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"As with the previous model, the upper section of the 3.8-liter engine's filter features actively switchable resonance volume. Additional volume is activated as a function of engine speed, with temperature compensation being provided by a vacuum-controlled butterfly, improving the engine's acoustics"
I have those in PDF format..... PM me and I can forward them to you along with a bunch of other stuff for '09 and 997.2.
I missed this... I actually have too much information on this car and I was looking at the Katalog where I was confused.
Does anyone hear a "Phsst" when this flap opens (or closes?) at around 27K RPM under light load?
OK, so you may be thinking "what voice is talking to him now?".... well I have that 27K power suckout/miss/hesitation/stumble... it has been with me all the time and now with 114K miles, it has become "charm". So last year, I was driving with the windows down and the sunfroof open, along a wall that reflected by sound. I got the stumble and heard "Pshsst" at the same time. Now that I am sensitized, this air sound is associated with the stumble.
Without going into a bunch of history, others, including two Porsche techs said this flap and the variocam may be actuating at the exact same time and their cumulative effect is most likely responsible for this stumble. Some of us experience this, others not. I drove with a dealership tech and he felt it too.... said he heard of complaints but Porsche has said nothing. "Keep an eye on it...."
Great.
Anyway, the voices in my head are thinking maybe this valve is sticking..... if I can just get at it and check its movement.......
Looks like I have to remove the entire intake plenum to get it back there. Anyone do this?
I will take a look at this later today now that I know where it is. Thanx all for pointing me to information I already had!
Bruce, I think I notice a similar sound around 2.7K rpm (my motor doesn't rev to 27K ) but not the stumble ..... I would describe the sound as electrical zapping/sparking noise for less than 1 second at the instant I apply heavier throttle under light load...
I don't know what it was and I sometime wonder whether that was the sound of the motor pinging/knocking but then I thought motor doesn't usually knock under light load then stop knocking under heavy load, right
I hope you can pin-point the sound source and better yet fix it and tell us what it was so I know what to do. TIA...
I have IPD racing plenum with GT3 TB. In this configuration (the plenum) the airbox/resonator tube is capped off. I mention this because I can hear, not feel, the "stumble" at 2700 rpm that you refer to. This being the case I don't think it is related to the resonator assembly. I do have a cure though and it is related to the gas pedal: Keep the revs up If I had to guess I'd point in the direction of the variocam mechanism but it is moot. Have fun out there
Edit function doesn't work for me so let me add that headers, cats and exhaust are aftermarket parts and the car is tuned. If you are crossing out possible causes you can rule these out together with the resonator.
Hey Bruce, I have the same issues you do at 2700-3000 RPM, and I have a 3.6, so I dont think thats the culprit.
Thanks
Rob
Darn....... I was all ready to tear something apart...... I peaked in there earlier today... I see the mechanism.... I was all dressed up in my Sunday-go-to-meetin' clothes... but I think I can get my arm back there to do some good damage.
That Heimholz Resonator is what a lot of people say contributes a displeasing "farting" sound from the motor. On a .1 the cap from an oil bottle is supposed to be a perfect fit to block it off. Try that and see if it effects the noise or flat spot. I don't think Variocam + starts to kick in until a little bit higher, like 3,500 RPM.
That Heimholz Resonator is what a lot of people say contributes a displeasing "farting" sound from the motor. On a .1 the cap from an oil bottle is supposed to be a perfect fit to block it off. Try that and see if it effects the noise or flat spot. I don't think Variocam + starts to kick in until a little bit higher, like 3,500 RPM.
Abit earlier maybe. I can feel/hear it about 3200. I always wondered if the "burble" (does that make it less of a problem?) indicated a transition stage. Thought: What model graduated to dual variocam set up and does it show up there?
Gerry
05-13-2017, 09:10 PM
3.8-litre switchable resonance volume - WTF?
) but not the stumble ..... I would describe the sound as electrical zapping/sparking noise for less than 1 second at the instant I apply heavier throttle under light load...
If I had to guess I'd point in the direction of the variocam mechanism but it is moot. Have fun out there
