Throttle Plate on Diesel Engines?

[santorta]

Hi All,

i heard that Throttle plates are used in Diesel Engines recently for controlling Air for meeting the emissions norms Euro 5 or so (in CRDI systems). But is it that the Efficiency of the Diesel Engine will drop bcos of the this of Throttle plate? If at all the throttle plate is used, will it be used to control the entire quantity of the air ( as it is done for the SI engine) or is it handled in a different way?

Thanks,
Santhosh T Arasan

 

[WGJ]

It's used to help control EGR and crank case venting, not for engine control as such.



Bill

 

[MikeHalloran]

Throttle- like butterflies or flapper valves are fitted to marine Diesels to allow shutting off the air supply in the event of a "runaway" (e.g. ring failure allows engine to run on its own lube oil, no longer controlled by fuel supply).




Mike Halloran
Pembroke Pines, FL, USA

 

[Rob45]

And in answer to a part of your question: yes, throttling a Diesel reduces its efficiency.

 

[WGJ]

I don't think you will find a fuel AND throttle control on a diesel unless you go back to at least the 1950s, if not before that.

Everything 'modern' certainly uses unthrottled inlet air.

The systems I have had some slight association with recently use what look like throttle plates to ensure that exhaust has and crank case gasses are preferentially consumed under certain parts of the speed-load map of the engine.
The 'throttle' position is controlled by the engine control module.
The 'throttle' is rarely, if ever, closed.
These are also turbocharged engines, without exception.

Bill

 

[BrianPetersen]

On the North American specification VW TDI "pumpe-duse" engines, if the EGR valve is fully opened and the system detects that there is still not enough EGR flow, it will close the throttle plate partly to encourage more EGR flow (and less intake air flow). It also closes for a few seconds when the key is switched off, to control what would otherwise be a massive judder from the high compression ratio.