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Old 12-11-2017, 02:47 PM   #1
1998 Boxster Silver/Red
 
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Entertaining the Pedro intake mod...



1998 Boxster.

The piece/connection in the yellow circle.

What purpose does it serve? And... what would be the workaround if installing that Pedro intake mod... or something similar? How would that be bypassed, as it wasn't mentioned in the Pedro instructions.

Thank you.
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Old 12-11-2017, 03:20 PM   #2
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Its my understanding that its a resonator that cuts down on intake "noise". Pedro's modification replaces the whole pipe that this is connected to with a piece of straight 3" PVC pipe. I plan to do Pedro's modification this winter.
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Old 12-11-2017, 03:24 PM   #3
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Its my understanding that its a resonator that cuts down on intake "noise". Pedro's modification replaces the whole pipe that this is connected to with a piece of straight 3" PVC pipe. I plan to do Pedro's modification this winter.
The resonator is at the near corner of the pipe before the throttle body. You can see it 6 o clock position of the photo.

The pipe/tube/line/hose in the yellow circle, I believe, isn't capped off. It's leading under the manifold.

Are you telling me there's 2 resonators?

Thank you.
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Old 12-11-2017, 04:14 PM   #4
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Originally Posted by Starter986 View Post
The resonator is at the near corner of the pipe before the throttle body. You can see it 6 o clock position of the photo.

The pipe/tube/line/hose in the yellow circle, I believe, isn't capped off. It's leading under the manifold.

Are you telling me there's 2 resonators?

Thank you.
Red is the resonator.

Anyone?
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Old 12-11-2017, 04:30 PM   #5
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No idea what that is but it doesn't look stock to me. I've had two '98's and the area in yellow is where the MAF sensor was located. I don't see it on your car.
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Old 12-11-2017, 04:35 PM   #6
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No, maf would be at 10 o’clock from the yellow circle.
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Old 12-11-2017, 04:37 PM   #7
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No idea what that is but it doesn't look stock to me. I've had two '98's and the area in yellow is where the MAF sensor was located. I don't see it on your car.


Blue is the MAF.
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Old 12-11-2017, 04:37 PM   #8
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tipronic i bet. provides addnl vacuum.
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Old 12-11-2017, 04:39 PM   #9
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tipronic i bet. provides addnl vacuum.
Yes. I have the Tiptronic. But, vacuum?
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Old 12-11-2017, 07:38 PM   #10
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No, maf would be at 10 o’clock from the yellow circle.
You're right..I didn't look close enough!
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Old 12-11-2017, 07:51 PM   #11
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Yes. I have the Tiptronic. But, vacuum?
sure, why not. where does it go? if you follow it, it is connected to ... the vacuum system. really, although it is a big tube (it gets small at the other end, however) there couldn’t be any airflow in it as it is after the maf, so that air has been metered. tiptronic needs more vacuum than a manual car for all the geewhizzery on it, so porsche added an additional vacuum source. the air rushing down the main tube creates a bit of a venturi effect on as it passes over the opening of your mystery tube, and creates some more vacuum.
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Old 12-11-2017, 07:59 PM   #12
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here’s a link to a similar thread ...

What's the function of the Venturi Tube on a Tiptronic?
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Old 12-12-2017, 05:36 AM   #13
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A bit of a side discussion... In very simple terms a resonator (that extra appendage looks like an extra resonator) increases the volume of air in the intake tube without making it flow farther. In doing so it acts as a buffer for the vacuum.
In more precise language:
https://itstillruns.com/air-intake-resonator-do-12156112.html

Deeper still is the discussion of intake runner length. A few years ago I was swapping an SUV engine into a small car and noted the SUV had a much longer intake. In simple terms, length mainly effects where the torque peaks in the power curve. Longer tubes make the torque peak sooner:
https://mechanics.stackexchange.com/questions/25236/how-does-intake-manifold-runner-length-effect-the-power-curve-of-a-car

Then there's the 2000 and later M96 engines with the cross tube and resonance flap that can spread the torque peak across a wider range:
Quote:
Originally Posted by 78F350 View Post
...
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."
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Last edited by 78F350; 12-12-2017 at 05:38 AM.
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Old 12-12-2017, 06:22 AM   #14
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Originally Posted by 78F350 View Post
A bit of a side discussion... In very simple terms a resonator (that extra appendage looks like an extra resonator) increases the volume of air in the intake tube without making it flow farther. In doing so it acts as a buffer for the vacuum.
In more precise language:
https://itstillruns.com/air-intake-resonator-do-12156112.html

Deeper still is the discussion of intake runner length. A few years ago I was swapping an SUV engine into a small car and noted the SUV had a much longer intake. In simple terms, length mainly effects where the torque peaks in the power curve. Longer tubes make the torque peak sooner:
https://mechanics.stackexchange.com/questions/25236/how-does-intake-manifold-runner-length-effect-the-power-curve-of-a-car

Then there's the 2000 and later M96 engines with the cross tube and resonance flap that can spread the torque peak across a wider range:
Thank you. I find a lot of value in your posts and responses.

That hose coming off the intake tube... in the yellow circle...

You can see that the intake tube wasn't modified for that hose to attach. The hose attaches to the tube, held with the hose clamp. The photo I took a couple months back... and haven't returned to the engine to see exactly where did the hose lead under the intake manifold.

Because the intake tube wasn't modified... I'm turning to the Pros: The forum members.

Thank you.
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Old 12-12-2017, 06:58 AM   #15
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Quote:
Originally Posted by Starter986 View Post
... You can see that the intake tube wasn't modified for that hose to attach. The hose attaches to the tube, held with the hose clamp. ...
The parts catalog (PET) has 5 variations of intake tubing by year/model. Yours looks like is the stock tube for a 1999 and earlier Tiptronic. Here's the parts diagram (M249 is the option code for Tip.):
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Old 12-12-2017, 07:55 AM   #16
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The parts catalog (PET) has 5 variations of intake tubing by year/model. Yours looks like is the stock tube for a 1999 and earlier Tiptronic. Here's the parts diagram (M249 is the option code for Tip.):
Thank you. Just found it and wanted to report. You beat me to it.

It is the "Throttle Valve Tube". I read what generally it does. Seems necessary.

So... it came with the Tiptronic. I'll assume, unless otherwise corrected, that the manual tran arrived absent that pipe.

Does that mean that the Pedro mod won't happen on the Tip, or only with some additional fabrication to accommodate that valve tube?

Finally, if you know, what exact function is that valve tube providing?

Thank you.
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Old 12-12-2017, 08:24 AM   #17
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sometimes i wonder why i bother to reply to posts ...
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Old 12-12-2017, 08:51 AM   #18
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sometimes i wonder why i bother to reply to posts ...
It takes a team. The Captain sets the course. The bridge staff works out the details. Everyone has a role.

Well done as usual.
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Old 12-12-2017, 08:57 AM   #19
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sometimes i wonder why i bother to reply to posts ...
Because you are awesome.

My comments were intended to expand the conversation, not diminish yours.
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Old 12-12-2017, 09:32 AM   #20
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sometimes i wonder why i bother to reply to posts ...
This "sometimes"... how often is that? Were you being facetious?

You've ~2,000 posts to your credit. Obviously you've answered every imaginable inquiry. However, aside from sharing with me that the tube provides vacuum... actually, there is no aside. Me thinks that in those ~2,000 posts of yours lies the answer to my inquiry:

What purpose does that vacuum serve on the 98 Boxster? Further, to further massage your intellect, what changed after 1999 that rendered that line absent? What method did Porsche employ in later models to achieve the same result enjoyed on the 97/98/98 models? What was the workaround?

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