Jump to content
Sign in to follow this  
MarcD

Supercharger whine - Hermholtz Resonators

Recommended Posts

looking for some words of advice from the team!

I have fabricated some brackets and fixed an AMR500 supercharger to cold side of Mazda MX5. Made the throttled volume small, and got it in a nice tight package. Have a bypass working for 100% boost dump at idle, progressively closing around half throttle.

all up and running drives well on a really safe tune and I'm working through getting a decent tune into it. (have noted the intake temps rise rapidly under full throttle boost so might add secondary injector to plenum in future, but thats WIP) getting around 6psi boost at WOT which is within the range I was anticipating.

However,  it whines like crazy which I am told Roots type blowers will do, but they can be quietened down. At some revs its nicely quiet (2800 for example). At 100km/hr in 5th, approx 3200rpm (daily driver) its loud, not unbearable, but will quickly become tiresome!

I know a bit about Hermholtz resonators, pressure waves and destructive frequencies, and fortunately the stock MX5 intake has one, so am going to try to incorporate that piece of the intake into the new intake.

 

my questions...

are Hermholtz the best solution? are there any other workable solutions (apart from taking off the SC!)?

is it best to put the hermholtz before the SC or after?

thanks in advance!

Marc

 

 

Share this post


Link to post
Share on other sites
On 4/24/2018 at 9:16 AM, MarcD said:

my questions...

are Hermholtz the best solution? are there any other workable solutions (apart from taking off the SC!)?

 

 

A Helmholtz resonator only really works at one frequency, which in your case, means 1 particular rpm range. 

The first thing to do though is quantify the frequency that you are trying to cancel out. 

So record the noise as best you can, isolated from other noises. So maybe try hold the engine at the rpm where your car normally cruises at. 

Then save it as a .wav file and load it into this program 
http://www.artalabs.hr/download.htm

Then you can load one of the analyzers which will show you what the main frequency of the noise is. 

Then you can calculate dimensions for a helmholtz resonator that will be able to cancel out this frequency. 

An easy way might be to get one 3d printed so you can experiment. Generally the higher the frequency the smaller the resonator needs to be. 

 

Share this post


Link to post
Share on other sites
13 hours ago, Davidv said:

A Helmholtz resonator only really works at one frequency, which in your case, means 1 particular rpm range. 

The first thing to do though is quantify the frequency that you are trying to cancel out. 

So record the noise as best you can, isolated from other noises. So maybe try hold the engine at the rpm where your car normally cruises at. 

Then save it as a .wav file and load it into this program 
http://www.artalabs.hr/download.htm

Then you can load one of the analyzers which will show you what the main frequency of the noise is. 

Then you can calculate dimensions for a helmholtz resonator that will be able to cancel out this frequency. 

An easy way might be to get one 3d printed so you can experiment. Generally the higher the frequency the smaller the resonator needs to be. 

 

thank you!

I have tried the dual throttle body setup (one pre SC and one stock location) and that didnt make a difference. I'm about to take the SC off its so noisy. I'll give this a try. appreciate help

Share this post


Link to post
Share on other sites
18 hours ago, Davidv said:

If you're based in Auckland flick me a PM if you like as I've got some good recording gear and so on. And this sounds like a fun challenge haha.

thanks for the offer Davidv, am in Hamilton. I'll give your methodology above a shot, and see how we get on.

last night I replaced the pod intake with the stock air filter box, but no luck. I do have a smaller bypass valve, which I might try in case the issue is the openness of the Tial 50mm component.

its more a howl than a whine. I'll take a sound file and attach it.

Share this post


Link to post
Share on other sites

In that case a helmholtz resonator wont really help. You would end up with some rpms being dampened, and some with the noise increased. 

Also worth noting - Apparently the AMR500 is the little brother is the little brother of the Toyota SC12 and SC14 superchargers. 

With AMR500 apparently being the TX10 listed below:

tx15superchargerspecs_zps8d83f2c2.jpg.33

So you might find that the clutched pulley from an SC12 or SC14 will fit to your setup? Then you can just have the supercharger turn itself off when not at full throttle or whatever.

Also - I assume you're running V belts? If you've got Gilmer drive belts, that could be where the noise is coming from. Not the supercharger itself.

And it's also a really small supercharger, do you know what your pulley ratio is? 
You might be overspinning it in order to make boost...

Even with an SC12 or SC14 people dont make that much power (like 220ish hp?) before it just starts becoming a heat pump.

Share this post


Link to post
Share on other sites

running 4 rib belt.

ratio 2.2 : 1

info I have is 16000rpm max continuous, 18500 max short time.

500cc discharge per rev.

am now thinking its the inherent design of the old style roots blowers, and no matter what i do its going to be the same.

 

looking at a MP62 / 90 charger or similar to replace it.....

 

 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×