What to datalog? (and what to look for?)

[DarkMesa8]

I recently installed a V2-SQ system on my 01 Cobra, and used my xcal2 to upload a temporary tune to support the LMAF and 39lb injectors.

During cruising, it feels like the car is bucking when the rpms are between 2000-2500, and I think I can hear backfires in the exhaust (more like hiccups).

I'm going to datalog tomorrow to see what the problems is, because otherwise the car starts, idles, and accelerates perfectly fine (haven't gotten hard on the throttle yet because of no dynotune).

I want to see what the problems is before I drag the car 4 hours to my tuner. When I datalog, what parameters should I datalog and what should I look for? I have no wideband.

 

[HMUSN]

http://www.tricktuners.com/data_logging_info.htm

 

[Quadcammer]

Id put money on it being maf wash.

Take a look at maf ad counts and maf voltage at that rpm.

 

[DarkMesa8]

How should they correlate?

What's the sign of backwash?

 

[DarkMesa8]

Here I am cruising for about 20 seconds at 2400rpms. The stumbling is occuring and I can hear the backfiring.

How do I interpret this?

 

[DarkMesa8]

So is this a graph of backwash?

 

[Janstang]

It would have been nice to see the MAF counts also, but it doesn't look too bad based on airflow. When mine had washout issues if you looked at the MAF counts it looked like a bad earthquake, squiggly as hell on the readings. It would also be nice to see the STFT and LTFT to see if its just fuel related.

 

[DarkMesa8]

Sorry, I'm very new at this with the Xcal2. The last datalogging software I used was a TwEECer with an EEC-IV in a 95GT.

What's the difference between MAF AD COUNTS and regular MAF counts?

What does STFT and LTFT stand for, and what should I look for when I log it to see if its fuel related?

 

[01 Venom]

Hmm let me ask you guys something, this is a pic of my datalog, I am having the same stumbling issue. This would be an example of MAF wash right? What causes this? I found that my aif filter had fallen off in the fender, think that could be it?

 

[Janstang]

Sorry, I'm very new at this with the Xcal2. The last datalogging software I used was a TwEECer with an EEC-IV in a 95GT.

What's the difference between MAF AD COUNTS and regular MAF counts?

What does STFT and LTFT stand for, and what should I look for when I log it to see if its fuel related?

STFT(short term fuel trim) LTFT(long term fuel trim) Usually your choices for MAF datalogging will be AD counts or voltage(depends on the software).They are basically one in the same. The AD counts are the MAF voltage times 205, and is the same set of numbers you will see when you go into the transfer function portion of tuning to change the A/F. I prefer to log the ADcounts over voltage primarily because its quicker with it already being converted. On my version of the software the STFT are perfect at 1.00 anything more than 5% lean or rich from this number and I adjust it. Once its within the 5% I look also at the LTFT to ensure its behaving itself. My technique for this is to start datalogging sitting in the driveway with the car warmed up and the 02's sweeping properly while datalogging. Log at idle for 10-15 sec. go up to around 1500rpm for 10-15 sec., go up to 2500rpm for 10-15 sec., and finally 3000-3500rpm for that amount of time. Stop the log and look at all this. First, are the 02's at idle sweeping back and forth? Next what are the STFT's looking like. Are they within 5%? If not they need adjusted. Once the area we talked about looks good, go for a drive and datalog. Do the same thing while driving, hold it at around 1500rpm, 2500rpm, 3500rpm etc.. and see what the trims show and adjust accordingly. WOT tuning is slightly different with it being an open loop operation and I recommend the dyno for that portion of the tuning. This is just a quick overview of some of the tuning "techniques" I use, so don't consider them the gospel in any way, but they work very well for what I do..