GT4
Well-known member
- Joined
- 8 Nov 2008
- Messages
- 30,181
NOTE: If your car has the additional Tiptronic gearbox "smog pump" vapour extraction breather line THIS WILL NOT WORK without modification. SEE PAGE 4 FOR REQUIRED TIP MOD
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Thought I'd finally get round to summarising the process and all the replies I had made on this.
AIM: More noise and hopefully some more air flow.
Helmholtz Resonator chamber:
CAI:
Filter Panel:
So in reverse order ...
FILTER PANEL
The filter panel is pretty straight forward, just swap your old paper filter for a BMC, K&N et al high flow filter panel.
Improves the airflow and therefore, hopefully, the power. Irrespective, as long as you look after it (hoover every year and re-oil as appropriate), it will save you money on the paper filters over its 1,000,000 mile lifetime!
Just remember to wrap it in kitchen roll or newspaper overnight when it is new or re-oiled to wick out any excess oil and save your MAF from oil droplet contamination.
Also, it is alot easier to insert the panel in the airbox lid first (so with the airbox removed, fit upside down). This isn't an issue if you have already removed the intake tube (two/three jubilee clips) as it is held in with just one brass bolt at the front of the airbox. Just unclip the oil filler tube and remember to be careful with the MAF cable that runs though clips on the airbox rear. If you are thinking of washing your MAF too, do this first then it is off the airbox.
See here:
http://911uk.com/viewtopic.php?t=57605
CAI
Cold Air Induction (as opposed, pressumably, warm or hot), in this sense it is simply a more slippery tube from the airbox to the throttle body with the Helmholtz spur removed (more later...).
Standard 996 airbox
As the 997 is just a heavily face-lifted 996 lots of bits are interchangeable, like this 3.6 airbox
Standard 997 Airbox (in a 996)
There is no functional advantage, but it looks nicer.
The airbox is quite a nice design, the "snorkel" receives slightly pressurised air at speed from the airstream over the top of the engine bay. The GT models even have scoops for an even greater "Ram air" effect.
Ram Scoops
However, the standard "Y-pipe" that joins the airbox to the throttle body leaves a few things to be desired.
Y-pipe
For a start it is quite corrugated and hence turbulent, which seems a shame after the plastic grill and metal mesh air straighteners in the airbox exit. So fitting a nice smooth tube seems sensible. For a second there is that odd second pipe?
So what does the Y-spur do? - it allow the addition of a Helmholtz Resonator (anti-noise chamber).
Helmholtz Resonator
The second smaller leg of the intake tube, or the Y-spur of the Y-pipe connects the airbox-intake system to the Helmholtz Resonator chamber (also called the HHR).
The noise is increased (improved?) by the removal of the standard airbox Helmholtz resonator (this is a noise cancellation method using harmonic anti-sound resonance of the natural air pulses into the throttle body during cylinder induction - by creating an opposite signed standing wave in the cavity).
Its removal results in a louder (and more pleasing) noise. The original inclusion of the HHR is just for drive-by noise regulations, rather than some clever intake tuning, like the VarioRam.
HHR in the lid of the airbox:
Removal of the HHR from inside the top of airbox allows clean airflow across the full filter surface (upto 1/3rd of the filter surface is restricted or turbulent with HHR in place) and liberates between 0.5L and 0.75L of post-filter air.
As the HHR removal leaves a hole in the post-filter side (top) of the airbox, it is necessary to cap this hole otherwise dirty and warm air will enter from the engine bay.
HHR removed
The FabSpeed kits came with a ready made bung for this purpose.
They supplied a blanking piece in the kit, but this seems to have been dropped now (after 997.1 glued the HHR in?)
However, the Schnell one and others don't, so I made my own for £2.52 from plumbers merchant bits:
Plumbing bits
The panel filter needs the post filter air-straightener to streamline the flow. Some people discuss removing the straightener THIS MUST NOT BE REMOVED - firstly the air will be more turbulent, secondly any large particles somehow getting past filter panel (either ill fitting or panel missing etc) will not get stopped prior to throttle body and engine ingestion!
Linear (non-turbulent) air-flow is required for accurate MAF (air-mass flow) readings, non-linear (turbulent) air-flow will result in incorrect fuelling.
STRAIGHTENER (and finer metal mesh behind this grid)
Conclusion:
The noise is a lot more interesting and louder, perhaps not quite an induction roar (well it might be, but my ears are at the front and the engine is in the back). The noise through the rear bulkhead is a pleasing engine sound and the throttle response is definitely a lot crisper.
EDIT: FOUND MOST OF MY PHOTOS THAT HAD BEEN LOST TO NTL/VIRGIN HOSTING, SO INITIAL POST EDITED TO ADD BACK:
-------------------------------------------------------------------------------------
Thought I'd finally get round to summarising the process and all the replies I had made on this.
AIM: More noise and hopefully some more air flow.
Helmholtz Resonator chamber:
CAI:
Filter Panel:
So in reverse order ...
FILTER PANEL
The filter panel is pretty straight forward, just swap your old paper filter for a BMC, K&N et al high flow filter panel.
Improves the airflow and therefore, hopefully, the power. Irrespective, as long as you look after it (hoover every year and re-oil as appropriate), it will save you money on the paper filters over its 1,000,000 mile lifetime!
Just remember to wrap it in kitchen roll or newspaper overnight when it is new or re-oiled to wick out any excess oil and save your MAF from oil droplet contamination.
Also, it is alot easier to insert the panel in the airbox lid first (so with the airbox removed, fit upside down). This isn't an issue if you have already removed the intake tube (two/three jubilee clips) as it is held in with just one brass bolt at the front of the airbox. Just unclip the oil filler tube and remember to be careful with the MAF cable that runs though clips on the airbox rear. If you are thinking of washing your MAF too, do this first then it is off the airbox.
See here:
http://911uk.com/viewtopic.php?t=57605
CAI
Cold Air Induction (as opposed, pressumably, warm or hot), in this sense it is simply a more slippery tube from the airbox to the throttle body with the Helmholtz spur removed (more later...).
Standard 996 airbox
As the 997 is just a heavily face-lifted 996 lots of bits are interchangeable, like this 3.6 airbox
Standard 997 Airbox (in a 996)
There is no functional advantage, but it looks nicer.
The airbox is quite a nice design, the "snorkel" receives slightly pressurised air at speed from the airstream over the top of the engine bay. The GT models even have scoops for an even greater "Ram air" effect.
Ram Scoops
However, the standard "Y-pipe" that joins the airbox to the throttle body leaves a few things to be desired.
Y-pipe
For a start it is quite corrugated and hence turbulent, which seems a shame after the plastic grill and metal mesh air straighteners in the airbox exit. So fitting a nice smooth tube seems sensible. For a second there is that odd second pipe?
So what does the Y-spur do? - it allow the addition of a Helmholtz Resonator (anti-noise chamber).
Helmholtz Resonator
The second smaller leg of the intake tube, or the Y-spur of the Y-pipe connects the airbox-intake system to the Helmholtz Resonator chamber (also called the HHR).
The noise is increased (improved?) by the removal of the standard airbox Helmholtz resonator (this is a noise cancellation method using harmonic anti-sound resonance of the natural air pulses into the throttle body during cylinder induction - by creating an opposite signed standing wave in the cavity).
Its removal results in a louder (and more pleasing) noise. The original inclusion of the HHR is just for drive-by noise regulations, rather than some clever intake tuning, like the VarioRam.
HHR in the lid of the airbox:
Removal of the HHR from inside the top of airbox allows clean airflow across the full filter surface (upto 1/3rd of the filter surface is restricted or turbulent with HHR in place) and liberates between 0.5L and 0.75L of post-filter air.
As the HHR removal leaves a hole in the post-filter side (top) of the airbox, it is necessary to cap this hole otherwise dirty and warm air will enter from the engine bay.
HHR removed
The FabSpeed kits came with a ready made bung for this purpose.
They supplied a blanking piece in the kit, but this seems to have been dropped now (after 997.1 glued the HHR in?)
However, the Schnell one and others don't, so I made my own for £2.52 from plumbers merchant bits:
1 1/2" STRAIGHT tank CONNECTOR + securing nut
1 1/2" socket plug x1
1 1/2" poly washer x2
Plumbing bits
The panel filter needs the post filter air-straightener to streamline the flow. Some people discuss removing the straightener THIS MUST NOT BE REMOVED - firstly the air will be more turbulent, secondly any large particles somehow getting past filter panel (either ill fitting or panel missing etc) will not get stopped prior to throttle body and engine ingestion!
Linear (non-turbulent) air-flow is required for accurate MAF (air-mass flow) readings, non-linear (turbulent) air-flow will result in incorrect fuelling.
STRAIGHTENER (and finer metal mesh behind this grid)
Conclusion:
The noise is a lot more interesting and louder, perhaps not quite an induction roar (well it might be, but my ears are at the front and the engine is in the back). The noise through the rear bulkhead is a pleasing engine sound and the throttle response is definitely a lot crisper.
EDIT: FOUND MOST OF MY PHOTOS THAT HAD BEEN LOST TO NTL/VIRGIN HOSTING, SO INITIAL POST EDITED TO ADD BACK: