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Bruce correct me if I am wrong, but you disconnected the vacuum solenoid near the air box? The vacuum solenoid for the distributor tube is located behind the distributor tube near the vacuum diaphragm that operates the distributor tube flap. I believe you disconnected the "hemholtz" or whatever it is inside the air box.
Originally Posted by Bruce In Philly
Stay tuned, I have something brewing........
I am driving this car every day since Saturday AM when I unplugged that air valve thingy...... I can say this without doubt, most of the hesitation is gone. There is no doubt in my mind (today at least!!!) this flap is a big cause... but not the only cause.
When the engine is cold and still warming, I drive it and don't rev past 3500..... occasionally I can feel something going on around 2700 or more like 2900 RPM... It is not at all bad.... I summize, that this is the variocam doing its thing. As others have theorized, it is the combination of the flap and variocam activating at the same time that give the feeling of a quick hit of fuel starvation. Once the engine warms up to full hot, I can't really tell anymore.
So.... given I was hearing a "Phsst" when that flap flipped, maybe there is an issue with this system... sticking? vacuum leak or pinched hose? I see the tube part number is superseded by a new one (just and increment). A new part number may mean they fixed it or maybe they are getting it from another supplier..... who knows.
On Sunday, I ran the car pretty hard and frankly I can not tell any performance hit with the flap disconnected... even Porsche literature notes it is for sound.... other information about this flap?
One voice in my head just leave it disconnected 'cause it is fixed, while another competing voice is saying I just knocked off 100 HP...... sheesh.
Anyway, stay tuned, more to come on this.
C'mon, guys, just disconnect the electrical to the little valve thingy and report.... it takes all of three minutes to do.
Peace
Bruce in Philly
From my literature library..... I was in error above where it says just the sound is effected... apparently is does effect torque.... read on...
You know what? Maybe I got Kim Ks undies stuck in there.... clogging the vacuum...?
I believe by disconnecting the hemholtz vacuum solenoid you decrease the volumetric efficiency gained by the hemholtz "trick" utilizing the intake pulses to create a pressure wave that helps air flow into the cylinders better. Probably not losing much TQ or HP by deleting it, just not getting the extra boost at those rpm ranges. Full out, probably won't be losing hp or tq at all.
Where is the connector for the engine coolant shutoff control valve?
I doubt that is my issue, if I disconnect the Sports Exhaust connection it's on all the time.
Will try the other disconnection a bit later today.
I believe by disconnecting the hemholtz vacuum solenoid you decrease the volumetric efficiency gained by the hemholtz "trick" utilizing the intake pulses to create a pressure wave that helps air flow into the cylinders better. Probably not losing much TQ or HP by deleting it, just not getting the extra boost at those rpm ranges. Full out, probably won't be losing hp or tq at all.
You know, you may be right about this..... I could have been wrong about how the parts link together... my Katalog diagrams look cool until you try and do something like this and then you see the ambiguities ...... Look at the description below. Apparently, there are two things happening, both controlled by a vacuum valve....
So, there are two things happening in a 3.8 (S): the flap in the intake plenum tube on top of the engine, and another thing going on in the air cleaner. The one on top, as described by the Porsche literature I posted prior, denotes it effects torque in the midband.... this one in the air cleaner is for sound.
I know this for sure, by unplugging the electric on the air cleaner valve, the 2700 hesitation has been greatly reduced and almost gone... I find it hard to believe this little sound enhancement feature is the real cause. I wonder if by unplugging that valve, I deactivated the other in the rear. Hmmm..... I am going to take the air cleaner out tomorrow and see if that sound feature is a flap or what in there. ... is their sticking or a leak or whatever..... That "Phsssht" I hear is coming from somewhere.
I spoke to my local dealer's parts guy today to see if he had any information.... he did tell me that those little valves, the one attached to the air cleaner, the one that I disconnected "go bad" and Porsche has a new part number for those.
The hunt goes on!
Peace
Bruce in Philly
Last edited by Bruce In Philly; 09-01-2017 at 08:27 PM.
Anybody know the price of the valves? If not too much maybe just replace and see what happens.
I put the part prices in post #13 above..... about $40 ea for the latest Porsche part ... no biggie.... Pelican has a cheaper OEM version for $20 some.... replacing the airbox one should take all of 10 minutes.... the other one is behind the air tube.... I can get my hand back there but boy, it would be fiddly.
Thanks Bruce, your effort is much appreciated . Please take some pics when you change out the part . Although my car doesn't have the 2700rpm hesitation , I do have the ""Phsssht" sound. Hope you find out which part will get rid of that annoying sound. Thanks again
Update.
I removed my connector and rechecked the entire vacuum system.
After a 1 hour test drive the issue persisted.
However, no fault codes appeared.
Update.
I removed my connector and rechecked the entire vacuum system.
After a 1 hour test drive the issue persisted.
However, no fault codes appeared.
Interesting..... do you have a 997.1 or .2 and S model? As I show in my first post here, the 1043 fault code shown by Durametric. That code was thrown and accurately describes, the disconnected electrical from the changover valve.
FYI: I have been driving for one week now with that valve disconnected and have almost no symptoms of hesitation. I can still occasionally feel a slight "transition" when the engine is cold which may be the variocam or the 2nd flap in the tube.... but nothing like the hesitation that drove me nuts for the last 100K miles of ownership.
I have some parts on order from my dealership (they came close to matching internet pricing)..... stay tuned.
Bruce - The flap in the airbox must be Helmholtz resonator. Sounds like it by the description. And it will not reduce performance by disabling it. It's purpose is to reduce resonance which it does effectively. Removing it is what many of us do with 997.1. By blocking it you get the wonderful intake noise above 5.000 rpm. No performance losses as it is there to reduce intake noise in the first place.
I found this thread where it's discussed. On 997.2 It seems to be internal and not as accessible as in the 997.1. See answer from Fabspeed below.
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Originally Posted by nicholas9976 View Post
Hi John, many thanks for your reply, will contact Fabspeed to place an order in the near future.
I noticed that you offered a CAI for the 997.1 that also had a cap to seal off the Helmholtz resonator (sealing it off increased the intake sound significantly). I believe a number of other suppliers produced 997.1 resonator caps as well, but I haven't found any 997.2 resonator caps so far. I am wondering why your 997.2 product doesn't have such a cap? I noticed an item labelled "resonator" on the engine diagram in the 997.2 PDF brochure on the Porsche website. I am wondering if you may know whether sealing this is possible and if so will it increase the intake sound?
Thanks.
No problem! Just give me a call/email directly when you are ready to make it happen, i'll be sure to take care of you
If the factory 997.2 airbox has a resonator it is an internal construction that can't be accessed like the 997.1 I don't have a factory airbox to double check for you but I know there is nothing we can do to cap off like the 997.1. Pictures below compare to the two factory airboxes. You can see have the 997.1 has that resonator tube to block off while the 997.2 does not.
09-01-2017, 03:27 PM
