Corvette C5 1999: Odd GM Original Tune -- Runs only in OL with this

[suojasto]

Backround;
My MY 1999 Corvette C5 A4 has been originally manufatured as Middle-East Export version in 12/1998. Since that until mid-2012 it has been running in United Arab Emirates and I exported the car from Dubai to Finland 9/2012. Ever since that I have been making changes and tunes for the car. Main mods are (LS6 heads, GMPP Hot cam, BBK intake and larger TB, LS7 Exhaust w Borla Atak in rear, recently also HD Gearbox w Alto/Raybestos parts/Beast Sunshell due tor breakdown of gearbox, Vigilante 2600 Turbine, 3.90 Diff)

It runs quite OK- around 150 different tune versions done by myself - however few things are causing question marks ?

1. When I bought the car 2011 -- no Cats , neither any single O2 sensor was in place. At that time I was a beginner w tunes -- so what we did: We installed CATs (Flowmaster) and all 4x O2 sensors + developed a normal tune with this --- everything seemed to work quite OK -- car moves to CL Fueling after typically 5-10 minutes. I did not bother myself very much with this topic -- I just thought that somebody wanted to have car in OL all the time and that has been a purposeful tune in Dubai by "Some real expert".

2. I have had few problems with the tuning however --- LTFT has not been working at all, DFCO has not been working and max fuel increment w STFT has been +- 6.3%. OK when the tune is good this does not bother much -- however I have been worried a bit that I may end to too Lean condition sometimes. My fellow tuning friend from Finland has been proposing to me that pls Reflash the whole PCM with original factory tune and then start from clean table --- there may be someone in history who has used other tools (Efi or LSEdit) to "Tune" the car and that may have impact on odd behaviour for my Tune.

3. On Monday we finally reflashed PCM - look what we got --- Flashed Tune attached.
- Car will never go into Closed Loop as Closed Loop entry criteria is 141 Celsius. (284F).
- This tune was exactly the same as was in the car in 2011 when I bought the car.

We used official GM tools for reflashing --
Procedure was: 1) diagnose car with Tech2, 2) download from server the correct SW based on Tech diagnose and reflash SW to Tech2, 3) Install reflash from Tech2 to Car using OBDII, 4) VATS relink with Tech 2.



read from car after reflash orig.hpt


MAIN QUESTION:

Did GM have a LS1 version for some markets which was only running with OL mode ? No Cats, neither O2 sensors ?



wbr
Marko

[MikeOD]

I believe some cars intended to countries with leaded fuel were shipped with no O2 sensors and setup to always run in open loop...as leaded fuel kills O2 sensors fast. I haven't seen the cars in person, but I've seen some official GM calibrations that do essentially what you described.

If you have unleaded fuel in Finland, and you have the O2 sensors wired up to match a 1999 C5 Corvette sold in the US, then you could probably use a different VIN number to flash in a USA calibration, and you'd have what you need...you could also probably download a stock 1999 C5 file from the HPTuners site and do a "Write Entire", but it will cost you more credits, and then when it finishes, you'll need to change the VIN back to match your car.