HPT and LM-1 not equal

[02Z0h6]

Hi guys. I have my HPT and LM-1 running but can't figure out why the LM-1 is reading from 3-5 points lower than tuners at all times. I have everything hooked up per Checkmates instructions and the Lm-1 is programmed for 0V-10AFR and 5V-20AFR. I checked my connections and they are ok (not soldered, just twisted and taped). Does anyone have theirs working perfectly? Even at idle when the AFR is rock solid on the Lm-1, HPT is 4 points higher. I also tried to configure my own PID by dividing by 0.5V and adding 10. When I first start the car and the AFR is around 19-20 it looks to be right on but when it drops to 13 is when the offset occurs. I'm having a hard time tuning because I can't trust what I'm seeing in HPT. Any ideas?

[Dragman]

seam like mine is not the same so is there any help on this?

[JCMGTO]

You beat me to posting this.

What is the default WB in HP Tuners? Cause my LM-1 is reading lower(richer) then HP Tuners?

[Keith@HPTuners]

the WB formulas are all listed in the help files.

[Chris@HPTuners]

you can also log the raw voltage we are receiving on the EIO input to double check against what the LM1 should be putting out. It is not a complicated thing, we simply take the voltage measured on the input and convert it to AFR using the manufacturer supplied formula's.

[jimmyblue]

From what I've seen posted I tend to think people
are having ground loop / offset problems with the
EIO A/D input and the LM-1 analog output. I believe
the LM-1's heater drive current may be offsetting
the output as it pushes up the local ground relative
to the EIO. I don't know to what degree the EIO
cable A/D interface rejects ground offsets and I
have not seen this problem myself, so can't debug
it for y'all. But I think it bears looking at. Folks who
are having problems ought to put a DMM to the
LM-1 output cable (not connected to EIO) under
some steady operating condition (like hot idle with
sufficient smoothing turned on) and record voltage,
then plug it into EIO and see what's read for raw
voltage there. Ideally you'd then re-confirm the EIO
voltage reading w/ DMM simultaneously. You're looking
for discrepancy between EIO and DMM, or change from
unplugged to plugged-in output voltages. You might
also want to measure EIO ground to LM-1 ground with
the two disconnected from each other. Watch it for a
little while to see if it surges w/ the WB sensor heater
turning on & off.

Perhaps the HPTuners guys can shed a little light on
the A/D circuit used, whether the input is true differential
or ground referenced, etc.

[Casey]

Perhaps the HPTuners guys can shed a little light on
the A/D circuit used, whether the input is true differential
or ground referenced, etc.

The input to the EIO is not differential. Its a unity gain setup (buffer) so the negative input pin needs to be tied to the op amps output. The input pin is not referenced to any source. That's why you see it float midway when nothing is connected to it.

If the LM1/LC1 is trying to use our EIO black wire as a ground instead of its own, the offset should have minimal impact unless the ground loop is really excessive. Disconnect the black wire from the EIO and see if it clears up.

I tried to get them to send me a couple of those things when we first heard about this. They decided to send me a distributor application instead.
Maybe one of you guys can convince them to send me a couple so I can throw a scope on it and see where the problem is coming from.


Ken