GT350 and resonance

It wasn't until someone mentioned that their e-brake handle was vibrating while making contact with it that I wanted to look at my own car. Since day one, before any mods were done, I've had a small amount of NVH that emanated from the driver side A-pillar area (in other words, the metal structure that sits between the windshield and the side window glass). Since I just added a Borla/FRP cat back, I wanted to run the car to burn off some of the assembly/manufacturing oils on the tubing anyway.

So I documented the range in a few different videos, showing the tach so that you can follow when it happens. OF NOTE - in the first two videos, both windows are rolled all the way up. Resonance begins at around 3200 rpm, sounding like loose coins in a tray, and then shifts to what sounds like a trim panel vibrating. It is over by 4500 rpm.

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Another clip just to verify. Same resonance range, windows rolled all the way up.

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Something that caught me off guard - when I rolled the windows down the resonance went away. Difficult to express in a YouTube audio clip based on a recording on a cell phone but I think you get the idea. In person it is clearly gone and not just washed away due to the exhaust system now being more audible. I switch from "quiet" to sport mode at the 27 second mark so that you can get a taste of the new exhaust system.


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I asked my good friend Rick from TMO if he could test the same range, windows up and windows down, to see if he could replicate what I saw. He found that his vibration did not go away with the windows down but he commented that the vibration that his car has been exhibiting is in the exact same range.

In a perfect world, each and every GT350 would be the same (and they wouldn't have any NVH). But they aren't. I'm honestly interested in what everyone else sees in that range. Resonance or not?

What shifter do you have in your car?

Is it hard on the engine to run the rpms up like that without a load on the engine?

johnny1 said:

Is it hard on the engine to run the rpms up like that without a load on the engine?

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Listen. Abuse is bad for any engine. This is not abuse. Actually, lots of times it is required to modulate throttle just for trouble shooting purposes. Load or no load. The engine is not going to break because of the revs. Common sense must prevail.

Anyone out there that can mimic the range and report back with what they see?

Epiphany said:

Anyone out there that can mimic the range and report back with what they see?

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I will try and replicate tonight.

Good man.

Not at my car, but I have similar, but not as loud. At first I thought I had vibrating change. With windows down, Its there but I dont hear it.

Windows up in quiet mode its super annoying , and embarrassing.

wildcard....
stock audio?????

can you pinpoint the locaton?

sounds to me it could be the "simposer" supplemental exhaust tone or ANC???
sounds like a saturated speaker.....

when windows are opened, the ANC is deactivated....


like I said, just a wildcard.....

Ramb

I respect wildcards Ramb.

Location is the driver side A-pillar.

As I mentioned, the resonance shown/heard in those videos was present when the car was new and hasn't increased or decreased with mods. I did swap the '16 Track Pack stereo for the '17 8" navigation, etc, using factory hardware. Again, no impact from the change. Beyond that, I shut the piped in audio off using Forscan. That made the cabin slightly quieter.

ok, but the fact that you have made audio changes to headunit, and software, still has me curious
I know many on the board are trying to confirm which bits truly disable the engine sounds with conflicting opinions.....

as an automotive engineer with 25 years in interiors prod dev, and also currently developing audio aftermarket for the mustang I am extremely intrigued to trouble shoot your NHV LOL

I would take off my A pillar, and maybe then disconnect the tweeter......
and then run with door open and closed and then.......

Ramb

Exactly what I plan on doing.

I have noticed that if I exert a lot of pressure onto the pillar that the noise decreases. I do believe the window glass has something to do with it as well when fully extended it seemes to be carrying a harmonic through it and into the pillar when the windows are up. When down the pathway is severed.

JMHO

Everything vibrates, including the transmission. Most components will have secondary frequencies. Windows up or down is a variable as well.

Im not sure I follow this thread. Are you trying to prove something is wrong with you car or is this a scientific method exercise so that we all know.

As I mentioned, I didn't pay much attention to the A-pillar noise until someone else complained about resonance in their e-brake handle at around 4,000 rpm. Hence why I took a look at the range on my own car. When I noticed the difference between windows up/down it became a matter of curiosity regarding other GT350's.

I'm in Georgia for a few days doing a few things at MGW with George. As soon as I got there I asked if we could run his car through the same test battery. He has none of what I'm seeing on my own car with his GT350.

Epiphany said:

Anyone out there that can mimic the range and report back with what they see?

Click to expand...

I just did a few slow sweeps up to ~7200 RPM (120Hz. I suppose) with both windows up and down and parking brake down (disengaged).

I did not experience any resonances at all. The A pillar, parking brake, rear view mirror, dash panels, center stack & console were all solid, nothing was taking off. Slight vibrations were felt through the gear shift, but very minimal.

There are definite vibrations behind the center stack that can be heard, but I'm not sure if something was resonating back there, or it was just the engine sound coming through. It definitely is buzzy behind there. I think it is just the engine. It's not that difficult to keep the resonant frequency of these types of items above 120 Hz, in my experience.