Went to the track today I think I am seeing a slightly leaning AFR with increase in IAT (Intake Air Temp)? Anyoby see anything like that?

One guy posted that he was seeing in increase in AFR after letting the car sit for a few 5-20mins when warm then re-starting it.

I Sent this to Tunercat see what they thought:


"Hello again!

I’ve been running the modified 2bar tune for LT1 for along time now and been doing good using the updates references below regading BARO reset,

Now, I noticed when I go to the track and log AFR, I get about 0.25% increase in overall AFR each time I shift gears and Im trying to figure out what it’s linked too, I also see the Injector % Duty Cycle decrease slightly each time I shift which seems to be causing this problem (between 4000 and 6000rpm) so that rules out a fuel pump/pressure problem.

To clear this up I mean when I shift in my manual trans car from 4000-6000 and let off throttle between each of the 3 or 4 gears, the ARF leans out slightly each time I re-apply power, in 2nd gear I have 12.6AFR at 4000 and 12.3AFR by 6000rpm, then shift to third and again at 4000rpm I start now at 13.0 and end at 12.6AFR by 6000, and shift to fifth now I have 13.4AFR at 4000, and end at 12.9AFR by 6000rpm. Seems to reset when I shut off the car, and Im not sure if It keeps leaning out because I shut the car off between laps, and it starts out in the same pattern again.

The 2 bar MAP sensor reads consistent pressure from 4000-6000 in each gear, not decreasing at all, battery voltage is also staying the same.

I cant tell if it’s the return to 0% TPS doing it or if it’s the Intake Air Temp which is also increasing due to supercharger heat… not sure.

Is there anything you can think of that would do this, or look for? It seems to be linked to either IAT (which does climb) or TPS returning to 0, not quite sure.

Thank you!! "

 

I just got my car running with the new engine (fully forged 355 LT1 built for turbocharging), STS turbo with plans to run ~12 pounds of boost. I am reading through this thread (currently on page 7, lots of stuff to absorb). I have an OBDII vehicle with LT1Edit. Is this tune available in LT1Edit format so I can start looking through it? Or do I need to use something else, Tunercat, OBDI, etc.?
Thanks in advance.

 

i believe there is a file converter available online.look it up.I used it earlier this year.

 

Not sure if OBDI files of any type can be converted to OBDII, or if conversion even needs to happen or can happen.

As far as .bin to .LT1 (OBDI) let me speak from my personal experience on this one since others might be diffrerent,

Before I fried my original LT1_Edit registered PCM (by not turning off Scanmaster before attempting to flash my PCM... Im an idoit) I was able to use LT1_Edit and Tunercat interchangeably, no problems. Tunercat will recognize LT1 files and save as LT1 as well.

If you download the file from this forum you will also be downloading my VIN#, which when you go to load into your PCM using LT1_Edit you will (or should) get a VIN mismatch error upon load, and it will end, unless you have an open version of LT1 Edit.

You could try to switch the VIN# using Tunercat, never tried it. Since my PCM swap I have been programming with Tunercat, however have only loaded 3 files with it compared to over 100-200 with LT1_Edit so Im a little worried since the history isnt there.. but so far so good.

Whatever you find report back and let us know!

 

Thanks for the replies.
lt170chevelle, I was unable to find a file converter for Tunercat --> LT1Edit, either by Goggling the web or searching this forum. I saw several requests, but no actual converter. If someone knows more on this, it would be appreciated.
dookie454, it sounds like you are staying with OBDI. I am currently attempting to procure an OBDI PCM. I have found the thread to solder a resistor on the PCM so I can swap between my OBDII PCM and an OBDI PCM. I am certain that LT1Edit is h/w locked to my PCM, I checked with Ion on this. I can read your file Dan_156_Openloop.lt1 for display only, but I can't compare it to my OBDII Lt1 files, it tells me "This is not the same file type!".
When I get the OBDI PCM up and running, I will be obtaining Tunercat at that time.
At any rate, thanks again and I hope to join you in the land of 2 Bar MAPs.

 

Here one of the many sites to get the converter from:
http://www.wotelectronics.com/links.html

As far as the obd2 computers, all of the tuning software for these are vin locked?!? Well that sucks. Im OBD1 Tuner cat and love it.

 

Well, wotelectronics linked me to webrats, which turns out to be a sex site. Not quite sure what to do after that (for my PCM, at any rate).
Yes, all OBDII s/w that I have found is VIN locked, with LT1Edit being the worst offender, and also the most poorly implemented, with absolutely no support. They used to have a mailing list where the users could talk to each other and help each other out. But that died last year, and when I asked carputing about it, they said "Oh yeah, the server died and we never got around to fixing it."
Yet another reason I am trying to convert to OBDI.

 

OBDII software is also far more expensive than OBDI software, and so far I see no advantage to running OBDII other than misfire detection. Tunercats is open to all OBD1 LT1 PCM's, LT1_Edit is not.

 

I agree. I just picked up a couple of OBDI PCMs on Fleabay. After I verify they are in good working order, I will mod them for the knock sensor, get the OBDI-OBDII cable, Tunercats, and a scanner package and be on my way. Woohoo! All for less than I paid for LT1Edit, much less my scanner package.
BTW, is there any OBDI scanner that will let me add my LM-1 analog output as an input, like the LSx packages do? If not, how is everyone doing it? If there are any specific recommendations, I will pay attention. Currently using Autotap, which is OBDII only, and has no easy way to add an analog input.

 

Sorry about that link koolaid. As far as whats got an analog input..i would like to know myself.

 

Only way I have added the LM1 Wideband data to the OBD1 input is using the AC pressure port, it works but not directly, you have to create custom calculation in Datamaster to convert the AC Pressure display to AFR, major side affect is you lose your AC function.

 

I posted on this before, however I believe I've actually figured out what causes it, and know what should fix it, but dont really understand it.

I see a similar thing happen, a slight increase in AFR between shifts last time I was at the track, by the beginning to the end I leaned out about 0.5-0.75 to 1 on the AFR scale, I also noticed my IAT numbers were increasing, so I tested it in the garage using a new and improved benchtop simulator (really just a 12v motor attached to an old opti with the PCM installed in the car).

My first try didnt look good for some reason, maybe cause I was holding a drill trying to heat and cool the IAT sensor, but the second try showed a big drop in Injector Pulse as IAT temps went up, but the pattern is a bit confusing: here's the results:

IAT------Injector Pulse (ms)
(Injector going down)
45.1-----8.58
89.6-----6.85

(Injector Going Up)
154------6.88
120------8.44

(Injector Going Down)
64.0-----8.53
96.4-----6.94


So, as IAT goes up, Injector Pulse Goes Down, and vise Versa, but not at the same points.

If you graph it, it looks like the injector pulse direction matches the change in direction of the pressure closer then it matches the actual switch points, if that makes sense (when IAT changes direction, so does the Injector Pulse width)

Also, changing the values in the "Inverse Temp Correction Counts vs MAT Temp" to a constant value, the Injector Pulse stays exactly the same.

One other thing I noticed, I have all fuel tables including VE set to the same value, PE also all 0'd out, and still I get a jump in Injector Pulse from 6.27ms to 7.42ms, just from twisting the throttle in and out of PE mode. ???? ? That doesnt make sense either unless there's a section I didnt know about.

using the 2 Bar tune I think magnifies this x2 in the higher and lower numbers, and is maybe why it's so noticable, so I started around normal driving temps in the "Inverse Temp..." section and removed up to 2x at the highest and lower numbers, and blended the numbers in between, centering around "normal" summer temps which is around 80F since it seems to run very consistent there.

 

You can convert the VIN in lt1-edit files with a hex editor so not to get the display only message. Open a hex editor, google for a free one, open lt1 file of your VIN goto to address 00010e00. Then open the lt1 file you want to change and goto 10e00. Copy all the bytes from 10e00 thru 10e38 (the highlighted portion in the pic) then save the file. Lt1 edit will work with the new file. You can also edit tunercat files the location is 00e00 thru 00e38

 

Hello, I just got done reading the full sticky- lots of great info! I have a used SC kit coming and I have a couple questions.

1. Where (part number) can you get a $20 2 bar map sensor? Budget is tight and I see they are like $50-60.
2. When you run SD mode, I'm noticing you don't even have the MAF plumbed in. Will leaving the MAF sensor wire unplugged throw a check engine light?
3. I'm going to be running my stock 24# injectors with FMU/255 walboro. Should I set the inj value in tunercats to 15 (half).... maybe 12??
4. I plan on leaving o2 sensors plugged in, should work right?


Thanks,
James

 

Thanks,
James[/QUOTE]


1. Where (part number) can you get a $20 2 bar map sensor? Budget is tight and I see they are like $50-60. I got mine from ebay, searched for Sunbird 2 Bar sensor, should have three wires and have teh same shape, one of the connector stubs has a different shape to avoid using a 2bar on a 1bar setup but just push extra hard and it will go in.
2. When you run SD mode, I'm noticing you don't even have the MAF plumbed in. Will leaving the MAF sensor wire unplugged throw a check engine light? Yes you will throw a code but you can disable the MAF code in LT1 Edit or Tunercats
3. I'm going to be running my stock 24# injectors with FMU/255 walboro. Should I set the inj value in tunercats to 15 (half).... maybe 12?? There is no advantage running the 2bar sensor with small injectors, I kid you not, 0 advantage since that is the whole point. The problem is you are maxing the injectors so there's no advantage of using the 2bar when the injectors are maxed. Do yourself a huge favor and buy larger injectors preferably ones someone else used in this discussion so you know they work and you will only have to tune those in one time vs two times after you realize you need bigger injectors anyway like I did!
4. I plan on leaving o2 sensors plugged in, should work right? Yes, 02's work fine unless you have a larger cam which those of us that have a manual trans with a large cam notice strange leaning surges after the PCM has time to try to control fuel but this happens to standard 1Bar users with the "wrong" cam too , so it all depends on your cam specs and transmission, and of course your tolerance level.


One last item I noticed over the summer at the track (only place I can romp on it over and over for long periods of time - AKA 12 seconds) is the stock IAT settings are taking too much fuel out in the upper IAT temp readings which starts to lean out the AFR too much. I never noticed before since I have never been able to hold WOT so long and get IAT temps so high. I did some initial tests and found lowering the IAT numbers in pretty much all columns in the extreme uppper and lower temps should take care of it but until I get back to the track this summer I cant confirm it.