2010 vw golf 77tdi injector problems

[Snail Style]

There was issues with the 77tdi injectors which showed itself as pinging under light to moderate throttle at around 1500RPM. After replacing them however they need to be calibrated to the engine module and also have a minimum quantity adaption run through, hope the mechanic did that as well.

[gldgti]

what do you mean pinging? we are talking compression ignition here, pinging is not a term you would normally use or associate with a diesel.

If a common rail diesel is injecting fuel at the wrong time (for arguments sake too early) but under specific engine load and rpm parameters, surely it would equate to some kind of sensor or ecu mapping problem... if it was a mechanical problem with an electronically actuated injector, I would expect the problem to present all the time - unless there was some kind of electrical interference under the specific conditions you mentioned...

[Idle]

I was under the impression that all diesels ping — that's what the diesel rattle is.

[Ryeman]

'knock' for diesel which is the basic idling noise but for petrol under significant load a higher pitched 'ping' ing more like nails in a glass jar.

[Idle]

That's more to do with the speed of the flame front — petrol evaporates quickly, the mixture explodes and the knock/ping is more high-pitched, diesel evaporates and burns more slowly with a deeper sound.

Compression ignition engines are designed to accommodate the pressures involved, petrol (spark ignited) engines mostly are not, hence the likelihood of damage.

[gldgti]

nope, you guys have missed the point of my post.

diesel ignites as it is sprayed out of the injector (usually) and all the associated noises are 'normal'

if you hear a kind of knocking noise from a diesel that isnt that, it can be because theres been fuel in the cylinder that shouldnt be there (like a leaking injector). But that should be evident at all times, not under specific circumstances...

[Snail Style]

You also forget that modern diesels tend to inject at 4 different points through the stroke of the piston. ECU mapping is obviously not going to be the same through the entire RPM range(or under all conditions for that matter), thus the problem only being present at ~1500RPM.

[gldgti]

You also forget that modern diesels tend to inject at 4 different points through the stroke of the piston. ECU mapping is obviously not going to be the same through the entire RPM range(or under all conditions for that matter), thus the problem only being present at ~1500RPM.

I am aware. That doesnt actually explain the problem though - only that it can be the result of the injectors not ding what they are told, perhaps, under very specific circumstances...

Anyway, doesnt matter.

[Ryeman]

You also forget that modern diesels tend to inject at 4 different points through the stroke of the piston. ECU mapping is obviously not going to be the same through the entire RPM range(or under all conditions for that matter), thus the problem only being present at ~1500RPM.

That's what's referred to as a 'stratified' charge in our 95RON 1.2 Peugeot triple.