Help calculating resonator/sound suppressor for X-47

[NJBooST]

The whistling from my X47 is getting a bit old. Especially driving around town when part throttle and low speeds are unavoidable. I was looking at the Helmholtz resonator that Mountune sells as a sound suppression chamber and want to add something similar to the inlet of my X47. I'm looking at ordering an extra inlet and adding an adjustable resonator to adjust until I find and cancel out the offending frequency.

Does anyone know how to calculate the necessary volume and hole size to cancel out the whistling?
Any ideas on how to construct an adjustable unit to test this with?

Link to explanation of how suppressor works:
https://performanceparts.ford.com/part/2536-SSC-AA

 

[letitreign]

Before I bother looking through the numbers, can I ask why simply going with a plastic elbow is out of the question?

 

[NJBooST]

Before I bother looking through the numbers, can I ask why simply going with a plastic elbow is out of the question?

Because you have to find the specific frequency you're trying to cancel and then create a resonator with the correct volume to create an opposing sound wave. Look into 1/4 wave or side branch resonators for exhaust. Same principle here.

 

[letitreign]

Given my background in physics, I would love to help you figure this out. Unfortunately, you and I had spoken before. Best of luck bud.

 

[Black_BerryST]

Must not have known what you were getting into I take it? Turbo whistle is like music to the ears

 

[NJBooST]

Given my background in physics, I would love to help you figure this out. Unfortunately, you and I had spoken before. Best of luck bud.

Thabk you for once again contributing nothing to a thread. Glad to see you've kept your sense of humor as well.

 

[NJBooST]

Must not have known what you were getting into I take it? Turbo whistle is like music to the ears

Turbo whistle on the exhaust side I'm fine with. But having a constant howl/whistle while daily driving between 1800-2700rpms is different.

 

[letitreign]

anything for you sweetheart.

 

[NJBooST]

anything for you sweetheart.

The last time I heard from you, it was when you sent me an insulting PM. Now you're posting to a thread I started just to do the same. Why post? What are you contributing to the community?

 

[Black_BerryST]

Probably because your car is faster, but good point

 

[letitreign]

lol k dude. I asked you for help cause I was new to the forums and you replied by being a dick. I contribute plenty, just not interested in helping you.

 

[NJBooST]

You asked for parts advice in a For Sale thread. Advice on COBB intercooler pipes. I gave you a non-sensical answer as it was obvious you didn't even try to search beforehand. I was being humorous, but definitely not a dick.
You then sent me a PM about your multiple university degrees and how I must be an illiterate high-school dropout. It was a bit out-there, and definitely not the type of response warranted by a joke refrencing kanuder valves and iPhones.
Time to let it go.

 

[letitreign]

There's so much wrong with what you just said, I won't bother correcting you. Like I said, best of luck.

 

[NJBooST]

There's so much wrong with what you just said, I won't bother correcting you. Like I said, best of luck.

Corrected:

 

[Goingnowherefast]

The only way to do this is to get a car and instrument it with high quality microphone equipment and take several runs of it happening. From there you can plot the sound waterfalls to identify the frequency where the resonance is happening. I can do this easily (it's my job), but I'd need to borrow and X47 Fiesta for a day lol.

Alternatively, send me a video of it happening with a decent microphone with NO windnoise.

PM me if you want more details (I'm an powertrain NVH engineer)

 

[NJBooST]

Thanks @goingnowherefast !
I have a GoPro4 Black and can borrow an external mic. Would that setup provide enough fidelity to capture what you need? PM me what you need and I'll get everything together.

The only way to do this is to get a car and instrument it with high quality microphone equipment and take several runs of it happening. From there you can plot the sound waterfalls to identify the frequency where the resonance is happening. I can do this easily (it's my job), but I'd need to borrow and X47 Fiesta for a day lol.

Alternatively, send me a video of it happening with a decent microphone with NO windnoise.

PM me if you want more details (I'm an powertrain NVH engineer)

 

[kivnul]

This could work out well if others are having similar noises from the x47. I am looking for a stealthy build and a noise like this could keep me from this turbo.

 

[Goingnowherefast]

Thanks @goingnowherefast !
I have a GoPro4 Black and can borrow an external mic. Would that setup provide enough fidelity to capture what you need? PM me what you need and I'll get everything together.

Should be good enough for me to get an idea of what frequency it's operating at and I can give you some suggestions on resonator or NVH material placement after that. Just get me 3x 5-10 second clips of it happening. WOT, POT doesn't matter. Mic in the engine bay if possible. Send it to me when you get it. For those interested, I'll post a screenshot of the waterfalls afterwards and walk people through what's happening at X frequency so hopefully it can help some more people out.

No solution will be perfect though. NVH is sort of a black art. We've got senior engineers that have been in NVH for 15+ years, and they still say they've barely scratched the surface.

 

[bgrazman]

Any progress? (getting my x47 installed this week).

 

[NJBooST]

I received another cold-side housing from Puma that I need to swap on first before I take any recordings. The X-47 I currently have doesn't allow for an electronically controlled BPV. I've grown tired of running a vent to atmosphere, so will take recordings once I've made the swap and am fully tuned. Should be within a couple weeks.

Any progress? (getting my x47 installed this week).