I finished the break in for my new clutch yesterday. I was messing around last night and the car was fine. AFR by the ZT-2 LCD was spot on with what I had tuned for before the clutch went out.

Today, on the way home from work I wanted to get some logs before I started messing around some more. I dropped it into 4th @ 4k rpm and went WOT. Immediately the car started bucking like I had a boost leak. I pulled off into a parking lot and checked everything over, nothing was loose or blown off. Got back on the highway and tried again in 4th @ 2krpm. This time, everything was OK until 6k rpm. AFR went way rich and the car noticeably lost power. Reviewing the logs, 2 byte load went on a trip. I think maybe the used GMMAF I have has taken a crap on me from all the humidity today. In the logs below, AFR is scaled to x5 for better resolution. In the logs from today, I believe AFR was below the ZT-2 rich threshold.

Log from last month, 2byte load tracks with boost:


4th @ 4krpm:


4th @ 2krpm and up, 2 byte load no longer tracks with boost :


I want to log 2byte airflow to see what the MAFT Pro is actually outputting to the ECU, can someone point me in the right direction for adding 2 byte airflow?

 

1) Add these two entries to your ECUFlash "88590015.xml" file:

<table name="MUT02 2-byte airflow MSB" category="MUT" address="3ee8e" type="1D" level="1" scaling="Hex16"/>

<table name="MUT03 2-byte airflow LSB" category="MUT" address="3ee92" type="1D" level="1" scaling="Hex16"/>

2) Save the file, restart ECUFlash, open your ROM, and find the new entries. The entries should read:

MUT02: 6A29
MUT03: 6A28

Change the values to:

MUT02: 6B9E (type 0x6B9E)
MUT03: 6B8F (type 0x6B9F)

Save the ROM and flash your ECU with it.

3) Open up the EvoScan "Data.xml" file, and add/modify the 2-byte airflow entry to:

<DataListItem DataLog="Y" Color="" Display="2-Byte Airflow" LogReference="AirFlow2Byte" RequestID="02" RequestID2="03" Eval="6.29x/64" Unit="Hz" MetricEval="" MetricUnit="" ResponseBytes="1" GaugeMin="0" GaugeMax="3000" ChartMin="0" ChartMax="3000" ScalingFactor="1" Notes=""/>

Save the file, launch EvoScan, and check to be sure that 2-byte airflow is enabled.

 

Thanks dude. I set it up, just haven't reflashed yet. I pulled the MAF and sprayed some cleaner on it, seemed to help a bit. AFR was at 10.8:1 from 6k to redline, but I wasn't logging to see what load was doing.

 

Relogged tonight after the 2byte airflow mod. Cleaning the MAF seemed to help, but I think the MAF may be on its way out. AFR curve was back to normal, but 1 full point richer than I had tuned it for previously. Here's the graph from today:




IF someone with the 2 byte airflow could post up what their airflow trace looks like, I'd appreciate it. I want to compare "smoothness" between the GMMAF and a stock MAF.

 

Should this be 8 or 9?

 

9 ...

 

Bumping up an old thread - I'm doing the break in for my Exedy Twin HD and I'm having a very similar problem. The car starts bucking around 4500-5000 - it feels almost as if you are hitting a rev limiter. I am not full throttle though since I have about a hundred more miles of break in - did you ever get it figured out Matt?

 

As quoted by him

"Cleaning the MAF seemed to help, but I think the MAF may be on its way out"

 

What spark plugs are you running, and how many miles on them? Could be spark break up.

 

It's under partial boost conditions - I'm running BPR8es's - about 300 miles on them. It started right after a clutch change. I saw that he cleaned his maf and that seemed to help, but I was wondering if he found anything definitive.

It *looks* like it might be the front o2 sensor taking a dump - which is odd because this one only has 300 miles on it too (put it on with the new turbo kit). However, I did have an HPC coated manifold/downpipe so who knows if that stuff baked off weird and ruined it.

Current plan - clean maf, replace plugs and change front o2 sensor. Hopefully that'll do it

 

Not sure if you've tried this yet, I didnt see it mentioned.

Your MAF may need to be calibrated. This only occurs on a hard ECU reset, not when flashing. Reset your ECU and start the car with all accessory's on and let it idle for 5 minutes, drive normal for another 5-10 minutes. The easy way to reset the ECU is to pull the 20amp fuse closest to the front of the car in the engine bay fuse panel. I think it's the 4th fuse back and it has an engine symbol on the cover. This way you wont lose your radio stations.

 

Definitely worth a shot after the maf cleaning. Do you have to do anything after driving normal for 5-10 minutes? Or just shut the car off and all should be good? Thanks a bunch.

 

No, I dont think you dont have to do anything more. In fact the ECU learning phase is optional but will get your fuel trims more where they should be than if you just go out and start beating on the car right away. Any time the MAF is disconnected from the ECU it needs to be recalibrated by reseting the ECU.

 

Here are some 2byte airflow plots with the stock maf, stock maf 2byte looks much smoother than yours.

 

Wow, old thread. My problem ended up being the MAF, which I ended up getting rid of shortly after that.

Thanks for the data though, razorlab.