I'm using the LC-1 for my NB signal for the ECU. It's currently around 15.7:1 at idle/cruise. It's working as intended, but I do have a little surge (barely noticeable) at times from AFR variance. The 1v signal from the LC-1 isn't responding exactly like the stock O2 sensor. It may be due to my settings or maybe just the location.

 

Question for TouringBubble or anyone else running the narrowband output from the LC-1 (or similar) into their front o2 sensor input: When you reprogram it for 15.x:1 crossover point, does that affect your fuel trims? I'm thinking of doing this but just curious how it will affect them since the computer thinks it needs X amount of fuel to reach 14.7 but then its correcting itself based around the 15.x value, I'd think that would make the fuel trims go negative...

 

You're just changing the AFR at which the signal changes from 0 volts to 1 volt (or is at 0.5v) trims just care about the signal being at 0.5 volt. It doesn't matter if the signal is at 0.5v at 14.7 AFR or 5 AFR or 16 AFR. So long as it is at 0.5v trims will stay at 0. So don't worry about it.

Trims would change if your signal was at 0.4v or 0.6v all the time.

PS They would change if you bought a thing off eBay to change your O2 voltage to be say a little bigger, like 0.6 in order to "trick" the ECU to run leaner. The trims would keep building negative. So the trick would be kinda on you

 

Scheides is correct ... the trims will change. Mpl ... you are correct to say that it only cares about .5v, but when you change the NB signal, the amount of fuel needed to reach that .5v changes (because it's now 15.x and not 14.7), and that's exactly what the trims adjust for.

To answer your question, I bumped up the injector scaling by one increment to correct for the AFR change ... my trims are within 2% or so. I haven't logged in a while so I cant give you an exact number.

 

If you wouldn't mind taking a sample log and reporting back, that'd be cool. Otherwise, I'll try this out and report back sometime in the near future.

 

hmm..

Something has to take out or add fuel in order to reach 0.5 i suppose. Should have thought about it a bit more, sorry Scheides

 

Dang it Igor! I'm totally mad at you

This just occured to me the other day, I would think it would make tuning new injectors or fuel a little awkward if your fuel trims are off or change randomly

 

I'll try to get a log tonight ... sending myself a note. I haven't flashed in a couple of weeks so the trims should be set nicely.

 

Here we go ... log from cold start to (nearly) operating temp.



You can see the oscillation I mentioned. This is what causes that minor surging that you can sometimes feel.

As you can see, the surging lessens as the engine warms up. You can also see the LTFT Low start to move toward 0 just before the log ended ... I didn't notice or I would have kept logging to see where it ended up.

 

Wow, that STFT is really all over the place.

 

It's only correcting about 3% either way ... 6% total. Stock O2 corrects 2% or so either way. I think it has a lot to do with the location of the LC-1. Mine is in the test pipe.

 

Yeah, I'm going to be locating my WB as close as possible in the downpipe to see if it really improves response time. It should to some degree at the very least. Plus it minimizes the possibility of exhaust leaks between the engine and the WB.

 

Okay ... I made some changes a little while ago and it seemed to help the AFR oscillation. I want to test a little more before posting graphs or settings though.

 

I logged my drive to work this morning ... it seems that the changes I made last night did help with the oscillation (based on the real time readings). I'll analyze the log this evening and post results.

 

Some interesting info on tuning the LC-1's analog out ...

The changes I made recently (widen the curve to .9v and .1v from .82v and .13v and average readings over 1/3") did in fact smooth the idle AFR. However, cruise AFR is very ugly.

This makes perfect sense though ... averaging the reading is great for idle where the exhaust flows slower and exploits the distance of the LC-1 from the head. I was able to get idle AFR to stay within .15 AFR of my target with these settings. STFT moved about 1% either way (2% total).

Cruise however hates the averaging ... AFR's bounced down to 14.9 and up to 16.3 as the STFT applied 6%-8% correction either way. This actually "felt" smoother than my previous settings but only because the STFT corrected slower due to the averaged O2 reading. The AFR range was nearly double than what my previous settings provided.

I'm going to test some more. My thoughts on tuning it well ...

1) Very little averaging or none at all. This will help cruise AFR keep steady but will possibly cause a small variance in idle AFR.
2) Tune for cruise AFR and not idle. This has been my biggest mistake so far. The location of the LC-1 is the issue so we just have to deal with it.
3) Wide voltage span for the 1v curve. I think that .82v is about where the high side should be for stock-like response.

when i know more I'll update ...