Tuning larger LT-5 cams

[XfireZ51]

Thought I would share one of those tuning "mystery" stories. Sometimes you've got to play detective. I have been busy tuning my LT-5 for the last 2 months. Over the winter I added a set of ported cylinder heads (AFR or Trick Flow don't make DOHC 32V high flow heads) and decided to take advantage of the additional airflow by installing larger single pattern intake cams. This is all on a stock block 5.7L LT-5 motor w 1 7/8" Watson headers and 3" Magnaflow exhaust. These babies LOVE to breathe. Very much a top end motor. Not much tops an LT-5 at full song around 7000rpm IMO.
Anyway, have been playing with the tune for a couple of months when I noticed the BLMs are not updating. The LEARN flag is OFF although motor was going into C/L. I thought possibly there was a problem with my new copy of TPRT 5.0. I also "noticed" that the bin where all this started had a Checksum that reset, IOW it went beyond the 65xxx. I do multiple changes to a bin but none were of the kind that should affect LEARN control. Or so I thought. It took me a couple of days of eliminating the parameters that had changes between the bin that DID work from the bin that DID not. It turned out to be coincidence that the Checksum reset at the same bin change but had nothing to do with the LEARN staying off. Using Craig's Ostrich 2.0 and Mark's TPRT 5.0 really made the sleuthing a much more effcient process. Still took me most of the morning today BUT I finally got it. With the larger intake cams, you invariably get the rich smell at idle and I had lowered the O/L change v CTS table to take some fuel out. Apparently the code doesn't like too much fuel pulled out because it appears to prevent LEARN from turning on. Essentially you are running O/L although the ALDL says you are in C/L.
Made the change to the bin, download and bingo LEARN ON. I re-input the stock values but for grins I would like to find out how much I can decrease fuel before re-creating this issue again. Maybe one of the hack gurus can tell us what the logic is behind this outcome. After going thru this, I thought I would have LOVED to have an ECM bench.

[HAWAIIZR-1]

Originally Posted by XfireZ51

Thought I would share one of those tuning "mystery" stories. Sometimes you've got to play detective. I have been busy tuning my LT-5 for the last 2 months. Over the winter I added a set of ported cylinder heads (AFR or Trick Flow don't make DOHC 32V high flow heads) and decided to take advantage of the additional airflow by installing larger single pattern intake cams. This is all on a stock block 5.7L LT-5 motor w 1 7/8" Watson headers and 3" Magnaflow exhaust. These babies LOVE to breathe. Very much a top end motor. Not much tops an LT-5 at full song around 7000rpm IMO.
Anyway, have been playing with the tune for a couple of months when I noticed the BLMs are not updating. The LEARN flag is OFF although motor was going into C/L. I thought possibly there was a problem with my new copy of TPRT 5.0. I also "noticed" that the bin where all this started had a Checksum that reset, IOW it went beyond the 65xxx. I do multiple changes to a bin but none were of the kind that should affect LEARN control. Or so I thought. It took me a couple of days of eliminating the parameters that had changes between the bin that DID work from the bin that DID not. It turned out to be coincidence that the Checksum reset at the same bin change but had nothing to do with the LEARN staying off. Using Craig's Ostrich 2.0 and Mark's TPRT 5.0 really made the sleuthing a much more effcient process. Still took me most of the morning today BUT I finally got it. With the larger intake cams, you invariably get the rich smell at idle and I had lowered the O/L change v CTS table to take some fuel out. Apparently the code doesn't like too much fuel pulled out because it appears to prevent LEARN from turning on. Essentially you are running O/L although the ALDL says you are in C/L.
Made the change to the bin, download and bingo LEARN ON. I re-input the stock values but for grins I would like to find out how much I can decrease fuel before re-creating this issue again. Maybe one of the hack gurus can tell us what the logic is behind this outcome. After going thru this, I thought I would have LOVED to have an ECM bench.

This is like speaking Greek or Japanese to me. Having the SGC Stage 1s on my 350, one day I hope to understand this stuff and get mine tuned right.

[XfireZ51]

Originally Posted by HAWAIIZR-1

This is like speaking Greek or Japanese to me. Having the SGC Stage 1s on my 350, one day I hope to understand this stuff and get mine tuned right.

Well thanks for taking the time to read and comment on this anyway.
Just a small caveat. Once you go down the tuning road, it's addictive because there is ALWAYS something else you'll want to tweak.

[XfireZ51]

Originally Posted by Paul Workman

Dom...I'm intrigued! Congratz on the perseverance and the stick to itiveness, and not giving up (and all that sort of rot!)! Sounds like a thorny one to figure out - another FBI triumph, I recon!



P.

Paul,

I could have tuned this thing in Open Loop, but decided I wanted to take advantage of some of the controls available in C/L. A bit more of a challenge but I'd done something similar when I modded my old Xfire that ran low 13's on street tires. Actually beat a stock ZR-1 at Byron once. But he was coming up fast!

[mike100]

I read your post last night, but didn't reply...Thanks for putting up that detail. These older controls do have range limits on a lot of things and get wacky when you exceed them and never find equilibrium. Obviously lots and lots of things going on with the strategy of operations that are not apparent.

[XfireZ51]

I've been reviewing the def file for my 92 ZR ($D0A) and I noticed there is a constant for O/L Change Bias v CTS of -13.67%. Coincidently?, the table values in the O/L Change Bias v CTS do not go below -13.67% beginning at 80C on up.
I had set the O/L Change to -11.67% from 80C on up in an attempt to lean out O/L idle. I have a suspicion that anything less or should I say leaner than the Change Bias number prevents the LEARN flag from flipping to ON. At 80C and above with a Change Bias of -13.67, the ECM won't modify the AFR produced by using the appropriate VE table value (RPM x MAP). Makes me wonder if there's a way to run O/L idle. Perhaps setting the O2 idle voltages to the point where the O2 sensor doesn't swing thru the O2 window at idle. So O/L idle and C/L cruise. Hmmm?:huh:

[HAWAIIZR-1]

Originally Posted by XfireZ51

Well thanks for taking the time to read and comment on this anyway.
Just a small caveat. Once you go down the tuning road, it's addictive because there is ALWAYS something else you'll want to tweak.

Yes, I have a friend with an LT1 Vette that does his own tuning and keeps telling me how easy it is the Moates Ostrich and some tools and software that he has. He'll show me the next time I go back home to Hawaii on vacation so I'm excited to learn. All the mail order tuning is good, but I know only so much can be done without having the car and dyno too. First I want to at least get smart with the Datamaster and understand all that it provides. I admire all you smart guys with this technical stuff. I forget the guys name or the exact program but I remember on a TV program some guy had a C4 that had extracted good power gains just from proper tuning. I understand that you can bolt on all you want, but if you can't get it tuned properly you're wasting a lot of power and money.

[XfireZ51]

That's what got me started on this stuff about 10 years ago. I decided I wanted more power from my Xfire so I started scoping out heads and cam. Then somebody said well you'll need a different tune for that. And I said how do you do that? Connected with some guys on the Crossfire Forum, and then I heard about a guy who had modded a Xfire to run 13's.
He was Bruce Plecan otherwise known as Grumpy on 3rd Gen. Pretty much the father of tuning as we know it now. Then read some tuning articles from Bruce and Robert Rauscher (owner of dynamicefi.com). Back then, no Ostrich and using a slow TBI truck ECM, 7747, datalogged at 1 frame/1.2 sec. I had to erase and burn chips for each cal change.

[HAWAIIZR-1]

Thanks for the info and motivation. Marc H has mail order tuned a few chips for my application and one especially to help me out with the emissions testing that I will encounter soon. The thing is if I still have problems or to get maximum benefits from the heads and cams I need to do as you said and get smart with this stuff. My friend also mentioned something about Tuner Cat and have not checked it out in detail yet.

[XfireZ51]

I prefer using TunerproRT. Started tuning using TC.