What does the air doser do on the 2.0 HDi engines?

[rwb]

HDi 90 vacuum, no air doser. The 110 is similar, but has a second control solenoid that supplies the turbo.


HDi 90 vacuum, with air doser. The 110 is similar, but has a third control solenoid that supplies the turbo.


And the air doser itself. This is for the 90. The 110 only differs because of the extra intercooler pipework.


So, I definitely have one of these buggers, but what is it up to?

Note: the 2.2 136 is completely different.

[jasper5]

I believe it's something to do with the crankcase ventilation system to recirculate the fumes to help lower the emissions....akin to the EGR valve function, but don't quote me

[Captain Jack]

Nothing. Mine is disconnected - now need to fabricate a pipe to get rid of it completely. All it does it leak oil on the engine

[steve_earwig]

I (think? Suspect? I'm getting sick of using these words) venture that they are similar to the 2.2's throttle bodies but all they seem to be is chief suspect when things start going wrong. Later cars don't have one so I also theorise that they're more trouble than they're worth and serve no real useful function.

[madmadmax]

if they are like the flaps used on other makes they are for improving egr recirculation and engine shut down

[Welly]

I believe at idle speed they close, say, by half forcing greater egr recirc and then they slam-shut when you switch off to choke the engine of air so that it doesn't stop with that old Diesel 'shudder' due to high compression. Diesels don't have a throttle butterfly to vary the air inlet volume rather it is just a big hole where each intake stroke takes in the same amount of air regardless of the throttle position - as such they do shut-down with a bit of a shudder.

[rwb]

That all sounds logical

Maybe worth keeping for the shutdown, but given that my EGR is disabled it sounds like this ought to be disabled too. I venture that it's simply a case of pulling and bunging the vac supply, as with the EGR.