Definitive answer on the Hermann von Helmholtz resonator?
 

Hi all!

Have been in two minds about removing my Helmholtz resonator for quite some time now, specifically because of this reference to smoothing the incoming air for the MAF to read:

https://cimg3.ibsrv.net/gimg/rennlis...91e8e2c424.jpg

Can anyone share some insight? *cough* calling Porschetech3 *cough* I know the GT3 and Turbo don't have a resonator but that's a whole different setup.

I know plenty of people have removed it but I'd like more information :)

Thanks!
:cheers:

If you cap it off (orange cap mod etc) there is no effect on the airflow through the MAF, since the return tube from the intake hose is after the MAF. I guess removing the resonator entirely could theoretically change the airflow before the MAF but I've not heard of any problems with that as long as both the airbox and hose are capped.

Correct, it uses the Helmholtz resonance theory to reduce engine intake noise. However the literature makes mention that it does more than reduce intake noise and helps smooth the flow of air.

I guess the literature makes it fairly clear that its been put there for more than one reason, I think im in the ill leave it alone camp.

Have you removed yours?

Mine's had a Helmholtzectomy. gone. No issues.

Hoping to gain at least +5hp from it :roflmao:

Guess I wont know until I do it if there are any negatives. The 997 actually has a vacuum actuated resonator box that closes over certain RPM.

LOL..OK I have the answer you are looking for. The Helmholtz resonator does smooth out the pulses and quiten the sound, but does not affect the TOTAL air flow, or the AVERAGE air flow.

For instance full throttle at 7000 rpm would read 255g/s air flow for 320hp ,Helmholtz resonator in place.

Full throttle at 7000 rpm without Helmholtz resonator would bounce quickly between 250g/s and 260g/s, same result. 320hp. It happens so fast there is no change in A/F ratio or timing.

Same thing happens when using Helmholtz resonators in the exhaust to quiten them down, it smoothes out the pulses, but does not increase the flow, no extra HP.

Intake and exhaust pulses CAN be used to increase HP as in timing the pulses to help evacuate the cylinders in header/collector design, and to increase cylinder charging by timing the pulses as in Variable Ram Tuning of the intake manifolds/plenums.

Awesome thanks all and Porschetech3 extremely insightful as always.

So in summation, there is no negative affect by removing the resonator :cheers:

I'd say that's a fairly definitive answer!

Im going to try and get one fabricated metal so I can use my original intake boot :)

Right !!. Like jllphan mentioned, the only negative is your fuel mileage will decrease significantly !! Especially if you don't have a real aggressive muffler and can hear the engine scream , you"ll be deep in the throttle and high in the revs all the time !! I liked the sound so much I went a step further in retrofitted the 991 "sound symposer" into mine to amplify that sound !!

Tell us more please!! :D

The 991 guys are blocking theirs!! :rolleyes:

https://www.6speedonline.com/forums/...poser-mod.html

https://cimg6.ibsrv.net/gimg/rennlis...00431598bb.jpg
Yea I know they are blocking it off !!.. IMO stupid. I love the sound !!

I did some of these about 5-6 years ago

I did some with Lexan heat shield and some with aluminum heat shield.

I tested the temp against the factory box and above 40 mph they are the sametemp, below 40 or stopped the open filtered air would heat up quicker,but would cool off quicker once above 40. the factory box would take longer to heat up once slow or stopped, but would take much longer to cool off once above 40 again. On my design there isn't much to hold heat, just mainly the small aluminum MAF housing. On the factory box , all the plastic ducts and box would get heat soaked and take a long time to cool off.

Correct! It was coined "the orange cap mod". Heaps of threads on it so the idea isn't a new one. I just don't trust plastic when its post the air box filter screen...

https://cimg9.ibsrv.net/gimg/rennlis...6a11c08817.jpg
First one I connected the "sound sympose"r into the silcone elbow..