVC system? I'm curious about the answer to this question...

+1 rep for blueroadster for noticing this difference.

[DirtKurt]

Theres a Diagram on the bottom of the hood.

[Chase]

on this note, what is the benefit (if any) of capping off the PCV system and just putting a breather on the valve cover?

[chilipepper]

Originally Posted by DirtKurt

Theres a Diagram on the bottom of the hood.

Thanks, I'll go take a look...

[chilipepper]

I looked at that diagram, but it doesn't give the complete picture of the airflow in/out of the valve cover and PCV system.

I guess I'm wrong about this, but I don't remember a take off upstream of the MAF on my stock intake and I can't get to it to look right now. I looked at my wife's '07 CR-V engine (looks very similar) and the connection to the valve cover is downstream of the MAF.

blueroadster, are you sure that connection was upstream of the MAF?

[PR_S14]

I agree with the above. I don't remember seeing any hoses "before" the MAF.

But there is an intake that DOES place that hose before the MAF. Weapon-R.

[blueroadster]

Alright...I want everyone's vote for the idiot of the year award.

On the stock intake, both hoses are routed back after the MAF just like the intakes referenced in the first post.

[nbilyue]

It's okay blue we could never be mad at you. Whenever I see a pic of your engine bay it makes everything all better.

[chilipepper]

Originally Posted by blueroadster

Alright...I want everyone's vote for the idiot of the year award.

On the stock intake, both hoses are routed back after the MAF just like the intakes referenced in the first post.

OK, -1 rep from earlier post, +1 rep for a fun thread! Net: +1 rep

[chilipepper]

Originally Posted by PR_S14

I agree with the above. I don't remember seeing any hoses "before" the MAF.

But there is an intake that DOES place that hose before the MAF. Weapon-R.

OK, any idea why Weapon-R would do this?

[DirtKurt]

The flow of the pcv system is in through the sri and then back out into the intake manifold. The vacuum is much greater in the intake manifold behind the throttle body which therefore creates flow through the system.

Whats it take to get some rep around here?

[chilipepper]

+1 for DirtKurt. Good info!

Now, how 'bout that weapon r question?

[DirtKurt]

Im not sure about the weapon r, that pretty much seems like a design flaw to me.