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On 2 May 2002, at 9:34, Iamkeen@aol.com wrote: > Would someone please explain the construction and use of a "U-tube manometer"? > I'd love to believe that there's a way to actively balance the carbs TOGETHER, > as opposed to the "separate but equal" method with the UniSyn. If you want to compare two different pressures/vacuums then an easy way to do this is to bend a clear tube into a U shape and fill the U 1/4th up with some easily visible liquid (which is why I suggested ATF, which is red.) Attach a flexible hose to each end and connect these to each of the carb ports. If there is any difference in pressure between the 2 ends, the liquid in the U tube won't fill to the same level on the 2 sides. If there are pressure/vacuum pulses on the 2 sides which are not in sync, using a more viscous fluid will slow down the response time so that you can view the average pressure difference, which is what you really want. > But I wonder; is there a difference in the strength/fluctuation/"statistical > usefulness" of the vac signal from the balance port, way down in the throat, as > opposed to the very top of the stack where the Uni would mount? This question bothered me, too. The Uni-Syn allows you to adjust for equal FLOW into the 2 sides, but the manometer adjusts for equal manifold VACUUM. While they are actually measuring different things, I think the end result is the same, but I'm not sure about this. Anybody got a more informed opinion? If I understand correctly, Dave Hall's system measures vacuum on the supply side. This may also work, but it strikes me as having a number of sources of error, so the pickup tubes would have to be made REALLY carefully in order to be sure that the measurements on both sides were consistent. Both Dave's system and the manifold manometer method have the advantage of making the adjustment in the presense of the air cleaner, however, and this may have some advantage. All in all, I think I like your suggestion the best, but the Uni-Syn is readily available and easy to use, once you have a pair of the right lime cans or PVC tubes to adapt to the carbs. - Jim Adney jadney@vwtype3.org Madison, WI 53711-3054 USA ------------------------------------------------------------------- List info at http://www.vwtype3.org/list or mailto:help@vwtype3.org