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Discussion summary
YOUR RESEARCHHelmholtz resonator removal - a good idea?
Leading reported evidence
Install cia plug into the hole
Performed · outcome unconfirmed
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1
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Read evidence and context
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Performed · outcome unconfirmed
I was loathed to plug the hole with a "toilet part"so I push fitted the CIA plug into the hole
Leading evidence: 'Install cia plug into the hole' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Check whether everything in the engine bay was fine (i.e' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Discussions that performed work without a confirmed outcome
1
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Performed · outcome unconfirmed
I used the designtek kit, but I also removed the HHR and used some plumbing bits to block the hole.
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Discussions that performed work without a confirmed outcome
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
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Performed · outcome unconfirmed
I used the designtek kit, but I also removed the HHR and used some plumbing bits to block the hole.
Check whether everything in the engine bay was fine (i.e
Suggestion or failed attempt
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Reported fixes
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Unsuccessful attempts
1
Discussions
Read evidence and context
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Suggestion
I stopped off to check whether everything in the engine bay was fine (i.e.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that contain suggestions
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Suggestion
Clearly have to change the plumbing design enough to ensure the end cap doesn't get sucked up the pipe into the throttle body (eek!), and obviously there would now be a pipe-shaped acoustic chamber rather than pipe-plus-HHR-box-shaped, but the airflow improvement across the air box would still be achieved.
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suggestion
Clearly have to change the plumbing design enough to ensure the end cap doesn't get sucked up the pipe into the throttle body (eek!), and obviously there would now be a pipe-shaped acoustic chamber rather than pipe-plus-HHR-box-shaped, but the airflow improvement across the air box would still be achieved.
Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.
15 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
911uk: 1 discussions
0 evidence records excluded for query context · 0 excluded by outcome qualification · 0 adjusted by outcome qualification.
0 acknowledgements have no verified action link; they do not establish a repair result.
Generation: 20261026T203514Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
Hello fellow 996r's,
I have 2003 C2 Manual. 'Had the car for about a month now and its brilliant!!!
A few "mods" have already been carried out; including a CAI / CAIK installation. I selected the DesignTek kit which I'm well pleased with
However, although the resonator opening is now "capped" - is the HHR -still- restricting noise/airflow -within- the airbox. I've trawled the net/forums looking for definitive answers whether it's still a good idea to physically remove the unit from the airbox (i.e. even if it's been capped).
- Does anyone have an idea about this or, (hopefully) some intrepid 996'r has actually tried this and can hence report on the effect (more noise would be good!).
Many thanks in advance, Simon.
More noise (the HHR is tuned for anti-noise, cancelling induction noise for EU drive-by noise regs) + more air (the HHR both takes up 0.75L of post-filter air and restricts 1/3 of the panel filter!)
Search for Helmholtz on forum, here is a starting point:
http://www.911uk.com/viewtopic.php?t=53873
Thanks again GT4 - I can see from your number of posts that you're a bit of an "oracle" of 996 information
09:00 tomorrow the HHR is history!
Cheers again! Simon.
I did this to my 996.1 cab over the weekend.
I used the designtek kit, but I also removed the HHR and used some plumbing bits to block the hole. Tip - use the rubber ring of the HHR to create tight plumbing bit fit.
Anway, throttle response definitely improve - the car is crazy at 70mph+....slight tap on the accelerator and you feel the surge, just begging you to thrash it more. I stopped off to check whether everything in the engine bay was fine (i.e. that the plumbing bits hadn't melted/flown off)....i touched the blue hose and it was like touching ice...very very cold.
Soundwise, with the roof down not much difference. Within the roof close you can hear the difference - there is a slight whistling sound hidden in a loud roar. To be honest I am not sure whether this sound is better than when it was stock, but the throttle response makes the mod worth it....
I concur! A definite improvement - slightly more induction noise, better throttle response and increased torque. Quite amazing for a DIY fix!
Thanks GT4
The throttle response is definitely a lot crisper.
As for the "tight plumbing fit", that is the point of the two 12p silicone washers!
One each side of the connector and nut and you get a nice friction seal (I actually put some LocTite on the thread for "lifetime" maintenance free result.
Did you glue down the cap? Mine is pushed in and a tight fit (with rubber on the sides) - was thinking of loctiting it in....Also when i close the engine lid, it slightly touches the top of the plumbing bits - i.e. the cap - I guess that adds extra protection in keeping the cap in there...
Although designed as a solvent fit (in plumbing use), the cap on mine is quite a strong 1" inch friction fit.
Also, remember the airbox is sucking, so the cap is being sucked down onto the seating flange (holding it in even more firmly).
Although I LocTite'd the nut thread, the cap is free. As minimal use as it may be, and as improbable, if the airbox does experience a blow-back (back fire) through the throttle body, the cap will act as an escape valve and just pop off.
Not sure on your lid fouling, my cap only sticks up just above the airbox fins, and shadowed by the much larger CAI tube?
Shouldn't make any difference to the above, but my car does have a fixed wing. So no retracted rear spoiler mechanism?
Yes, glued down. To make a cap I cut a Gunk can's cap in half - it's a perfect fit and makes everything look stock (apart from the smooth DesignTek) hose.
I am considering spraying the top of the airbox, HHR cap and (bright blue) pipe in Matt or satin black so it looks even more stock.
Any ideas for a paint that would be safer on the rubber pipe?
Has anyone tried this without changing the Y-tube - ie block off the hole, remove the HHR box, but still re-connect the Y tube?
Reason being I have a tiptronic and there is that little breather pipe thingy to complicate things. Plus I like the idea of the engine bay still looking "stock".
Clearly have to change the plumbing design enough to ensure the end cap doesn't get sucked up the pipe into the throttle body (eek!), and obviously there would now be a pipe-shaped acoustic chamber rather than pipe-plus-HHR-box-shaped, but the airflow improvement across the air box would still be achieved.
Anyone done it - or hazard a guess on the outcome?
(I'm almost ducking already)
Having read this and time to spare I pulled my resonator out on Sunday
I was loathed to plug the hole with a "toilet part"so I push fitted the CIA plug into the hole
I think a close fitting grommet will be the final solution though.
The Price of the "toilet part" was not an issue.
Growls now, I can report.
I have a moderate 3/4"od x104 thou wall bypass on the mufflers as well.
It all comes together at 4000rpm
Just enough for the older end
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