tici

iTrader: (1)

Who is logging the AF ratio using the wideband output of the PLX M-300? (0-5 volts).
In my case the voltage doesn’t match with the display (about 0.2 volts too high).
This makes a difference of about 0.4 AF units (so according to the voltage I’m richer than the display).

What is your experience with this unit?
Should I trust the display or the voltage?

pknowles

iTrader: (1)

I see the same result. I trust the value I see in HPT, because when I dialed in my tune and my LTFT's went to 0, my AFR was 14.7 across almost all of the non-PE mode cells.

tici

iTrader: (1)

Today I asked PLX about this problem: they told me 0.1 - 0.2 V error is normal and that I should add a correction factor in my log....

NO COMMENT!

02SOMWS6

iTrader: (6)

I just ordered the HPT 1.6 and now I need a wb02.I was thinking of going with the PLX unit. Not so sure now.If you had it to do over which would you get.

pknowles

iTrader: (1)

I here of small problems with all of them to be honest. I would buy my M-300 if I had to do it again.

tici

iTrader: (1)

I think the PLX is not so bad and it's not a problem to add a correction factor, the boring job is to find out the factor.
My real problem is that I go with the WB signal to the PCM through the A/C connector and read it using Atap.
Atap sees only one decimal, on top of this Atap (or the PCM) rounds up the values.
Example: 2.01 volts from the WB is logged as 2.1 V; but also 2.10 is logged as 2.1V.
The PLX formula is AF=(V*2)+10
0.1V is already 0.2 AF units, to my opinion a too big error. It would be better to go directly to the interface as EFILive (or maybe also HPTuners) and log the real numbers.

I made a test (pls don't call me stupid!): I recorded the display values and the RPM using a digital camers. Then watched the movie in slow motion to see what happens.
The display is refreshed about 8 times in a second (too fast to follow in real time) and I was able to draw a nice curve (excel).

Really time consuming but this would be a way to find out the correction factor, in fact PLX told me to trust the display...

HumpinSS

iTrader: (1)

With the car off cant you cross reference the voltages from the display and the output divide the two and come up with a correction factor to use for input in the formula?

tici

iTrader: (1)

Yes, it works. As said, the correction isn't a problem, it's just that the values I see using Atap are too raw for a nice AF log (because it rounds up the numbers).
Looking at the display during WOT it's a little dangerous: 2nd gear goes up to 90 mph and I do log on the highway...

SSpeedracer

iTrader: (8)

Tici- I have not quantified the issues that you noticed. However, my M-300 appears to display about .1 AFR above stoich when both shortband O2's are averaging stoichiometric. The M-300 analog output seems closer to the shortband O2's.

In otherwords, when car is in closed loop, M-300 display spends more time above 14.7 than below. Its too bad we cant increase the time average on display. It has too much resolution.

tici

iTrader: (1)

Same here: during cruising I see an AF average of 14.9. THis is not the WB output but the display.
I'll soon try to use the narrow band output to the PCM and compare the LTFT before - after. Just to see how precise is this thing...