Please Explain 160 Thermostat Requirements and Aluminum Heads run hot.

They're trying to get the overall temperture down. Since these chips increase the advance, temp makes a big difference. If the thermostat is open at 160F and they turn the fans on at say 180F and you have a good cooling system, overall temps will be lower in theory. In practice, cooling systems are pretty marginal and you'll often end-up with no real change. Your engine should not run hotter with aluminum heads.

"Jim" wrote

Where did you get the idea that even if you put a 160 t/stat in, the car "eventually" will run at the "normal" temp anyway? There is no such thing as a "normal" temp. The temp is determined by the thermostat as long as you have airflow through the radiator. If you put a 160 t/stat in, all things being equal, that engine will run at 160. Most cars run with a 195 t/stat, which is maybe why you think that "that" is a "normal" temperature.

Ian

Only in your dreams....

The t-stat only controls the bottom end heat. If the engine wants to run at 210 there is nothing about a thermostat that 'opens' at 160 is going to do about it.

LOL!

That is just plain silly thinking.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

I believe there are performance benefits to running with a lower temp thermostat. However - many of these out-of-spec thermostats and cooling fan switches are illegal in California due to emissions regs. Catalytic converters are less effective when the exhaust runs cooler.

Other stuff I've read seems to indicate that if it's too cool, combustion may be incomplete and moisture could be a potential problem.

How does the engine decide what temperature it "wants" to run at? Bob

It would seem to me that if the chip sets the fans to come on at a new lower temp and one left the original thermostat in place you would end up with fans running all the time trying to cool a radiator that isn't hot.

"Mike Romain" wrote

Wow, Mike...you are dumber then the "proverbial" sack of hammers. Heh heh...time for you to head on back to "cooling system" school. By the way, you might just have missed my "all things being equal" statement.

Ian

"shiden_Kai" wrote

And let me add: "airflow through the radiator" which appears in my original post.

"If the engine wants to run at 210" heh...that's a good one!

Ian

Where did I get the idea?? I've done it!! Just take your thermostat completely OUT and see what happens. It will take a while, but the car will eventually reach some "normal" temperature....which is mostly determined by the size of the radiator. If you have a radiator that's as big a house, then yes, your car will always run at "room" temperature, however given the size AND air flow contraints of car-sized radiators, the temp WILL go up.....until that equilibrium point is reached. In some cars this equilibrium point may be only 150 degrees, but in many others it will be 180 or 190.

As Mike says, the thermostat only determines the bottom end...that point at which the cooling starts.

However I'm still waiting to see someone answer the question as to why the chip makers tell you to run the low temp thermostats. Yeah, the idea is to reduce spark knock, give more power, yada yada yada, but when the temp goes up eventually....what have you accomplished?

Maybe I am just used to engines that work to capacity? The size of the rad, the design of the fan, etc. determines how the engine cools and where it 'wants' to run.

A 160 t-stat and a 195 t-stat are physically the same size. When fully open they both allow the same flow.

When the engine internally reaches 160, the first one opens. When the engine internally hits 195, the second one opens.

Once the engine has passed this 160 or 195 degree mark, the thermostat never budges from wide open.

Take a Jeep TJ for instance. No matter what t-stat you put in it, it 'will' run at 210 degrees on the highway or off road in 4 low. It just warms up faster with the hotter t-stat.

My 86 CJ7 is the same as well. I tried a 160 for the summer and the 192 for the winter and on the highway or in 4 low my engine always runs just over 210.

This means in the winter on short trips when the fan can supercool the rad, you will only see 160 degree water in the heater core and will freeze your butt off with the cold t-stat. With the 195, you will have heat inside the vehicle.

Thermostats are only for the low temperature control, not for top end heat.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

It sounds more like you are used to driving vehicles with marginal cooling systems. Bob

the temperature rating of the thermostat is the temperature at which it opens to let the coolant (water) flow through the radiator and engine.

I marked the dashboard temp guage on a piece of masking tape and changed the thermostat to the one the parts store gave me which is rated higher (5-10 deg, I forget how much). the guage rises above where it was before then falls back down to where it was before and stays there. I assume that is because the thermostat is opening at a higher temp but I don't knwo why the coolant temp then drops back to where it was before.

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They are thinking by turning on all the fans early and running a cold t-stat, the engine stays in 'choke' mode which is about the only 'easy' way to get more gas into a FI engine.

They then set the timing, etc to try and use this extra gas.

These chips are for sale all the time because they just plain don't work for shit for the very reasons you are thinking and we are saying. People buy them then figure out they got scammed so try and sell them. 'Most' engines are going to find their own 'normal' eventually.

Hey, these suckers will likely work up here in our Canadian winters where the engine just might stay at the temp the t-stat sets....

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

Jim wrote:

Other practical considerations would include thermal breakdown of motor oil and a wider range of thermal expansion - i.e. parts will be really loose with a cold engine if they have to expand for the hotter running temps.

The theoretical Carnot efficiency (1 - Tambient/Tinternal) is too simple a model for the real world. While letting the engine block run hotter is going to lead to hotter combustion temps, the ambient temp is effectively a combination from the block, exhaust, and outside air. The heat of the engine block contribution to the effective ambient temp.

"z" wrote

I believe that I covered those items. If you have sufficient airflow through the radiator, and the cooling system is in it's original factory state (my "all things being equal" statement), then the engine will run at the thermostat temperature. Obviously if the cooling system is too small for the engine, or there is no airflow thru the radiator, the temp will go up. You see that all the time with cars with electric cooling fans in stop and go traffic. That's not what I'm talking about. What I'm saying is that if you install a 160 t/stat and run down the road at 40 miles an hour (pick whatever speed you want that generates proper airflow through the radiator), the engine will stay at 160 degrees. Simple as that.

Ian

"Jim" wrote

In your case, since you don't understand how things work, you will accomplish nothing. If you have an engine that will go past

160 degrees with a 160 degree thermostat installed, "and" you have proper airflow through the radiator....you have other problems.

Ian

If the equilibrium is above the thermostat opening temp, then the cooling system is inadequate.

They probably want the efi to stay in warmup strategy.

I had a problem with this when I retrofitted a 5.0 Mustang to my 351 Cleveland, in which I have a 180F thermostat. The mustang uses a 195F thermostat AFAIK, and the EFI would never enter warm cruise strategy, which is needed for adaptive to work properly AFAIK.

As I have an EEC-Tuner in the EEC, I could lower the temp when it switches to 170F, and it has been working fine since.

Thomas

Bob wrote in rec.autos.tech

If you read Ian's other post you will see what he means. A few decades ago cars had fans driven by belts (fan belts :-)). The fan was running all the time, and would vary in speed with the engine, in other words the airflow through the radiator depended upon engine speed, not temperature It was a system that worked fairly well. During the summer, the cars would tend to run hotter, and people would speed up the engine to while in traffic to cool it down. Newer cars, with electric fans, work a bit different. The t-stat opens at a certain temperature, allowing cooler water in. But since the fan doesn't run yet, there is little or no airflow over the radiator. The engine will reach a point where the radiator will remove heat at a rate equal to what the engine is producing, and that depends upon the ambient temperature. If the ambient temperature is cool then the car will not get too much above the temp that the t-stat opens at. And will cool down when the car starts moving. However, in warmer weather the radiator will remove less heat, and the engine will warm up more, until the fan is turned on. Then the air flow is usually sufficient to keep the engine at a certain temp. As you drive the temp will drop off, and the fan will quit. Rather than being marginal, the cooling system is working very well at keeping the engine at the most efficient temperatures. I purchased a Buick with a 3.8 engine, and was not used to the way it worked, For over 30 years most of my driving was in cars that did not have the electric fans. So what I was used to seeing was the engine hitting one temperature and holding there. But with this car I was suspicious of the t-stat, thinking it was stuck open. But Ian explained to me that the it was acting normally, and putting some thought into it I realized that in the winter the car never warmed up enough to turn on the fan.

Mikes Jeep doesn't use electric fans and I know exactly what Ian is saying.... like usual he is right on the money. Mike is the one talking smart about things he doesn't understand. Bob