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Safe A/F ratio?

PostPosted: Tue Jun 10, 2008 9:19 pm
by Joeyboy
I'm using a wideband and simulated o2 signal. I was wondering what the safest setting is for the switching point? With the price of gas and all, i'm looking to run as lean as possible without doing any damage. Currently i've got it set to 15.0:1 and I get about 500 km's to a tank.

PostPosted: Tue Jun 10, 2008 9:43 pm
by tlcoll1
I don't really know the answer to this, but I'm planning to experiment a bit. I'll probably try mid 15's and see what happens.


PostPosted: Wed Jun 11, 2008 11:13 am
by honki24
I've run 15.7 w/ the EGR disabled for some time now with no issue. You have to add timing to the cruise area though b/c going leaner decreases power and you will notice the switchover between closed and open loop if you don't add the power back in with timing. I picked up 3mpg this way. I would guess you could possibly have more if you keep the egr in tact too. I just installed an EGT, so when my car gets off the jackstands and I can log again I'll see if it really effects EGTs. But I've gotten no knock.

PostPosted: Thu Jun 12, 2008 8:30 pm
by Joeyboy
Ya, i've been running 15.5 and I get about 500 km's to a tank. My egt's seem to sit about 1200 while cruising 3000 rpm. I didn't notice much of a difference in the egts from the 14.7 afr. I've been told that 16- 16.5 is safe too.

Re: Safe A/F ratio?

PostPosted: Wed Jul 02, 2008 7:33 am
by SSkilla
what do you recomend on the timing settings..... im currently running 15.0 but i intend on leaning it out a bit more to save some more gas...........

Re: Safe A/F ratio?

PostPosted: Wed Jul 02, 2008 1:59 pm
by honki24
In my lancer I run mid to high 30 degrees, whereas stock was mid to low 30s in the cruise range. You can benefit a lot in throttle response and transition between OL and CL by adding timing. I've seen NO knock increase as a result. Once I get many many other things done I will experiment with more timing. My car doesnt seem to even mind 40ish degrees and higher.

Re: Safe A/F ratio?

PostPosted: Tue Oct 07, 2008 11:17 pm
by da1sexmonk83
I have a question about this too, and maybe it is stupid but I had rather be informed than let something screw up.

if I put 14.7 in that box that means the my front o2 sensor will never allow me to dip below that number correct?

Also, my afr oscillates like crazy at idle, is it suppose to do this? Will it even out when I am driving/at full throttle. The way it was the other day I didn't to drive it without knowing (we had just installed the innovate LC-1)

With the LC-1 do I need to modify the values of 0-5 volts, or will the reading be accurate enough to tune on?

Sorry for so many questions.

Re: Safe A/F ratio?

PostPosted: Wed Oct 08, 2008 7:57 am
by honki24
Some oscillation is normal. I'll post a screenshot. The screenshot is from a 5th gear cruise last night. It oscillates ~.5AFR altogether but that is the nature of how an O2 sensor feedback loop works. Make sure you use smoothing when looking at AFR. What you see there I believe has a smoothing factor of 2 added to it b/c its very "fuzzy" without any smoothing. (I smooth my boost, EGT, and AFR)

If you put "14.7" in the box it will cycle around 14.7. Probabbly go from 14.1-15.3ish. That's no big deal. That's how it should work. Just put something like "15.7" in there so that it oscillates around 15.7 AFR. Your setup is different b/c I have no EGR any more but you may find you need to add some timing when leaning out more because you will lose power by leaning out another point. ~5 degrees will do it. Just do some logs beforehand where you log knock and then change timing and AFR and log more and see if you get more knock. If so then back off the timing a bit.

For scaling: I have an LC-1 and I use PLX scaling and I've changed my LC-1 output to match the PLX. I do this for better resolution, but to answer your question: yes it will simply work if you set it to LC-1 and log. Like I said though, use a small amount of smoothing when tuning the AFR. Makes things much easier.

Re: Safe A/F ratio?

PostPosted: Wed Oct 08, 2008 10:59 am
by da1sexmonk83

Thanks, I guess I will be picking up my car this weekend!