LM-1 Ground Offsets

[Dragman]

I have EIO and was wondering if u guys with LM-1 have to use a offset to get HPT to match AFR in LM-1??

[MeentSS02]

With the LM-1, it should be pretty easy to tell. Just put the box next to your computer screen, and watch. Should be able to tell pretty quickly whether or not they agree.

I'd think there would be some sort of ground offset with any type of system like this.

[Dragman]

mine do not agree thats the reason for post!

[jimmyblue]

My opinion is, it's be better to fix the source than try to
factor it out, because I believe the source is also going
to be variable in its error contribution.

I think the source of ground offset is the heater current
thrown by the LM-1. That returns through the (fairly long)
power cord and the cig lighter (my setup) ground. The
EIO ground meanwhile is the OBDII connector. These tap
different sheet metal, one is in the current path and one
is not.

Thing is, the heater current is a variable; it's chopped by
the LM-1 to maintain a fixed element temperature in the
sensor, and the current required is going to depend on
the EGT at any point in time. That's not going to be an
easy thing to deal with, by simple arithmetic.

I'm thinking the EIO (OBDII) ground and the LM-1 ground
want to be put to the same post (star ground, not a
distributed one), and probably the cheeseball cig lighter
adaptor wants to be hard soldered to the ground point
instead of plugged in.

Now, there could be other error terms as well but my
gut says ground offsets are the main deal, and it's the
crappy automotive save-a-nickel setup that's to blame
when you really want something instrumentation-grade.

It's unfortunate that the EIO input is single-ended, not
differential. That would enable you to kill the problem.
Maybe "somebody" ought to rig up a little instrumentation
amplifier circuit that runs off a pair of 9V batteries (so
as to float it). That's about a $10 project. Hmm....

[S2H]

Ideally the main thing we want accuracy for is stoich
so you can set up your LM1 to report the same value that it would normally at stoich..then do a compare to the EIO...and add teh needed AFR to teh equation..basically shifting it over so atleast stoich is teh right voltage..or closer to it...

EGT doesnt effect the ground offsets as much as it sounds..its very minimal...either way you have to solve it somehow..wheteher its at the EIO or whether you do it another way..the EIO is teh simple fix...al the rest may take some serious electrical power...
I'm pretty good at this electrical thing..I have tried many many things...
and it seems to be pretty close just shifting your EIO Equation to make it happen...
other rhan that you can send all grounds to teh PCM ground...just dont go thru the EIO grounds to the pcm (per request of HPT..you will burn up the signal traces in the unit)

if these companies that sold budget widebands would up the wire gauge just a few notches they could fix most of this issue..especially if they upped the heater hot and ground wires where most of the problems stem from

[Dragman]

well today I set output on LM1 to 1 volt output and HPT shows about 1.15 to 1.25 volt in scanner and jumps around. I checked output volts of LM1 and it was 1.02 volts. Still searching for a fix.

[Dragman]

So am I the only one having this issue with LM1 matching HPT??

[S2H]

I had an issue with an LM1 I had to borrow when I sent my LC1 in for replacement....

I just used the math and adjusted accordingly...
worked fine for me

though a physical hardware fix would be better..

have you tried taking all the grounds to the battery terminal ground...and only taking the hot to the EIO..no ground attatched there..
as I understood from a post from the guys..the analog inputs dont need ground connected to it...just your device(the wideband) needs a ground..

[Dragman]

ok here is what i had to do!
I made my own LM-1 AFR PID and in volts I put .625 (dont ask Y just a guess) and 9.6 volts in chart. Started with 10 and lower alittle at a time till I got it to match. This got me within .1 -.15 so I guess and I ready to tune VE with new software. What do u guys think about this approch??

[S2H]

ok...

you need to know exactly what your LM1 is set to...
volts and AFR...
otherwise it will be wrong
2 volts setup or 5 volts setup??
10-20 default settings or less range??


its not a guessing thing...
its an EXACT formula

[Dragman]

LM-1 is set to 0 to 5 volts

[WS6FirebirdTA00]

i set the LM-1 to

0.230 v = 10.61 AFR
4.350 v = 18.76 AFR

This will keep the 14.7 value right on and the furthest its off is 0.05 AFR. What I did was command a heater voltage to find what woudl average 14.7 ( used the histogram to get an average during WB heatup). Then I played with the ends values to keep the 14.7 correct and make sure the ends were in line. I did this by commanding the min and max voltage to see what AFR would be displayed on the scanner. I did it this way so if I have to take the wideband to another car its already set up and I dont have to scrwe with the scanner at all.

[turbomark7]

I had an offset compatibility issue between my LM-1 and my Apex-I P-FC ECU and Datalogit© hardware on my RX7. I had to use 0v = 9.2AFR and 5v = 19.2 AFR and still things weren't right. Yesterday, I replaced the 14 y.o. main engine wiring harness and now I'm able to utilize the default 0v = 10AFR and 5v = 20 AFR settings. I believe the devices' display differnetials can be relieved in large part by establishing common grounding and using generally fresh engine wiring, even same gauge wiring.

I am new to this forum but not to WBO2 tuning. I want to learn about this brand of ECU & software; a friend recently replaced his blown 13-BREW rotary engine with a 2000 Corvette LS1 and conversion kit from Hinson Supercars. He is considering buying HP Tuners products.

[S2H]

LM-1 is set to 0 to 5 volts

ok..so 0~5 volts and 10~20 AFR

volts/ 0.50 + 9.6 (you have an offset of [-.2] volts or [-.4] AFR)

[PurplePiss]

SE, if I set my LM-1 to 0-5volts and 10-18 AFR, the equation would be volts/.625 +9.68. Can you set the AFR to 10-18 or is the LM-1 supposed to be 10-20?

Do you have to turn the LM-1 on to power the O2 from the cig lighter or can you leave the LM-1 off and just plug the cig in to power the O2 so it doesn't get killed when I'm not want to log but don't want to take it out?

Thanks

[IanB]

SE, if I set my LM-1 to 0-5volts and 10-18 AFR, the equation would be volts/.625 +9.68. Can you set the AFR to 10-18 or is the LM-1 supposed to be 10-20?

Do you have to turn the LM-1 on to power the O2 from the cig lighter or can you leave the LM-1 off and just plug the cig in to power the O2 so it doesn't get killed when I'm not want to log but don't want to take it out?

Thanks

When you turn on the LM1, it goes through the warm up of the sensor before giving any readings, so yes you need it turned on to keep the sensor alive. It's a bit of a PITA, but it's also very portable, so you can't win them all.

I'm also having issues with the LM1 readings not matching up to the HPtuners logged AF's, I"m going to try a different ground for the analog output, and see if that works. I"m also starting to suspect my soldering job on the mono plug for the analog out cable I made, but I'll look into that later.

[jimmyblue]

I have built myself a simple little instrumentation amp
that runs off a 9V rechargeable battery and can take
out up to about +/- a volt of common-mode offset.

Actually a pair of them are in my next-generation
"WidgetII". I'm probably into it about $20 with the
battery and hardware miscellany. I used the AD620
instrumentation amplifier which is about as simple as
you can get, 78L05 (for other stuff) and a couple of
2N2222 transistors.

If anyone wants a schematic of the inst amp circuit
I can make a pretty one; hand-drawn is all I have
at the moment. But if you're getting nowhere rewiring
the power feeds, you may want to just fix the problem
this way. It's something you could easily do in an
evening if you can solder.

[Phil99vette]

ok..so 0~5 volts and 10~20 AFR

volts/ 0.50 + 9.6 (you have an offset of [-.2] volts or [-.4] AFR)

My setup is exactly the same:
Volts /.5 + 9 . 6

I usually do a 2 minute log on the LM1 and HPT and compare the averages.

[PurplePiss]

1.) I have a cig light cord that allows you to select 5v, 9v, or 12v. Could I use that to power the LM-1 instead of running off a 9v?


2.) Instead of programming the LM-1 to 0-5v 10-20 AFR and using volts/.5 +9.6, can you do 0-5v 10-18 AFR and volts/.625 +9.6? How does it affect the output if your AFR range is smaller?

3.) When I pick the LM-1 canned PID in HPT, it doesn't matter if I program the LM-1 to 10-18 or 10-20 AFR, it doesn't match. Why?

[S2H]

SE, if I set my LM-1 to 0-5volts and 10-18 AFR, the equation would be volts/.625 +9.68. Can you set the AFR to 10-18 or is the LM-1 supposed to be 10-20?

Do you have to turn the LM-1 on to power the O2 from the cig lighter or can you leave the LM-1 off and just plug the cig in to power the O2 so it doesn't get killed when I'm not want to log but don't want to take it out?

Thanks

LM1 default from factory is 10~20 AFR I believe...
you go into LM programmer and set it to be 10~18 and then you would use the volts/0.625 + 10

LM1 has to be powered up to use teh wideband o2 and it needs tobe on when the car is on and exhaust is hitting the sensor or it will kill the sensor...

you could always make a splice in the sensor cable and take it directly to a 12v key on source and then you wouldnt have to worry about the cig lighter......
LM1 would still function the same as well...you just wouldnt be getting th e12v power for the o2 from it...the cig lighter would only be to power on the lm1 for data logging reasons