Interesting to hear. I lived in St. Louis and just moved to Colorado a few months ago. And that's when the noise started. You might be right in it only happens at high altitudes.

You should definitely keep me/us posted


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im at 800ft and heard the sound yesterday in third gear. switched to fourth and immediately went away. lasted about 3 seconds haven't heard it since

Update: I've got 2300 miles on the car now. The first time I heard the noise is still the worst its been. Following my last post, I started the car and heard it slightly while the car was still cold. That was at ~8000 ft. After the following fill-up, I have yet to hear it. While I was still at high altitude, I could hear the faintest clatter noise between 3-4000 rpm.

I haven't heard a thing since getting on the interstate and heading home.

My instincts tell me that the noise is caused by a combination of fuel, altitude, and temperature interacting with the high pressure fuel pump.

I'll post back if I ever hear the noise again. I'm in Iowa at 1000 ft and will be using 93 octane.

Was it between 3000-4000 rpm?

I'm having an issue with a noise similar to that, but it seems to be coming from after 2500rpm for me and I have only hit 5500 RPM once, but the power was much greater after 5000rpm.
Its been happening for about 1 week now and is always there after 2500rpm.
I only have 600KM on my frs and don't exactly drive it hard yet.

So I just talked with our resident performance car expert/racer (I'm an engineer at a diesel engine manufacturer) and he is 100% confident that this noise is spark knock.

The charge is detonating in this engine speed range when the spark fires. His solution is to run at a higher engine speed when under load at this engine speed. This does two things: reduces peak cylinder pressure for the same power, and mixes the charge better.

The ECU is responding to the knock by retarding timing and injecting more fuel. This explains why mine got quieter each time and has since gone away. The ECU is learning where the knock is occurring and compensate.

I thought this was from a loose heat shield, or is this another noise. I also have somewhat similar vibration noises at higher RPMS

I've had a heatshield rattle in my old wrx and it sounds way different than this. Well atleast my rattle did.

I have heard this noise a few times. Few questions… Was it hot out and have you been driving some? Were your windows up and A/C on? This is when I seem to notice this noise the most.

For me it happens more when its warm. Windows up. Ac off (haven't even tried ac yet)

I have noticed it happens more at around 50%+ throttle pressure.

Unknown Engine Rattling (Video)
 

I'll second that. I was in the same driving scenario as you. About 74 out. Ac off. My driving was mixed, but I think it's when in driving more aggressively that it seems to happen. in boulder Colorado so about 8000ft above sea level.

It hasn't happened in a whole for me. I'll update if it does. Last time It happened I got a better video. I'll upload later today

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Unknown Engine Rattling (Video)
 

Not sure who is still subscribed to this thread. But I thought Id share. I'm still getting that sound about every other time I take my car out. It's been happening for about five months now. The engine still feels strong despite the noise.

Got a decent video of it.

I'm stock besides OFT stage 1 tune.

[ame]http://youtu.be/nvHnLm-EtkA[/ame]

not trying to dog ya, but that video is pretty hard to distinguish on Dell stocker 2-way speakers. The first ones were better able to give a sound through the engine noise. I'll listen with headphones after work and see then.

Unknown Engine Rattling (Video)
 

No worries. Glad you're being honest.

I just gotta a pair of binaural microphones for 3d audio recording. I'll see if I can capture it with that. It will be much better