3800 AFC tuning help

[98 TGP TOY]

Hey guys, Im confused out of my mind about what im doing wrong. In the past month I have gotten a dhp 1.0, dropped to a 160 t stat, and ran two bottles of GM Top End Cleaner through my engine. So I recently bought a used afc 1.1 off a member on the national board. Well I got it today, and thought I would go out and try to tune my car. He left me instructions. He said as you increase over 100% then you will richin the mixture, and below 100% will lean out the mixture. Is that right? Well I took some logs and tried to tune with no success. I took a base run. Then went to 99% and saw an increase in O2s. Then to 98%, still an increase in O2s. Thinking the guy wrote the wrong info down, I switched to 101%, and O2s went down. Went to 102%, and O2s stayed down in the 920-940 range. So I tried 103%, and O2s went up. Then tried 104% and O2s stayed high. So I tried 99% again, and O2s stayed high. Tried 98%, and O2s came down. Tried 97% and O2s stayed down. Tried 96% and O2s went up. The KR readings just seemed to bounce around and have nothing to do with the O2s. So I just set it back to 100%, logged the run, and called it a night.

So basically, im confused. What could be causing my problems? And is there a better way to tune. Here are some info on my runs.

1 month ago ranges (no afc):

KR ~ 0 - 3.11
IPW ~ 16 - 18.58
Boost ~ 6 - 9.7
Timing ~ 12.5 - 15.5
O2 ~ 940 - 950

First run tonight (afc = 100%)

KR ~ 1 - 2.5
IPW ~ 14.92 - 18.93
Boost ~ 5.92 - 8.68
Timing ~ 14.5 - 18.5
02 ~ 955 - 980

Last run tonight (afc = 100%)

KR ~ 0 - 7.42
IPW ~ 14.45 - 17.64 (mostly in upper 15s)
Boost ~ 5.77 - 9.12
Timing ~ 8.5 - 17.5
02 ~ 925 - 945

Click to read more...

 

[iliveonnitro]

Not sure how it converts to a 1.1, but heres tuning instructions on the 2.0:
http://www.stlclubgp.com/tech/afc20/

 

[imported_Ron Vogel]

There are some vaiables to consider here...First off, 100%+ is richer. Several things will play in fueling, so you need to keep these vaiables consistant. IAT temps: for tuning drop a resistor in the connector to fix the IAT temps (this will affect timing a bit. Coolant temps: monitor and and stick to one temp for each run (this will affect fueling, and SC temps which can raise KR if too hot) Always try to monitor kr and fueling from a stop, the transition from regular to power enrichment mode when monitoring punching it while rolling will almost always induce kr. As the motor is pushed hard, oil temps wil rise lowering it's viscosity (even in the trans). This will cause seepage into the valve guides (lowering octane of the gas), and noisiness of the trans (possibly causing false kr). I know this is really nitpicking a lot of little things, but removing these vaiables is really the only way to get a good baseline. I usually do all this stuff after I make changes to the car, then go to the track with this baseline and tune from there for et.

 

[98 TGP TOY]

What ohm resistor is recommended?

Do you think it may be best to tune over the course of a week. Like go out and do a base run today. Then adjust the afc 1-2% as needed. Then wait a couple hours till everything cools off again, or wait until the next day. Then do another run and adjust another 1-2%. Or would that just be overkill, and not work. Thanx for the suggestions.

 

[imported_Ron Vogel]

SnM made this chart, it coes in handy. A good cool down is more than sufficient between runs.

 

[98 TGP TOY]

Im sure the chart will be helpful but I cant open it. I see the lil tiny picture in your post, but it wont let me expand it.??

 

[imported_Ron Vogel]

Temperature Resistance (K ohms)
104 1.459
95 1.802
86 2.238
77 2.796
68 3.520
59 4.450
50 5.670
41 7.280
32 9.420
23 12.300
14 16.180
5 21.450
-4 26.680
-22 52.700
-40 100.700

Remember, temps below 57 will allow an additional 1.5 degrees of timing. Temps below 75ish will not allow the A/C to blow cold air. Fan turn on points are also affected, but don't at what temps.

 

[98 TGP TOY]

Awesome, thanx for the help Ron. Hopefully Ill get to that before this weekend. School load is kicking my ass, but only a week and a half left