23-03-2008 11:34:41
Hej allesammen
Jeg faldt lige over et læserbrev som stod i det nye mini magazine som jeg syns jeg vil dele med jer allesammen, og som jeg vil håbe måske kan starte en diskution omkring emnet.
[I]In your”The originals – Fuelling” article you have perpetuated the myth that twin split Webers are the ultimate in A-series carbs. They are not; they are an expensive and unnecessary complication. Think about it; a single twin choke Weber is basically two carbs in one, each identical choke (or barrel) supplies two engine cylinders through the siamesed ports in the head. Split Webers consist of one barrel from one carb supplying two cylinders and the other barrel from the other carb supplying the other two cylinders. There is no difference. How can two barrels, one from each carb, be any different from two barrels both from the same carb? It’s nothing to do with straighter manifolds either, the slight curve in the well-developed Maniflow manifolds make no difference to airflow.
The myth started in the rallying homologation rules from the 1960’s. Group 2 rally cars were allowed certain modifications over the basically standard Group 1. One of these modifications was that the carb could be changed, but two single choke carbs (like the twin SU’s on Cooper S) could only be replaced by two single choke carbs of another make and not a single twin choke carb. Now, the BMC Works team knew that the best carb for a five-port A-series is a twin-choke Weber, but they couldn’t use it at it is a single twin-choke carb. So, being inventive chaps, they decided to use twin-choke Webers, but not use one of the chokes from each, converting them into two single choke carbs thereby complying with the rules. Because the kit had to be homologated it had to be offered to the public, so split Webers came about as a dodge to get round the rules banning twin-choke carbs.
[B]Steve Walker, East Yorkshire[/B][/I]
Alt dette kan også læses i bogen "BMC competition department - Secrets"