Autonerdz forums

Had a couple of hours tonight in the garage with my new picoscope and my car, its a 1990 daihatsu 3 cylinder 660CC turbo petrol! I worked my way through the pico diagnostics looking which was great.
I then looked at the map sensor which looked ok. Then i looked at number 1 injector..had a go with the measuring rulers

Next i looked at the oxygen sensor, on this engine its just got a single wire mixture control sensor. I tried various time scales but couldnt get it to display a decent waveform. I was using the battery negative as a earth.

Any help or guidance would be great.

Robski wrote on Jan 25^th, 2012 at 12:55pm:



I'd thought i would try my luck over the pond on here as it seemed a little quiet in england.
My engine just has the one oxygen sensor located ontop of the CAT after the turbo. I refer to it as a mixture control sensor...
It has a single black wire coming from it. The engine was fully warmed up and ticking over at idle.I'm still using the presets as its all very new to me, but i couldnt seem to make any sense of the displayed waveform.
To be honest i suspect that i was getting quite a bit of noise and interferance as the connector for the sensor is right next to COP 3.

Russ

I back probed the connector and connected the earth lead to the negative side of the battery. I need to try the low pass filter as I've seen it in action on the videos. Connecting at the Ecu would be tricky as its buried up behind the dash.
Are my screen settings ok?
I wanted to check the sensor as my mpg has gone down. I did try revving the engine but all I got was a mess on the screen.
The preset for the map sensor was spot on though

I've just got in and loaded the 02 waveform up on the laptop and tried the low pass filtering.. what a difference!
Whats the difference between the resolution enhancement and the filter, i presume the filter is the favoured choice as any more than 14 bit (12 bit default) then the vertical lines start to slope. i read this was a side effect of using the resoultion feature.
I will have to connect the pico back upto to the engine and carry out some more tests on the o2 sensor now i'm armed with this new info!
I have a wideband innovative LC-1 sensor and controller on the exhaust as well,its a standalone unit not connected to the ecu. I have a fuel controller which works on the map signal wire so i can adjust the AFR's etc. During normal cruising i'm getting a steady 14.7:1 so the o2 sensor must be doing something, i just suspected it was a little lazy when the engine was cold as it has no heating element..

When i attach files can you guys load them up in pico and make changes or can i only do this?

Does my injector waveform look ok then?

Thanks

Thanks for that!
How did you turn the color red? And is that just with a 1khz low pass filter?

Mick wrote on Jan 26^th, 2012 at 12:19pm:


Mick
Yes my car is mildly tuned but the waveform is from the original O2 sensor that is located just after the turbo. I installed the LC-1 to monitor the air fuel ratios as I increased the boost pressure so wanted to ensure I wasn't running lean, I actually found that on a wide open throttle I was getting a 10:1 AFR which is very rich. I then fitted an special safc which is a standalone fuel computer, it basically fools the Ecu into thinking how much air it's recieving. This is done on the signal wire on the map sensor. But it only does this under hard acceleration, so normal driving and idling is still factory spec.
On a run I get a really good mpg but just driving to work daily it's not brilliant hence why I wanted to scope the O2. Hope this makes sense as I'm typing on my iPhone.

The LC-1 is fitted after the standard O2 sensor (approx 1.5 feet if you measure the exhaust front pipe and bend etc)
There are no leaks on the exhaust system as I have it on the ramp at work every couple of weeks to give it a check over.

Mick
The LC-1 is jus a standalone wideband sensor with it's own controller, it's not connected to the ECU in any way. It does have output wires that could connect to a standalone ECU or data logger. The apexi SAFC is connected to the signal wire on the map and simply intercepts the signal voltage going back to the ECU, a crude method but works well. This however only works under hard acceleration or full throttles it's connected to the tps.
I know when cruising that the LC-1 is displaying a 14.7:1 airfuel ratio which is spot on, so I'm assuming that the factory sensor is doing something at cruise. Does that make sense? Sorry if I've confused matters.
Will retest the factory single wire O2 today and apply some revs and see if it's swings.