Need help. MPGuino GPH jumps around.

[dcb]

I dunno, some folks have loaded the cpp file into arduino and it just worked IIRC. The cpp is the only one being maintained, and isn't guaranteed to work with arduino though.

[theforce]

OK. I'll give it all a try and report back.

[msc]

I think your injector signal may not be going low enough to be consistently recognized as a low by the MPU. When looking at signal levels on my 91 CRX HF the signal was only dropping to about 1 volt for low which the MPU logic levels still register as a high.

Try adding a resistor in parallel with the Zener diode to create an input voltage divider. Try a resistor of about 1/4 the value of the input series resistor.

Mike

[theforce]

Sorry about not getting back with the serial output sooner. Had other project to finish.

Anyway here is a snapshot of the serial output during idle.

000.00,000.00,063832,006.00,000.00

000.00,000.00,066376,007.00,000.00

000.00,000.00,013104,005.00,000.00

000.00,000.00,013156,005.00,000.00

000.00,000.00,013040,005.00,000.00

000.00,000.00,063940,006.00,000.00

000.00,000.00,064160,006.00,000.00

000.00,000.00,013508,005.00,000.00

000.00,000.00,112796,007.00,000.00

000.00,000.00,013240,005.00,000.00

000.00,000.00,065672,007.00,000.00

000.00,000.00,162256,008.00,000.00

000.00,000.00,063300,006.00,000.00

000.00,000.00,013192,005.00,000.00

000.00,000.00,063472,006.00,000.00

000.00,000.00,013228,005.00,000.00

000.00,000.00,013012,005.00,000.00

000.00,000.00,063804,006.00,000.00

000.00,000.00,015748,006.00,000.00

000.00,000.00,013136,005.00,000.00

000.00,000.00,013240,005.00,000.00

000.00,000.00,064008,006.00,000.00

000.00,000.00,063984,006.00,000.00

000.00,000.00,013100,005.00,000.00

MSC did you build yours or did you buy one? Your explanation does make sense. I hope thats whats going on with mine. It will be an easy fix if thats the issue. It cant hurt to try so I will try it and hope to report back by this weekend.

[theforce]

The voltage derider did not help. The GPH is still fluctuating. I just dont get it. Its built to spec.

[nickdigger]

My 95 civic has 100k ohms on the injector input, 5k on the VSS. Aside from your jumping value problem, 0.07gph is probably too low; at idle it should run 0.14-0.20, depending on engine temp.

[theforce]

Well I think I may have found the issue. I swapped out the atmega328 chip with a spare. It now has a steady GPH reading and iMPG reading. I'm hoping that the chip was just damaged from a previous failure and not because of the injector pulses.

As far as the numbers go thats a non issue. Those numbers came from my Insight and I was playing around with the settings. The Civic owner has put in the correct values for his car and so far its working fine. 58MPG on one of his trips the other day I think he said.