ACE1252

Been playing around with some of my logs. It appears that I'm not going to be able to do the above(the way I wanted to...). I can get into the ballpark, but my calculations are always more than the PCM(0.5-1mS greater). This is not surprising as not all of the air calculated on the back side of the MAF is consumed(most gets there but, intake design, headflow, etc play into the flow...but it's not all consuming of the incoming air).

I figured this would not be easy, but it has been more of a task than what I thought it would be when I bought the programming software.

Having LS stuff would make this much easier....as GM has made OEM power 500-600hp+ with the Z06/ZR1. This gives us properly engineered injector data from the factory to pull from(with the injectors/data from those engines/PCMs).....

ACE1252

Ok, I'm getting some progress made.

A few weeks ago I bought an AFX wideband system. It's paying off already.

A word of caution, AIR injection will cause a false lean condition on startup. I have not timed it in MAF mode, but in speed density mode, the AIR pump appears to stay on for 4 minutes after startup(even on a warm startup).

I was getting a maxed lean reading(greater than 16:1) on startup and was concerned until I noticed that after some time, the readings got reasonable. So, I started to time the readings and like clockwork, the lean readings changed at the 4 minute mark. The AFX manual does caution that AIR injection will cause a false lean reading....and it was right. I'll confirm what I'm seeing by scoping the AIR relays in both MAF and SD mode later.

I have been able to get rid of my bucking in SD mode. It appears to be a lean stumble in MAF mode, on tip in, that is causing my bucking in parking lots.

With a 14:1 ratio, the bucking is present in SD, but when bumping the AFR to 12.85(via a 15% increase in the low end of the VE table) the bucking is gone. So...I'm not sure what exactly to do in MAF mode since it seems to be locked to 14.7:1 most of the time. I suspect that my MAF calibration may be to blame for some of what is happening. However, I need to do more testing.

Nice to finally get some repeatable progress made.

The AFX system is really nice too. Easy to free air calibrate and it's accuracy has a proven track record(AFX 91101).

Injuneer

I would expect the AIR pump to turn off at least when the PCM goes into closed loop. That typically occurs at 206 seconds (assuming the coolant temp requirement is met). It wouldn't make any sense to keep it on once it's in closed loop.

ACE1252

Just a few more notes.

In SD/open loop, the commanded AFR matches what the wideband tells me. For MAF mode, it does show a bit lean. It runs anywhere from 16:1 to 14.7:1(commanding 14.7:1 the entire time)....and stays lean on tip in...

In SD/open loop, I was able to fix the bucking by making the VE richer just off idle. The idle pulse widths were in the 3.8mS range and when tipping in, they would go to upper 4's low 5's. For MAF mode, idle pw is 2.8 and 3.0mS. Tipping in does not really change them and hence the stumble and bucking.

That explains the bucking just off idle at light throttle. I just don't know what to do to fix it. Without having a table to tweak off idle fueling or the ability to tweak the closed loop AFR, I'm at a loss at the moment....

ACE1252

I was in SD open loop when I timed it and have verified that the output from the PCM does open the ground 4 minutes(240 seconds) into startup(verified with a multimeter). I could also pull the AIR relay and see the change in the AFR on the wideband.

A couple things to consider might be that I had the MAF unplugged and did have several parameters set in the PCM to force it SD and open loop. Fuel trims(short and long) showed 0% , which seems to verify I was SD/open loop.

I don't know how the above might effect it vs "normal" mode. I'll do some more testing with everything "normal" and in MAF mode to see what happens then.

ACE1252

The answer to my lean CL mode may be right here....

https://www.camaroz28.com/forums/com...eshold-702035/

The key may not be tweaking the switching points so much as to enabling PE mode at lower throttle settings. That may provide the enrichment I need on tip in. PE("Power Enrichment" for others who may not know the acronym) is allowed all the way down to 400 rpm.

I think I need to tweak "%TPS threshold WOT vs RPM(Low Cool)" table to allow for PE just off idle(0-15% throttle) say in 400, 800, 1200, 1600 range. Then tweak the "%Change to Fuel/Air Ratio vs RPM at WOT" table in that RPM range to provide the enrichment. So it appears that this table may be able to act like a "pump shot" on a carb.

This hopefully will allow me to fatten up the mixture at cruise to get the cruise temps back under 200*. I used to cruise with a temp of 190*. Since installing this cam, the cruise temps are up around 200-210*.

I'll need to thank WS6T3RROR for the post if this works.

I guess the only thing I'm not sure of is does this lock the fuel trims when this mode is enabled? Looks like I do have a little more home work to do.

ACE1252

The more reading I do, I'm not so sure it would be wise to use PE mode in the idle regions. My concern is that it appears to lock the fuel trims which would turn off it's learning ability off idle and I don't want to do that.

Kinda frustrating not to have a way in closed loop to add in an offset on tip in to compensate for a bigger cam.

ACE1252

The other issue may be that I simply have too much air on idle. The fix may also involve reducing the amount of air that the idle air control valve is letting in...but more research is needed.

ACE1252

All the below is a quote from Bobdec on the WOT AFR calculation....posting it so I can find it easy.

--------------------------------------------------------------------------------------------------
WOT % Change To Fuel/Air Ratio Vs. Coolant Temp.
This table is the percent change to Fuel/Air Ratio used at or near wide-open throttle (WOT) versus coolant temperature. The values from this table and the WOT % Change To Fuel/Air Ratio Vs. RPM are summed to arrive at the WOT Air Fuel ratio.

The resulting air / fuel ratio can be calculated as follows:

WOT AFR = 14.7 / (1 + %Change vs Cool/100 + %Change vs RPM/100)

For the selected RPM, suppose the percent change to Fuel/Air Ratio from the RPM table is = - 5.1 and the percent change to Fuel/Air Ratio from the COOLANT table at the selected coolant temperature is = 22.7, then the approximate WOT AFR would be:

14.7 / (1 -0.051+.227) = 12.5:1 AFR
-----------------------------------------------------------------------------------------------------------------
Also there is a "TPS Threshold for PE Vs RPM Vs Coolant temp" table that sets when you enter WOT (PE mode) in case you want to enter WOT at different parameters for your setup.

ACE1252

This is something that may be a problem with the Windows/USB version of Autotap.

My Bank 2 LTFT has always never moved around like my Bank 1 LTFT. In fact, it hardly moves at all and always displays a negative number on startup.

I have the old dos version of Autotap and got it working in windows XP the other day(com port V1 cable). It does not have the trouble that the USB version does. In fact, it is reporting that my bank 2 LTFT is around 23% while the USB version reports 10%. The bank 1 reading is the same between the two(~7%-10%)....so it looks like the dos version may be right....as bank 2, on it, moves around just like bank 1.

The only way I can tell which one is right is to verify it with a tech 1 or tech 2.

The values are concerning as I didn't know the bank 2 trims were so high, but this may point to a bug the in USB version of Autotap.

I'm starting to get my ducks in a row to do some dyno testing in the next few months and have found out Tick Performance does have a dyno that will do constant speed testing. My plans are to rent their dyno to do my testing. Finding a dyno and trying to make sure what I log is accurate was the first things on my hit list.

The next thing is to is pull together a harness so I can plug my wideband into my AC pressure port to get logging ability from my wideband through the PCM. I also need to try and check the update speed of the input if possible.

ACE1252

I got the chance this weekend to check out the FMS injector settings from my sheet, in post #20, with my old Autotap setup. For anyone who downloaded an early version of this sheet, make sure you get the current one as my old one has an incorrect assumption from me that added some time to the values. This is wrong and my current sheet has omitted that screw up.

With the mail order tune, the dos Autotap was reporting LTFT 13% on bank one with 25% on bank two at idle. If I'm not mistaken, I think 25% is the max limit of the LTFT. The injectors settings for the Injector offset and short pulse adders were stock in this tune, but the flow rate was a little higher than I expected(32.12), but will tweak it later...the correct value should be 31.80 when you take the FMS high slope flow rate from g/s to lb/hr.

I changed the injector offset and short pulse adders to what I have in the spreadsheet in post #20. I also adjusted the Right and Left Fast Rich/Lean settings for CL mode 64 to 470mV. Which is what the LT4 stock program uses.

The fuel trims at idle are split, but they are -10% and +10%(bank 1 and 2 respectively). So, the "right" injector settings are not maxing out the LTFT's. Which is very good.

When cruising@65mph on I40 the average LTFT trims are -3.5% and -6.9%.

The car is also firing up much better with these settings. It would labor to start or sound really weak starting before(as if it barely wanted to start) and now it has a much more powerful sound when it fires.

The wideband was reporting 12.5AFR@WOT. Highway cruise, it reported 15.0-14.3.

I'm now not worried about running these injector settings. They have helped the bucking in parking lots, but it's still not completely gone. It is harder to get it into that condition, but as I tune more on it, hopefully it will get even better.

Now that I'm happy that the calculated injector data from the FMS datasheets looks good in the car, the next step is to wire up the wideband to the AC pressure port sensor to pull that data into the PCM. Once I've done that, my plan is to program up an excel spreadsheet(using VBA) that will do what EFI Live and HP Tuners does during live tuning. Only my sheet will process the data after the log is taken and not live as you can with the LS1 stuff. Then, once that is done, it will be off to Tick Performance to do some constant speed dyno testing for the VE tables. I'm not sure how I'm going to handle the MAF calibration as there is no option to view Hz, but I'll try to work on it later.

Just a couple of notes looking back. The reason my calculated injector settings scared me so bad back when I first plugged them in was because Autotap was giving me the wrong values for the fuel trims. Granted, I still have a mean split at idle(20%) between the two, but it's certainly much better to have a -10%/+10% than a +13%/+25% with the old settings.

So again, be aware that the USB version of Autotap reports the incorrect LTFT for Bank 2(Bank 1 seems to be correct). I think it's okay on all other parameters. The USB version with the enhanced GM parameters is much, much, faster(more data points per second) than the old dos stuff, but at least the dos stuff helped verify what my LTFTs were truly doing. Pays to hold on to some of this old stuff sometimes.

I'll try to get the driving logs uploaded later for review if anyone should need to see them.

Later down the road, I'll post up the above sheet I make and I'll also calculate out the offsets and short pulse adders for other FMS injectors and post the "bottom line table values" for them up. You can calculate them with my sheet in post #20 by getting the data from the other FMS datasheets, but it would be nice just to have bottom line table values if you don't want to drag through the numbers(although it's best to do it that way if you can).

Also, once I get my VE and MAF tuned up, I'll export the tune to a txt file and post it as well.

ACE1252

I was able to get my wideband controller to work with the AC pressure sensor port today. Unfortuantely, the dos version of Autotap that I have does not log the voltage correctly. It reports it on screen fine, but the logs report "%1.2F" all the way down the column.

The windows version logs the voltage fine, but I'm stuck without the bank 2 fuel trim being correct.

So....I've purchased ScanXL Pro with the GM enhanced parameters and will see what it can do. I got the wifi and USB version of the interface tool.

I know several have asked about a good OBD II PC scanner now that Autotap is down for the count. I'll let you know how it works....hopefully it will work well.

I am encouraged by seeing this.....


Looks like SAE values are used here(slow updates), but this would be a big help in dialing in a VE table for an LT1. It appears to almost be EFI Live or HP tuners like in it's logging ability. It would certainly beat having to do something manually in Excel VBA....

I don't see an AUX input on the interface device, so going through the AC port is still going to be necessary. Hopefully, this will log all my needed parameters correctly at one time. It does support some widebands, but the output of the AFX is just two analog wires....not something that is USB or a 9 pin com port.

I'll update once I get it and have the chance to use it(I hope I have not spent a bunch of money for nothing....LoL, would not be the first time).

A little info on the setup for logging through the AC pressure sensor port. There are three wires on the AC pressure sensor connector. Red/Black = Sensor value, Black = Ground, and Gray = 5V reference. You do nothing with the grey wire input(no connection).

There will be two wires from the wideband controller that get connected to the AC pressure sensor connector. The analog out + will go to the Red/Black wire terminal and the analog ground will go to the Black wire terminal.

Here is the wiring diagram from my 1996 factory service manual(huge image).

http://www.ace1252.com/1996_Z28_Fact...iagram_001.JPG

I cut the leads from a 1 or 2 watt resistor and soldered them to the wires coming from the wideband controller. For the AFX unit, Yellow is the analog + and brown is the analog ground. The wires are only around 12" long, so I extended them using red(connected to yellow) and black(connected to brown) wires.

I know the setup looks a little rough with wire ties used to prevent any shorts, but it seemed to work well. Once the leads were inserted in the connector, I lightly wrapped the connector with electrical tape to help hold it together and prevent shorts to the car body or other accessories. Just remember to not use probe leads that are too big in diameter that could possibly damage the terminals in the connector.....or you'll have to replace the pigtail. Again, the probe wires are soldered to each wire. The wire ties do not hold the probe wires to the wire...they just prevent shorts from occurring(no heat shrink on hand).

A few pics here.....




As a precaution, I pulled the AC compressor relay to prevent the compressor from ever turning on.

When you fire the car, the cooling fans will come on and stay wide open. I assume it's because the PCM thinks the AC pressure is so high. Because of the AIR pump working on startup, the wideband sees 16:1 AFR and that correlates to 5V on the AFX unit....thus high pressure(I assume). Also, anytime you are 14.7:1 they stay on as well with the AFX.

There have been some concerns that this might effect timing, but I'm sure if it does or not. Idle timing did not seem effected.

ACE1252

I just got the ScanXL Pro software yesterday and have been playing around with it. It's raining today, so I'm not going to get to do any good logging.

I must say that the software is looking impressive. It took me several minutes to figure out how to select the GM Enhanced PID's and unselect the SAE PID's(Settings tab then PID Config). However, once I did that, the data collection has been impressive.

The tables seem to do exactly what the HP Tuners/EFI Live scanner's can do....the table cells follow the MAP, RPM, and AC pressure volts(all GM enhanced) very nicely. It seems really fast too(will need to compare). I cranked up the com port bit rate to maximum(under windows device manager, com port properties) just to make sure it was as fast as it could go(no connection errors with doing this). I had to fight with the drivers just a little as I have other usb to serial com devices installed. Once I cleaned the drivers and got the drivers from FTDI's site installed(Virtual Com Port), all was okay.

My initial impressions are very, very, very, good. I think this is going to beat the pants off Autotap by a long shot. I think this is exactly what us LT1 guys need to do the logging for mapping out the VE table. Autotap was good for it's day, but this scanning software appears to be in a different league.

I would like to find a better way of getting the data from the Wideband controller other than the AC pressure port, but I'll try to explore other options for that later. I'm sure it will involve speaking with Palmer Eng. to evaluate the possible options for the AFX wideband.

I don't see a GM enhanced for the MAF yet, so I'm not sure if I can log MAF Hz.....so it may have to be graphed against the grams/sec of flow. The software does crash on me either on startup or upon closing(never once it is running) every now and again.... So I'll have to contact Palmer Eng. on that to see if we can figure out why.....might be a Windows XP thing I'm not sure. I'll attempt to try it on windows 7 later.

From what little reading I've done in the ScanXL forums, I may need to do a validate on the PIDs. That is a more extensive scan for supported PID's I'll report back as I get more experience with it.....there also some scripting stuff that can be done as well. I'm just scratching the surface of what this stuff can do.

So to outline what I got for those who may want to try it......

• ScanXL Professional(Software)
• GM Enhanced Parameters(Software option)
• OBDLink USB/Wifi(Hardware)

All told, it was a little over $400 dollars for me, but you may be able to catch some sales on Scantool.net to help out the price. I ordered mine on Palmer's website, but it appears that the package came from Scantool.net. Also note, this is scanning software, not PCM programming software.

You "may" be able to get away with just the SAE parameters and or the standard version of ScanXL, but I'd advise getting Pro and the GM enhanced if you can afford them.

I have not tried out the Wifi yet, but I'll get to that later today.

I really wished it was not raining today.

ACE1252

Just a quick update(it stopped raining and dried out enough to drive), it appears that the data collection rate from Autotap is faster. It is taking around 10-20mS for each PID with Autotap where ScanXL is around 20-30mS for each PID(according to the time stamps, for each parameter, in each log).

That is a fairly big deal, because it is not catching anything up in the 6000rpm range when logging several parameters.

I need to find out what kind of an interface protocol that Autotap uses compared to ScanXL. It seems that OBDLink is some kind of ELM protocol(not completely sure...need to do more homework).

Software wise, I like what ScanXL can do, but I really need to find out how to get the data collection rates better. I may simply need to log minimal parameters to get good fast data rates....but it would be nice to speed it up somehow.

Oh, no crashing whatsoever on Windows 7. Not sure what is causing it on my XP machine.

Ricardo

Is this when collecting data in USB mode or is it in Wfi mode?

Ricardo