Anyone know the temp when EEC switched from Open Loop to closed Loop?

Chythar · Apr 5, 2005

I just put in a Fluidyne radiator and 180 degree thermostat. Engine runs WAY cooler now. Problem now is on the freeway. The radiator is TOO efficient, it's cooling the temp down past "N". My code reader says the temp's riding at about 176 degrees (80 Celsius) on the freeway, which is about right. I want to double-check on the way home, tho.

I'm concerned that the temp's gonna drop too low, and put me back in open loop. If it does, I'm gonna have to put in a 195 degree thermostat.

I've heard that a 165 degree thermostat is too cold. But how hot is hot enough? 170? 175? Anyone know the temp threshold in the computer?

Thanks.

black945.0 · Apr 5, 2005

what is so bad about open loop so u wont have as much fuel control and ur computer wont take in o2 readings i still think it will go into it tho cause it also looks at o2 sensor oscilation and tps and a few other things so it might take a few seconds longer but u cant really tell till u hook up a scanner and watch it go and then drive or let it warm up then drive it after it is in closed loop i dont think it will go out but i am not sure

Zero Signal · Apr 5, 2005

Don't worry about it, it's plenty warm for CL. I don't remember the value, I haven't played with the TwEECer in awhile, but I want to say it was pretty low, 160° or less. Still, going into OL isn't going to hurt anything. Alot of guys with their own tunes, force OL anyway.

black945.0 · Apr 5, 2005

i agree i cant think of anything else than o2 sensor input to the pcm i am sure there are more but nothing stands out to hurt or cause driving problems

95BlackTan50 · Apr 5, 2005

I don't think the computer will force you into open loop if the temperature drops. That might depend on the processor/strategy of your EEC. What year is your car?

With my 95, It goes into closed loop about 60 seconds after startup and the temperature is below 100 degrees. At 120 degrees it switches from a cold fuel table to the stabilized fuel table. I don't think you should have a problem.

Chythar · Apr 5, 2005

The 'stang is a 94; I believe the same computers are used for both years.

I honestly don't know much about what the computers do, that's why I posted. If the temp threshold is that low, I won't worry about it. Thanks for the replies.

I also seem to remember reading somewhere that some engine parts are designed to work in a set temperature range. Anyone know if there's any truth to that?

black945.0 · Apr 5, 2005

of corse they are but they wont be hindered too much at least to my knowledge

slvrbullit302 · Apr 5, 2005

I thought the computer went into OL or CL based off the temp of the O2 sensors. Just wandering if I am wrong for thinking that.

WhiteDevil · Apr 5, 2005

slvrbullit302 said:
I thought the computer went into OL or CL based off the temp of the O2 sensors. Just wandering if I am wrong for thinking that.

When the car has been on for a certain amount of time then it goes into closed loop. I dont remember if there is a certain temp i think its a time thing. Also you are only in closed loop when you are on the gas. When you let off like between shifts or while coasting you go into open loop. Open loop takes its values off set tables, while closed loop targets a 14.64 A/F ratio.

slvrbullit302 · Apr 5, 2005

Ah thanks for the info.

final5-0 · Apr 5, 2005

If you want a specific answer it would be helpful to know if we are talking about a t4m0 GTor a j4j1 Cobra pcm.

I had to come back and include the auto pcm ...... w something or other as I don't remember what its called, lol.

Later
Grady

S/CBlack95GT · Apr 5, 2005

You will be fine with the 180. The computer mostly reads from the O2s, which must reach 600 degrees.

mo_dingo · Apr 5, 2005

Your gas mileage and emmisions output will suffer if you run it at open loop. How much, IDK.

The O2 sensors are heated O2's, which means it uses electric current to heat the O2's. The computer goes to closed loop much before the car reaches full operating temperature.
Scott

94-302-vert · Apr 6, 2005

My MIL light comes on only when my 180' Stat opens. When I pull the codes I always get the CTS sensor is bad. i already replaced it and verified the origina was OK. When I do the WP in a few weeks I am going to try going back to a higher temp t-stat as I am fairly confident this is the major thing that is causing my CE light.

Chris

WhiteDevil · Apr 6, 2005

94-302-vert said:
My MIL light comes on only when my 180' Stat opens. When I pull the codes I always get the CTS sensor is bad. i already replaced it and verified the origina was OK. When I do the WP in a few weeks I am going to try going back to a higher temp t-stat as I am fairly confident this is the major thing that is causing my CE light.

Chris

There is about 90% of people on this site that run 180 degree stats and have never seen a check engine light from it. most likely there is really something wrong with the Coolant temp sensor or the conection or wireing. There is no reason the car would throw a code because its only at 180 degrees.

Chythar · Apr 6, 2005

94-302-vert said:
My MIL light comes on only when my 180' Stat opens. When I pull the codes I always get the CTS sensor is bad. i already replaced it and verified the origina was OK. When I do the WP in a few weeks I am going to try going back to a higher temp t-stat as I am fairly confident this is the major thing that is causing my CE light.

Chris

I'd read this thread (it survived the crash, fortunately):

http://forums.stangnet.com/showthread.php?t=470203&highlight=cts+ect

Best to check both the CTS and ECT. The CTS only feeds the dash guage; the computer reads the ECT. I could see the ECT tripping a CE light, but not the CTS.

tmoss · Apr 6, 2005

I have TwEECer graphs that show the EEC going into closed at various temps, but not below ~170°.

Chythar · Apr 6, 2005

tmoss said:
I have TwEECer graphs that show the EEC going into closed at various temps, but not below ~170°.

So....you're saying that the computer likely won't go into closed loop until the temps hit ~170°? Do you know if the computer will put it back into open loop if the temp drops below that?

I checked my temps on the way home last night. City driving, temps are around 175°-185°. If I hit some bad traffic it can jump up to 203° before the fan kicks in, then it drops fast. Freeway driving is another matter. Driving at 65 or higher, the temp dropped to 163°. This was my original concern.

How could I tell if the EEC is switching from open loop to closed loop? Any particular sensor reading I can check?

WhiteDevil · Apr 6, 2005

Chythar said:
So....you're saying that the computer likely won't go into closed loop until the temps hit ~170°? Do you know if the computer will put it back into open loop if the temp drops below that?

I checked my temps on the way home last night. City driving, temps are around 175°-185°. If I hit some bad traffic it can jump up to 203° before the fan kicks in, then it drops fast. Freeway driving is another matter. Driving at 65 or higher, the temp dropped to 163°. This was my original concern.

How could I tell if the EEC is switching from open loop to closed loop? Any particular sensor reading I can check?

Did you drill your stat or something? Because below 180 degrees it should close and your engine should heat up. I have a Fluidyne Radiator, 180 stat, and my fan temps set even lower with my tweecer and im always between 182 and 190 on my autometer gauge and my tweecer reading the ECT. I dont see how you could be that cold if the coolant isnt flowing(closed thermostat).

final5-0 · Apr 6, 2005

Chythar said:
So....you're saying that the computer likely won't go into closed loop until the temps hit ~170°? Do you know if the computer will put it back into open loop if the temp drops below that?

I checked my temps on the way home last night. City driving, temps are around 175°-185°. If I hit some bad traffic it can jump up to 203° before the fan kicks in, then it drops fast. Freeway driving is another matter. Driving at 65 or higher, the temp dropped to 163°. This was my original concern.

How could I tell if the EEC is switching from open loop to closed loop? Any particular sensor reading I can check?

I don't know how you could tell other than using some diagnostic or tuner interface.

I'll give you a short list of ol & cl conditions speaking kinda sorta in a rule of thumb point of view to give you some idea.

Several things could cause you to switch back and forth between cl & ol when at operating temps.

For our pcm's the MAIN thing that controls that switching is the amount of load.

If you are crusing at a steady speed or even picking up speed with very very light throttle you most likely will be in cl cause the load is light during those conditions.

If you take off from a stop with say something over 1/4 to 1/3 throttle then you most likely will be in ol cause load will be at about mid range. If you do this same thing but with say something less than 1/4 throttle and you pick up speed very slowly you most likely will be in cl due to light load.

Wot conditions will be ol cause of high load.

Later
Grady

Anyone know the temp when EEC switched from Open Loop to closed Loop?

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