Been thinking about connecting my single LM1 "narrowband simulation output" to the stock PCM's 02 input (on both sides if possible). The LM1 02 sensor is in the Y-Pipe therefore sensing from both sides giving an averaged output.

Ever since I sealed (that's right, sealed) my exhaust (only slightly leaky header to y-pipe joints) I get more low RPM cruise stumble... seems like my L-Terms are off ever since (sounds better but runs worse). Almost feels like 1/2 of the motor is misfiring (one of the two banks) since there's a really strange shimmy/misfire only happening under very light cruise/low rpm... never did this before the seal up job, and it doesnt seem to do it in open loop mode.

Seems like I've finally gotten somewhere with this entire project and I go and do something I thought was good and ends up putting me a step back.. ha, such is life I guess.

Anyway... Anybody try using the single LM1 output for the PCM 02 input for both sides from the single LM1 output? I plan on setting it up within the next month depending on weather.

 

I'd be interested to know if this works. I suspect hooking it to both inputs might skew the voltage though. Keep us posted.

 

I will post results, Im thinking the PCM might set a code with both sides seeing exactly the same signal.

 

The PCM will not set a code for both sides getting the same signal. There is no diagnostic that compares the two.

What Vince is pointing out is that the voltage output of the sensor/emulator circuit may be affected by the fact that it is now subjected to the combined impedance of the PCM's two O2 channels.

Using a combined signal to control the two banks will probably cause more problems than help. Lets say one bank it running lean.... the PCM will only see 1/2 of the problem, since in effect the single sensor is averaging the two banks. But the PCM will make 1/2 the correction to both banks. Now one bank is really running lean, and is only getting 1/2 the extra fuel it needs, and the other bank that was running correctly is now running rich, because its getting the same "1/2 extra fuel" that the lean bank is getting, and it doesn't need it.

 

for the same reasons you say it might hurt it makes me think it will help.

Open loop runs in much the same way you descibe, each bank could be running lean or rich, but you can make it run really good in open loop becuase no fuel correction is being made (just not the most efficient)

The problem alot of people have is split BLMs. This might be a way to reduce the effect, or mask it. This is what I think Im feeling when running load under 1300rpm... feels like 4 cylinders are weak... probably from leaning out. In open loop this is not a problem at all. Only in closed loop, and only since I sealed my exhaust. ha

Reason I say this I ran open loop for a long time because I was having closed loop problems. Seemed like Closed loop was exaggerating everything, like it was doing too much correction. Just as each 02 averages 4 cylinders, now the 02 will average 8 cylinders.

Especially if the 02's are picking up false readings from large cam overlap, this might help reduce the problems.

I think it's worth trying. Wish there wasnt any ice in my uphill driveway or I would have tried it by now.

 

Bringing this back from its grave to see if anyone has done it. I would like to do this so that i can use vemaster. And i currently dont have any o2's hooked up.

 

I did not try it yet, I actually bought new 02's instead since my stockers finally died. My WBO2 died as well but all that is new now.

 

Well... finally I am seeing LEAN actual running conditions with my setup according to the WB02, but the PCM and NBO2's are showing rich therefore pulling fuel causing the lean condition. Happens around 900-1200rpm the most under slight load due to my cam.

Searched other places as well and people having similar problems and it seems the WBO2 reads accurately.. http://www.ls1lt1.com/forum/showthread.php?t=11783

That guy says his LM1 accurately relay's narrow band info while the LC-1 does not. He also say he purchased two of each, probably one for each side. If injuneer is right the PCM cant detect the same signal and this will work perfectly.

I'm actually going to do this mod next since I am actually seeing false richness which I thought I was tuning out but driving long enough without resetting the PCM is showing it's ugly face of lean... not too bad though - still quite driveable just a bit annoying.

 

Well I finally connected my Wideband output to the PCM, it seems to run alot better, overall much less cam surge down low... cruising in 1st and 2nd is much better, but I need to get some miles on it. One major change with wiring this up is one 02 signal feeds the two PCM inputs. This might be the reason for the smoother low RPM power... not totally sure.. I guess I could wire up one stock 02 to both inputs and see what happens.
Couple things I noticed:
the low rpm (900-1100rpm) slight load "chug" is totally gone.. I blamed the chug on bank to bank rich/lean that occurs because the stock 02's cant sense accurate AFR at very low idle with bigger cam, one side is weak, one side stronger and ends up feeling like a very slight missfire? Hard to explain or notice.

I datamastered it and noticed I had to run VE Master again since the fueling was different now so maybe that means the WB is reading better than the stock 02's?

The WB02 sensor is in my left pipe only, not both like I originally thought so one day I'll have to add a port to after the y and see what happens.

Something strange happens with the BLMs at a cruise with slight accel .. very slight accel... ~1350rpm and 35kpa only at certain RPM and MAP.. in my case it's around with both 02 mV reading the same voltage since wired from the same sensor, Lterm BLMs end up split with 110 on one side and 138 on the other.. injector flow rate also shows the split 1.74 and 2.15ms with 83lb injectors.. this is quite a bit. , also noticed most or all of this happens in FUEL TRIM CELL 5 and 6. It runs ok when this is happening (better than with 2 stock 02's). How can this be happening? Same 02 mv inputs create split BLMs?? This split also goes the other way at around 1500rpm and 31kpa... mostly crusing at that speed, any increase in load makes it go away. Lterms are within 1 of each other when this happens anywhere in the log. Again, it runs good.. little cam surge but maybe it's actually right/left bank rich/lean creating the slight chug (reason why it feels smoother in open loop than closed loop)?

BTW, wiring right to the PCM wires is much easier than crawling around under the car.

 

Interesting results.
I wonder if the split BLM's would go away if you moved the O2 sensor after the Y. Sice your sensor is located in the left pipe only, there is absolutely no feedback to whatever the PCM does to adjust the right side fuel trims. This could be the cause for a runaway condition, on the right side only.
I gave up trying to run in closed loop with my 847 cam due to cam surge. This makes me want to try closed loop again.
Did you use any kind of isolator to feed both O2 sensor inputs from the same signal or did you just hard wire them together?

 

Yea, Im a little confused about the results too.. so far I only see the split in "fuel trim cell" 5 and 6.

Would Split BLMs go away if 02 moved... shouldnt matter cause Im only using one Wideband 02 sensor original 02's are disconnected. Both PCM inputs are getting the same signal I verified that in Datamaster in the area's of the split, therefore the PCM's feedback for right and left bank is the same so there's no reason for a split. Very strange! I could see if I was monitoring right and left using stand alone equipment showing split AFR's because of this but the PCM is reading the same signal and splitting the BLM's.

No isolator.. simply tie the two signal input wires together and wire it to the wideband "narrow band simulation" input, and same for the grounds.
Injuneer said the PCM would not throw a code seeing the same signal left/right and he was right (no code in ~35miles anyway).

Im thinking using a single 02 sensor (unsure what is better.. WB or NB 02) will improve 50% of the problems people have using a larger cam in closed loop... I havent tried wiring both PCM inputs together on one narrow band sensor but I think it's also worth trying... ideally the sensor would have to be placed in the Y, and dont know if it will work that far away from the heat but might be worth a shot... or how about an "averaging" circuit - right and left 02 signals go into a box with only one output then feed the one output to the PCM.

From what I see so far.. one 02 signal for both inputs is the way to go with cams... just want to understand why the PCM splits BLMs reading from the same signal... What are details for fiel trim cell 5 and 6?

 

I believe what ricardo is saying........ that the pcm is changing fuel trims for one bank of the engine and not recieving any change from the 02 sensors. Remember the pcm sweeps back and forth between rich and lean to achieve the target a/f ratio. Its just not picking up that sweep from the 02 sensor since you have it on one side of the y pipe.

This can only be done with the lm-1? i was really hopeing to get the lc-1 and x-16 guage.

which input are you ising into the pcm high or low? Could you draw a simple schematic?

 

hmm, maybe then I'll see what happens with the 02 sensor in the y pipe. Maybe it will be enought to not do the split. The other guy I read used two LM-1's, one for each side.

I read the LC-1 should also work but same guy was having a problem with it, and not a problem with the LM-1 so he was thinking something was slightly different between the two.. programming or something.

I cut the signal and ground wires for each front 02 by the PCM, then tied the two signal wires together (C8 and C20) with the signal wire from the LM-1, then tied the grounds together (C7 and C19) with the ground from the LM-1. Leave the power going to the 02's so the PCM doesnt throw a code.

The PCM connector is: C3 (Grey/Clear)
C7 = Right Low (Ground)
C8 = Right High (Signal)

C19 = Left Low (Ground)
C20 = Left High (Signal)

 

I got this from the lc-1 instruction manual printed online

"Analog output one is 1.1V = 14 AFR and .1V = 15 AFR. This is
a simulated narrowband signal. Analog output two is setup as 0V = 7.35 AFR and 5V = 22.39"

Is this why people are having problems with using the lc-1 as a narrow band sim?

I wondered if you can program the lc-1 to output differently.

What voltages does our pcm use for those afr's ?

I really want the lc-1 w/ x16 guage. Dont really want the bulky lm-1 but do want to use the wb02 to simulate both nb02's

lets get the lc-1 to work!!!!!

After reading over the site, the analog output can be sloped as needed. Just need the afr vs voltage at two points for our pcm. Does anyone have these values?

 

The guy that said the LC-1 didnt work sounded extremly familiar with the programming, his point was he didnt think the LC-1 was actually outputting the same signal as the LM-1 when both units were configured the exact same way. He said he tried it on more than 1 LC-1 and more than one LM-1 and both LM-1's worked fine and both LC-1's didnt. He thought it was due to some hard coded difference in the software that maybe a firmware update could resolve.