From: Dave Darling [darling@simlab.arc.nasa.gov] Sent: Wednesday, May 19, 1999 9:51 AM To: wayne@pelicanparts.com Subject: [914] Re: Halon and distributor questions >Date: Wed, 19 May 1999 09:34:03 -0700 >To: gt0003a@prism.gatech.edu >From: Dave Darling >Subject: [914] Re: Halon and distributor questions >Cc: "914" <914@rennlist.org> >Bcc: >X-Attachments: > >At 7:25 AM -0700 5/18/99, Jurgen Hartwig wrote: >>Obligatory 914 content: We are in the programming stages of the >>distributorless ignition system now. We only need to resolve issues >>about a source of vacuum for the MAP sensor. I know my Dellortos have a >>single vacuum port. Is this where the vacuum advance is connected? > > The MAP vaccuum line should plug into the manifold somewhere. >If the single vaccuum port on the Dells is sufficiently far below the >throttle plate(s), that would probably work. I don't know how far is >sufficiently far--but you definitely don't want the fitting for a MAP >sensor just at or just below the level of the closed throttle plate. >If you do, at part-throttle you will have high-velocity air flowing >through the small opening between the throttle plate and the throttle >venturi. The high-velocity air will have lower pressure (higher vaccuum) >than the air in the manifold. > Another thought--is Manifold ABSOLUTE Pressure actually the >quantity you want to be measuring? Would a measure RELATIVE to the >ambient air pressure (such as the D-jet MPS makes) be more appropriate? >It might help if you ever take the car up in the mountains... > >>Would it be more appropriate to drill and tap a hole in two of the >>intake runners and take the vacuum off a balance tube? > > Well, that would be more in the lines of a manifold. I don't >know what the flow through the pipes will do to the pressure, though. >Note that on the 2.0, at least, the MPS vaccuum fitting is out of the >direct path from the throttle body to the intake pipes. > >>I apologize for being somewhat ignorant. > > Don't apologize--you're trying to learn!!! Plus, you have a lot >more guts than most of us, actually *making* a high-tech system to >improve your car. Not only that, but you are really trying to do it >*right*, which is even more impressive. > >>My car did not have a vacuum distributor when I >>got it. Where does one connect the lines on the FI cars? > > I don't know about the 912E, whether it uses the 1.7/1.8 style >horizontal throttle body, or the 2.0 style upright throttle body. But >on my 2.0, the advance and retard lines go to fittings on the throttle >body itself. The advance points right-front, and the retard points >left-rear off the TB. > The retard port is a bit below the "closed" position of the >throttle plate, on the side where the plate goes upward when it twists >open. The advance fitting is a bit closer to the closed position of the >throttle plate, but on the side where the plate goes down when it twists >open. The advance fitting, at least, taps into the air moving past the >throttle plate, which has very low pressure from moving fast. > I think CD has a good eye for where the fittings go on a 2.0 914 >TB, hopefully he will speak up. He has, after all, seen a bunch of 'em! > ;^) > >--DD > Dave Darling 74 914 2.0 (decapitated) darling@simlab.arc.nasa.gov "OFF WITH ITS HEADS!"