I'm reading in the FSM that at idle the ECU wants to see 1.0v from the 02 sensor indicating Stoich conditions "about 14.7AFR".

Under acceleration it's looking for 0.4-.5v... Anyone know what this should be in terms of AFR?

I'm trying to setup my LM-1 to provide the correct voltage to imitate an analog lamda signal.

any help would be much appreciated.

thanks.

Edit:
I guess I should clarify... Is <1.0v Rich or Lean?

 

you cant tell. narrow band can NOT be used to tell A/F
all it knows is lean, rich, and stoich.
4.5 is the switch point. anything above is rich anything below is lean.
so if you are at stoich under boost....
and 1v is rich.

 

I understand that it' can't tell AFR, the FSM says 1v is STOICH at idle.

I was just wondering how I should set the LM-1 to tell the ECU what is rich/lean/stoich.

as in... 1v = Stoich?
and <1v = rich?
and >1v = lean?

 

.... i beg to differ sirr ... a narrow band o2 sensor does read voltage between .5 and 1.5 ... on cars with progammable ecu's eg most gm cars ... for one to tune via the narrowband o2 they tune to milivolts ... withch can be monitored with a god enough volt meter .... so yes the stock o2 can read af ratio and the ecu does read af ratio ... just the after market gauge seems to be erratic only because of the closed loop fuinction ... if one was to pair narrow band and wide band aftermarket gauges beside eachother on the same vehicle at the same time one would see that the readings can be translated very simalarly

 

lets face it if that were true their would be no reason for wideband to be made.
heres a narrowband sim graph off a tech edge

now a wideband graph

 

i would check to see if the LM-1 has a narrow band simulation mode like my tech edge has.

 

Correct me if I'm wrong, but the problem with a narrowband in anything other than cruising around stoich is that different AFR's can produce the same voltage. A narrowband is affected by temperature.

 

It does, that's what i've been talking about the whole time.

I set it up to something like this (you can do this in the LM Programmer software)

.527 volt at 10 AFR (on the wideband)
.996 volt at 14.7 AFR (on the wideband)

So in summary to avoid anymore confusion, the LM-1 will be sending a .527 volt signal at 10AFR and .996 volts at 14.7 AFR, and it will calculate on a curve in between those two numbers.

After setting it, I went out and test drove the car and it hesitates at light cruising idle. So something is wrong.... back to the drawing board.

Edit:

Now that I look at that graph, I realize my voltages are upside down.

 

ok i will try to explain....

stoich with a narrowband sensor is ~.5 volts, a narrowband does not sit at a constant voltage like a wideband does so i am not sure how the computer would interpret just a .5 volt signal since it is looking for multiple "crosses" in other words how many times the voltage crosses the .5 volt threshhold since it will create an analog wave when the exhaust is actually stoich.

narrowbands will read one constant voltage, you would need to set stoich voltage at .5 volts not .9 as .9 is actually rich. now the constant voltage may trick the stock ECU since it is looking for a wave signal, it may be confused by a constant voltage and disregard the signal and go into a default programmed mixture mode.

 

To give you guys an idea of what I'm dealing with, I'm posting a screenshot of the default settings of the analog 02 output program from the LM1.

according to this it is showing 14.08 to be rich at 1.099v.

 

the ECU only takes a range of 0-1 v from the stock narrowband sensor, do not feed it more than 1 volt.

as Karack mentioned, it is not so much the voltage the ECU is looking for, but a "switching" point. it will look for around 0.5v for stoich (14.7), but it will not be constant, fluctuating lower and higher than 0.5v. that's why you see the sharp slope of the curve around your switching point (usually 14.7).

if you have it setup properly, and you have 0.5v at 10 AFR, your ECU will think 10 AFR is stoich!

you have to set 14.7 to 0.5 volts. is 10 AFR the richest the wideband will read? if so, set it to 1.0 volt.

i don't really understand that analog output setup, is there more options to it?
the stock voltage response should be like this:

full lean (21+ AFR) = 0.1 volt
stoich (14.7 AFR) = 0.5 volt switching point
rich (10- AFR) = 1.0 volt

edit:
here is a good diagram,

 

should read:

"widebands will read one constant voltage.."

 

This is considered a "lean surge", so shift the points richer just a tad...


-Ted

 

Thank you sir, I will give it a shot.

 

he still needs to change the range to 0-1v, with 0.5v being stoich switching point, as per my first post. not just shift it richer.

 

this output appears correct, if it is hesitating using the generic values given on this table then there is another problem, likely the one i pointed out earlier about the switching threshhold and how the ECU interprets crosses not just a steady voltage.

 

I noticed just the other night when it started to get colder again that I needed to richen the voltage points up again in order to prevent the lean surge hesitations that Reted was describing. Just a follow up to anyone that searches for this same problem.

again just to restate the problem:

Light throttle ( <20% throttle ) was causing a hesitation at cruise. Most noticable in 4th and 5th gear when hwy cruising at 60-85mph.

The volages I'm now using are

.890 = 12.7 AFR
.98 = 14.5 AFR

The ECU seems to accept these well as the stock 02 signal. It maintains outstanding highway gas mileage. On a recent trip home from Florida I maintained 400 miles to a tank of gas which put me at 21.9 miles per gallon on a 18.2 gallon tank. I cruised at 80-85mph with AFR's in the 14's and no detonation. I have the S-AFC zero'd running low boost (9psi) and the car makes an excellent daily driver while still making some better then stock HP. I'm very happy with it.

 

so the stock ECU is causing a leaner mix as the outside air gets colder? hmm, interesting. i would think with the correction factors based on intake temp it would try to keep things even, but i have seen the stock ECU is not very good at keeping a constant AFR. i will tune to one AFR one day, and then the next day it will be off by a bit.

in any case, you could probably lean the cruise out even further. you are in vacuum with low load, so you do not have to worry about detonation (as long as your timing is fine of course). i tune cruise by leaning fuel out until the car starts hesitating, then i richen it up a bit. i run about mid 15s AFR for cruise, and i can manage about 25mpg on a good day. but, that is a stock port NA. i'm not quite sure about your turbo streetport, but i think the same method can be applied. just lean out until it starts hesitating, then richen up a bit (this is your LOW map on the SAFC of course).