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>Heads Together Systems - Steve Farmer wrote: > >> I belive that originally there were larger venturi available for the >> solexes. Stock is 23.5mm. I belive the venturi effect creates turbulence >> which helps vaporise the fuel better. I think the only other alternative >> is "Baby Dells" which can be fitted without major surgery. >> > >Steve, > >The Venturi is more important than creating turbulance, it works as >follows, > >As the air enters the carb it makes it way down the body, as the >diameter gets smaller through the venturi, the air speed increases, this >increase in air speed causes a decrease in the preasure (same as >aeroplane wings) The famous bernouli effect this decrease in presure is relative to ambient, and >thus there is a slight vacum in the venturi. This vacum then sucks fuel >from the float bowel through the jet in to the air stream, and on in to >the engine. > >If you make the venturi bigger then the air speed increases less, ther >is less vacum and thus less fuel sucked in. With an increase in engine capacity and a change in the cam I would imagine that the airflow through the carbs would be higher, hence the need for bigger carbs to feed the engine. This is why you have bigger >jets. When the venturi gets so big, the carb body does not taper at all, >then I gues you no longer have a carb. > >Running 34mm venturi in a 40mm carb is much better than a 34mm venturi >in a 36mm carb. (Tuning the smaller carb across the whole rev range is >also harder). Interesting, I believe HOT VW's or some similar mag had an article on venturi mods, any listers got a copy? > >Nic Webb >71 Fastback >Team Roobarb & Custard Regards, Steve Farmer --------------------------------------------------- Heads Together Systems Pty Ltd PO Box 2103 Dee Why, NSW, 2099 Sydney, Australia 1970 Type 3 Squareback (Driving) 1972 Type 3 Squareback (Restoring) Net: hts@hts.com.au Tel: 612 9982 6767 Fax: 612 9981 3081 Visit our Web Site at http://www.hts.com.au/VW.html Minds are like parachutes, they work best when open.