thermostat, which one?

[djcslice]

i have an 87 accord dx carbed. I live in mn and i am wondering which of the two oem thermostats i should get. I think the temps are 160 and 180

[MessyHonda]

i have an 87 accord dx carbed. I live in mn and i am wondering which of the two oem thermostats i should get. I think the temps are 160 and 180
if you want the car too run cooler get the 160. if you live in a super cold place get a 180...the 160 will take a while to get the car warm and have the heater running....i would go with the 160 since im in california and it does not snow or anything.

['89AccordLX(Rus)]

Usually lower temperature thermostats are recommended for their ability to keep the engine at a lower temperature. Considering the fact that you live in a state with actual winter temperatures, you may want to stay with the 180 degree unit to allow the engine to warm up to a slightly higher temperature during the cold season. Just my $.02

[88Accord-DX]

Depending on what part of the country you live in. Colder weather- 180; Hot weather- 160.
IF you want to put a few more pennies and go the route I recommend. Get a "Fail Safe" thermostat, good insurance for thermostats that want to stick in the closed postition when going out.

[DBMaster]

Actually, the ultimate operating temperature of the coolant will not be influenced by your choice of thermostat. The 160 simply opens sooner than the 180. In cold weather the 160 would actually get you heat SOONER due to allowing full coolant flow at a lower operating temperature, but since the normal operating temperature of the fully warmed engine is well above 180 you car will NOT run cooler with the 160.

[ChaseR]

what are the consequences of not running a thermostat at all?

[shepherd79]

well, IMO the stock one is rated at something around 180 or 185deg. runing any lower than that can affect yuour performance and gas mileage.
running without thermostat is plain STUPID. your car will never warm up and if it does, it will never run efficient.

i just changed my thermostat from regular autoparts store to OEM honda one. man what a diff. car warms up a lot quicker and it performs a lot better.

[BITESIZE]

If your thermostat goes bad your car will overheat, since it doesn't open to let the coolant flow throughout your engine. This happened to me.

[Tailfin]

I can feel a little heat in mine before the temp needle even gets off the C. This makes me think that there are bypass hoses which let the coolant flow through the heater core before the thermostat opens. I'm not positive, since I haven't checked, but it seems to me the only explanation for that heat....or no...maybe mine's stuck slightly open lol... In fact...yeah...I need to go to the store...

Anyhoo...the heat on will slow the warming up of the car regardless. The outside temperature should not affect which temperature you choose much because the thermostat will stay closed until it reaches it's operating temperature. Just because the 180 thermostat doesn't open until then doesn't mean it's going to get to 160 faster. They're both closed until 160, so it just depends on what you want for your engine.

As stated above, lower temperature will nick at your fuel mileage a bit. You will also tax emissions, since the hydrocarbons get burned up better at the higher temperature. A plus of a lower thermostat is you might get away with bumping the timing up another degree or two, since the warmer the engine is, the more likely it is to knock. Bumping the timing can give you a little bit more power....also because the oil may maintain a slightly thicker viscocity, which may in turn do a teeny weeny bit of good for compression, as well as oil life since it is not being heated and cooled to quite as much of an extreme...again with the emissions trade-off. If you're going to go that route, it would also be wise to get at least mid-grade fuel, if not premium.

[Tailfin]

One other thing...unless this was changed from 87 to 88 (which I have), the stock thermostat is 195, and the alternate option mentioned is 180, not 180 and 160 respectively... 160 is a little cool, I wouldn't suggest that, particularly in Minnesota.

[shepherd79]

it is not 195. 87 honda shop manual says that thermostat starts opening:
primary at 82 deg C. (180 F)
secondary 85c (185F)
fylly open at 95c (203 F)

the optional thermostat started to open at 86-90 C (187-194 F).

If you go to autoparts store and ask for one, they will give you 195 and tell you that is stock replacement. I used to manage autoparts store, and a lot of the shit is wrong. if you go to a delear you may be able to get 86 C one.

[Blkblurr]

Here is my take on this whole thing. Use the higher temp one becasue it is close to what Honda puts in it. A properly warmed engine will give you better gas milage and performance as Shepard79 said. It makes no difference what your outside air temp is in the winter as far as what Thermostat to choose. Next, your heater is not in the thermostat circuit but in the engine cooling circuit. As your engine gets warm, you will feel heat in the car becasue the water pump is pushing coolant to the heater core no matter if the thermostat is open or closed. Also, a thermostat can fail in the open or closed postion. In the closed position the car will overheat unless you run the heater on full. Failed in the open position you will get no heat showing on the temp guage because it never has a chance to build up in the engine block. You will get only a little heat in the car if the heater is running in this case. I think that's about it.

[thegreatdane]

Blkblurr nailed it.

[Tailfin]

Sorry, yes, my shop manual says that too (about the temp). I just remembered the secondary -194 part I think and my brain transformed it somehow lol. I agree though...go with the warmer one unless you're doing modifications that require otherwise...or you have engine knock.

[DBMaster]

Yes, but I was trying to clear up the misconception earlier that a 160 degree stat would make the engine run COOLER than a 180 degree stat. It would only open sooner, but the engine'e ultimate operating temp will not be affected. The only way I could see that happening is if one stat has a bigger opening for coolant flow than the other, but I do not think that is the case.

[Blkblurr]

The temp of the thermostat will be the operating temp of the engine because the radiator has the ability to cool more than is needed to run the engine at it's normal operating temp. The lower the thermsotat temp is the more often it will open, therefore replacing the hot water with much cooler water more often. It will not allow the temp to climb higher than it's opening temp. If you take it to it's extreme by leaving the thermostat open all the time, the engine temp will barely register on the temp guage.

[bobafett]

my oem honda thermostat says 190 degrees.

but my autometer gauge tells me the car runs around 210 once it gets all the way heated up. :) temp needle on the dash registers right in the middle still. :D

[Blkblurr]

The sending unit measures the temp of the coolant in the engine but that isn't going to mean that other parts of your engine are not hotter. the exhaust manifold is going to be around 600 degrees I would think and areas of the engine that don't have as much cooling are going to be hotter.

[Tailfin]

The temp of the thermostat will be the operating temp of the engine because the radiator has the ability to cool more than is needed to run the engine at it's normal operating temp. The lower the thermsotat temp is the more often it will open, therefore replacing the hot water with much cooler water more often. It will not allow the temp to climb higher than it's opening temp. If you take it to it's extreme by leaving the thermostat open all the time, the engine temp will barely register on the temp guage.

I don't think that's quite true, unless the cold weather is cooling the radiator enough. If the thermostat being open all the time was enough to cool the engine under any circumstance, and moreso than the engine required, then you could take out the cooling fans and see no difference, and it would never overheat. Actually, in a situation where the car would otherwise overheat, the lower temp thermostat would have little effect once the car was warmed up, because the cooling fans would not come on at a lower temperature. The car will take longer to get up to that temperature, certainly, but once it's there, it's not too fruitful unless you can have the fan(s) come on at a lower temperature. They may cool it down to 160 just from the blast, but when they kick off, they'll just wait until it gets back up there again.

If you're on the highway a lot...and it's not boiling outside, the lower temp thermostat would make a difference most of the time...but in town and really hot weather (not there :-P), that fan gets used. In that case, you'd just be increasing the range of the temperature the engine experiences.

If the thermostat were stuck open, it might not climb up much, but if you were driving around town in a heat-causing condition, it would get the temp up, it would just take much longer.

[Blkblurr]

If the thermostat being open all the time was enough to cool the engine under any circumstance, and moreso than the engine required, then you could take out the cooling fans and see no difference, and it would never overheat. Actually, in a situation where the car would otherwise overheat, the lower temp thermostat would have little effect once the car was warmed up, because the cooling fans would not come on at a lower temperature. The car will take longer to get up to that temperature, certainly, but once it's there, it's not too fruitful unless you can have the fan(s) come on at a lower temperature. They may cool it down to 160 just from the blast, but when they kick off, they'll just wait until it gets back up there again.

In general I agree with you. I didn't say I was not using the fan. The point I was making was that the temp of the water coming from the radiator after it returns to the engine block is much cooler than the thermostat temp setting. I also did not say "In all conditions this is true" I know from experience that when the thermostat fails in the open position during cold or warm weather my temp guage barely registered. Of course I was driving and not stopped and my fans and radiator are on good working order.

[Tailfin]

Yeah of course, I was mainly talking about when you said "the radiator has the ability to cool more than is needed to run the engine at it's normal operating temp." Especially at operating temp, the engine may need the fan, thus more than just the radiator. I see what you meant, but I was making a separate point, which is even if you meant the radiator with the fan's assistance (not trying to be an a$$ here lol), then the radiator's "ability" to cool more than needed would be conditional on the fans running..and since they don't run until the thermostat is wide open, then the cooling the radiator does would not matter to which thermostat is being used, unless you're talking about the speed at which it reaches that temperature, not the cooling once it's at operating temperature.

[DBMaster]

I am willing to bet that the temperature of the coolant coming from the radiator is higher than either of the thermostat choices mentioned and that once the car is warmed up the thermostat IS open all the time.

Anyone know how to test that theory? :)

[88Accord-DX]

About the closest you will get to testing that theory, is to use a infared light thermometer.

[AccordEpicenter]

yeah that will work or an accurate contact thermometer on the thermostat housing. Using a thermostat thats too low is harder on parts because they dont warm up to what they were designed to work at. In race cars, they often use a lower temp thermostat but its still harder on parts (who cares its a RACE CAR) It is better on gas mileage to use a hotter one, it also keeps emissions down too. For power, using cool water with hot oil temps usually makes the most power. I still run a stock oem honda one even in the race engine.

[Vanilla Sky]

ok, you guys just confirmed everything i've pretty much figured out. maybe then you can answer this.

hot engine and cold air is the best combination for efficiency? i've been told that warm air is best for fuel economy, but i hear of lots of people that go CAI and gain fuel economy. so is cooler air better?

[Tailfin]

I am willing to bet that the temperature of the coolant coming from the radiator is higher than either of the thermostat choices mentioned and that once the car is warmed up the thermostat IS open all the time.
Anyone know how to test that theory? :)

It depends on what kind of driving you're talking about, as well as the efficiency of the car's cooling system; but generally that's not true. It also depends on what temperature the fans come on at. The thermostat usually won't stay open constantly if you're on the highway and if it's not warm outside because the air blowing by the radiator fins serves the same purpose as the radiator fan would, just not as strong. I've monitored the coolant temp on my Cadillac several times, and that thermostat opens around 85 degrees C. It usually climbs up to about 88, then just goes right back down to 85. The first fan speed kicks on in that car around 93 C, so that shows that the only thing cooling before that point is the opening of the thermostat, which is enough under certain driving conditions, as we've gone over here.

When it's warmer, or I'm driving in town, or both, then usually the fans make a big difference in how much the coolant is cooled, enough so that even though they kick off, the effect often gets the temp back down to the thermostat temp. Radiator size and efficiency would matter here. If the radiator is larger, it's going to have a larger quantity of "cooler" coolant stored for going into the engine block, thereby making the effect created there last longer, or be more powerful, if you will. Also, if the system handles more gallons per minute, more coolant gets affected while the fans are on (or just going through the radiator).

Basically, the only way the thermostat would stay open all the time is if the cooling system were JUST cooling the car enough, and that would not be the case, because the cooling system has to be designed to cool the car under a variety of conditions.


ok, you guys just confirmed everything i've pretty much figured out. maybe then you can answer this.

hot engine and cold air is the best combination for efficiency? i've been told that warm air is best for fuel economy, but i hear of lots of people that go CAI and gain fuel economy. so is cooler air better?

Cold air is more to gain power than fuel economy. That's why a race engine would want that. The reason people want colder air is because cold air is more dense, i.e. there are more molecules of air getting in, which means there's more air to burn... The engines (aside from older ones here) use MAP/MAT sensors and the like to determine what pressure and temperature the air coming in is at. The car can then adjust the fuel delivered in order to get the optimum air-fuel ratio. An engine is just an air pump on a basic engineering level. More air in, more air out=more power. If more air molecules make it in, whether it be because of a turbo charger, more dense (cold), or lower restriction, the car then adds more fuel that can be burned at the optimum ratio, thereby increasing power. It is possible to gain fuel economy with CAI if you're not heavy on the pedal. The air can also result in a more complete burn of the fuel. Also, if you can lower the temperature of the combustion chamber, you might be able to get away with advancing the timing a little bit. This can bost both power and fuel economy some, since it usually results in more compression.

Another reason people doing CAI may gain fuel economy is not so much because of the cold air, but because they remove restrictions in stock intakes. A lot of them don't have a large enough "throat" or have one with turns in it, which creates turbulence, and thereby doesn't let the "air pump" do its job optimally. This is also a good reminder that you will not see the full efficiency of an intake modification without having good flow out the exhaust. Getting more air in doesn't do as much good if it's having trouble getting back out.

The reason a hot engine is better for emissions is because hydrocarbons and such get burned up better at the higher temperatures.

All of this usually raises questions about EGR, since it is related. EGR actually cools the engine air, even though it's from the exhaust, because it does so chemically. The exhaust gas is inert, meaning it can't be ignited... So when it's recirculated into the combustion chamber, it cools it because of the fact that it can't explode like the rest of the mixture. This lets timing be advanced under those conditions by thwarting the knock that might otherwise occur. It helps NOx emissions because it recirculates some of those as well to get burned the second time around.

[AccordEpicenter]

Usually engines add fuel when the air is pretty cold so for best fuel efficiency it shouldnt be too cold (cooler air=denser air, more power!) most CAI's ive seen especially short rams have a higher intaker air temp than the stock system, but usually make more power based on better flow (as mentioned above). Ive seen guys get better fuel mileage with a CAI and a header etc, but somtimes they will lose some if they get a cam or too big of an exhaust system. The stock intake system is plastic too, the CAI's are usually metal but there is alot of heat in that engine compartment. Ive personally experienced the best fuel mileage on a stock honda with the temps between 70-80 degrees no a/c.

[Blkblurr]

The more efficient an engine is, the better the gas milage. This means the better it does the job of pumping air, burning fuel etc the better milage it can get. This of course means that you compare apples to apples if you make changes. If you end up making more power because you have cooler air or better flow the idea is to use less throttle to get to the same mph. Most just use the extra power to have more fun and fuel economy suffers.