Member Since: 22 Jul 2012
Location: staffs
Posts: 28
Butterfly valve
Some time ago I blanked the EGR valves and removed the butterfly valve. However I then thought that engine braking was reduced, so I put it back in again but it was all in my mind the engine breaking is no different.
On looking at the mechanism the valve is normally fully open by spring pressure and driven closed electrically. In the closed position there is still a 5 mm gap top and bottom. That amount of airflow on a petrol engine would probably equate to 2000rpm or so. I did consider modifying it to close fully but I do not think the spring would be powerful enough to open it again against the vacuum created. Moreover I have not confirmed that the valve is actually driven closed during overrun.
This does confirm that the valve has no effect on engine braking. In the event of engine runaway due to some other fault the the normal reaction will be to switch off and then the valve springs open so will be of no help.
In the end if blanking the EGR I would leave the butterfly in place just to save a bit of effort it must have a negligable effect on air flow but removal does not cause any subsequent problems.
7th Aug 2013 12:07 pm
H16UUP
Member Since: 01 Dec 2012
Location: Stockport
Posts: 271
Even when blanked, the ECU will still be sending the signals to the EGR's and butterfly to open and close - so there will be times when the EGR's are "Open" and the butterfly closed - so the only air getting in will be around the gaps. so there will be an element of starvation.Mark.
2006, D3 SE Auto - gone but not forgotten.
2014 BMW 530d M Sport Tourer.
1977 Triumph Spitfire 1500
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