1997 C5 Tuning: Does this look right so far?

[fasthotrod]

Just looking to get a little constructive criticism regarding how my tuning has been going so far. I have been reading the guide that has been posted here, as well as the book I bought on tuning. (Master EFI Tuner by Dan Maslic.)

My stock tune is listed below. The only changes to the car at the beginning of my tuning was a Vararam cold air intake, K&N filter, and a set of LG long tube headers.

I started off by changing some things in the transmission tables based on what Russ K posted in another thread. My transmission shifted great after those changes.

(Thanks, Russ K. )

I think I got the torque management taken out of it at that point, too.

Anyway, I got my wideband and I connected it up into the EGR pin on the PCM. I was able to go in and enable the EGR so that I could monitor the AFR as I was scanning. So I decided to start off with some VE tuning. I disabled the MAF, but I left it plugged in so I could see what it was doing.

I logged the first run was surprised at how far off my AFR was. The first correction was large enough that I did it with a full percentage change, but the remaining changes were all 1/2 percent as is recommended. After the 5th log and change, I saved the primary VE and secondary VE tables over to the original tune.

The files are listed below.

[fasthotrod]

I then took the 'new' tune with the updated VE tables and set it up for MAF tuning. I logged the data and was surprised at how far off my MAF was. When I first bought the car, I made the mistake of 'punching out' the MAF screen, so before I started tuning I decided to replace it with one that was not 'raped' by the screen.

So after a few runs back and forth to work and such, I wrapped it up. I hand picked some points and did some interpolation between the cells to make sure it was close, then saved the MAF data to the 'new' tune.

The files are listed below.

[fasthotrod]

From there, I let the PCM take over with the long term and short term fuel tables. I was curious as to how the O2 sensors were going to respond, being at the end of the long tube header like that. I drove it around and things seemed like they were okay... or so I thought anyway.

This was the second time that I had gone through this process. The first time I thought I had it setup, but when I drove my car from OK to AZ I noticed that my AFR was off while I was in the desert. I didn't know if it was because of the heat, lack of humidity, or what... so I figured I would stat over from scratch... which is what I posted above.

So a while back I ran a scan on my way to work and I thought I had some trans slip when downshifting from OD to 2nd to pass. It dropped to second, but it was right at the shift point so it bounced off the rev limiter then shifted to third. It did it once or twice, but has not occurred again. I wrote it off to a gremlin in the machine, as it's been fine since. The scan is listed below... same config file as listed above I think.

The thing is, I noticed that I was getting some spark knock. It wasn't there before, but for some reason it was there now. Is this because the O2 sensors are making adjustments to the LTFT and STFT and I am running lean when I hop on the gas?

So last weekend I took my C5 to the drag strip and made a few runs. My best time was a 13.424 @ 107.01. The car has run a 13.2 in the past, before I got my hands into the tune... but I figured that maybe it had more to do with local conditions than anything else... but I can't be certain.

I logged the runs, and they are listed below.

I looked at the results and it looked like I was running lean... so i figured that the O2 sensors were trimming things too far out. I did a quick +5% adjustment to my VE table and set the car to run VE only, and I wiped out my fuel trims. That took care of some of the spark knock, but not all of it... I still had a bit during the burnout...

I decided to stop for the day and see if I could figure out what was going on. I put the 'new' tune back into the car and let it re-learn the long term fuel trims and stuff.

[fasthotrod]

So after last weekend I decided to get off my lazy butt and install the new Z06 rear end I bought a while back. That would change my gear ratio from 2.73 to 3.42, which should help me get out of the hole a bit quicker... or so I thought.

My best 60' time with the 2.73's last weekend was 2.133 which is pretty bad.

So this weekend I put the car into the air and a friend and I swapped out the rear end. I used HP Tuners to change my PE table to 12.5 AF and update the gear ratio, and it was good to go. We took it for a test drive afterward, and logged the data below. It looked like I was just starting to get some spark knock, but there was beer to drink so I decided to work things out at the track yesterday.

I stopped and got about 5-6 gallons of premium fuel on my way to the track and couldn't wait to see what the car would do. Imagine my surprise when I saw no real difference in ET or 60' times. While I was slightly quicker than last weekend (13.313) my 60' time was still bad (2.117) and my top speed was lower. (I expected that... it was 106.08 MPH)

I pulled the logs and the amount of spark knock was insane.

It looks like the car is running stoich when I line up to the tree, and when I mash the gas it's still lean for a little bit as it launches. I figured that might be the source of my spark knock. Thoughts?

A friend asked me if I had some bad gas, and I told him that I had no idea... so when the pumps opened up I got about 4 gallons of 114 octane added to the tank. I made some more runs and the spark knock was gone.

I figured that something is going on... either my VE table is wrong, my MAF table is wrong, or my O2's have made adjustments to the LTFT or STFT that caused it to go lean. (Or both?)

So I went into the VCM Controls and I told it to run in open loop. I cleared the fuel trims and I commanded it to run at 12.5 AFR. The results are below. I then made a few more runs where I commanded it to run at 12.6 and 12.7 AFR to see what difference it made. It had just a touch of spark knock, but the actual times on the strip didn't change much.

So I guess I need to know if I am moving in the right direction with what I have done so far, and if not, can I get some feedback regarding what I need to improve upon? Did I get all of the torque management removed? Do I need to use the smoothing function vs. interpolation between the cells and across the board? Do I need to make changes to the 'switching points' of the O2 sensors so that they reflect the 14.7 AFR switch point?

Thanks in advance.

Mark

[mild7]

Can't see your logs as I have the 'other' tuning software, but have been tuning on my 97Vette MN6.

If your PE table is 12.5 straight across try using the stock values up to 4800rpm.

Using the VE from post#2, if your LTFT are 0 +/- 1 then richen up the MAF table by 2% up to what ever your flowing at 4800rpm.

Log your KR and subtract it from your HiOct table as needed.

How fast are the ox sensors switching at idle compared to at 1800rpm?