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yetimus · 02-26-2009, 10:34 PM

rm-

You may recall that I replied to your post on 2/15 in the release one workspace thread expressing my interest in tapping the ECU fuel consumption signal on a VW TDI. Well, I finally received and assembled my Fundamental Logic v2 kit and tapped into my VSS and fuel consumption signals. I installed the MPGuino and went for a test drive with no changes to the pre-installed code. I did, however, play around with the preset parameters and changed "Injector Delay uS" from its default setting to 100. IIRC, the default setting was 500 and I somewhat randomly chose 100 uS based on the oscilloscope graphs you posted showing much shorter pulses from the ECU. On test drive #1, I noticed the same behavior in GPH reading as you originally did (i.e. GPH read higher when coasting and lower when accelerating).

So, my next step was to change the code as you did:
attachInterrupt(0, processInjOpen, RISING);
attachInterrupt(1, processInjClosed, FALLING);

The next test drive looked a lot more promising. My calibration values were obviously way off, but not only did the GPH readings display as expected (rising when accelerating/falling when coasting) I also didn't notice any strange behavior with the GPH value rising when coasting. It went to zero and stayed there - which is correct for the TDI because it cuts off all flow to the injectors when coasting in gear.

So I spent a little more time calibrating the VSS and uS/gal settings and everything seems to be running correctly. I still have a little tweaking to do with my uS/gal setting, but it appears that this setup is going to work.

I hope to get around to playing with the sound card oscilloscope program you've been using so we can see if our ECU signals are similar. But I think they are. I recently installed an instrument cluster in my TDI that originally came in the VR6 Passat. The reason I did this is that the VR6 cluster has a built-in MPG gauge that displays average MPG (not instantaneous). The TDI, though it was never originally equipped with the factory MPG guage, obviously uses a nearly identical signal from the ECU as the gasoline powered car. Read more about it here.

So I wish I could provide a bit more insight as to why my particular setup is working so far. Have you tried messing with the Injector Delay uSec preset at all?

Thanks for all the excellent info you've posted on this topic!

02-26-2009, 10:34 PM	#31 (permalink)
yetimus EcoModding Lurker Join Date: Feb 2009 Location: colorado Posts: 16 Thanks: 0 Thanked 3 Times in 1 Post	rm- You may recall that I replied to your post on 2/15 in the release one workspace thread expressing my interest in tapping the ECU fuel consumption signal on a VW TDI. Well, I finally received and assembled my Fundamental Logic v2 kit and tapped into my VSS and fuel consumption signals. I installed the MPGuino and went for a test drive with no changes to the pre-installed code. I did, however, play around with the preset parameters and changed "Injector Delay uS" from its default setting to 100. IIRC, the default setting was 500 and I somewhat randomly chose 100 uS based on the oscilloscope graphs you posted showing much shorter pulses from the ECU. On test drive #1, I noticed the same behavior in GPH reading as you originally did (i.e. GPH read higher when coasting and lower when accelerating). So, my next step was to change the code as you did: attachInterrupt(0, processInjOpen, RISING); attachInterrupt(1, processInjClosed, FALLING); The next test drive looked a lot more promising. My calibration values were obviously way off, but not only did the GPH readings display as expected (rising when accelerating/falling when coasting) I also didn't notice any strange behavior with the GPH value rising when coasting. It went to zero and stayed there - which is correct for the TDI because it cuts off all flow to the injectors when coasting in gear. So I spent a little more time calibrating the VSS and uS/gal settings and everything seems to be running correctly. I still have a little tweaking to do with my uS/gal setting, but it appears that this setup is going to work. I hope to get around to playing with the sound card oscilloscope program you've been using so we can see if our ECU signals are similar. But I think they are. I recently installed an instrument cluster in my TDI that originally came in the VR6 Passat. The reason I did this is that the VR6 cluster has a built-in MPG gauge that displays average MPG (not instantaneous). The TDI, though it was never originally equipped with the factory MPG guage, obviously uses a nearly identical signal from the ECU as the gasoline powered car. Read more about it here. So I wish I could provide a bit more insight as to why my particular setup is working so far. Have you tried messing with the Injector Delay uSec preset at all? Thanks for all the excellent info you've posted on this topic!