What are, or where can I find the perimeters that a stock chip will go into closed loop?

and Thanks -JRC-

 

Iam not sure if this is what your looking for, But i think it is... in order for closed loop to occur the oxygen sensor should reach above 600 degree's "F" and start switching from lean to rich. If these conditions aren't met the vehicle will stay in open loop at a set control operation. Some vechiles need to be off idle (driven) to maintain closed loop control. A good method used to make a vechile go into closed loop is rev the engine to approx 2000 RPM for a few minutes to get the Oxygen sensors nice and hot. Hope thats what your looking for????

 

If I understand you correctly, you are looking for the typical "data values" that the scanner will read when a stock engine is in closed loop.

For the 1990 L-98 they are listed on page 6E3-A-12 of the factory (Helms) Service Manual.

I assume that for other years the info is similarly located.

(if you need a copy of the page, e-mail me)

 

This is the info that I'm looking for. Is water temp a factor of closed loop? What would be the lowest temp thermostat possible without changing the chip?

 

the thermostat won't change your temperature range (operating temp)- it WILL however increase the time necessary to *reach* operating temps, especially in cooler weather.

All the T-stat does is open coolant flow to the radiator, so to change operating temps you'll want to cause the fan to turn on sooner or increase the efficiency of the cooling system (water wetter, increased % of water, clean out the radiator, etc). And none of these changes should make your car run so cool as to negate closed loop, because the O2 sensor is heated by exhaust gases that will stay relatively hot regardless of other engine variables. Coolant and oil temps have desired ranges to increase combustion efficiency and whatnot... but your O2 sensor should still be plenty hot.

I think there is also a timer setting for closed loop... but I'm not entirely sure?

 

So the chip change for a 160 T-stat is for switching "ON" the fan at the lower setting. Not for establishing a "normal operating temp".

Veddy interesting..... Thanks, -JRC-

 

In the computer for my 92 there are values for "minimum coolant temp for closed loop"

There is both a cold MAT value and a hot MAT value. This is basically used to say ok, if it's hot outside go closed loop after it reaches x temperature, if it's cold outside wait until you get to some higher temperature.

At this point the car will attempt to go closed loop, if the O2 sensor is warm enough it will work just fine. If the O2 sensor is too cold it probably won't go, or it will but the O2 feedback will be bogus and the car will run for ****.

In the stock program these numbers are pretty warm, they are probably warmer on my 92 than on the later cars, this would give the non-heated O2's time to warm up.

On a stock 92 the warm value is about 91 degrees, the cold value is about 140.

With my heated O2 sensors I have tweaked these values a little bit. I left the hot value alone but set the cold value for 120. My logic was to get the car into closed loop faster for better fuel economy. I drove it all last winter like that and it worked perfectly. I have an A/F ratio guage in my car and you can watch it happen. The A/F will basically sit dead in the middle when you start the car. The instant it hits 119 degrees the A/F starts bouncing back and forth like it's supposed to. Of course if it's hot outside this doesn't take very long at all, the coolant gets to 90 degrees pretty quickly.

So to answer the thermostat question, so long as the car is allowed to get above 140 degrees it'll still go closed loop. Since a 160 thermostat is going to set the minimum operating temperature at 160 degrees, you'll be fine.

 

That statement isn't entirely accurate. I know where you're coming from though so let me see if I can clarify it a little bit to avoid confusion.

The radiator in the car is overly efficient, it will remove a lot more heat from the engine that is required to keep the engine running efficiently, in fact it can remove too much. The thermostat is there to set the MINIMUM temperature.

Take two identical cars but change only the thermostat. They will both take the same amount of time to get to 160 degrees because neither thermostat is open. Once the thermostat opens the 160 will heat up a little bit slower because water is already circulating through the radiator, while the 180 hasn't opened yet. Eventually though if allowed to idle both engines will reach the temperature where the fans kick on, they will both stabilize into operating in the same range because the fans are programed to come on and off at certain temps. So either car will fluctuate in this range. Now that's all well and good so long as you're sitting still!

Start moving and it's a different story. Assume both cars start traveling at 60 mph in the same gear, etc, etc. The fans can now not control the temperature, in fact they don't even come on if you're moving about 35 mph. The only thing controlling temperature is the air going into the radiator and the thermostat. Remember the radiator is overly efficient, it will easily drop the coolant temperature of both cars to 180 degrees at 60 mph. At this point the 180 thermostat starts to close. This restricts water flow from the radiator and limits the engine from getting any cooler. As it heats back up it will open, etc. The engine will stabilize at a temperature AROUND 180, although it's usually higher for various reasons. Now the 160 is still allowing coolant flow from the radiator. It's temp will continue to drop until it reached close to 160, at which point it will stabilize.

So, as long as there is an excess of air moving through the radiator the car with the 160 will always run cooler. If both cars are sitting still, temperature will ultimately be determined by the cooling fans and the values programmed into the computer. Will the car with the 160 take longer to heat up to 230 degrees while sitting still, probably but not a whole lot longer. Remember it starts circulating more coolant earlier, but by the time the 180 starts, it's already hotter. Ultimately it's gonna be a matter of a minute or two, not a profound difference.

This is also the reason why if you install a 160 thermostat, you want to adjust your fan settings. If you don't the engine will get just as hot sitting in traffic, which is where they overheat anyway.