Hum from air filter/turbo inlet
#1
Senior Member
Thread Starter
Hum from air filter/turbo inlet
It's been slow progress, but I've got the FD up and running. Seems to work OK, but it has a very loud hum from the air filter/turbo inlet.
I'm guessing that it's some sort of resonance and the 4"pipe between the air filter and turbo inlet is tuned just right to sound off.
Question is, has anyone else run into this?
And is there a solution?
Here's a link to a video I posted on youtube.
Victor
I'm guessing that it's some sort of resonance and the 4"pipe between the air filter and turbo inlet is tuned just right to sound off.
Question is, has anyone else run into this?
And is there a solution?
Here's a link to a video I posted on youtube.
Victor
#2
Senior Member
Thread Starter
OK, I think, just maybe, that I am on to something.
Being an automotive technician I've heard similar noises associated with idle valves, usually when the airbox is not secured.
So, knowing that the BACV is set to operate at 244hz, I went online and found a tone generator and and listened to a 244hz tone then compared it to the noise from the car. As best my ears can discriminate, it's spot on.
Here's a link to the tone generator, set it to 244hz and compare this to the hum in the video. tell me what you think.
I had originally discounted this because I can't really envision a noise generated in the intake manifold making it all the way back to the turbo inlet. But with the matching frequency it's nearly impossible to discount it now.
I'm guessing that the resonant frequency of the intake plumbing must be about 244hz. So maybe if I change the frequency of the valve I can move it out of that frequency range.
I'll give that a try tonight and report back.
How far off 244hz can I go without creating a problem for the valve?
Being an automotive technician I've heard similar noises associated with idle valves, usually when the airbox is not secured.
So, knowing that the BACV is set to operate at 244hz, I went online and found a tone generator and and listened to a 244hz tone then compared it to the noise from the car. As best my ears can discriminate, it's spot on.
Here's a link to the tone generator, set it to 244hz and compare this to the hum in the video. tell me what you think.
I had originally discounted this because I can't really envision a noise generated in the intake manifold making it all the way back to the turbo inlet. But with the matching frequency it's nearly impossible to discount it now.
I'm guessing that the resonant frequency of the intake plumbing must be about 244hz. So maybe if I change the frequency of the valve I can move it out of that frequency range.
I'll give that a try tonight and report back.
How far off 244hz can I go without creating a problem for the valve?
#5
Senior Member
Thread Starter
#6
Senior Member
Thread Starter
Changing the frequency of the idle valve is the trick.
As I moved it away from 244hz the hum changed pitch and diminished to the point where it's tolerable.
Right now I have it set to 300hz and if you listen to the air filter, you can hear it but nothing like it was.
I still would be interested in feedback about the actual range of operation as far as frequency settings for the BACV. I haven't tested to see if the valve is still responsive. I guess it could need to have the PID re-adjusted.
I guess it's not too likely that many people will have this issue, but hopefully this thread will help someone out.
Thanks Jetlude for your support.
Victor
As I moved it away from 244hz the hum changed pitch and diminished to the point where it's tolerable.
Right now I have it set to 300hz and if you listen to the air filter, you can hear it but nothing like it was.
I still would be interested in feedback about the actual range of operation as far as frequency settings for the BACV. I haven't tested to see if the valve is still responsive. I guess it could need to have the PID re-adjusted.
I guess it's not too likely that many people will have this issue, but hopefully this thread will help someone out.
Thanks Jetlude for your support.
Victor
Trending Topics
#8
Senior Member
Thread Starter
And one other thought, for tonight,,,,
If this system is tuned for 244hz, does that create a Helmholtz effect at (244x60)/2= 7320rpm?
I'll be looking at the dyno charts when it gets tuned
#9
Newbie
Victor,
I appreciate your post!
My Rx7 has a loud "hum", particularly on start up, from the air filter/turbo inlet which is quite annoying!
I'll look into the BACV and report back in due course.
(Custom garrett single turbo/motec etc etc etc)
Regards,
Roger
I appreciate your post!
My Rx7 has a loud "hum", particularly on start up, from the air filter/turbo inlet which is quite annoying!
I'll look into the BACV and report back in due course.
(Custom garrett single turbo/motec etc etc etc)
Regards,
Roger
#10
Eye In The Sky
iTrader: (2)
Join Date: Feb 2001
Location: In A Disfunctional World
Posts: 7,892
Likes: 0
Received 114 Likes
on
66 Posts
Where is the return discharge pipe from the ACV unit.
Flow is air pump to ACV with excess air coming back forward with the other pipe.
That one make sounds including the stock seq moo-fart sound.
Flow is air pump to ACV with excess air coming back forward with the other pipe.
That one make sounds including the stock seq moo-fart sound.
#11
Senior Member
Thread Starter
I've heard the sound you describe and it's not really like what you can hear in the video.
My plan is to put together a video that shows the settings and resulting different tones.
Thread
Thread Starter
Forum
Replies
Last Post