When you underfuel a petrol engine, you get detonation/pre-ignition which tends to melt pistons...

When you overfuel a petrol, you wash all the oil off the cylinder bores...

So, what happens when you over and undefuel a diesel engine? :confused:

over fuel and you get more power (up to a point) and smoke

Underfuel- nothing. That's normal- unlike a petrol there's no restriction of airflow by a throttle, so a diesel effectively runs a lean mixture at idle/part load. Like ric04vrs says, overfuelling produces power up to a point, then smoke.

Can it damage your injectors?

Can it damage your injectors?

Or pistons?

Have seen a few diesels at work now, with melted pistons etc, with no real explanation of how its happened... :confused:

Or pistons?

Have seen a few diesels at work now, with melted pistons etc, with no real explanation of how its happened... :confused:

i'd be asking the owners what they have been running them on , and whether the engine has been remapped

i'd be asking the owners what they have been running them on , and whether the engine has been remapped

Not on high performance diesels, every day run-of-the-mill engines. Not been mapped etc...

underfuel usually leads to boost surge, which isn't healthy for a turbo. overfuelling just causes black smoke - not really an issue in my mind. I usually get the latter.