Injector voltage

[kachemakian]

Does anyone know what voltage the 2L injectors run at? What percentage of the time do the injectors stay open at WOT? Also, does the system run at 35psi regulated pressure like the D-Jetronic Jag systems?

Leon

[Dave at Pelican Parts]

According to Brad Anders' amazing D-jet website, the injectors see about 5V steady-state, but more to open them. The ECU

On his http://members.rennlist.com/pbanders/Djetfund.htm page, he shows graphs of the pulse width ranging from just under 3 milliseconds to just under 10 ms. To get duty cycle, you'd have to do some math. Let's see, 6000 RPM (over stock redline but a convenient number) would be 100 revs/sec, half that because the injectors fire every other revolution is 50 rev/sec, and that's 20 ms. So at (over) redline at WOT, a 10 ms open time gives us a duty cycle of less than 50%.

The 914's D-jet system is regulated to 2 bar, or just over 29 PSI.

--DD

[kachemakian]

Wow! A lot of information there, thank you. So am I right in thinking that if I "bump" the injectors with 12 volts I should hear them "click" if they are not jammed with shellac? To my knowledge this injection system has not been run in at least 20 years. By looking at the injectors they must of been replaced shortly before this engines very long hibernation.
Where is there some good, clear pictures of how all of the fuel plumbing, and vacuum plumbing was routed from the factory on this 2L 4? I have already installed an updated fuel pump up front, so mostly I would be talking about everything on top of the engine.

Leon

[John Rogers]

That is not how to test the injectors. Generally cycling the throttle by hand with the key on should result in a faint buuurrrp sound. Again, this is all on Brad's website.

[Dave at Pelican Parts]

I have heard that a 9V battery is a good way to test the injectors. Portable, too.

Diagrams of the hose layout can be found here:

Pelican Parts: Porsche 914 Technical Forum

--DD

[kachemakian]

All right! A 9 volt. Thanks John, but I have the injectors out of the car, so I was looking for a way to "click" them 1 at a time. The last D-Jet car that I had running was a V-12 Jag. When you twisted the throttle (which was horizontal) there was a whole lot of clicking going on with 4 groups amplified to run 3 injectors off of about the same logic as the 914.

Leon