Consolidated Operating Temperature Thread (4 Viewers)

[RavenTai]

And RT, it's perfectly fine for the Tstat to be fully open, that's taken into account in sizing the rad.

I am not sure I follow,

if the T-stat is already fully opened and more btu's are made in the engine then there will be no more cooling left to remove these excess BTU's, so the temperature climbs,

as the temperature of the coolant climbs there is a higher diffrence between ambuent and radiator temps so it can stabilize but it is at the expense of engine temperature (CHT)

when the temp get up higher I get pingning on acceleration, earlier in spring waether it was just with regular gas, now that it is hot I am getting it with premium also, I do not like it, I would much prefer that it stayed below 200. and the temps did not swing so violently.

 

[cary]

when the temp get up higher I get pingning on acceleration, earlier in spring waether it was just with regular gas, now that it is hot I am getting it with premium also, I do not like it, I would much prefer that it stayed below 200. and the temps did not swing so violently.

I get the pinging also, right off idle then it goes away. I ignore mine because it is only under light throttle, but happens with regular or premium.

 

[e9999]

I am not sure I follow,

if the T-stat is already fully opened and more btu's are made in the engine then there will be no more cooling left to remove these excess BTU's, so the temperature climbs,

as the temperature of the coolant climbs there is a higher diffrence between ambuent and radiator temps so it can stabilize but it is at the expense of engine temperature (CHT)

snip

that's right. When the Tstat is fully open (I thought that was about 185F or so, btw, from testing it, and observing temps coasting down) then the temperature would go up if the power needed goes up and the air speed does not change. However, the rad and fan and clutch can be sized in such a way that the temp will still not exceed the design specs (I'm happy thinking that is 226F or a bit more) for predictible situations. You can be still be on the upper side for unusual situations of course, but if the cooling system is designed properly and in good condition, that should not be a problem for reasonable driving (i.e. not trying to pull a 15,000 lbs trailer up a 45deg slope in 130F weather in D ) . So I guess we mostly differ in our setting our comfort threshold for max temps. Seems to me that you are bound to be unhappy if you don't want more than 200F since the numbers I see / read suggest the engine is designed to run much hotter than that.

The beauty of this cooling stuff is that some situations are self-helping. The hotter your engine, the more cooling you get since convection heat transfer is basically a linear process. Also, air speeds helps. E.g. the freeway where the faster you go (the more heat generated), the more convective cooling (faster air speed) you get too. In fact, it's quite clear from compulsively checking my gauge, that freeway driving at speed is the easier condition for my engine, cooling wise. I always see the temp on the freeway at 65mph or so to be less than 190F, just about the coldest of any driving besides coasting down a hill, same for my ATF temps.

I suppose conversely you could say that some situations are self-defeating: e.g. going slow cuz the load or the slope are too much. And that's where a bad fan clutch will hurt you.

 

[SUMOTOY]

1) Year of truck and any mods to the engine,

94 FZJ80 Supercharger

2) What gauge you have and where the sensor is mounted (if not the raventai mod),

Temporary autometer guage sensor at water neck (front of head)

3) Any cooling system upgrades, replacement parts, etc (radiator, fan clutch, which ones).

er, stock radiator, 6-10 cores welded, stock fan clutch, clipped radiator fan, no shroud, mnor ducting in front of radiator.

4) Coolant used, mixture ratio, and any coolant additives.

50/50 green from autozone

5) Temperatures observed while driving around town, sitting idling (i.e. drivethrough), on the highway at highway speeds, and the air temperature when you recorded these temperatures. Was the A/C on?

200-220 70-100 ambient towing trailer. Highway speeds had lowest temps.

6) Highest coolant temperature observed.
225 idling after a grueling uphill

7) Thoughts on the highest safe operating temperature.
220, and believe toyota picked 226 and 217 as A/C cutoff and A/C cuton

In my recent tests, I'm pretty convinced that trapped heat in the engine bay is what causes these big temp variables. Most modern engines are designed to run at 100c, since this allows blowoff of moisture in the crankcase, and oil is at optimal operating viscosity. Running lower temps track or street, isn't necessarily a good thing, especially in EFI cars. I personally like to see ALL gasoline automotive and truck engines get to 100c, then have enough reserve capacity to not exceed 110C (230). It has been pointed out that a lot of high speed fans don't kick on until 110c. That's how my wife's audi v8 quattro all aluminum engine works exactly (and actually most of the audi lineup - turbos included). It would appear from Toyota 226 A/C cutout sensor that's a pretty standard rule of thumb.

 

[landtank]

I run at 82*c 8 months out of the year. If Toyota wanted the engine to run at 100*c then it would during those months as well as the summer ones.

Some might find it comforting that their engine temps fall in with the national average, but for me I want my engine temps the same year round.

While the engine might not mind those increased temps, your tranny will suffer directly from them. There was a chart around here somewhere which showed how fast a tranny's life is shortened with increase operating temps. It was pretty frightful.



Just because the choir is singing the same song doesn't mean they have the words right.

 

[SUMOTOY]

I run at 82*c 8 months out of the year. If Toyota wanted the engine to run at 100*c then it would during those months as well as the summer ones.

Some might find it comforting that their engine temps fall in with the national average, but for me I want my engine temps the same year round.

While the engine might not mind those increased temps, your tranny will suffer directly from them. There was a chart around here somewhere which showed how fast a tranny's life is shortened with increase operating temps. It was pretty frightful.



Just because the choir is singing the same song doesn't mean they have the words right.

LT
We can agree that we want our oil temps the same year round, I just go for the 100C for my number.

I just don't see 82C as optimal oil temps in engine or transmission. The biggest issue is moisture relief. At 82c, water isn't able to separate from the oil and be burned off thru vaporization. As such, you have actually increased sludge and acidity of the oil. This is a known byproduct of running oil too cold. This also changes the aeration and saturation of any given oil in your engine.

Remember, most of the additives in oils are designed to reduced sludge and acids. By definition then, they work a lot harder on a motor that never reaches the boiling point of water.

This isn't preaching to the choir, there is very little documentation to support sub 100C oil temps. A quick look to every single audi production (and race) model made (turbos included), the oil thermostat is the same on them all. 100c.

I'm all up for creative uses of systems, but I haven't seen more than anectdotal evidence to support sub 100C oil temps as optimal. Even the Viscosity indexes of oils themselves are at 0 and 100C for a reason. Unfortunately, in our toyotas, the oil system was designed to reach a max temperature only under maximum abient or load heat. Fortunately, they also put in a 8quart system so that during those 8 months of overkill you point to, you have more additives to address the sludge and acids.

SJ

 

[landtank]

LT
We can agree that we want our oil temps the same year round, I just go for the 100C for my number.

I just don't see 82C as optimal oil temps in engine or transmission. The biggest issue is moisture relief. At 82c, water isn't able to separate from the oil and be burned off thru vaporization. As such, you have actually increased sludge and acidity of the oil. This is a known byproduct of running oil too cold. This also changes the aeration and saturation of any given oil in your engine.

Remember, most of the additives in oils are designed to reduced sludge and acids. By definition then, they work a lot harder on a motor that never reaches the boiling point of water.

This isn't preaching to the choir, there is very little documentation to support sub 100C oil temps. A quick look to every single audi production (and race) model made (turbos included), the oil thermostat is the same on them all. 100c.

I'm all up for creative uses of systems, but I haven't seen more than anectdotal evidence to support sub 100C oil temps as optimal. Even the Viscosity indexes of oils themselves are at 0 and 100C for a reason. Unfortunately, in our toyotas, the oil system was designed to reach a max temperature only under maximum abient or load heat. Fortunately, they also put in a 8quart system so that during those 8 months of overkill you point to, you have more additives to address the sludge and acids.

SJ

I don't have a oil temp gauge and was refering to my water temp, which most people I beleive consider to be what is watched, when looking at Operating temperatures.





and Oh ya........... Audi

 

[SUMOTOY]

I don't have a oil temp gauge and was refering to my water temp, which most people I beleive consider to be what is watched, when looking at Operating temperatures.

and Oh ya........... Audi

LT
If you never get over 82c, your oil temps aren't there either. Oil tends to trend behind water temp, and usually finds an equilbrium (reference) to water temp longer term. Again, I see water temps 210>220 as quite normal. I can't remember ever seeing oil temps exceeding water temps unless oil blowby gasses are extreme (read bad rings).

Sorry for the audi reference, they just use a lot of oil coolers from the factory with thermostats. You can take satisfaction in knowing that any time my 80 is near an audi, it's usually because it's towing a broken one.

Cheers

SJ

 

[cruiserdan]

Running lower temps track or street, isn't necessarily a good thing, especially in EFI cars. I personally like to see ALL gasoline automotive and truck engines get to 100c, then have enough reserve capacity to not exceed 110C (230)

Interesting how this dovetails with Gumby's wear chart. It shows the lowest cylinder wall wear and lowest fuel consumption with the coolant temp at 210 F (might as well be boiling or 212 F, or 100 C.)


D-

 

[Darwood]

This weekend I did some monitoring of my temperatures with an OBDII scanner.

Traveling down highway 99 my temperature read 212-214 while traveling at 65-70mph with a roof rack and roof mounted tent. Outside it was probably 90-95.

Going uphill into the Sierras I reached a maximum temperature of 221 going 55 mph in 3rd gear. Going down to 2nd gear reduced the temperature to 214.

While offroad in 4lo my temperature never went over 200, even when climbing.

With the new modifications to my temperature gauge, 221 read at about 2 needles widths below the red line. 214 was at about the 3/4 mark.

 

[Rich]

Derek, what value of resistors have you used on your temp gauge? What actual temp now drives the needle to the beginning of the red? Do you care to post the formula you are using to estimate gauge performance versus resistance values?

 

[landtank]

This idea of having high temps is all well and good but I would still like an explanation to why the truck is set to run at 180*F/82*C in cold weather. If these higher temps are wanted then why not just run the truck hotter all the time.

 

[cruiserdan]

Perhaps it's difficult to keep it around the 200-210 range in hot weather unless the thermostat starts to open at 180?



It would be interesting to look at a different engine, say a 350 Chevy, and see how it would swing with a mechanical temp gauge attached.

 

[landtank]

Perhaps it's difficult to keep it around the 200-210 range in hot weather unless the thermostat starts to open at 180?

Currently I have a 180*F T-Stat and maintain 180*. I'm pretty sure if I had a hotter one it would be just as easy to mainatain that as well.

My thinking is it would require less of a difference between ambient temps and engine target temp so less cooling would be required.

 

[cary]

This weekend I did some monitoring of my temperatures with an OBDII scanner.

Traveling down highway 99 my temperature read 212-214 while traveling at 65-70mph with a roof rack and roof mounted tent. Outside it was probably 90-95.

Going uphill into the Sierras I reached a maximum temperature of 221 going 55 mph in 3rd gear. Going down to 2nd gear reduced the temperature to 214.

While offroad in 4lo my temperature never went over 200, even when climbing.

With the new modifications to my temperature gauge, 221 read at about 2 needles widths below the red line. 214 was at about the 3/4 mark.

I think you have a partially plugged radiator. If you want to try a different one, I have the aluminum one from my 1996 that needs to be cleaned and I am nearby you. You could have it cleaned (boiled?) and swap it. I believes Benson's still does this.

 

[Darwood]

Derek, what value of resistors have you used on your temp gauge? What actual temp now drives the needle to the beginning of the red? Do you care to post the formula you are using to estimate gauge performance versus resistance values?

For the R1 resistor I used 100 ohms which centers the gauge around 194. For the diode replacement I used 150 ohms. I think when the needle is in the red the tempurature should be about 236 or 240 ish. The data for the higher tempuratures is a little sparce and weird which is where my uncertanty is coming from. I'll post what I've calculated later when I'm near my notes.

I'll also post my formula for determining R2 given R1, the diode replacement, and voltage across inductor 3 (I think that's the right number).

 

[Darwood]

I think you have a partially plugged radiator. If you want to try a different one, I have the aluminum one from my 1996 that needs to be cleaned and I am nearby you. You could have it cleaned (boiled?) and swap it. I believes Benson's still does this.

Thank you for the offer.

I think I might just bite the bullet and get a new radiator. I'll let you know.

I like the plugged theory since it fits with the visible deposits that I can see inside the radiator.

 

[semlin]

Darwood i think you either have a blocked rad or a bad fan clutch or something making your coolant warm .

just curious about your offroad temps in 4hi. 4-lo would let the tranny run cooler i think. I find I run cool offroad in 4-lo or 4-hi.

 

[landtank]

This weekend I did some monitoring of my temperatures with an OBDII scanner.

Traveling down highway 99 my temperature read 212-214 while traveling at 65-70mph with a roof rack and roof mounted tent. Outside it was probably 90-95.

Going uphill into the Sierras I reached a maximum temperature of 221 going 55 mph in 3rd gear. Going down to 2nd gear reduced the temperature to 214.

While offroad in 4lo my temperature never went over 200, even when climbing.

With the new modifications to my temperature gauge, 221 read at about 2 needles widths below the red line. 214 was at about the 3/4 mark.

You need to do my fan clutch tweak, I've got a pdf explaining the proceedure. Real simple and it costs a whole lot less than a radiator. PM me your e-mail address if you want it.

 

[Darwood]

You need to do my fan clutch tweak, I've got a pdf explaining the proceedure. Real simple and it costs a whole lot less than a radiator. PM me your e-mail address if you want it.

I'm game. I'm PM'ing you now.