Replaced L03 with an L31 in my Firebird and it has been a tuning nightmare ever since

[pmkls1]

Those are all good points that I have considered and here are my thoughts on thoose points.

If I had set this up I would have done the following:

Use Vortec based spark tables as starting point.

I originally began with the ANTT bin with the BPC altered for the engine size just to start the car and drive it in and out of the shop. The engine appeared to run so well on short trips that I decided to just stick with what I had and tune from there. Once I had the car ready to go back on the road I started noticing the little bugs and started tuning from there. I knew that the vortec heads were very "picky" when it comes to the timing so I tried to stay conservative with the timing. I had been searching for tunes for a vortec-headed tbi setup and only found a couple. Once I looked at a few spark tables I only became more confused because the tables I could find had way more advance than what I was running. I had always read that the combustion chamber design on vortec heads was very efficient and thus did not "like" as much advance as a typical small block head.The biggest obstacle I ran into was that I could not find any tunes for a '746 ecm and $61 mask. I did view all of the tunes that I downloaded with the appropriate xdf, but found a lot of figures very different than any of the $61 bins. Anyhow, back to the point, I did eventually find more tunes for a vortec-headed tbi setup and used them by copying and pasting and then shifting the entire tables to more closely resemble the $61 applications. I only recently began using the timing tables that I borrowed from and the problem is that the engine runs a lot better and really came alive, but then I started encountering issues with the spark plugs appearing blistered and a true misfire began appearing. It was at this point that I finally stumbled across the info regarding knock sensors and ESC modules and them being specific to a particular bore size. Once I change over to the correct ESC module and knock sensor I should be able to adjust the spark tables more accurately and much faster.

Use correct size injectors. Pressure corrected TBI never behaves as well IME. Always suspected wire gauge in injector circuit should be increased.

I have done a lot of reading the last couple years on TBI injectors regarding flow rates and fuel pressuress etc...... I am aware that as fuel pressure increases the injectors become more erratic and can also behave in an unpredictable manner or malfunction. I haven't really ever been concerned about the injectors only because I never encountered any known issues in the last 3 years. And from what I have read TBI injectors usually can handle increased pressures up to ~40psi before they begin to have problems operating properly.

Dump 160 stat. No need for it. Vortec heads burn well and intake manifold has no coolant based heating. You lose less power and improve combustion efficiency with a higher temp block.

Dumping the 160 degree thermostat was definitely in the plans for the near future as I had noticed that the engine ran very cool and it just wasn't necessary.

One thought: O2 readings are affected by timing. More advance tends to produce leaner O2 readings. If you've got light throttle issue try backing off timing in that area 2-5 degrees and try again.

The problem I had with lean readings was that, for the most part, the ecm would see the lean reading and would take a very long time to alter the INT and BLM values as if there were some sort of malfunction. I also noticed that when cruising the engine would surge and the surge exactly matched the switching of the o2 sensor as observed with my dash mounted gauge.

Prolly be soggy on top regardless thanks to exhaust configuration. TPI with same manifolds was great due to low end torque without the exhaust restriction causing a problem.

I am definitely in agreement with the limitations imposed by the current exhaust configuration. I would have preferred to install the engine with a good set of headers, but I was on a very limited budget. Some of the soggy feel on the top end can be eliminated when I happen to stumble upon a good timing and AFR combination.

No logs, no real diagnostic trail to follow, lots of assumptions. Hard to offer solid advice.

I totally understand and agree with that statement. I mainly wanted to get a dialogue started in anticipation of slower and fewer responses as that's what I am used to. I have barely scratched the surface regarding what I know and don't know about ECM tuning and the thought process that has led up to this point. I had also anticipated having time to upload a couple of my latest tunes and logs already, but my schedule is just too busy and unpredictable. I haven't had the time to get on the laptop that I use for tuning in the last few days to upload some tunes and logs. I have 3 laptops and one of them is dedicated to all of my tuning and logging which is why I have been able to hop online and post, but not upload something for youguys to look over. I will be driving my car a bit today so I will try my latest tune and log the drives and upload them once I get back home.

Thanks for your time and input,
Phil

[1project2many]

Once I looked at a few spark tables I only became more confused because the tables I could find had way more advance than what I was running. I had always read that the combustion chamber design on vortec heads was very efficient and thus did not "like" as much advance as a typical small block head.

Yeah. It's very tough to find calibrations you can count on. I really only trust OEM and a few people that I know have similar tuning strategies to mine. And as I'm sure you know, there are many levels of "runs perfect" on the internet that would never get a passing grade with a good driveability tech. The OEM Vortec / TBI cal gives a good starting point to compare spark tables. Aluminum heads generally require more advance because the aluminum tends to pull heat out of the chambers fairly quickly so don't be surprised to find a lot more timing in those cals. And cals in lightweight cars with numerically higher rear end gears will often have more advance even though it's not needed because 1) people think more advance is better, and 2) the vehicle combination isn't heavy or loaded enough to tell them they're wrong... at least not right away. There's also the problem of the calibration adding and subtracting several different tables and constants to get a final result which can dramatically change the values in the main advance tables before they're delivered to the distributor. This sometimes makes an apples to apples comparison very difficult.

Straight out, almost every vortec headed engine I've played with in the 8.0 - 9.5:1 compression range has made best peak power with max advance no more than 36 degrees advance. Often they end up around 32-34 degrees. If you're looking at a cal with 38 or more degrees advance combined between PE spark and main / 100kPa column then something isn't copesthetic. Cruise OTOH can be quite variable as the vehicle specifics are at play. Trucks are aerodynamic like a brick and the engine tends to be under greater load at cruise. They usually don't tolerate running as lean as a car and therefore may not have as much advance at light load. Cars like your firebird with a lower coefficient of drag will often tolerate more advance and less fuel. And if engine rpm is higher, maybe 3000+, on the highway then a little more advance may be possible. Light cruise timing values are not good indicators of the overall usefulness of a specific timing table. After all, the TPI Vette tables have timing values exceeding 40 deg at cruise! But I've used plenty of those cals as starting points for heavier vehicles.

FWIW there are many, many subtleties which I've found over the years which can really affect tuning efforts. You might consider using a B body cal from an L05 with a transplanted OBDII timing table. Or I have a very good cal here from an L03 B body which had LT1 exhaust and cam with 1.6 rockers and a modified intake you may use. That cal with L31 spark and corrected BPW val might also work well as a starting point.

I understand busy. Believe me. Will wait to see uploaded data.

Shannen

[pmkls1]

I'm going to go ahead and submit this post with my last couple tunes attached, but I could not upload my logs as they are in .adl format so I couldn't attach them. I'm still running TunerPro version 4 for now. I'm not sure if you can simply change the file extension on data log files or if they need to be converted. I gotta run for now because I have something to do like always. So, maybe between now and tomorrow morning someone can answer the question of if and/or how to upload my logs. I have plenty to say regarding the tunes that I have attached, but that will have to wait for now.

Thanks,
Phil

[EagleMark]

adl is now a supported attachment.

[1project2many]

Can you load an .adl log with TP? I thought that didn't work. Or was it maybe with TP4? Seems like comma delimited was the only way to view TP logs for a while?

[EagleMark]

Not sure, I was just taking his word that TP V4 was adl, we will try when it comes through?

[pmkls1]

Here's the log file. The extension assigned by TP v4 was .adl . I tried TP v5 temporarily, but had a hard time adjusting and also had to convert files and dl new definitions etc.. I had too much going on to mess with trying to learn the new layout etc. so I just went back with v4 for now. Just a quick couple of notes though. I just figured out how to setup the map trace feature earlier this week. I also just recently learned the importance of getting the VE tables correct in order to properly tune. Just those two things alone could allow me to make leaps and bounds with getting things right. With the v56 tune I uploaded above the engine runs quite well although a LOT of work still needs to be done to keep the BLM from jumping all over the place. The v57 tune did not work as well due to the timing changes I made. I drove the car about 50 miles from the shop back home, but I didn't have the laptop plugged in long enough to get a charge so it died on me and I didn't log the drive with the v57 tune. Anyhow, I have already learned volumes since starting this thread and given a little time and more instruction I can definitely refine my tune significantly. I have figured out that the issues leading to the blistering of the plugs was overly aggressive timing at WOT and most of the cruising issues have been resolved. My problems with this venture have been due to my lack of knowledge and understanding of the computer/software aspects of tuning. I fully understand how to tune an engine and the effects of timing and fuel mixtures etc., but making that happen with the ecm is a different story. I still plan to get the proper knock sensor and ESC modules, but I can still significantly improve the overall driveability of the car until then. Other than a set of headers and mandrel bent front exhaust section I do not have any plans for upgrading anything on the car until I have settled on what type of ECM/PCM I am going to use. I plan on replacing the 700r4 with a 4L60E and going with a MPFI induction system at the same time that I upgrade to a better ECM so I have not decided what I am going to use yet. While I did anticipate an improvement in performance, this swap was more about reliability than power. The old L03 used about as much oil as it did gas and the oil pressure was getting pretty low. Since I already had 3 L31 longblocks it was actually cheaper to repair one and acquire the parts I needed for the swap than it would have been to overhaul the L03. I also have plans to stuff that L03 in an S10 and dumping the ragged 2.5 it currently has. Well, I gotta run for now. I look forward to seeing what input I will get on the bins and logs I uploaded. But, given what I have learned recently, I kind of have an idea what I will hear.
Thanks again guys,
Phil

[1project2many]

Sorry it took so long to get back to this. Finally had a chance to sit down and look at the .bin files. There's a lot to discuss. :)

VE is dictated by engine flow. The engine itself, cam plus head(s), tends to dictate a basic curve for VE. That curve is then modified by exhaust and intake components. An L31 engine VE curve should be recognizable in any L31 calibration. A calibration with better flowing intake and exhaust might have a wider curve, or a long runner intake like the L31 OE might have a higher curve in the low and midrange, larger rockers might give the curve more of a peak, and more restrictive exhaust might clip the top end. But the basic curve should be recognizable. Look at the screenshots of a dyno tested Vortec TBI cal for $42 vs the cals you posted. These are a graphic representation of the VE plus VE adder tables with RPM running along the X axis (L to R in first image) and MAP along the Y axis (F to R). The lower RPM portion of the two graphs look similar, up to about 2400 rpm. But the divergence at that point is very noticeable. The spike at the RH side of the $61 cal is due to a very rich entry in the 4400 rpm row of the main VE table and a couple of rich entries on either side of that. Without that spike much of the low RPM and low MAP curve would look similar. But what's really worth noting is the difference in VE as MAP increases. The rotated view showing the RH side of the table really demonstrates this. In the $61 table the VE gets lower as MAP increases. This makes for a lean engine when it most needs to be rich. Even with a vacuum referenced FPR this is quite a drop.

<more to follow>

[1project2many]

Ok, now for the big issue... spark. There is one helluva lot of spark advance in this calibration. Were you advancing timing looking for knock on the sensor? That's not the best method for generating an optimum advance curve. Power will tend to fall off one or two degrees before the knock limit is reached. Once knock starts it can take up to six degrees of spark retard to make it stop. And, depending on the rate at which advance is returned after KR, knock can reccur with 2-3 degrees less advance than the initial occurrence. Knock = bad. There's no surprise you're experiencing the problems you've described. I'd recommend starting again with a fresh set of tables. Looking at the stock truck L31 tables is a great place to start.

[EagleMark]

Always have to be careful comparing spark from one bin to another and possibly one program to another? From bin to bin example, $42 warm spark bias is 9.84 degrees in small block and 0 in big block. That's a 9.84 degree difference in main spark timing table. Both have 20 when cold. Both are same Mask ID. Other masks have different bias.

So in $42 look at main spark table in a small block bin and take out 9.84 degrees across the board. In big block take out nothing. Then the distributor setting, Initial spark advance for SB is 0 so add nothing, BB is 3.87 to add across the board. Figure in if EGR spark is still active and DFCO spark! Then calculate spark latency values which are different from SB to BB and neither is correct from factory. Also 2 different EST modules, one takes away 4 degrees by 4000 RPM and one adds 2 degrees timing between 4000 and 5000 RPM.

Now look at that timing table and whatever cell your in is interpolated with the four surrounding cells to come up with spark advance at crank! Plus other factors mentioned above. With that in mind GM did not care what spark table looked like in the end if it did what they needed. Starts with max power spark advance on dyno, then has to pass drivability, then emissions, so what does the spark table look like?



Notice the four dots pulled in the air where someone needed more timing? As Robert would say "OMGWTFANNOUYING!"


So where did you say your timing was?

[pmkls1]

Thanks a lot for your time. Some of what you said I knew, some I thought to be true, and some I had no idea lol. Since my last post, I have made big advances with the ve tables. At the same time those advances only led to more confusion too. I have pulled some timing too, but I think some areas need more pulled. A big question I had was if it is possible to run $42 code in a 746 ecm. I know it is possible to run different masks in p4 ecm's i.e. running $58 or $59 in a 730. I rode the motorcycle to work today so I don't have the laptop with me, but I will post my updated tunes and logs after I get home. Thanks,
Phil

[EagleMark]

A big question I had was if it is possible to run $42 code in a 746 ecm. Thanks,
Phil

I have read yes! But never tried.

I have run same vehicle and exchanged a 1227747 ECM with 1228746 ECM, only wiring difference was 8746 has IAT sensor. Also 1227747 will plug and play in 16146299 vehicle.

But I don't think that will solve your issue. If your just doing it for the available Vortec Spark table you could use it in your bin, use highs lows, idle midpoint and build rest of table and smooth.

[EagleMark]

Back to what I was saying ealier... I just looked at same $61 bin with 2 differant masks. One included the 20.04 main spark bias and the other one did not. So depending on what mask/XDF you are using your entire spark table could be 20.04 degrees off to start.

So I compared your Vortec57 bin to a stock F body bin and your bin is approxamatly 15 degrees more spark advance across the board then stock! Same with other mask. So if I take the one that shows a higher number top spark advance at 3200 RPM 100 MAP is about 36, your top advance is about 52. Same results across table, I think we found your issue!

Your spark bias is stock at 20.04. Initial distributor setting in bin is 0 so if your distributor is advanced it is adding on top of that!

If you didn't see knock I would say your knock does not work...

[1project2many]

Initial spark advance for SB is 0 so add nothing, BB is 3.87 to add across the board.

Ummm.... Initial advance is for the ecm to subtract out, not for tuner to worry about. Tuner sets table for 20 deg, ecm says "I already have 3.87 so I only need to deliver 16.13 deg to make 20."

Spark latency is microseconds, not going to be an issue. Microsecond is .000001 second. At 10,000 rpm that's equal to about 1/16th of a degree. At 5000 rpm it about 1/32 of a degree.

Spark tables viewed in TC already have spark bias added where necessary. WYSIWYG. Thought TP did the same?

A big question I had was if it is possible to run $42 code in a 746 ecm.

I believe yes. But! The "code" is the set of instructions that the ecm follows to operate the engine. the "calibration data" is what represents the specifics of the engine and vehicle configuration to the code. In a C3 ecm such as the 7747 and 8746, the data on the chip is mostly calibration data. The code is maintained in a ROM chip soldered to the ecm circuit board. Plugging in $42 calibration data to a $61 ecm will result in problems as the data is not organized the same way. When you get to later ecm/pcm's the code and calibration data are both contained in the memcal which means the instructions and the variables can be moved from one ecm to another.

The 7747 is almost a pin for pin swap for the 8746. On of the downsides to the 7747 (and one I've fought many times) is no air temperature corrections. Intake air is ducted through a thermac on the stock engine and the calibration for the most part assumes incoming air is at least 90 deg F. Start playing with different manifolds and breathers and this can become an issue. I would stick with the 8746 for now and consider a pcm upgrade for the future. You will see a huge improvement all around if you decide to swap to the later S10 / 94-95 TBI pickup pcm.

[EagleMark]

I've found 2 $61 masks/xdf for TunerPro. One takes Bias into consideration, one does not, that is a 20.04 timing advance mistake?

Latency is usec / deg so proper time for 400 RPM would be 208.3333333 , bin is set to 0, using proper latency can get your timing table to be exact at flywheel. For example 1666.666667 would add 8 degrees timing, so the 208.3 above is about a degree, bin says 0 But as RPM rise it gets worse! All stock bins are no where near close. For example SB chevy correct for 6400 RPM is 26.14379085 bin file says 137.34 about 6 degrees, for BB it says 305.2 usec which is 12 degrees. That's a lot!

Good read!
http://www.thirdgen.org/techboard/di...ncy-table.html

Point was where is timing? Then I looked at his bin and the entire spark table is about 15 degrees over stock without other factors...

So stock bin with bias idles at 11.95 degrees, no other factors, his with bias idles at 29.88! Sorry that is an issue. WOT 100 MAP at 3600 RPM is as high as table goes in TP $61. Stock with bias and no other factors is 16.17 reasonable for a street motor on pump gas. His is 33.4! Sorry that is an issue unless built race motor on race fuel... oh lets add the PE spark for fun of 3.87 so total advance 37.23! On a used 117k mile L31 bottom end paired with some 96k mile heads and pump gas? Not me!

He also mentions e85 which I know nothing about so maybe he did put timing there on purpose?

But with the 20 degree bias shown in spark table on one mask and not in the other I can see where he is 15 degrees over entire spark table, still to much for Vortec heads. If not his issue, it is a big issue! With latency on BB bin equaling about 12 degrees... back to my origanal statment and point. So where did you say your timing was?