darguy

On my stock 99 FRC I've got the following Closed Loop Enable ECT vs IAT table:



Considering the ECT value is 92 F for all but sub-freezing IAT, that implies to me that putting in a 180 thermostat would have no effect on going into Closed Loop. And that changing the fan speeds would be the only thing to do with the tune. Am I missing something? (I'm a noob to tuning)

With the stock thermostat, I have already changed the fan speeds to:

Fan 1 On Temp: 209 F
Fan 1 Off Temp: 200 F
Fan 2 On Temp: 219 F
Fan 2 Off Temp: 210 F

Should they be changed further for the 180 thermostat?

I'm doing my first track day in a month and am looking at getting one of the Evans E3023 180 high-flow t-stats, and opening up the air-flow to the rad a bit...

Opinions?

Pumba

I have questions:

1) Have you replaced you stock radiator with either a DeWitts or Ron Davis Racing radiator?

2) Have you installed an oil cooler?

3) Have you replaced your stock fans with the DeWitts high-flow fans?

4) Have you changed your water pump to the Evans high-flow water pump?


Next, according to GM Engineers, a 180 degree F thermostat is not desirable for peak performance. A 180 degree F thermostat STARTS to open at 180 degrees and is not fully stabilized in the open position until 193 to 196 degrees F.

The GM Engineers recommend that engine coolant for peak LS engine performance should be between 180 degrees F and 189 degrees F. In fact, the C6 race Corvettes built by Pratt and Miller turn their idling engines off if the coolant temperature reaches 190 degrees F. That being the case, you shoul purchase and install a Vinci Hi-Performance 170 degree F thermostat that will stabilize the coolant at approximately 185 degrees F.

With the 170 degree thermostat, you should set Fan #1 to come on HIGH at 195 degrees and turn off at 189 degees. Fan #2 should turn on HIGH at 196 degrees and turn off at 189 degrees.

In addition, if you are serious about track days, you should upgrade to the components listed at the beginning of my response.

darguy

Thanks for the feedback. The car is stock, none of those mods have been done - all I've got going on is a K&N air filter, a short throw shifter, and Hawk pads. As this is my first track day (and the end of the season), I figured I'd get my feet wet before doing too much - I don't know how serious I will get about it untill after the first few events. I'm guessing maybe 4-5 next year after this one - max.

I'm not necessarily looking for 'peak performance' at this point, as the car is my daily driver and needs to pass emmission testing, and I'll be driving it right up until it snows. I'd rather not change out my thermostat just for the day - I'm just looking to keep my engine temp in a reasonable range for when I do take it out on the track, and have it still go into closed loop when I'm driving to work (and warm up nicely when it's cold out).

So, the question remains:

Considering the ECT value is 92 F for all but sub-freezing IAT, that implies to me that putting in a (160/170/180) thermostat would have no effect on going into Closed Loop. And that changing the fan speeds would be the only thing to do with the tune. Am I missing something?

RedRiderZR1

Changing the fan speeds will keep the car running cooler over the stock settings on the street. But if you are running on a track, temps will still get up there without adding the above mentioned mods. If you are just getting your "feet wet" then you're probably OK to just run the course and see how you like it, but just watch your temps (water & oil). Then if you like it, MOD it. And of course there is no Closed loop issue with changing the fan ON temps. Thermostat makes sure of that regardless.
Have fun.

darguy

Thanks for the feedback. What temeratures would you consider 'too high' for the water and oil?

RedRiderZR1

Loaded question there. Different views from different people I am sure. But for me 230 water and 245 oil is too hot for me. During the summer months I watch the water temp guage and set the DIC to monitor oil temp. So I can look down and see what they are. Like I said, Around town not really an issue, but on the track it can be. Was for me anyways. Have a dewitts radiator in now. Just need to get the fans now. These stock fans suck (as in not sucking air very well).

Y2Kvert4me

The left and right fans always operate simultaneously.

Fan1 refers to low speed (when the fan relay supplies power to the fan motors in a series-wired configuration, which causes both fan motors to operate at approx half of full-voltage speed.

When Fan2 is called for, power to the fans is supplied in parallel, so each motor receives full voltage, and they run at full speed.

Thus, turning Fan1 on "high" isn't possible. Fan1 simply means low fan speed operation.



As for your recommended settings, you would likely be turning the fans on high speed operation almost immediately, because of the mere 1° difference in turn-on points.
That's way overkill, and in practice, most with adequately maintained and efficient cooling systems normally never find a need for fan2 at all (consider it a backup setting).

A more reasonable suggestion would be:

Fan1 on at 195, off at 189
Fan2 on at 205, off at 196

Try it, and I'll bet you'll still find coolant temp never exceeds 200, and it did so w/o high speed fan operation.

darguy

Thanks for the feedback! Would the Fan1/2 settings you've reccommended also be appropriate for the stock 192 F thermostat and stock cooling system?

Y2Kvert4me

No.
You need to keep the fan turn-off points above that of the Tstat rating, and/or what you find your normal moving temps are.

With the stock Tstat, you may likely find your car normally runs right around 192 when cruising on the highway. In this example, if you have your fans set to not shut off until 189, what happens is once the fans are commanded on (which will happen at a stoplight or while idling), they will never shut off, even after the car is moving again, because the Tstat will not allow it to run down to 189. Conflict of components.

For a stock Tstat, better settings would be:

Fan1 on at 205, off at 197
Fan2 on at 215, off at 206

Again, taking into consideration fan2 will not likely ever come on...and if it does, it's a good indicator the cooling system could use some work.

darguy

Thanks - I was thinking about the fan never turning off scenario on the drive home while monitoring my temp, I should have thought of that. I'll try out those settings, they're a little lower than I had put in there, and may be more appropriate for the initall track day.

Y2Kvert4me

For track day, the fans really don't (or shouldn't) have an effect. If you're moving the whole time, the airflow, Tstat, and radiator efficiency are what's determining where your coolant temps sit. The fans are only there to move air through the radiator when the car is still.

If you find it runs too hot running around the track, a lower rated Tstat, and/or a more efficient radiator will help in lowering your temps while the car is moving.

And, as already stated, a lower temp Tstat won't affect it going into closed-loop.

vettman10

I recommend a 160 thermostat which is readily available from several after market parts manufactures. I set the fans up ia a manner similiar to what Pumba mentioned, and I have been using this sequence for many years, on many cars. Fan 1 (low speed) On at 187, Fan 2 (high speed) On at 188, Both OFF at 182. This keeps the engine in the mid 180's. Keeping the engine a little cooler will enable a good tuner to get more agressive with the tune-up ( leaner air/fuel, and more spark advance). Also, this sequence brings the fans to high speed right away which brings the temp down within a couple of minutes and allow them to shut off. Whereas the traditional settings of having a 10 degree or more spread between fan 1 and 2 settings basicly keeps the fans running at low speed thie entire time the car is stationary, thereby putting far more wear on the fan motors.

BaseballDude

Great thread. Mid 180's intuitively sounds too cool for me. My '02 Z06 is a daily driver (stock tune...no plans to change it either) and I'm after keeping the temps no higher than the mid 190's. As a previous poster said, on the freeway I tend to stay at 192 (stock thermo and fan settings) until I hit traffic.

What's the recommendation for staying in that 192-195 zone for my DD?
Said another way, idling in traffic I would LOVE to see no more than 190-195, tops.

Thanks,

-Dean

Billf6531

Set fan 1 to your highway cruise coolant value +7* on and +3* off. Fan 2 +11* on and +5* off. Works like a charm.

BaseballDude

Bill, with my stock 187* T-stat my highway cruise is at 192. Assuming the 5 degree differential would stay the same with a 180* T-stat, my updated highway cruise temp would be ~185. Using that logic, the fan settings would look something like this:

Fan1 on = 192
Fan1 off = 188

Fan2 on = 196
Fan2 off = 190

You agree?

BTW, just bought a 180* (not installed yet) and now need to locate a local tuner in The OC that can help me with the reprogramming. Just need to figure out exactly what range I want to hit with all these settings.

Billf6531

I agree with the logic, but I wouldn't assume anything. If you're going to change the thermostat, and I wouldn't, get on the highway at your normal driving speed in cruise, and let the coolant stabalize. Use that value as your starting point.

BaseballDude

With the stock t-stat I'm cruising at 70-75mph on the freeway holding 192*. So using your model I would set the fans as follows:

Fan1 on = 199*
Fan1 off = 195*

Fan2 on = 203*
Fan2 off = 197*

Seems too warm to me. I know these cars are "designed" to run hot, but anything north of 195-200* is just not healthy over time (and that's just the water sensor temp...doesn't account for what is actually occuring in the oil at the crank/bearings). 190* water will get the oil hot enough to boil off any water vapor and contaminants.

I appreciate the advice, but I think I will tweak your values a bit lower.