Open loop, closed loop temperature?

2000tjguy said:
Makes sense, maybe I should talk to someone who tunes these I’m sure they would probably have my answer I guess.
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I would check with someone that tunes these pcm’s they may be able to give you some information. I don’t think it is 100% temp related but if you are looking for minimum temp they may be able to shed some light on that number.
 
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bluescapegoat said:
There is a minimum temp in the PCM to trigger closed loop, yes. Don't know what it is off the top of my head but I can try to remember to check when I get home.

I've manually increased that number to the moon in the past to facilitate tuning/troubleshooting in open loop.

There are others factors as well, like a time delay and I believe that may be based on OAT but I'm not sure either, from memory.
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2000tjguy said:
Hey! Someone actually read what I was asking lol… I appreciate your response!
I’m going to go ahead and do some calling around and send a few emails to tuners to see what they have to say. If I can manage to hit closed loop with a 180* stat I’ll go that route.
Thanks again!
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So there is a closed loop enable temperature like I recalled, but the default temperature is pretty much irrelevant. -40°. I suppose for the purpose I used it before, forcing open loop, is probably the only time it'd be of any use.

On the '04 stock tune I have pulled (97-04 JTEC+) there's a 176 second delay. On the '05 stock tune (05-06 NGC) The time delay is based on startup coolant temp, with an additional provision for ECT Rear o2 sensor specifically, which is interesting. No idea what that's about. I'm not a tuner. There are also warmup enrichment tables.

Anyway, just to echo what others have said, there's something wrong with your cooling system if you're overheating, and a lower thermostat does nothing for you.

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I believe the HPTuner software, VCM Suite, is free to download. And tunes can be downloaded off the repository on their website once you have an account. Anybody can look at this stuff. You just need to pay to actually use the software to write to pcm
 
2000tjguy said:
Trying to figure out at what coolant temp we go from open loop to closed loop?
Been reading anywhere from 165*-190*.
I have been testing year to year on different thermostats… ya ya 195 is the only way to be…
So far I have tested 195* and 160*, only difference has been with the 195 I did experience over heating from time to time and with the 160* I’m running 160*-170ish.
Over heating happened in 107* outside temps, with the 160* I ran up to 170* in 105* outside temps.
Keep in mind the only time my rig sees the street is a short trip to close trails, no more than 10mins of street time with most times its on a trailer right up to the parking area/trail head… the over heating happened on a trail not the street.
I’m tempted to move up to a 180* stat if it will get me into closed loop to see if there is a difference in the way it runs at all. Not exactly looking at moving back to a 195* and possibly experience overheating again.
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JTEC Closed Loop

There are two types of closed loop:

Short-Term: Immediate corrections are made to the pulse-width in response to the oxygen sensor, but these values are not stored in memory. The parameters are:

• Engine temperature exceeds 30-35° F
• O2 sensor is switching
• All timers have timed out, following the START to RUN transfer (the timer
lengths vary, based upon engine temperature at key-on)

Long-Term: Values are stored in non-volatile memory based on short-term corrective values. The parameters are:

• Full Operating Temperature
• All timers have expired

Note: These times and temperatures may vary for each engine package.


The values stored in long-term adaptive memory are used for all operating conditions, including open loop so it’s very unlikely you will see any immediate difference in operation when switching from open to closed loop unless you have reset the PCM.
 
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2000tjguy said:
Stat is the only thing changed… this winter while going to a new radiator I will be doing water pump, fan clutch, and another stat as well along with ditching the radiator tras cooler and going to a straight aux cooler.
I get it the factory put a 195* stat in I get it but my jeep is no where near stock form and I don’t exactly do easy trails and of course because of all of that I’m putting way more strain on everything thing including the cooling system. I have not had a chance to test trans temps as of yet but I’m thinking running the radiator trans cooler isn’t helping either and actually making things run warmer.
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I chased a overheating issue on my TJ for 2 years. Mine isn't stock either BTW. I had a 5.2 V-8 swapped in. It started overheating so I did the normal things like water pump & thermostat. Did tons of compression checks to see if I had a blown head gasket which I didn't. I took the brass radiator out and installed a aluminum radiator that was also thicker. It helped some but it was still running warm.

My point here is that IMO you're looking in all the wrong places. If your cooling system is up to par then there has to be something else wrong.
 
bluescapegoat said:
So there is a closed loop enable temperature like I recalled, but the default temperature is pretty much irrelevant. -40°. I suppose for the purpose I used it before, forcing open loop, is probably the only time it'd be of any use.

On the '04 stock tune I have pulled (97-04 JTEC+) there's a 176 second delay. On the '05 stock tune (05-06 NGC) The time delay is based on startup coolant temp, with an additional provision for ECT Rear o2 sensor specifically, which is interesting. No idea what that's about. I'm not a tuner. There are also warmup enrichment tables.

Anyway, just to echo what others have said, there's something wrong with your cooling system if you're overheating, and a lower thermostat does nothing for you.

04
View attachment 493828

05
View attachment 493830


I believe the HPTuner software, VCM Suite, is free to download. And tunes can be downloaded off the repository on their website once you have an account. Anybody can look at this stuff. You just need to pay to actually use the software to write to pcm
Click to expand...

Awesome! All good information!
To touch on the overheating… it happened twice with the 195* stat so I switched to the 160* stat, since the switch I have been no where near overheating. I have only seen roughly 170* in the same exact situations I was seeing the over heating with the 195* stat.
That’s the reason I was wondering if a 180* stat would be my best bet cause I was un sure of what temp it would go into closed loop.
I figured with a 180* stat I would be hovering 180*-190*.
In all honesty I don’t even know why I’m on a quest to get into closed loop if it isn’t now cause it runs fine the way it is, maybe it cause I like doing random crap to see the out come lol
 
Wildman said:
I chased a overheating issue on my TJ for 2 years. Mine isn't stock either BTW. I had a 5.2 V-8 swapped in. It started overheating so I did the normal things like water pump & thermostat. Did tons of compression checks to see if I had a blown head gasket which I didn't. I took the brass radiator out and installed a aluminum radiator that was also thicker. It helped some but it was still running warm.

My point here is that IMO you're looking in all the wrong places. If your cooling system is up to par then there has to be something else wrong.
Click to expand...

This winter is getting the entire cooling system rebuild… water pump, aluminum radiator, pulling the trans oil out of the radiator and going straight to a aux cooler and a new fan clutch.
The only place I'm looking is a different temp stat, seems a lot of people are confusing my open/closed loop talk with my overheating issue which I’m not all.
 
2000tjguy said:
This winter is getting the entire cooling system rebuild… water pump, aluminum radiator, pulling the trans oil out of the radiator and going straight to a aux cooler and a new fan clutch.
The only place I'm looking is a different temp stat, seems a lot of people are confusing my open/closed loop talk with my overheating issue which I’m not all.
Click to expand...

Well it seems you got your answer to open/closed loop.
 
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2000tjguy said:
This winter is getting the entire cooling system rebuild… water pump, aluminum radiator, pulling the trans oil out of the radiator and going straight to a aux cooler and a new fan clutch.
Click to expand...

Regarding your overhaul plans, my advice is to look at your cooling system before you start changing other things. Removing the transmission fluid from the equation is a bandaid at best (kinda like blaming a steering stabilizer for death wobble). Fix the root cause.

I'm running 6-7 psi of boost with an auto trans and I'm good to go crawling, trailing, pulling a trailer, and daily driving with 35 inch tires. This includes when my transmission was in 4hi at 222*f sustained in Moab and local mountain trails (bc 4low was too slow). My cooling system was at or around 200-208* in these conditions.

Note: I keep close attention to my ECTs, transmission temps, and IATs using gauges on my A-pillar, so those numbers are accurate.

When I had cooling issues this past summer (when ambient temps Tucson and PHX were 117*+), it was due to debris in my cooling system causing the radiator to be restricted. I flushed and back-flushed the system and have been good to go ever since (using G05 coolant).

—

Some folks have good luck with aluminum radiators and others have issues with them improperly cooling or cracking. I went with Mopar for the cooling system because my rig arrived with an overheating issue using an aluminum radiator and e-fan, and I didn't want to risk seeing the temp gauge read 260+ again. Do as you wish with that info. Best of luck.
 
If you learn one thing here, please learn that a thermostat that is operating as designed has NO ability to cause or help an engine run even 1 degree cooler in warm or hot conditions. Really. Learn that the thermostat has just two jobs and two abilities: 1) to help the engine warm up faster and 2) to help set a minimum operating temperature in cold conditions. If it's hot out the engine will run at the same temperature whether it's running a 165, 180, or a 195 degree thermostat. Really.

If you need an engine to run cooler in hot conditions look at the radiator, fan shroud, fan clutch or water pump.
 
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2000tjguy said:
Trying to figure out at what coolant temp we go from open loop to closed loop?
Been reading anywhere from 165*-190*.
Click to expand...

If you run a 195*, then you are guaranteed to reach CL and you can get on with your life once you fix your overheat issue.

2000tjguy said:
I have been testing year to year on different thermostats… ya ya 195 is the only way to be…
So far I have tested 195* and 160*, only difference has been with the 195 I did experience over heating from time to time and with the 160* I’m running 160*-170ish.
Click to expand...

Have you considered running a different 195*....that's what I would have done. If that doesn't work, then you need to pay attention to the circumstances that caused the overheating issue as that can help tell you what part is likely faulty.

2000tjguy said:
Over heating happened in 107* outside temps, with the 160* I ran up to 170* in 105* outside temps.
Keep in mind the only time my rig sees the street is a short trip to close trails, no more than 10mins of street time with most times its on a trailer right up to the parking area/trail head… the over heating happened on a trail not the street.
Click to expand...

This isn't a 195* thermostat problem, and if you knew how this all worked you'd know this as well. For example, don't mistake a stuck 195* for a properly working 195* thermostat. And don't forget there's items in the cooling system that limit how high the temps will get.

2000tjguy said:
I’m tempted to move up to a 180* stat if it will get me into closed loop to see if there is a difference in the way it runs at all. Not exactly looking at moving back to a 195* and possibly experience overheating again.
Click to expand...

You have invited the schooling you are getting due to your misguided statements about how to address an overheat issue. If you want help, it would be wise to keep an open mind to those who freely give their time to help educate you.

You want to know if you can achieve CL with a 180* because you don't want to run a 195* because you had overheat issues. This exposes that you are looking in the wrong direction to properly tackle the issue.

I fear you may be wasting everyone's time. Fix your cooling system and then you won't need to worry about when the the system goes into CL.
 
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MikeE024 said:
Regarding your overhaul plans, my advice is to look at your cooling system before you start changing other things. Removing the transmission fluid from the equation is a bandaid at best (kinda like blaming a steering stabilizer for death wobble). Fix the root cause.

I'm running 6-7 psi of boost with an auto trans and I'm good to go crawling, trailing, pulling a trailer, and daily driving with 35 inch tires. This includes when my transmission was in 4hi at 222*f sustained in Moab and local mountain trails (bc 4low was too slow). My cooling system was at or around 200-208* in these conditions.

Note: I keep close attention to my ECTs, transmission temps, and IATs using gauges on my A-pillar, so those numbers are accurate.

When I had cooling issues this past summer (when ambient temps Tucson and PHX were 117*+), it was due to debris in my cooling system causing the radiator to be restricted. I flushed and back-flushed the system and have been good to go ever since (using G05 coolant).

—

Some folks have good luck with aluminum radiators and others have issues with them improperly cooling or cracking. I went with Mopar for the cooling system because my rig arrived with an overheating issue using an aluminum radiator and e-fan, and I didn't want to risk seeing the temp gauge read 260+ again. Do as you wish with that info. Best of luck.
Click to expand...

Everything is getting replaced and the system will be flushed so there is no reason it should overheat.
Pulling the trans fluid out of the equation is just another step in the process, no reason to add extra heat from the trans fluid to the cooling system plus a aux cooler will cool the trans just fine. There is a reason most people use separate coolers in the world of wheeling I do.
Crawling is a vague term… some people consider booping around an easy trail crawling and then there are other people that consider pictured crawling. To say the least when I get together with my buggy buddies I put my jeep through a lot more than just the normal “crawling”.

IMG_8636.jpeg
 
2000tjguy said:
Everything is getting replaced and the system will be flushed so there is no reason it should overheat.
Pulling the trans fluid out of the equation is just another step in the process, no reason to add extra heat from the trans fluid to the cooling system plus a aux cooler will cool the trans just fine. There is a reason most people use separate coolers in the world of wheeling I do.
Crawling is a vague term… some people consider booping around an easy trail crawling and then there are other people that consider pictured crawling. To say the least when I get together with my buggy buddies I put my jeep through a lot more than just the normal “crawling”.

View attachment 493967
Click to expand...

Pictures of your friend's buggies don't change how your system operates. You should be able to climb/crawl all day locked in 4low without having any issues. Guys in here have beat on their vehicles in the heat of summer in Johnson Valley, AZ, UT, and CO without any issues. Super awesome photo though :)
 
MikeE024 said:
If you run a 195*, then you are guaranteed to reach CL and you can get on with your life once you fix your overheat issue.



Have you considered running a different 195*....that's what I would have done. If that doesn't work, then you need to pay attention to the circumstances that caused the overheating issue as that can help tell you what part is likely faulty.



This isn't a 195* thermostat problem, and if you knew how this all worked you'd know this as well. For example, don't mistake a stuck 195* for a properly working 195* thermostat. And don't forget there's items in the cooling system that limit how high the temps will get.



You have invited the schooling you are getting due to your misguided statements about how to address an overheat issue. If you want help, it would be wise to keep an open mind to those who freely give their time to help educate you.

You want to know if you can achieve CL with a 180* because you don't want to run a 195* because you had overheat issues. This exposes that you are looking in the wrong direction to properly tackle the issue.

I fear you may be wasting everyone's time. Fix your cooling system and then you won't need to worry about when the the system goes into CL.
Click to expand...

Guess I wasted a lot of your time by making you type out that long winded response to everything I was having an open mind about.
Sorry for wasting your time sir I will put a 195* stat in since being actually open minded is a no no on this forum I guess.
 
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