A brand new MPS!, $610 !!!!! Wow! Options

[JawjaPorsche]

Never seen a new one. I guess this is the going rate? Like how they spelled PROSCHE in the ad, not once but twice!


http://www.ebay.com/itm/Prosche-914-Fuel-I...851&vxp=mtr

[stugray]

You can set up something that will vary the inductive coupling on two pair of wires depending on a vacuum signal? For that cheap? Color me impressed; I wasn't able to come up with a decent way to do that, even just brainstorming.

I'll give up my secrets and work with anyone that wants to pitch in.
If you used a modern Manifold pressure sensor like McMark used with an arduino:

http://www.914world.com/bbs2/index.php?sho...amp;hl=manifold

Those sensors just put out a voltage that is proportional to Man. Press.
You could sense the voltage with a $7 microcontroller with Analog input to read it:
http://www.dfrobot.com/index.php?route=pro...product_id=1075
(IMG:http://www.914world.com/bbs2/uploads_offsite/www.dfrobot.com-10819-1389901285.1.JPG)

(Or McMark's Arduino would work just fine)

Here is the diagram of the MPS output signal wrt the input signal
courtesy of pbanders site(http://members.rennlist.com/pbanders/ecu.htm#PL):

(IMG:http://www.914world.com/bbs2/uploads_offsite/members.rennlist.com-10819-1389901286.2.gif)

The microcontroller would sense the TL trigger signal (this falling edge identifies the start of a injector pulse), then the micro would have an output that simulates the secondary output signal.
The beauty is that the stock ECU system senses when this secondary signal recovers from a large negative voltage and reaches -0.7 volts and then stops the injection pulse.

The microcontroller could just use a digital signal output to simulate the secondary signal.
It would just need to go negative at the start of the TL trigger signal, then return to zero volts when it wants the injection pulse to end.
The ECU would sense this (essentially instantaneous) transition from -5.0 Volts to 0.0 volts as the transition across -0.7 Volts and it would end the injector pulse.

A second analog input to the micro could be a temp sensor.

The micro would use the Manifold pressure & the temp to adjust the injector pulse width.

Since the code on the micro can be changed via a basic USB connector, you would change the internal software parameters with any PC.

I am not sure of the amplitudes of the voltages in the signal diagram above, so the drive circuitry might require some external discrete components to generate those voltage levels.

McMarks gadget from the thread posted above gets you 90% of the way there.

[Dave_Darling]

The beauty is that the stock ECU system senses when this secondary signal recovers from a large negative voltage and reaches -0.7 volts and then stops the injection pulse.

It just senses voltage? Heck, that's a ton and a half easier than I had been thinking!

When can we expect your prototype? (IMG:style_emoticons/default/wink.gif)

--DD