AFAIK there was not a general switch to the Aboukir type. It was purely a local modification made in Egypt.
Aboukir was an RAF base in the Nile Delta from pre-war days on which was based an RAF MU. Their filters were an effort to improve on the Vokes type which was standard on the Spitfire V Tropical versions manufactured in Britain for overseas use. I don't think it has ever been clear just how many were converted. One other suggestion I've seen is that the need for a local modification became apparent with the arrival of the first PR Spitfires in the Med. These PR. IV arrived without the Vokes filter.
Does anyone know why the Aboukir filter should be any better than the Vokes one? Both rely on passing the air through a convoluted filter, which removes any of the pressure recovery that could have been expected from a well-designed intake. The Vokes has greater surface area, hence more skin...www.key.aero
And it seems that there were at least 2 types of Aboukir filter
Dear Forumites I'm almost 100% sure that similar question has occured before but UG hasn't help me with it. That's why I decided to ask it here as there are lots of people who have huge knowledge about Spitfires. I have a question about famous "custom" dust filters made by MU in Abou Kir/Abukir. ...www.britmodeller.com
Good stuff. It's funny how much of this stuff about the filters seems to be on the modeling forums, that is what I was finding too.
Yes i was aware that Aboukir was one of the depot bases. I had been under the impression that they had made a general transition away from the vokes type, but I guess by the time this was getting underway the war was already shifting north into Italy where the problems with dust were not as severe and I think they stopped using tropical filters altogether eventually.
And I guess they never brought this useful innovation over to the Pacific, but when you see the later model Sptifires (Mk VIII etc. ) in the Pacific Theater they don't seem to have the big vokes type filter housing.