I've changed spark plugs on a few different cars and I've noticed the idle engine noise changes.
For instance on an Acura 3.2L J32A1 engine, The exhaust was boomy and the valve ticking was clearly audible. I did nothing but change the spark plugs, and now the exhaust is no longer boomy and weirdly, the valve noise is much less. And there is no longer the rapid tapping/spitting noise of the valve heads themselves. I've always wondered what causes this tapping/spitting noise to come and go.
Mainly what I wanted to know is whether you want to go from boomy exhaust to quieter whooshing noise, or the opposite. I've heard a very bad spark plug choice will give a sort of jet engine sound, but that was for racing and perhaps not applicable here.
In one vehicle I noticed the change in exhaust sound, and checked the spark advance. There was no change in the spark advance.
My theory at the moment is that with bad combustion, the fuel burns slowly and for longer, so the cylinder pressure is higher when the exhaust valve opens. Hence the spitting noise and increase exhaust pulse noise. But maybe this is completely backward. Maybe slower burning fuel will always have a lower cylinder pressure when the exhaust valve opens. But then again maybe the booming exhaust comes from the unburnt fuel hitting the cat?
For instance on an Acura 3.2L J32A1 engine, The exhaust was boomy and the valve ticking was clearly audible. I did nothing but change the spark plugs, and now the exhaust is no longer boomy and weirdly, the valve noise is much less. And there is no longer the rapid tapping/spitting noise of the valve heads themselves. I've always wondered what causes this tapping/spitting noise to come and go.
Mainly what I wanted to know is whether you want to go from boomy exhaust to quieter whooshing noise, or the opposite. I've heard a very bad spark plug choice will give a sort of jet engine sound, but that was for racing and perhaps not applicable here.
In one vehicle I noticed the change in exhaust sound, and checked the spark advance. There was no change in the spark advance.
My theory at the moment is that with bad combustion, the fuel burns slowly and for longer, so the cylinder pressure is higher when the exhaust valve opens. Hence the spitting noise and increase exhaust pulse noise. But maybe this is completely backward. Maybe slower burning fuel will always have a lower cylinder pressure when the exhaust valve opens. But then again maybe the booming exhaust comes from the unburnt fuel hitting the cat?