85 300zx na

After speaking with various people I decided to run my 300zx with out the thermostat. Is there any problems I may encounter. Or how will it affect performance if any. I live in Los Angles California and from my understanding the thermostat "is designed to open and close at predetermined temperatures to allow coolant to warm up or cool the engine" To me that translates to if you live in sunny California you dont need the thermostat to do the warming up just the cooling down. I think I'm right i just want to get more advice from you guys before I take it out on the freeway tonight. Thanks

No you're not right. You need a thermostat.

In the winter your car will never reach operating temperature, which will mean gasoline won't fully burn, causing more pollution and lowering your gas mileage.

Also, the thermostat regulates the waterflow through the radiator, not just the temperature. Without a thermostat, its possible for coolant to flow TOO QUICKLY through the radiator and therefore not have enough time to actually get cooler. This can cause a car to overheat, since the radiator is too small for the new flow rate.

Do yourself a favor and fix the real problem with your cooling system. Don't ghetto hack your car together, and don't remove things from your car based on assumptions. You should ask first if you're not sure. It doesn't seem like it does much, but the thermostat is pretty important.

---

----------
1985 300ZX n/a

See my Z project

You ABSOLUTELY need a thermostat.

It ain't going to affect anything in a place with a warm climate. It will give more flow and the temps needed to ignite fuel has nothing to do with cool temperatures. As a matter of fact cooler fuel temps produce more power. Higher fuel temps give you more problems. The ignition system has more than enough spark to ignite temps well below freezing point.

A cold engine is bad yes, nothing any of us can avoid unless we live on the equator. But an engine will warm up even with no thermostat after a minute. There is not enough cold coolant in the radiator to stop those temps from getting the engine metal expanding to run at normal specs within minutes.

Blah, i've removed my thermostat just one less problem to deal with.



Edited 2 time(s). Last edit was 2009:06:21:22:03:05.

You are failing to take into account one of the essential aspects of thermal transfer, that is the time spent in the heat exchanger. The flow of the entire system is gauged properly to maximize thermal transfer with the thermostat in place (in addition to running the engine at the prime temperature for minimalizing engine wear). By having it removed your system operates LESS efficiently, as the time spent of the coolant in the radiator is too small. I had this happen when I installed a "freer flowing" "high performance" radiator in my old 93' TT. The OEM single core radiator created a certain restriction to where coolant was kept in it as long as possible to make up for its small size. When changing to a dual core with wider channels, the coolant did not stay long enough in the radiator, and subsequently the car overheated in peak AZ temperatures with the A/C on. Returning to the OEM radiator obviously solved the problem.

In addition, I have read studies that show considerable increases in carbon deposits, emissions, and o2 sensor/catalyst failure without a thermostat in place. Your oil will also lose its TBN quicker due to the engine at times never maintaining its running temperature. I will see if I can dig links to it up, its been a while.



Edited 4 time(s). Last edit was 2009:06:21:22:48:29.

You do have a point there Red, I trust your research.

When my thermostat went bad and was stuck open,
my fuel milage took a huge drop and I am pretty sure
I ran more rich and it loaded up my O2 sensor that was relatively new. : (

Put a new thermostat in.

Quote:

swampman
It ain't going to affect anything in a place with a warm climate. It will give more flow and the temps needed to ignite fuel has nothing to do with cool temperatures. As a matter of fact cooler fuel temps produce more power. Higher fuel temps give you more problems. The ignition system has more than enough spark to ignite temps well below freezing point.

Most automotive petrol engines are calibrated to run with a coolant temperature of between 190*F and 220*F. Automotive engineers have discovered that when the coolant temperature is maintained at about 195*F, the engine runs at its most efficient point. At this temperature, the heat transfer from the cylinder walls aids the spark in burning the fuel completely by transferring the heat from the cylinder walls to the burning gasses in the cylinder. This is the temperature where the engine produces most power, because the fuel is burning faster and more completely. Fuel mileage will be best at this point too.

Yes, fuel will still ignite at sub-freezing temperatures. However, you should know as well as anybody with Z31 experience that engines don't run as well when cold as when hot. Thats why when the engine is cold, it has a special mode (open loop mode) where the fuel mixture is richer and there's more air going to the cylinders (via the air regulator) to help keep the engine running until it gets warm.

Trust Red and I on this one. There aren't very many places that get as hot as AZ, consequently we learn very quickly how to keep vehicles running propely in the heat. A thermostat is an absolute necessity regardless of the environment. It is the temperature regulator. If you remove the regulator, the temperature is controlled by... well nothing. If the coolant gets stays too cold cause its too cold out, it can't warm up and the engine will not run its best. If its too hot outside the coolant can't get cooler cause its not spending enough time in the radiator.

---

----------
1985 300ZX n/a

See my Z project

It isn't about the fuel temp at all, it is about the temperature of the metal itself, the cylinder bore, the piston rings, the cams and bearings, the temperature of the oil. At a certain temp they are within specs and the engine is efficient.

swampman Wrote:
-------------------------------------------------------
> It isn't about the fuel temp at all, it is about
> the temperature of the metal itself, the cylinder
> bore, the piston rings, the cams and bearings, the
> temperature of the oil. At a certain temp they are
> within specs and the engine is efficient.


I never said a word about fuel temp. Your exactly right, except its the temperature of the coolant that keeps the cylinder bore temperatures and all other engine temperatures in spec. Therefore if the coolant temperature isn't right, the cylinder wall temperature will not be either. There is an absolute reason why 195*F is the most efficient temperature for the coolant. There is also a reason why if you decided to put the NISMO 160*F thermostat in your car, you will reduce your fuel economy and increase your emissions output slightly.

An engine is an equilibrium system, so if one variable is affected, the others are too in some way. The thermostat is the regulator of the engines temperature equilibrium, and its temperature range and flow rate was carefully engineered based off the average combustion temps, flow rate of the water pump, size of the radiator, flow rate of the engine fan, etc.

You can argue all you want, but the fact of the matter is and always will be that the thermostat IS important and should be in the car for it to run as it was designed. Effects of not using a thermostat may not be perceivable to the driver depending on the environment or the drivers ability to pay attention, but it will have an impact regardless.

---

----------
1985 300ZX n/a

See my Z project

1985 300zx na

After reading the posts from yesterday I decided to get the thermostat back on there. I haven't driven on the freeway just the streets but I haven't had any issues. Thanks for all the input.