Widebands not stable...

[mulot30th]

I log two LC1 widebands using VCM Scanner and the AFR value is nowhere near stable...

It jumps from 13-14-15-14-13-14-13-15-14... or something like that...

Even with the engine off, it will not stabilize, it just jumps very quickly between AFR values like that...

I was expecting a rocksolid output, was I expecting too much?

[horist]

I've never used an LC-1 .. but i know HPT can only report what it's fed..... the EIO cable logs 0-5 volt and converts to values (in this case AFR) based on your chosen conversion formula......


My LM-1 was pretty much dead on (reported via log vs HPT log) ....

if it's jumping when the engine's off... you sure everything's wired correctly? HPT is only as accurate as the voltage the external outputs are feeding it.......

[mulot30th]

I will check with a voltmeter before going crazy about this!

[mulot30th]

I will check with a voltmeter before going crazy about this!

Okay checked with a voltmeter and it seems stable, but the voltmeter refresh rate is about 100 times lower than HPT...

So I have no way of knowing what is wrong??! I'll try some more tests later!

[tici]

I see the same fluctuation with my PLX300 and apparently it's normal.

[Keith@HPTuners]

You can log raw voltage in HPT as well.

Make sure all your connections are solid and secure. You need good grounds.

[mulot30th]

Okay I did some voltmeter tests.... and.... the LC1 output voltage is extremely stable....


So I programmed my LC1 to output 1.5V whatever AFr it reads...

On the voltmeter I see a constant 1.492V

But on HP tuners I see anywhere from 1.3 to 1.7 volts and it is going evewhere in between these two values extremely fast at random...

Then I tried to hook up a 1.5 V battery to HP Tuners, and tada... a steady 1.59V....

So... Steady LC1 Output, and battery voltage indicate steady in hp...


Now what is my problem here????

BTW I use a desktop computer for these tests...

[jimmyblue]

In closed loop the PCM -forces- the fuel shot to dither
about nominal to obtain sensor cross-counts. The DMM
is a slow sampling device and will average things. Look
at the O2 sensor voltage (narrowband) on the graph
display and, guess what? Bops around like mad, unless
you're WOT, cold, or otherwise open loop (or your O2s
are messed up).

Measuring LC-1 output, be sure you have the signal
output reference ground (not chassis) as your DMM
reference. Make sure the same reference is used as
the return to the EIO box. The WBO2 heater is a real
power hog and is driven in a chopper mode, if the
two share a ground loop it could whack the readings.
(Hell, the two managed to melt my Y-cig adapter so
a few hundred mV offset is nothing...).

I know I've seen this kind of thing talked about before
though I don't recall the solution or if there was any
entirely satisfactory one. I do believe it's electrical
noise related.

[98_LS1]

If it was me, I would make the car run in open loop. (Change through flashing a new cal with open loop disabled, not the Scanner Tool). I would also think this would be the best way to get your VE table Dead On. Just some food for thought.

[mulot30th]

I made a custom RC Lowpass filter at 50hz and it removed 99% of that noise!!

[tici]

Could you please post some details? Schematics?

Thanks - Stefano