Can't seem to get AFR idle right

Two40sPlease · Post by **Two40sPlease** » Fri Jan 09, 2009 1:54 pm

Mods:

Red top sr20det (stock bore)
5 angle valve-job + P&P
P&P Intake manifold
Jim Wolf S3 cams
gt2871r
MSD 72# Top feed injectors
z32 maf
new wide band 02 sensor
boost leak tested
recirc. bov
fuel pressure 43#without vacuum
base timing 15 degrees

Symptoms:
I tuned my K value on the highway and whenever I'm driving along with constant load I always get 14.4-14.9. However when I come to a stop its a 50/50 chance of me being lean(15.8-16.5) or rich(13.0-14.5). The car is at full operating temp.

What Ive tried:
1.) Adjusting main Injector latency has fixed this problem several times. I say several because usually the next day the car will be doing the same darn thing sometimes even later the same night. I tried playing with latency with voltage change seeing as the car varies(13.3-14.4 volts)

2) Ive tried making the map rich both with 02 feedback on and off with values set to 0

I've noticed when I adjust my Primary mixture map I have to command low to mid 10's to get 11.5-11.8's for full throttle. In addition my k value is 30,800. Which is way more than the (18,512) the injector& maf change calculator was calling for.
Coldstartups give me afr starting 14 flat and end up in the mid 15s.

I spend all my time and even some at work reading trying to learn how to tune. I know engines well its my passion and I spend time interrogating a good friend of mine who is Proffesional ls1 tuner for advice(unfortunately our programs are worlds apart). I want to be able to tune but there just doesn't seem to be enough literature on the web.The nistune tutorials and a long tutorial on nissan rom tuning found here http://www.240sxforums.com/forums/ecu-t ... -ecus.html is just some of my reading material.

Sorry for the novel, I just wanted to get the point across I'm not some lazy guy asking how to tune. I want to be able to tune badly . And I would appreciate all good advice and suggestions.

kenbam · Post by **kenbam** » Fri Jan 09, 2009 5:17 pm

Just out of curiousity, what is your A/F alpha lean doing during these changes? This gives you an indication of changes being made to the fuel maps based on O2 sensor feedback. Anything above 100% is richer than the base setings, anything under 100% is leaner than base settings.

Two40sPlease · Post by **Two40sPlease** » Sat Jan 10, 2009 1:44 am

I'll let you know asap. Tried to find out this morning but the car would cut off everytime I tried to ecu recync my consult. BTW where can I view the AF alpha lean reading?In the Consult Gauges?

UNISA JECS · Post by **UNISA JECS** » Sat Jan 10, 2009 2:56 am

I believe 128 is in the middle not 100.

kenbam · Post by **kenbam** » Sat Jan 10, 2009 6:23 am

its 128 in the counts which some systems use (earlier delco). My 2 nissans at least use the percentage readings (lower half of your picture). They start at 100 though, and will show -% for lean and +% for richer. Both mine are type 2 boards though (hcr32 and z32) so they may have changed it in later models.

Two40sPlease · Post by **Two40sPlease** » Sat Jan 10, 2009 11:36 am

Im trying to find out my A/f alpha lean but my car is now dying when I try to resync. Its never done this before?

MichaS14a · Post by **MichaS14a** » Sat Jan 10, 2009 1:31 pm

@Unica: This makes sense! Thank for this informations!
This will be the reason why I have mostly the value 135 in A/F Base selflearn! (S14a (SR20DET) with 550 ccm Nismo Injectors, Stage 2)

UNISA JECS · Post by **UNISA JECS** » Sat Jan 10, 2009 4:15 pm

My tunes in cruise condtion sit pretty nice around 128 +/- ~8 with my KA24DET with my cruise AFR being 14.7 +/- ~.4

MichaS14a · Post by **MichaS14a** » Sat Jan 10, 2009 10:40 pm

Well then I have to do a little fine tuning the K-Constant.

Two40sPlease · Post by **Two40sPlease** » Sun Jan 11, 2009 8:25 am

Ok back on topic, my afr alpha lean correction was 128 I saw it at 124 once but that was about the extent of its activity.

sprout · Post by **sprout** » Thu Mar 19, 2009 11:41 am

|Hope its ok I add a comment on this thread....my idle setup is really troubling me

With o2 off (shift + O) on the fuel map, and all cells set to 0 I try to change the K value till the afr is around 14.7. This is sometimes ok. however on after about 15 seconds it will lope a little and afr will rise to 15.8 or so briefly, 5 seconds or so then go back to whatever it was before.

When saved, then engine turned off and left in exactly same condition (o2 still off, cells at 0) and come back 5 minutes later the afr reads 16/17/18. I have checked the cold start and so on - knock map is also same as primary fuel just in case.

Any clue as to what's causing the difficulty in getting the K value right? Just when i think its sorted so I can tune it stuffs up and I'm finding it really hard to get any idea of what to set the K value to....