[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [New Search]
On 28 Apr 2004 at 21:37, Mark Seaton wrote: > I just had a look at some identical throttle bodies and found that actually > the vac takeoff is just below the butterfly valve at idle, though it would be > above if the throttle closed completely. It remains below the valve > throughout operation, so I guess it should always have vacuum which is what > I'm seeing- but why? I agree with you completely. I don't see why one would want this vac advance in effect most of the time. It looks like I'm just going to have to revise my view of what the vac advance's job is when coupled with a mech advance. This makes it that much more interesting to do the test with the vacuum gauge while driving. I'm hoping that we find that in actual driving there is seldom actually much vac advance, except while cruising, but the position at idle makes it look like there's a significant amount of vac. advance at idle. > I guess that the vacuum would be strongest with a venturi effect when the > throttle first opens up and the air flow is fastest and close to the hole, > and then again when you're over-running and the throttle is closed but the > momentum of the car is driving the engine- which would give you an increase > in advance when you're cruising at a steady pace. This is what I would hope for, too. > I took some photos: > > http://www.mo-sys.com/throttlebody/ -- Jim Adney jadney@vwtype3.org Madison, WI 53711-3054 USA ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ List info at http://www.vwtype3.org/list | mailto:gregm@vwtype3.org