pontiac

would it be possible to cheat some of the ECM sensors, so i could adjust between air/fuel ratios 12.6:1(power) and 15.4:1(economy)? it would be very nice-to-have feature if i could change car mode from cabin just by one click.

just wondering...

Vader

Pontiac,

It would be possible to retune the car for more performance, but if the original PROM is used in the ECM, many of the sensors would have to be adjusted or changed to create the conditions necessary to make a significant difference.

Some people have worked on developing a means of switching the PROMs in the ECM while running, but I have not seen an example of this myself. This would require a multi-line data switch, a remote PROM socket, and custom programmed PROM for performance use. I'm not sure how succesful a change "on the fly" would work, since teh ECM may have difficulty changing parameter without powering down and re-writing Block Learn Memory mode tables for the new PROM.

There are other ways to accomplish similar results, but require a lot of tuning.

------------------
Later,
Vader
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"I'm'a do Things My Way - It's My way or the Highway."
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pontiac

those things can be change by reprogramming prom, but i wasn't think about it my idea is to cheat computer by modifying some sensor input signal for ex. oxygen sensor voltage readings. letting computer to think that everything is ok, even you're running lean mixture.

any ideas where to start?

Vader

Pontiac,

Many of the engine fuel curve adjustments are dependent upon the Coolant Temperature Sensor (CTS) and Intake Air Temperature (IAT) sensor. Changing the coolant temperature, or just changine the CTS reading, will affect fuel enrichment, timing advance, and several other engine operating parameters.

This is a partial listing of CTS dependent parameters:

AUM/BUA Closed-Loop Operation Parameters
CTS < 14.7°C (58°F) for 75 seconds;
CTS >14.7° (58°F) and < 40.7° (105°F) for 51.4 seconds;
CTS >40.7°C (105°F) for 12.5 seconds;
O2 >0.699V & O2<1.99V for 10 seconds;

Coolant Temperature Sensor Related Parameters
BLM enabled between 50°C (122°F) and 140°C (284°F)
Cold spark advance disabled above 56°C (133°F)
Hot spark retard begins above 116°C (240°F)
Highway Mode spark advance > 59.8°C (140°F)
Knock sensor disabled below 66.5°C (152°F)
Power enrichment at base A/F ratios > 56°C (133°F)
Target IAC idle RPM >80°C (176°F)
IAC multiplier at 1.0 (base) > 32°C (90°F)
Knock Control enabled > 67°C (153°F)
EGR Duty-cycle enabled at 56°C (133°F)
EGR Duty-cycle at MAX >80°C (176°F)
TCC lockup enabled >50°C (122°F)
SHIFT light enabled >50°C (122°F)
Diagnostic communication enabled at 70°C (157°F)
DTC 43 enabled > 90°C (194°F)
Cooling fan #1 enabled at 107°C (226°F)
Cooling fan #1 off at 104.7°C (220.5°F)
Cooling fan #2 enabled at 115.2°C (239.5°F)
Cooling fan #2 off at 110°C (230°F)
Cooling fan duty cycle at 100% at 80°C (176°F)
Acceleration enrichment multiplier at 1.00 below 80° C (176°F)
Acceleration enrichment multiplier at 0.75 above 80° C (176°F)
Acceleration enrichment multiplier at 0.50 above 104°C (220°F)
Acceleration enrichment decay factor at 25% below 80° C (176°F)
Acceleration enrichment decay factor at 40% above 80° C (176°F)
Acceleration enrichment decay factor at 50% above 104° C (220°F)
Acceleration enrichment decay factor at 60% above 128° C (262°F)
Fuel limiting factor timer at 217 counts below 80° C (176°F)
Fuel limiting factor timer at 169 counts above 80° C (176°F)
Code 13 (oxygen sensor fault) enabled above 70°C (157°F)
Code 14 (CTS high fault) enabled above 130°C (266°F)
Code 32 (EGR fault) enabled above 30.5°C (87°F)
EVAP canister purge enabled above 70.3°C (158.5°F)
Hot closed-loop timer enabled above 70.3°C (158.5°F)
Rich/Lean O2 offest at 16 counts between 20°C (68°F) and 92°C (197.5°F)
A/C clutch disabled above 150°C (302°F)

Miscellaneous
25.3° maximum allowable knock retard when not in WOT

And a listing of CTS/IAT sensor readings at various temperatures:



------------------
Later,
Vader
------------------
"I'm'a do Things My Way - It's My way or the Highway."
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pontiac

WOW

where did you got all the information of related parametres? any URLs?

i got your point. cheating computer in one place may cause problems elsewhere (connecting CTS wire to constant 185 Ohm resistor is good way to boil engine since computer never turn on the fans).

too bad begging PROMs is not allowed here i'd love to have arap.bin PROM with highway mode tweaks...

-p