Here you can see a plastic tubing that goes to the cyl head
The other end is connected to an old stethoscope
These are my findings using this listening device:
I lowered total boost to 4 psi because I want to learn, not to break this engine
Using 1 degree retard per psi of boost
As I leaned the a/f mixture around 0.5v the engine made loud 'clunk' mechanical noises associated with acceleration and boost clearly audible above the engine's mechanical noise
This noise is audible with bare ears too, but gets masked by the engine noise from 3000 and more rpm
I enriched it back to around 0.7v at 4000 rpm, and now I disconnected the pneumatic ignition retard unit
Now, a/f ratio around 0.7v at 4000 rpm, but there is a different sound It is a higher pitched ping ping noise, lower in intensity but perfectly audible with the device, audible from 2500 rpm and on
This noise is not audible with bare ears
Now the discussion
I know detonation is uncontrolled explosion ahead of the flame front
And I know preignition is spontaneous mixture explosion
Could it be that the loud, heavy clunk noise is preignition?
Could it be that the higher pitch sound is detonation?
Could it be that the pitch and noise intensity is advance dependant?
Need your opinions please
Thanks in advance
Linear Mode
