Flat Exhaust 102's

[rosbullterier]

I really should have gone to bed but the overwhelming concern of which engines have the flat exhausts and why has prevented that.

It seems the SD is earlier than the D which both have flat exhausts. The AC is later with the protruding tube exhaust and precedes the AD.

Are there others which have flat exhausts-the letters without order are starting to confuse me . .

Now I do remember not long ago Mr Palfreeman (I think) explained the highfalutin description by the Seagull main man of the new protruding exhaust. But is it too technical a query to wonder whether the flat exhaust was really not as efficient?

And, at the same time the raked back propeller, which gave increased diameter was discontinued because the new exhaust was in the way.