I have a 85SC and am buying a lower temp thermostat than the stock 195. Now the part store said they have the low 160 or a 180. Everyone says get the 180 because 160 is to low. What should i get? What makes the car proform the best?

with the price of Thermostats and the extream ease that they can be changed in Fiero, I wish they were all this easy, why not just get both and see which one works best for you.

The 160 may work best in summer although you may find, depending on your local winters, that 160 is to low in winter.

I know I'm a little late on this,but....
The best performance is attained by using the 160 degree thermostat.
By keeping the engine cooler it "fools" the computer into thinking it's still in the warmup mode. This causes the injector pulse width to be longer(i.e. the injectors spray more fuel)which causes the mixture to be richer, hence, more power.
The only drawback is that your mileage may suffer.
Stroker

Another way to trick the ECM is to give the fuel pressure adjustment(the spring that the Haynes manual describes as having life threatening consequences from accessing)by giving the threaded perch a full turn.Follow this by adding a 15 ohm resistor to the temp sensor wire(solder or it'll haunt you).This alters the ignition curve a bit also.Must have a free flow exhaust to accomodate these mods.Used a 180 deg thermostat.This is on a 4cyl car.An adjustable form(rheostat or pot)would be better in the temp sense wire,for adjustment,then measure the resistance and add permanent form of resistance.15K might not work on all cars.Racing only,of course.

Is the HyperTech thermostat a good installation?- I've already added their chip to ECM.

it's just a standard 160F unit as I recall, maybe a 180.

Hey lowCG,
Question for you about the 15 Ohm resistor to be added in the temp sensor circuit. I have a TECH 1 so I can access the ECM inputs. What exact temp am I looing for if I put a rheostat in series to "fool" the ECM. Am I assuming you want the ECM to think the motor is very cold and not in closed loop? Or, just a little cooler than normal operating temp?
Oh, and giving the pressure regulator a quick turn isn't an option on a V6 unless it's been replaced with an adjustable one. I tweaked mine after my 3.2 swap by removing the intake and hot wiring the fuel pump on at the oil pressure sending unit. I then used a socket and a hammer and tapped the top of the regulator ever so slightly to achieve the fuel pressure I wanted (49 PSI at WOT)
Always looking for more power! RR RR RR
Dan-O

Oh yeah,it was a 4cyl.,but I've done this on other vehicles,you usually only add a little resistance to the circuit,maybe even correcting slop in the sensor.Sometimes you can't get the system to lean out properly at higher revs after getting results on the bottom.Neat trick with the V6 fuel pressure,did it help?

The fuel pressure bump-up was the ticket to compensate for the bigger motor and the more radical cam I put in with the rebuild.
It's a beast when accelerating, I'm just waiting for another speeding ticket.
Dan-O

Just a note of warning about using the low temp themostat or "fooling" the ecm into staying in warm up mode: This could cause your catastrophic converter (if you still have one- nudge nudge/ wink wink) to overheat and damage itself. Running in open loop for extended periods of time has caused many converter failures and fouled plugs. Maybe switch to a hotter plug and try an "off road only" exhaust. Good luck.

i have a 4 cyl 84 and was using a 195 thermostat but the car was running to hot ...i took it out and ran it without a thermostat ....meaning to get a lower one.
how bad is it for the car to run it over a period of time without a thermostat?

Just thought I would put in my $0.02 here.
The whole idea behind running with a cooler (ie..160°) system comes from a performance mod that incorporates not only the cooler thermostat, but also a 176° fan switch and a DIFFERENT eprom chip. These eprom chips, which are available from ADS and Hypertech, use programs that allow closed loop operation in the lower temperature ranges used. In addition to the alterered temp points, the chips incorporates a richer Air/Fuel ratio and a more agressive timing curve resulting in a much higher exhaust system temperature which will damage a cat. converter. They advertise these systems "for offroad use only", since, they do require removal of the cat and a free flow exhaust to function properly. Many problems and much confusion has occured from these components being offered as "separate" items.

Running without a thermostat is not something I would recommend, due to the fact that the heat exchange from the engine to the coolant is hindered due to the constant circulation. If you are primarily a non freeway driver, this will work for short durations without damage, but it would be hell in the winter. :-)

I've noticed that (stock) cars,that have a catalyst system, tend to run a bit rich,overall,from the factory.This was done in an effort to maintain cooler exhaust temperatures,and save the convertor from damage.
The richness that most chips will offer is only in spurts,not unlike a boosted accellerator pump in a caruretor,along with an altered spark advance curve,like you mentioned.
The exhaust oxygen sensor is a nice feature to have functioning, with it you can alter other inputs,like temp.sensor/thermostat,and still have the ability to lean out again after the momentary rich condition you've created.
However,if you modify/adjust too much,you'll be out of the systems parameters,or cababilities,and then oxygen sensor can't/won't compensate.
Don't think they made a chip for my four cylinder car anyways.

I may have phrased that a bit wrong in my post above. It is the timing curve that the chips such as the Hypertech Thermomaster use that creates the high exhaust temps, not the air/fuel ratio. :-)

If a chip will retard the timing,creating higher exhaust temperatures,then I wouldn't recomend buying one for performance reasons,unless it's a turbo application.
The advance curve on a performance motor is narrow,with lots of initial advance.

I would not place judgement on something I know little about, and I do not know the exact modifications that these chips use. There are several manufacturers of these chips and I am sure they each use their own ideas of timing curve and fuel ratio. I myself think that they are all a waste of money. :-) The point I was making above was that the use of a low temp thermostat "alone" is not a performance improvement on our cars and in fact may be the opposite. The fan does not even come on until around 200 degrees which will result in 2 scenarios:

A) At higher speeds (ie..freeway) the engine will run at 160 and the ECM will switch into open loop.

B) Stop and go city driving will result in very little cooling change at all, since the fan will be the primary factor in determining the engine temp.

One might say that they could just add the low temp stat and prevent the stop and go effects, thus running in open loop near constantly. I would suggest that one consider why open loop mode is also referred to by GM as "limp home mode" to decide for themselves if this is desirable.

You're right,there isn't much tolerance for changes within the computer,like drastically changing the operating temperature.And I agree that the chips are,almost always a waste of money for these cars.

I bought an ADS chip for on-road use about 4 mos. ago and haven't noticed any marked difference. What troubles me a little is that I'm reading that it may damage my engine in the long run. Is this true, or am I just out the cost of the chip?

The stock fan switch temp is 235F. If you have one of the few cars with the 2 speed fan low is 221F, and high is 246F. According to my data, only some 4cyls had the 2 speed fan.

There is a link in the general area to some documents I'm working on. One of them is about cooling. you'll need to dig it out, it's been there a few weeks now.

I have my fan locked on most of the time now. Even on 90F days the coolant temp reported by the ECM stays around 210F in any traffic flow. Without the fan, the temp hardly ever stays that low even at highway speed. This is on a car with a cooling system that is otherwise 100% good running a 190 stat.

Without the fan locked on in slow traffic, the car quickly hits 230+ and starts knocking. this starts Before the fan switch activates. Activate the fan, temp and performance return to normal in a minute or 3, and knocking stops in seconds. Kocking of a normally healthy motor is the first sign of over heating. Allowing knock to continue can do major damage quickly, including blow pistons and head gaskets.

Hate to say it but the "great " JC Whitney used to sell an adjustable fan switch for about $15 Turns on at 170 or so. The sensor probe goes in between the rad fins