More tuning questions

[Rex2342]

So I'm slowly but surely getting the hang of tuning this thing with a MAFT and an AFC but I still have a few questions that are probably pretty basic. I set up my MAFT base/aux setting so that it would run as close to 100% on my fuel trims as possible and have been fine tuning with the AFC. I've finally figured out how to check each trim low, mid, high by monitoring the airflow hz and keeping the hz in it's respective zone long enough for each trim to change. When I get the mid trim in 95%-100% range using the AFC low settings I turn my focus on the high fuel trim. I still adjust the high fuel trim using the low setting on the AFC and when I change it so the high fuel trim is 95%-100 my mid will drop back down to 85%-90%? I'm assuming this is because the RPMs are nearly the same and only the hz changes as I increase throttle slightly. Should I just set the high fuel trim and not worry about the mid being a little to rich? Also when does the high setting on the AFC come into play? I've got the AFC throttle points set to low 30% high 80% like RRE suggested so the high setting only factors in after 80% throttle, and the low setting is anything under 30% right? What about the space in between 30% and 80%?

 

[1SloColt]

Don't worry about low/mid fuel trims, the ECU will take care of them on its own. I usually will try to lean out my low throttle some to help with gas mileage but worrying about the mid is crazy. From all the tuning I've done with the translator, its just a lot easier to zero it out and use the SAFC for all the tuning. The translator works for converting the GM MAF signal to something the ECU can use, but other than that I don't trust it. Hell, sometimes it can't even do that correctly, so trying to use it for tuning makes it difficult more often than not.

 

[Rex2342]

I'm just using the MAFT for a baseline setup I guess you could say. I haven't messed with the mid/WOT knobs on the MAFT. I just set up the base settings so my trims would be close 100% and I've been tuning with the AFC/logger. The only other knob on the MAFT I touched was the idle so I could bring my low trim back into range.

 

[Rex2342]

Is it normal for my car to run richer when it is cooler outside? I went for a parkway ride on my way to work today so I could adjust the high setting on the AFC. Doing 4th gear pulls from 3000-6500rpm and I was getting a good amount of knock from 4k-5k. I richened it up from 4k up and the knock calmed down but it started breaking up around 6k like it was to rich so I leaned it from 5600 -7200. Why do I have to add so much more fuel from 4k-5k and is this normal?

 

[scottsee]

4-5k is when your peak cylinder pressure occurs. It's pretty common.

 

[GVR4592]

Volumetric efficiency is at it's highest point from 4500-6500 on a pretty stock engine(no cams, no smim, etc), and will require more fuel than any other rpm range. It's normal to have to add fuel and remove timing in this area, and add timing and remove fuel after volumetric efficiency falls off.