Cold air kit and 1000 to 4000 revs
Discussion
guys, am thinking of fitting a cold air kit and bmc filter but like to know if I will see a noticeable induction sound difference at low revs. We all know that above 5000 the engine comes alive but would like a little more at lower revs.
Not too bothered about the performance as its plenty for me at the moment.
Not too bothered about the performance as its plenty for me at the moment.
Jonesy997C4S said:
guys, am thinking of fitting a cold air kit and bmc filter but like to know if I will see a noticeable induction sound difference at low revs. We all know that above 5000 the engine comes alive but would like a little more at lower revs.
Not too bothered about the performance as its plenty for me at the moment.
If you're referring to the type of 'Cold Air Kit' that replaces the main, ribbed, air intake hose with a smooth silicone item, then yes, these are very effective at improving intake noise. Not too bothered about the performance as its plenty for me at the moment.
The factory airbox fitted to the 997.1 has a Helmholz resonator inside the top half of the box. This is connected to the main intake hose by the (approx.) 2" diameter pipe that exists the intake hose at right angles and connects to the top of the airbox. The purpose of this Helmholz resonator is to cancel-out induction noise. As standard, the Helmholz resonator is active at low rpm / part throttle and off at full throttle and high rpm. The 'switching' is via an electronically-controlled, vacuum-powered flap in the neck of the resonator.
The replacement, silicone intake hose has no pipe connecting it to the Helmholz resonator, meaning the resonator is inactive at all times and the engine's natural induction noise is always present. Most kits of this type also include a cap to block-off the neck of the Helmholz resonator, but this is purely cosmetic. Contrary to some (very misguided) claims, this type of kit produces absolutely no power increase as the standard intake hoses are not restrictive. It's also not really accurate to call them 'Cold Air Kits' as the air they supply to the engine is no warmer or colder than the air supplied by the standard setup.
Moving on to the BMC filter - this, IMHO, is a must-have mod on a 997.1. The results this part provides are out of all proportion to its cost and simplicity. The main difference is a much sharper and more immediate throttle response - you simply get the impression the engine is breathing more freely. The filter also noticeably adds to the engine's induction noise. The reason the part works so well is the standard air filter is borderline too small. The BMC flows more air per given area removing the restriction. Whilst the absolute, measurable increase in performance is tiny (you'd be lucky to see 5 peak BHP) the effect on how the car drives is anything but. I noticed this the most when I temporarily re-installed a standard paper filter in the 997.1 I owned at the time. The car really felt like the handbrake was permanently on by a couple of notches, when compared to the BMC.
Hope you'll report back with your experiences once you've installed the kit and filter.
Ian_UK1 said:
If you're referring to the type of 'Cold Air Kit' that replaces the main, ribbed, air intake hose with a smooth silicone item, then yes, these are very effective at improving intake noise.
The factory airbox fitted to the 997.1 has a Helmholz resonator inside the top half of the box. This is connected to the main intake hose by the (approx.) 2" diameter pipe that exists the intake hose at right angles and connects to the top of the airbox. The purpose of this Helmholz resonator is to cancel-out induction noise. As standard, the Helmholz resonator is active at low rpm / part throttle and off at full throttle and high rpm. The 'switching' is via an electronically-controlled, vacuum-powered flap in the neck of the resonator.
The replacement, silicone intake hose has no pipe connecting it to the Helmholz resonator, meaning the resonator is inactive at all times and the engine's natural induction noise is always present. Most kits of this type also include a cap to block-off the neck of the Helmholz resonator, but this is purely cosmetic. Contrary to some (very misguided) claims, this type of kit produces absolutely no power increase as the standard intake hoses are not restrictive. It's also not really accurate to call them 'Cold Air Kits' as the air they supply to the engine is no warmer or colder than the air supplied by the standard setup.
Moving on to the BMC filter - this, IMHO, is a must-have mod on a 997.1. The results this part provides are out of all proportion to its cost and simplicity. The main difference is a much sharper and more immediate throttle response - you simply get the impression the engine is breathing more freely. The filter also noticeably adds to the engine's induction noise. The reason the part works so well is the standard air filter is borderline too small. The BMC flows more air per given area removing the restriction. Whilst the absolute, measurable increase in performance is tiny (you'd be lucky to see 5 peak BHP) the effect on how the car drives is anything but. I noticed this the most when I temporarily re-installed a standard paper filter in the 997.1 I owned at the time. The car really felt like the handbrake was permanently on by a couple of notches, when compared to the BMC.
Hope you'll report back with your experiences once you've installed the kit and filter.
With my BMC kit, I've removed the Helmholz resonator altogether, thus (theoretically!) creating more volume for the cold air inside the airbox plus the better flow of the air-filter itself.The factory airbox fitted to the 997.1 has a Helmholz resonator inside the top half of the box. This is connected to the main intake hose by the (approx.) 2" diameter pipe that exists the intake hose at right angles and connects to the top of the airbox. The purpose of this Helmholz resonator is to cancel-out induction noise. As standard, the Helmholz resonator is active at low rpm / part throttle and off at full throttle and high rpm. The 'switching' is via an electronically-controlled, vacuum-powered flap in the neck of the resonator.
The replacement, silicone intake hose has no pipe connecting it to the Helmholz resonator, meaning the resonator is inactive at all times and the engine's natural induction noise is always present. Most kits of this type also include a cap to block-off the neck of the Helmholz resonator, but this is purely cosmetic. Contrary to some (very misguided) claims, this type of kit produces absolutely no power increase as the standard intake hoses are not restrictive. It's also not really accurate to call them 'Cold Air Kits' as the air they supply to the engine is no warmer or colder than the air supplied by the standard setup.
Moving on to the BMC filter - this, IMHO, is a must-have mod on a 997.1. The results this part provides are out of all proportion to its cost and simplicity. The main difference is a much sharper and more immediate throttle response - you simply get the impression the engine is breathing more freely. The filter also noticeably adds to the engine's induction noise. The reason the part works so well is the standard air filter is borderline too small. The BMC flows more air per given area removing the restriction. Whilst the absolute, measurable increase in performance is tiny (you'd be lucky to see 5 peak BHP) the effect on how the car drives is anything but. I noticed this the most when I temporarily re-installed a standard paper filter in the 997.1 I owned at the time. The car really felt like the handbrake was permanently on by a couple of notches, when compared to the BMC.
Hope you'll report back with your experiences once you've installed the kit and filter.
Not sure how much is the placebo effect, but the car certainly feels more responsive
Ian_UK1 said:
If you're referring to the type of 'Cold Air Kit' that replaces the main, ribbed, air intake hose with a smooth silicone item, then yes, these are very effective at improving intake noise.
The factory airbox fitted to the 997.1 has a Helmholz resonator inside the top half of the box. This is connected to the main intake hose by the (approx.) 2" diameter pipe that exists the intake hose at right angles and connects to the top of the airbox. The purpose of this Helmholz resonator is to cancel-out induction noise. As standard, the Helmholz resonator is active at low rpm / part throttle and off at full throttle and high rpm. The 'switching' is via an electronically-controlled, vacuum-powered flap in the neck of the resonator.
The replacement, silicone intake hose has no pipe connecting it to the Helmholz resonator, meaning the resonator is inactive at all times and the engine's natural induction noise is always present. Most kits of this type also include a cap to block-off the neck of the Helmholz resonator, but this is purely cosmetic. Contrary to some (very misguided) claims, this type of kit produces absolutely no power increase as the standard intake hoses are not restrictive. It's also not really accurate to call them 'Cold Air Kits' as the air they supply to the engine is no warmer or colder than the air supplied by the standard setup.
Moving on to the BMC filter - this, IMHO, is a must-have mod on a 997.1. The results this part provides are out of all proportion to its cost and simplicity. The main difference is a much sharper and more immediate throttle response - you simply get the impression the engine is breathing more freely. The filter also noticeably adds to the engine's induction noise. The reason the part works so well is the standard air filter is borderline too small. The BMC flows more air per given area removing the restriction. Whilst the absolute, measurable increase in performance is tiny (you'd be lucky to see 5 peak BHP) the effect on how the car drives is anything but. I noticed this the most when I temporarily re-installed a standard paper filter in the 997.1 I owned at the time. The car really felt like the handbrake was permanently on by a couple of notches, when compared to the BMC.
Hope you'll report back with your experiences once you've installed the kit and filter.
Thanks mate, exactly the type of info I ws looking for.The factory airbox fitted to the 997.1 has a Helmholz resonator inside the top half of the box. This is connected to the main intake hose by the (approx.) 2" diameter pipe that exists the intake hose at right angles and connects to the top of the airbox. The purpose of this Helmholz resonator is to cancel-out induction noise. As standard, the Helmholz resonator is active at low rpm / part throttle and off at full throttle and high rpm. The 'switching' is via an electronically-controlled, vacuum-powered flap in the neck of the resonator.
The replacement, silicone intake hose has no pipe connecting it to the Helmholz resonator, meaning the resonator is inactive at all times and the engine's natural induction noise is always present. Most kits of this type also include a cap to block-off the neck of the Helmholz resonator, but this is purely cosmetic. Contrary to some (very misguided) claims, this type of kit produces absolutely no power increase as the standard intake hoses are not restrictive. It's also not really accurate to call them 'Cold Air Kits' as the air they supply to the engine is no warmer or colder than the air supplied by the standard setup.
Moving on to the BMC filter - this, IMHO, is a must-have mod on a 997.1. The results this part provides are out of all proportion to its cost and simplicity. The main difference is a much sharper and more immediate throttle response - you simply get the impression the engine is breathing more freely. The filter also noticeably adds to the engine's induction noise. The reason the part works so well is the standard air filter is borderline too small. The BMC flows more air per given area removing the restriction. Whilst the absolute, measurable increase in performance is tiny (you'd be lucky to see 5 peak BHP) the effect on how the car drives is anything but. I noticed this the most when I temporarily re-installed a standard paper filter in the 997.1 I owned at the time. The car really felt like the handbrake was permanently on by a couple of notches, when compared to the BMC.
Hope you'll report back with your experiences once you've installed the kit and filter.
I will be pressing on with this mod and will defo report back.
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