What's the function of this valve?

[KRAM36]

I'm curious to know what the function is of this valve I have circled in red.



Thanks!

[Timco]

That's the Fetzer valve.

Needs Quaker State and ball bearings to fix.

[KRAM36]

I'm curious to know what the function is of this valve.

At idle if I spray some MAF cleaner on it, my engine will bog down. Raise the rpm and it gets sucked in and the MAF cleaner doesn't bog down the engine.


.

[Luv2Box]

I'll take a stab at it. I believe it is the idle speed control valve which operates by bypassing varying amounts of air around closed throttle valve in 1997-1999 models. In later models there is a throttle control module. Just my SWAG.

[philou320]

Inside the intake there is a flap, this is the axle, the actuator in underneath operated by vaccum
pressure

[KRAM36]

So this isn't a valve?

Then I have an issue here as during idle it's letting unfiltered air into my engine?

[philou320]

not a valve

This is how it looks from below,


you can see that the axle is crossing the entire tube

[KRAM36]

So I can cap and seal that axis point with no side effects?

[Luv2Box]

Originally Posted by KRAM36

So I can cap and seal that axis point with no side effects?

Don't you think you should find out its function before you make that decision? If it is there it has a purpose. Porsche engineers don't add useless things to their motors unless you count the IMS and water pumps.

[KRAM36]

Originally Posted by Luv2Box

Don't you think you should find out its function before you make that decision? If it is there it has a purpose. Porsche engineers don't add useless things to their motors unless you count the IMS and water pumps.

So you're not satisfied that this is just an axis point for the flap inside the tube?

I want to know why it's sucking in air at idle, make that unfiltered air.

Can I cap it? Do I need a new tube?

[Gelbster]

Try 'capping' it temporarily with the finger of a neoprene work glove. Does the idle speed change? Yes/no = your answer.

[KRAM36]

Well sure wish I knew more about that spot. I put a temp cap on it. Car seems to idle better and on the road she ran just as normal.

[philou320]

As long as the flap can rotate inside the tube, you can cap it, after you do the job, check it moves by actuating it from bellow, it is possible that it allows some air goes in because of the wear and tear.
anyway this flap opens at middle throttle and is closed at iddle.

a better view inside with the flap fully open

[78F350]

Try looking up 'resonance flapper valve' for more info.
I think that any air going in or out of that hole is negligible unless you have excessive wear.

Quoted from: http://press.porsche.com/archive/products/press_kits/press_kits_2001/PDF/Boxster_in_Depth.pdf

"The Boxster inherits its twin-resonance air induction system from the 911
Carrera. The system acts as a “resonance supercharger,” allowing the engine
to draw from higher velocity airflow at certain engine speeds. A crossover pipe
connects the individual air collector/resonance chambers for each cylinder bank.
A flap in the pipe remains closed from idle to about 3,100 rpm. When it opens,
each cylinder bank can draw from airflow “excited” by the resonance created by
alternating induction between all six cylinders. In essence, “dual resonance”
creates two induction paths for each cylinder. Below 3,000 rpm, the cylinders
draw air from a “short” path. From 3,000 rpm to about 5,100 rpm – when the
resonance flap opens – the cylinders draw from a long intake path, which
boosts torque. Above 5,100 rpm, the flap again closes to allow the cylinders
to draw intake air from a shorter intake path to boost horsepower at higher
engine speeds."

[KRAM36]

I would imagine that if it's drawing enough air to stumble the engine when I spray the MAF cleaner on it, it must be past normal wear?

That is the only spot on my intake system I can get any engine fluctuation when checking for air leaks.

[BrakeExpert]

That's what I call over engineering. There are so many other intake manifold valve designs, why they chose that is beyond me.