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And the dance begins. The crate has arrived or shall we say landed. "....the whole world , Chico. And everything in it." David V. Nelson 1969 Fastback FI (no matter what!) ----- Original Message ----- From: "Jim Adney" <jadney@vwtype3.org> To: <type3@vwtype3.org> Sent: Monday, December 01, 2003 12:08 PM Subject: Re: [T3] Injector interchangability? > On 30 Nov 2003 at 23:04, David V.N. wrote: > > > From: "Jim Adney" <jadney@vwtype3.org> > > > > fuel. At some point the PS will max out, however, and then there will be > > no > > > additional fuel as the airflow continues to increase. So you are lean. > > > > > > If you try to cure this by just increasing the fuel pressure you can make > > > things work right at some point, but the mixture at 36psi will be 20% rich > > and > > > the PS will still be maxed out. > > > > A "ramping" regulator has been suggested to take this into account. > > That is,using a microswitch,(or something similar),a higher pressure > > could be "activated" at some pre-set throttle position.I think I've heard of > > such a thing being used in turbo application. > > The problem with this is that the PS is already ramping the fuel delivery at > the low demand end. What you need is a pressure ramp that starts just as the PS > ramp stops (when it maxes out) which will be pretty hard to accomplish. The > better solution is to find a PS that has a wider range, or a PS/throttle valve > combination which has a wider range, and a brain that understands this new > combination. > > > > > >In my opinion, It MIGHT be possible to upgrade our FI to that of a > > > > >different car IF we also upgraded the throttle body either by machining > > out the > > > > >throat diameter to that of the other car, or by using the throttle body > > > > from that car. > > > > > > > > Is the porsche d-jet THAT dissimiliar?The internal volume doesn't appear > > to be that different. (The porsche bieng slightly larger) > > > > > > Internal volume has nothing to do with it. It's simply the throat diameter > > and > > > possibly a small effect from the air cleaner flow properties. I don't know > > what > > > the relative throat diameters are, or what effects that might have. > > > > I am assuming that you're referring to air velocity past the port for the > > MPC. > > Hmmmmm.If the relative diameters of the throat are close then perhaps it's > > only a matter of placeing the sensing port of the MPC at a distance that > > approximates the distance inside a T3. > > Virtually all the pressure drop occurs across the throttle body. Once past that > point I think we can safely assume that the whole intake air distributor is at > the same pressure. Air velocity inside the IAD doesn't really matter much, but > there will be a velocity-dependent pressure drop between the IAD and the > combustion chambers for which the FI system needs to have built in > compensation. > > You still need to get a PS that has a wider range. This means a wider range of > input pressures (vacuums, actually) with the usual range of outputs, since I > suspect that ALL the D-Jet PSs have the same output range. > > Then you have to adjust the brain, or find a different brain, which responds to > the usual PS outputs with proportionally wider injector pulses (or find > injectors which put out proportionally more fuel for the same inputs. > > So it just might be possible to do with a different PS and different injectors. > Finding the right combination of parts would be the tough part, and it's not > even certain that an appropriate combination already exists. I'll agree, > however, that there are enough options out there that it should be possible to > come close. > > > -- > Jim Adney > jadney@vwtype3.org > Madison, WI 53711-3054 > USA > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > List info at http://www.vwtype3.org/list | mailto:gregm@vwtype3.org >