I did a cheap block off cap of the hemholz rez on the stock air intake tube. There is a lot more drone in the cabin around 2-2300rpm other than that I can tell no difference in sound at part to WOT.

 

Guys,

Thanks for the reply re. block off/pay-off......... with the inexpensive DIY Home Depot mod, at least I can play before the AWE system arrives.....

As I told my wife, the kids are smart and will get scholarships, the college fund will still be put to good use..............

Regards,

UJ

 

How many ppl have tried this? Durability? Thanks!

 

Looks good. Nice sound and smoother throttle response.

 

so i don't get what this does.
i though thte resonator box made the 997S sound more "air cooled".
what does the plug do?
i just bought a used 997S and it has the kit unistalled (for CPO)
thanks

 

The resonator changes the engine sound frequency at lower rpm's
(presumably to comply with more strict noise regulations in certain countries)

The resonator volume box itself is located inside the air intake filter box and it's outlet is connected to the air intake hose (it's the smaller rubber hose)

There is a vacuum activated butterfly valve in the resonator outlet , which closes at higher rpm's and "disables " the resonator effect.
That's why the engine sounds more "aggressive" at higher rpm's.

You can disable the resonator effect by either disconnecting the vacuum hose , or putting a plug into the outlet rubber hose , or as some have done , remove the factory hose and replace it with an aftermarket one ( like the Fabspeed "cold air kit")
If you do that, put a cap on the resonator outlet just to keep the dirt out)

None of these mods will affect the engine or the air intake in any way .
Many who have installed the Fabspeed "cold air kit" think they got more performance when in fact all it does is make it sound a bit louder .
(unless of course you believe that you get xx hp from a ~ 6" long rubber hose elbow) Lol

 

thanks! great info.
so basically you'll get the louder "highway sped" sound at lower speeds? i am assumong thsis since you mention euro regs.

 

Like JCS said you will hear more of the intake sound of the engine and actually it really is not that much of a change in sound.

 

wow sorry to dig up a old thread but this maybe uselfull to people like me that never saw this and almost waisted 250 bucks at fabspeed :/

Any bypass muffler DIY and save me another $300


thanks 6speed rocks

 

This is a very interesting piece, because on the Ferrari chat sites this exact discussion has surfaced.

The intakes (on the 360) are ridged presumably for movement and vibrational purposes.

It was thought that by replacing these with smooth tubes would aide the air flow and add HP. Fabspeed's device to do this came up in the discussion as well as their unsubstantiated claims of increased HP!

A member their did a detailed flow anaysis to disprove the theory. He is well educated and schooled in fluid dynamics.

So, please, help me understand what the theory is here and what backs it up?

Also, why is this referred to as a Helmholtz resonator? The Helmholtz principle is based upon tuning between two different frequencies. Are there two different frequencies with the Porsche intake assembly?

So, help me out wizards so that I can evaluate if this is of value for my 360.

BTW, is there any way you can post a photo of what the OEM piece looks like?

 

OK, let me give it a try .

Dr. Helmholtz was a German Physicist in the 1800's who did research in the principles of sound ( to quantify sound in Scientific terms )

This is how the resonator works:
If you blow over the top of a bottle, you will create a resonance ( sound) .
Depending on the velocity of the air movement over the outlet and the volume inside the bottle ( or any other closed container ) , the resonance changes.
( that's how a flute or whistle or organ pipe etc. works )

The next principle in sound is, that two equal frequencies tend to cancel each other out.

The ONLY purpose of the resonator in the Porsche air intake is to lessen the car's air intake noise at lower rpm's due to noise restrictions in some Countries ( same reason why they have the low speed PSE cut-out )

It does NOT affect the air intake or the car's performance in any way.

The way it works is that as the engine combustion outside air travels from the filter box into the engine , it goes past the resonator outlet ( just like you blowing over the bottle top )
The resonator outlet is the smaller hose, which is connected to the main air intake hose (just above the Porsche name in the photo )

The resonator itself is a closed box, located inside the air filter box and
the resonator box volume has been designed to match the engine's sound characteristics at the lower rpm air flow.

The resonator outlet has a butterfly damper in it. It is open by default at low rpm and is closed (by the car's vacuum ) at high rpm, thereby disabling the resonator effect , which then makes the car's engine air intake sound louder.

The Fabspeed "cold air " kit replaces the factory air intake hose and gives you a cap to put over the resonator outlet .Which just prevents dirt from entering the resonator box .
Since the engine now " sounds" louder , many people think that they got a performance increase ( the human mind works in mysterious ways ) Lol

If you put a plug into the factory resonator hose, you get the same result . The car will sound more aggressive , sort of like a mild Sport exhaust .
But either way, you are not going to get more power .

Hope this answers your question .

 

JCS,

For a guy from NJ you are all right.

I do know Helmholtz well as I have in the past designed a very successful loudspeaker which was a Helmholtz resonator that went so low in bass the magazines who reviewed it could not believe their ears!

I was unaware of two things here: a) why a Helmholtz resonator would be used in a Porsche, and I believe you have well answered its purpose, and b) what difference the smooth inlet pipe was over the fluted one.

The 2nd part was more important since I wanted to compare this to the Ferrari situation. As stated, I did have a handle on the first but was unaware as to exactly why a helmholtz resonator would be used in a car. It's apparent it's sizzle and not steak in its functional value.

So, great wise one, can you answer if in fact there is a difference with the smooth over the ribbed inlet tube?

 

Well , I can try.

OK, let's assume an AVERAGE of 4000 rpm.

In the 3.8 liter engine @ 4000 rpm = ~ 7600 liters of air going into the engine per minute .
That's ~ 268.4 scfm ( cubic feet of air /minute )

Per the ASHRAE(American Society of Heating, Refrigeration and Air Conditioning Engineers ) handbook , this would result in an air velocity of ~ 4000 fpm , with a corresponding pressure drop of ~ 2.5 " wg (water gauge) thru the ~ 3.5 " dia. air intake elbow .

A standard fan at 270 scfm and 2.5" wg SP would require ~ 0.11 HP to suck the air thru the elbow ( at sea level ) Lol
For a "non smooth" elbow , add ....say 20% = 0.132 HP

Just for jollies, if you double the rpm to 8000 rpm , and therefore double the air flow , the SP wg ( and hp ) thru the elbow would quadruple.

So, at 8000 rpm, the engine would require 0.11 x 4 = 0.44 HP ,
vs. a non smooth elbow (+ 20%) = 0.528 HP

Conclusion:
you will gain ~ 0.013 hp @ 4000 rpm and less than 0.1 HP @ 8000 rpm with the smooth elbow.

If that's worth $250 to you, go for it. Lol

 

I just did this mod on my car and I can atest to the car sounding allot better and at 6500RPM before I could hear the car scream. not that scream is at 4500RPM and I love it

It was a pain in the *** geting the elbow the right size and fitting it on thier but well worth it.

thanks again!

 

Try? You did it?

I should give you a reference to the Stanford Engineering dept!

Ok so what you are saying is that there is effectively less resistance in the smooth pipe. No?

I might try this on my 360.

What's the reference to the $250?


Many thanks.