canbaufo

I haven't tuned for two years and ....well I know you are suppose to always start with a fresh stock file. I started with a fresh file and built two new tunes to try on a dyno but just realized something. I did a "file, save as" midway through, thinking there was a quick save option. There is no quick save option so I did a "file, save as" again and it asked me if I wanted to overwrite the existing file and I said yes. Then I realized ...isn't that equivalent to starting with a used file and trying to save over it? That causes rounding errors doesn't it? So this means I have to rebuild them all over again but at least I have the old files to copy tables from. This time I just have to remember to WAIT UNTIL THE END to save the file. Am I correct or was what I did actually ok (doing a file, save as, a couple of times and writing over existing file)?

...**** I hate this stuff, no wonder I left it alone for two years ...

sbs

It's hard to understand WTF you're getting at but here's my guess:

Is there something different about a file saved once versus a file saved twice in a row? no.

Is there something different about a file if it is saved, reopened, and saved again? no.

Save early, save often. It is Windows, after all.

canbaufo

LT1 Edit has "cumulative rounding errors" that occur when you try to modify a non-stock file, so you really have to start with a fresh stock file each time you do a new one (however you can copy tables of old files, you just can't re-use old files and re-save or you get the rounding errors). There is no "file-save" option in LT1 Edit, it is only "file-save as" and when you do it more than once it asks you if you want to overwrite the existing file. When you overwrite that's pretty much the same thing as modifying a file (which we know can cause cumulative rounding errors in LT1 Edit). I believe you really have to start with a FRESH FILE and WAIT UNTIL THE END to save so you only save one time and don't risk overwriting and causing cumulative errors. If you save several times while working in a new file it's not a "quick save" each time but a complete overwrite (save as)...which leads me to believe it would cause the same problems as modifying an existing file. Crap.

JP95ZM6

Is this your own statement, or a quote? If the latter, please link to source. I am still skeptical about this being a significant issue, as I have always just modified the last file I saved, and done save-as. About 50 times so far.

canbaufo

I've read this and heard it from others more than once and experienced the problems it can cause first hand. Maybe it depends on what version of LT1 Edit you're using. I can't remember where I read it but I am sure that is what was stated. I guess I'll see if anything whacky happens. As far as "looking the file over" goes everything looks fine. Well I'll see I guess ....

JP95ZM6

I should have mentioned that I use Tunercat, maybe that does not share the rewrite problem.

canbaufo

There we have it. Tunercat is a much better program, wish I had gone that route. Have too much time/data in LT1 Edit to switch and I'm not that computer savvy to begin with. Going to rebuild files ....

DOOM Master

Too much time? You do know there is a converter file that will let you change all your .LT1 files to .BIN files, right? Tunercat is only going to be $90, if this is a real issue with LT1Edit, I'd spend the $90 today and never touch LT1Edit again.

canbaufo

Just rebuilt three files for the dyno, took nearly two hours but I feel much more confident now. I don't tune much so I'm not so concerned about getting Tunercat even though I'm sure it would be better. I would have issues with the installation or some mundane crap like that, I can see me struggling with this converter file you speak of. I am not computer savvy and in a way have no business doing this stuff lol, but I do know a little about how to tune this thing and my files had other more knowledgeable people's input as a baseline before I began. They taught me a lot, especially one of our CZ28.com members Rog'

canbaufo

UPDATE (with SAE dyno numbers!):

Well I would have never guessed, but my main tune was actually a little too lean so I had no need for the two additional tunes I created (and re-created) as they were even leaner. Based on DataMaster and Scanmaster I always assumed my AFR of the tune I usually run was a little rich (.920 - .950) ...can't trust O2's so much though.

I did two pulls on a wideband dyno. On the first pull I used a tune that had some tables copied over from a file that I accidentally multi-saved (overwrote) and it ran way too lean at high RPM's (5,200+ it was 13 - 13.5:1 ...yikes, not good on non-intercooled boost) and pulled about 7 degrees of knock retard. My suspicions about rounding errors on multi-save-as files are now confirmed. I uploaded an old tune that had the same WOT and high KPA fuel tables but had never been over-written ....it ran richer and better. The first tune was created from a fresh stock file and contained some low load open loop tables that had been merely COPIED from a tune I had accidentally "multi-saved" and I suppose, created "cumulative rounding errors" even just merely copying the damn tables. Yet this tune had the same PE vs RPM and 90 KPA+ open loop tables as the other one. In spite of this, it ran much leaner. I double and triple checked everything and there was nothing in the tune that should have made it run leaner; so cumulative rounding errors are likely the cause.

I know this is hard to follow, I did NOT use the files that I had accidentally "saved over" but used a fresh stock file and modified it to a proper forced induction style file, but copied only a few tables from one of those files I had accidentally saved over. So what I'm saying is yes, multiple save-as and even copying tables from a file that had been multiple save-as'd in a stock file that you are modifying will result in cumulative rounding errors. I have never seen this thing run so lean, on my Scanmaster it said .860-.890 mv's ...which I NEVER see on the street in my other tunes that had never been multi-save-as'd (and if anything it should run leaner on the street due to moving air). This .860-.890 mv's was equivalent to 13.5:1 on the wideband (confirmed, it was hooked into my O2 bungs). Then when I ran the old tune that had the same WOT fueling but contained no tables that had been copied from a multi-saved file ..... it showed .940 mv's and the wideband showed closer to 12.8-13.0:1. I'm mostly talking about the high RPM's ...at lower revs it ran a little safer/richer being around 12.5-12.7:1.

Bottom line, start from a stock file and only copy tables from files that you are sure have not been multi-saved over. NOW, the numbers on the better tune (not bad):

Peak corrected RWHP: 446 @ 5,700 RPM (12.9:1 AFR)
Peak corrected RWTQ: 441-442 from 4,700 - 5,000 RPM (12.5:1 AFR)

RWTQ @ 3,400 RPM: 400 (12.8:1 AFR) - this is the best part, good torque down low!

RWHP @ 6,200 RPM: 430 (13.14:1 AFR)

I think it has a little more power in it (and safety of course) if I add some more fuel in the PE vs RPM, especially above 5,200 RPM. Would like to see AFR of more like 12.0 or even a tad lower to compensate for moving air on the road. I wanna shout out my thanks to Roger and Mark (fellow members/friends) for making all of this possible

sbs

Makes no sense and nothing shows up in a google search to corroborate your claims.

canbaufo

DOOM Master

There really isn't anything difficult about installing Tunercat or using the converter program. Neither one requires anything more than double clicking and typing. For all the time you are spending rebuilding files I think you would be much better off making the switch. If I had to spend 2 hours rebuilding files with TC, I'd immediately get another program.

canbaufo

If I get back into regular tuning I will certainly consider this, thanks.

NJ-LE

canbaufo:
The TunerCAT program's 'open file' action seems to support .BIN files (TunerCat's native tune file type) AND .LT1 files. It seems to imply that TC will import LT1 Edit files directly. You might want to email Tunercat.com for more info.
Good Luck