Spark plugs selection
 

Well, which one to pick?

There are several different models.
Anywhere from OEM like to "double electrode/high ignitability"... so what are the opinions?

I experience this RPM related chirp. It might be the spark plug, so since I will be doing it, maybe just replace them.


As for the chirp.
Happens when at low rpm under load. It goes away when engine is hot. Or I cannot hear it.
Each gear. RPM related (increases in frequency with RPM).
Does not really happen at idle or when revving the engine. Hence I thought mounts or such, but that would not make a chirping sound (like one squeak or so), right?

Overtime it became stronger, meaning started months ago with a few small chirps that would go away quickly, now it is more pronounced and stay for longer.
Yet, goes away when the engine gets hot.

Iridium and platinum plugs are more expensive but they are harder metals and tend to last longer then standard copper plugs.
The most important things with plugs are.

1. Proper plug for the application
2. Proper heat range.
3. That the gap is checked and verified to be in spec. before installation.

If you have to adjust the gap on an Iridium plug be careful as the center electrode is fine and brittle so is easily broken.

Other then that it is just a matter of preference.

A chirp could be a loose plug. Are you certain they are all tight?

No. I am not.

And because I do not have detailed info when they were changed, I could replace them.



On a side note.
I have 2.5, I5 VW. Turns out that some "standard" old style spark plug is way better than Irydium tip model. The engine gets smooth and very torque.

I have NGK BKR6EKUB (7969) in both my 986 and 996