Open loop, closed loop temperature?

[2000tjguy]

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.

 

[Jerry Bransford]

A different/lower temperature thermostat has no (!) ability to prevent an engine from overheating. If that little cheap device, the thermostat, could limit upper engine temperatures we wouldn't need our big radiators.

 

[2000tjguy]

A different temperature thermostat has no (!) ability to prevent an engine from overheating. If that little cheap device, the thermostat, could limit upper engine temperatures we wouldn't need our big radiators.

Just going off of my experience… either way I’m just wondering where closed loop starts, guess I could have left out all the other stuff and just asked the question I had.

 

[hear]

Just going off of my experience… either way I’m just wondering where closed loop starts, guess I could have left out all the other stuff and just asked the question I had.

as soon as you talked about overheating, I knew your actual question was never going to get answered.

 

[2000tjguy]

as soon as you talked about overheating, I knew your actual question was never going to get answered.

Probably should of never included all the other stuff I guess lol… I’ll just do my own testing since apparently if you don’t run a mopar radiator and a 195* stat then your wrong and nothing else matters just like the old Chevy truck forums if you swap a 350 tbi to a LS your stupid

 

[TJ4Jim]

Probably should of never included all the other stuff I guess lol… I’ll just do my own testing since apparently if you don’t run a mopar radiator and a 195* stat then your wrong and nothing else matters just like the old Chevy truck forums if you swap a 350 tbi to a LS your stupid

Really not like that, If you can get a Mopar rad then great otherwise get it going. I've been running an all aluminum for 9 years now without issues The thermostat at 195 deg is what the vehicle's design parameters are tuned to for optimal performance so anything else is basically pointless and most likely another issue involved. There are diehard originality nut jobs on every forum, a buddy of mine just completed a complete resto on a CJ7 and I could not talk him into using the Pertronix ignitor rather than plugs and points, but it's non original even though no mods req'd and nothing shows.

 

[Wildman]

Probably should of never included all the other stuff I guess lol… I’ll just do my own testing since apparently if you don’t run a mopar radiator and a 195* stat then your wrong and nothing else matters just like the old Chevy truck forums if you swap a 350 tbi to a LS your stupid

Jerry is correct that the thermostat has nothing to do with your rig overheating.

Since it sounds like you do not have a stock cooling system how about supplying some back information so maybe we can help you try to figure out what is happening.
When is it happening off-road? Is it happening as you're idling down the trail or when you're getting on it?

Mechanical fan? Electric fan? What type of radiator? Why do you think being in closed loop or open loop has any relationship to you overheating? IMO you should go back to a 195* thermostat since running those cooler ones aren't helping you any. Unless you have a tune to take advantage of running the cooler thermostat it's not doing anything.

 

[macleanflood]

I thought going from open loop to closed was triggered by the O2 sensors and a time delay in the PCM?

Or is there a whole cascading set of sensor checks? I suppose that list would be useful.

-Mac

 

[2000tjguy]

Jerry is correct that the thermostat has nothing to do with your rig overheating.

Since it sounds like you do not have a stock cooling system how about supplying some back information so maybe we can help you try to figure out what is happening.
When is it happening off-road? Is it happening as you're idling down the trail or when you're getting on it?

Mechanical fan? Electric fan? What type of radiator? Why do you think being in closed loop or open loop has any relationship to you overheating? IMO you should go back to a 195* thermostat since running those cooler ones aren't helping you any. Unless you have a tune to take advantage of running the cooler thermostat it's not doing anything.

Actually completely stock cooling system so that’s plays not a single roll in all of this. Only thing different is the stat.
Over heating happened while doing technical crawling, I don’t idle down dirt roads or hammer on it through the backroads.
I travel technical trails with buggies so none of the normal trail booping stuff.
I never said open loop or closed loop has anything at all to do with my over heating issue at all… I’m asking when the computer actually goes into closed loop.
The whole reason I’m asking at what temp these go into closed is cause when in closed loop they are most efficient and through my own testing I wanted to see if there was a difference.
I get it people want to be straight mopar are everything factory is the only way but there is also people that think outside of the box.

 

[2000tjguy]

I thought going from open loop to closed was triggered by the O2 sensors and a time delay in the PCM?

Or is there a whole cascading set of sensor checks? I suppose that list would be useful.

-Mac

From my reading temperature has a play in it too but who actually knows, main reason I was asking cause I have read all sorts of different things and honestly I have never see a concrete answer on any of this or seen a difference in my testing.

 

[NskLJ]

I thought going from open loop to closed was triggered by the O2 sensors and a time delay in the PCM?

Or is there a whole cascading set of sensor checks? I suppose that list would be useful.

-Mac

From what I’ve seen it seems to be a timer in the pcm. Once the o2’s are working then the computer can start using them to control fuel mixture.

 

[Wildman]

Actually completely stock cooling system so that’s plays not a single roll in all of this. Only thing different is the stat.
Over heating happened while doing technical crawling, I don’t idle down dirt roads or hammer on it through the backroads.
I travel technical trails with buggies so none of the normal trail booping stuff.
I never said open loop or closed loop has anything at all to do with my over heating issue at all… I’m asking when the computer actually goes into closed loop.
The whole reason I’m asking at what temp these go into closed is cause when in closed loop they are most efficient and through my own testing I wanted to see if there was a difference.
I get it people want to be straight mopar are everything factory is the only way but there is also people that think outside of the box.

OK if all stock then there is something else going on.

And NO I'm am not one of those who thinks it has to ONLY be Mopar to be right.

What else other than the thermostat have you changed in the cooling system if anything? When doing technical rock crawling it's putting a load on the engine. Is it the original water pump?

 

[2000tjguy]

Really not like that, If you can get a Mopar rad then great otherwise get it going. I've been running an all aluminum for 9 years now without issues The thermostat at 195 deg is what the vehicle's design parameters are tuned to for optimal performance so anything else is basically pointless and most likely another issue involved. There are diehard originality nut jobs on every forum, a buddy of mine just completed a complete resto on a CJ7 and I could not talk him into using the Pertronix ignitor rather than plugs and points, but it's non original even though no mods req'd and nothing shows.

100% get that and usually appreciate those types of people cause they usually respect me the same for thinking out of the box but heaven for bid I ask a simple question on here without getting hounded and saying I’m doing stuff wrong. If that was the case we would all be driving around in stock vehicles having no fun lol.
Btw I have a aluminum radiator sitting waiting to go in but that’s just between us, people will jump me saying it’s not going to cool right or it’s going to crack and leak.

 

[NskLJ]

From my reading temperature has a play in it too but who actually knows, main reason I was asking cause I have read all sorts of different things and honestly I have never see a concrete answer on any of this or seen a difference in my testing.

Yes, I believe temperature also plays a role in going into closed loop. Temperature will alter the time it takes to go in. You should be able to look at a scan tool and see the relationship. Your concrete answer would be, it’s in the programming of the pcm.

 

[2000tjguy]

OK if all stock then there is something else going on.

And NO I'm am not one of those who thinks it has to ONLY be Mopar to be right.

What else other than the thermostat have you changed in the cooling system if anything? When doing technical rock crawling it's putting a load on the engine. Is it the original water pump?

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.

 

[2000tjguy]

From what I’ve seen it seems to be a timer in the pcm. Once the o2’s are working then the computer can start using them to control fuel mixture.

Makes sense, maybe I should talk to someone who tunes these I’m sure they would probably have my answer I guess.

 

[TJ4Jim]

100% get that and usually appreciate those types of people cause they usually respect me the same for thinking out of the box but heaven for bid I ask a simple question on here without getting hounded and saying I’m doing stuff wrong. If that was the case we would all be driving around in stock vehicles having no fun lol.
Btw I have a aluminum radiator sitting waiting to go in but that’s just between us, people will jump me saying it’s not going to cool right or it’s going to crack and leak.

Yeah that gets old. I think the aluminum rads suffer badly on the QC side and not particularly performance. Lot of guys sucked into the lifetime warranty black hole.

 

[bluescapegoat]

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.

 

[2000tjguy]

Yeah that gets old. I think the aluminum rads suffer badly on the QC side and not particularly performance. Lot of guys sucked into the lifetime warranty black hole.

They get a bad wrap cause everyone goes off of what happens to the cheap China junk… there is a reason all of my buddies plus comp guys run aluminum coolers for every fluid. Just have to spend the right money or be good at tig and aluminum.

 

[2000tjguy]

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.

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!