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Can any of you guys with the latest .95 plenum measure the I.D. of the large and small tube? The non-RS one from the Cup measures 100mm for the large one and 64mm for the small one. Just curious if Porsche has reduced the size of the latest version or not.
i have successfully passed CA smog with a reverted-to-stock ecu from a cobb tune. be sure to make a backup of YOUR stock tune as part of the install process and don't rely on the one (if any) which ships with the cobb. i am almost certain CA flagged my car from before the checksum rule was in place (i had previously passed it with the cobb tune active and then got a scary letter to re-test 2 years later, not just the normal smog renewal notice, after the rule went into place).
it does require a long drive (1 hour+) to reset all the OBD monitors but you can use a scan tool to ensure it's all "OK" before heading to the smog check.
How long ago was this? I just talked to Dundon since I’m getting their plenum/Cobb tune so I don’t have to think about the intake failing at any point. They said their Cobb tune is CARB compliant and shouldn’t be a problem passing CA smog.
Hopefully the car will even run if I have to flash the car back to stock with the plenum. Having to uninstall it every other year would be a total PITA.
How long ago was this? I just talked to Dundon since I’m getting their plenum/Cobb tune so I don’t have to think about the intake failing at any point. They said their Cobb tune is CARB compliant and shouldn’t be a problem passing CA smog.
Hopefully the car will even run if I have to flash the car back to stock with the plenum. Having to uninstall it every other year would be a total PITA.
Its not really the lugging thats annoying when reverting to stock...the car will actually start to throw a few different CEL's when its running rich, so while the car is 'fine' you cant pass the test with the CEL activated. Just dont do anything on a tight timeline, get your smog tested and renewed before you do anything, because the first tune isn't always the best and running a drive cycle on purpose is a huge pain in the ***. My issues have mostly been the elevation.
Its not really the lugging thats annoying when reverting to stock...the car will actually start to throw a few different CEL's when its running rich, so while the car is 'fine' you cant pass the test with the CEL activated. Just dont do anything on a tight timeline, get your smog tested and renewed before you do anything, because the first tune isn't always the best and running a drive cycle on purpose is a huge pain in the ***. My issues have mostly been the elevation.
Thanks for the advice! I did already experience the runaround of the monitors not being ready when I initially smogged the car for registration last year so preparing ahead of time definitely makes sense.
I had modded cars in the past that I had to revert back to stock when it came smog time, but prefer not to have to repeat that experience again with this one. I'll be retaining the stock headers/cats for now so the visual inspection shouldn't be a problem and I live at basically sea level so elevation shouldn't be a factor either.
Best case is the Cobb tune with the CARB exemption can pass so I can be good to go without having to reflash to stock.
I did find the following CARB exemption doc for Cobb Stg 1 tunes:
I'll be retaining the stock headers/cats for now so the visual inspection shouldn't be a problem and I live at basically sea level so elevation shouldn't be a factor either.
Watch out that the Dundon resonance intake might also fail visual.
Doing a build right now and trying to decide how to address this potential failure point. Has anyone removed/disabled the valve/s as a preventative measure? My car is at sharkwerks for a 4.1 build at the moment.
Best I can tell my options are
1. Do nothing and hope it doesn't fail
2. Put the newest OEM part in - does not seem to be confirmation that it is better. Maybe advantage of having a new "zero mile" part in there???
3. Disable/remove flapper completely - Some loss in power down low, can't break if it ain't there!
4. Dundon intake - loss in power down low, but gains in other places (not sure if sharkwerks guys would want to put a Dundon intake on their build) have not asked yet.
Doing a build right now and trying to decide how to address this potential failure point. Has anyone removed/disabled the valve/s as a preventative measure? My car is at sharkwerks for a 4.1 build at the moment.
Best I can tell my options are
1. Do nothing and hope it doesn't fail
2. Put the newest OEM part in - does not seem to be confirmation that it is better. Maybe advantage of having a new "zero mile" part in there???
3. Disable/remove flapper completely - Some loss in power down low, can't break if it ain't there!
4. Dundon intake - loss in power down low, but gains in other places (not sure if sharkwerks guys would want to put a Dundon intake on their build) have not asked yet.
Would love to hear any thoughts/experiences....
a few years ago I talked them and it really came down to tuning… I’ve invested in the Dundon top and bottom already and wanted to keep it and thought maybe it added even ‘more’ potential to the 4.1 than the standard SW.
So my plan was to see if Alex could take the first shot and go with that tune for a while and then I’d send the logs over to Jaime to refine over time. I think both are interested in seeing the potential
Doing a build right now and trying to decide how to address this potential failure point. Has anyone removed/disabled the valve/s as a preventative measure? My car is at sharkwerks for a 4.1 build at the moment.
Best I can tell my options are
1. Do nothing and hope it doesn't fail
2. Put the newest OEM part in - does not seem to be confirmation that it is better. Maybe advantage of having a new "zero mile" part in there???
3. Disable/remove flapper completely - Some loss in power down low, can't break if it ain't there!
4. Dundon intake - loss in power down low, but gains in other places (not sure if sharkwerks guys would want to put a Dundon intake on their build) have not asked yet.
Would love to hear any thoughts/experiences....
I think removing the OEM flap is a good call. Either completely or just unplugging the vacuum line. When I talked with Alex after my recent failure, that is what he recommended. 4.1 extra power/torque should cover up for any losses. So it should be faster across the RPM range.
Still working on my solution. My first upgraded factory plenum is nearly complete.
Talked over the various options. In my situation, we discussed removing the valve completely from the factory intake. We did also discuss the Dundon option, the questionable part about going that route was the tuning as someone mentioned previously I believe. Might not be squeezing every little bit of performance down low with the valve removal.
Eager to see what @Elliotw44 comes up with for his factory upgraded plenum.
Last edited by bucky56477; 08-01-2024 at 08:44 PM.
Talked over the various options with Dan and Alex over at Sharkwerks. In my situation, we came to the consensus that removing the valve completely from the factory intake would be the best option. We did discuss the Dundon option, the questionable part about going that route was the tuning as someone mentioned previously I believe. Might not be squeezing every little bit of performance down low, but I'd prefer to drive the car without concerns of that part failing.
Eager to see what @Elliotw44 comes up with for his factory upgraded plenum.
I would use the 3.8 non RS / Cup intake. Those do not have issues. I suspect that the latest revision of the RS intake is simply the non RS version as the revision numbers are not the same for both.. There is a significant amount on performance increase in the mid range due to the flap that I wouldn't wanna give up.
Correct, the flap is there for a very good reason. When I was evaluating my options i had the same idea of removing the flap. I spoke with several engine builders as well as Greg from IPD Plenums, they all dissuaded me from removing it. That’s why we came up with the screen solution.
Correct, the flap is there for a very good reason. When I was evaluating my options i had the same idea of removing the flap. I spoke with several engine builders as well as Greg from IPD Plenums, they all dissuaded me from removing it. That’s why we came up with the screen solution.
Chris Cervelli did testing on his Mainline dyno and the resonance flap on a 996GT3 intake was worth 12% power at the wheels. This set up had a Motec ECU so he could control the resonance flap at will. Similar results, if not better, should naturally apply to the 997GT3 resonance intake. We will be using the resonance flap on my 4.0 turbo Cup motor but the flap shaft will be machined out of 300M vacuum remelt steel.
Last edited by powdrhound; 07-27-2024 at 01:56 PM.
How long ago was this? I just talked to Dundon since I’m getting their plenum/Cobb tune so I don’t have to think about the intake failing at any point. They said their Cobb tune is CARB compliant and shouldn’t be a problem passing CA smog.
Hopefully the car will even run if I have to flash the car back to stock with the plenum. Having to uninstall it every other year would be a total PITA.
this was over a year ago at my last smog check, with the first smog check done with the tune 4 years ago (before the new software checks were implemented). if cobb is now CARB compliant then there shouldn't be any problems, you'll probably want to ask cobb if there is a new tune to download or if the older tunes were registered with the state. no idea on that one, i'll probably dig into it when next smog is due.
to be clear i did not try smogging it with the tune after the new software check was implemented by the state. i did not want to get a fail on the record so i just switched it back before smog.
06-04-2024, 04:40 PM
