Exhaust Tone During Cold Start

nis350

It is apparent that the oem exhaust can produce nice sound, but just not quite sure how/why during the first 5 to 10 seconds on a cold start up.

However, I do know that it sounds pretty nice at high rpm.

ta-kid

I would argue that it has anything to do with the cats that the tone changes approximately 10 seconds after a cold start up.The rpm does not change either much if any in the first minute or longer for me, but the tone does go from a harsh raspy note to a softer note within that 10 seconds,like there is an exhaust valve in the system somewhere closing.I wonder if the ECU is changing the variable valve timing once the cold start has been sucessively established?

nis350

That's an interesting thought. The exhaust volume should go up with the engine rpm, but the raspy tone just can't be duplicated by reving the engine. However, it may sound similarly during higher rpm (5k+) driving.

FPenvy

you people hurt my head sometimes with this non sense.

its the car warming up so it revs at about 1200 for 10 seconds then drops to 1000 then 650 ish once its warm and the ECU has gone through its starting/warming protocols.

now for the sound change that has baffled all of you is due to the metal of the exhaust being cold. once the metal heats up a bit is when it drops off.

also the engine oil temp dictates some of that as well. not the oil itself but it's an indicator of the operation of the vehicle

trust me i have straight pipes. so I hear every change that the Z's engine and functions go through. cold starts in mine are fuckin MEAN lol after it drops off though its a nice V8 like rumble. once the metal heats up the tone changes. then again once the car is up to full operating temps the exhaust note changes and gets smoother and better sounding then as well.

you're all welcome

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