Understanding exhaust notes

Motordyne · 02-16-2012, 10:31 AM

Quote:

Originally Posted by RoshDawg

Just curious about what causes different type of exhaust notes. For example, rumble sounding exhausts are normally caused by unequal length headers (ex STi), but what about:

1. Deep/low pitched exhaust
2. High pitch (not necessarily exclusive to rpm's above 8/9k)
3. Rumble sound even with equal length headers (ex. GT40, SLS)
4. Exhaust crackle when you let off the gas

I'm simply trying to learn about the acoustics of exhausts so any relevant info is appretiated. Other types of sounds and their explanations are very welcome.

The engine type and cam phasing has a lot to do with all of it.

1. Deep/low pitched exhaust
Generally larger diameter tubing

2. High pitch (not necessarily exclusive to rpm's above 8/9k)
Generally small diameter tubing.
A system design that has sudden expansions or sudden contractions.
Chambered mufflers.

3. Rumble sound even with equal length headers (ex. GT40, SLS)
The "off beat" sound can be the total system design.

4. Exhaust crackle when you let off the gas
Engine tune and exhaust cam phase.
And it helps to have a high flow exhaust.

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