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How cold is too cold? With a 172/178 TSAT and a Vinci Fan Controller set close to the lowest setting, my car is running 171 degrees at highway speeds (75MPH) with an outside temp of 65 degrees. At the same outside temp of 65 degrees, in traffic it will not go above 185 degrees. Should I set the fans to come on later so the car will heat up more?

Thanks
MR
 

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180 is fine

Hi there,
The lowest that I would go is 180, as your want some heat for correct atomization of fuel.
Any lower, and you may have drivability concerns, unless you are racing.
180 is more than adequate.
Best to you, c4c5
 

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There are several issues your post raises. Let us address them in turn.

First, if your coolant temperature is running at 171 F, you do not have a 172-178 degree thermostat. Thermostats are rated at their "opening temperature". Actual operating temperature usually runs 6-10 degrees hotter. Your thermostat seems to be opening in the low 160s. This is probably too cold. Why?

Second, oil temperature usually runs about 10 degrees above coolant temperature. If your coolant temperature is only 171, your oil temperature is probably about 180, too cool to "boil off" the condensates that collect in the oil pan. These condensates can dilute your oil and result in severe wear. You probably would like the oil temperature to be 195-200.

Third, hotter engines make more horsepower. There is considerable evidence, however, that in a LS-1/LS-6, spark and fuel retard cut back power if the coolant temperature gets much above 190. So I would aim at a 190 coolant temperature. This should result in, say, a 198 oil temperature.

Many people offer a "180 degree" (opening temperature) thermostat. That should be about optimum for keeping the oil clean and making maxium horsepower.
 

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I'd have to agree. The trans-am guys run their engines at like 200-210, same with the winston cup people.
 

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Anyone know what the stock '02 Z06 Thermostat temp is?

I'm considering purchasing the Hypertech 180 Thermostat from LAPD and wanted to know if this is the best option for everyday California driving and drag racing on occassion. Their price is $59.95, seems to be a decent price from what I can tell.

Also, should I get a fan option that I can turn on during racing?
 

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We have a 178 tstat for 50 bucks that will allow you to run cooler for highway driving.

For complete cooling, we have a fan controller/tstat combo, which is a must for city driving and track results. The fan temps need to be adjusted for the constant cooling feature you may be after.


If you are in a cold weather environment, you may want to switch back and forth or leave the tstat stock.

RG
 
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For one the motor oil allows maximum performance when it is about 210 degrees.

2nd - the PCM has monitors ( software routines) that demand for a valid warmup cycle to reach 200 degrees. If that is not met, any type of error has a rule to maintain in the system for 40 to 80 trips ( certain functions reaching a set spec value as per EPA/OBD-II mandates).
Thus if the temps are maintained too low, it takes much more time and trips to clear DTC codes or PCM to relearn if it has been cleared either by erasing DTCs or PCM losing power for a period of time.

Three - if your engine makeup is keeping fuel trims to be on the rich side, making engine cooler only makes AFR worse which would cause lower timing ( esp at WOT).
Imagine if engine temps are too cool for summer how much worse it would be with winter temps.

Instead of cooling engine temps to correct for lean conditions or ping, try using one step cooler sparkplug and using a MAF translator to tune AFR to tune out leanness and ping/knock.

John

MARZ06 said:
How cold is too cold? With a 172/178 TSAT and a Vinci Fan Controller set close to the lowest setting, my car is running 171 degrees at highway speeds (75MPH) with an outside temp of 65 degrees. At the same outside temp of 65 degrees, in traffic it will not go above 185 degrees. Should I set the fans to come on later so the car will heat up more?

Thanks
MR
 

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Re: Re: Temperature Control

teamzr1 said:
For one the motor oil allows maximum performance when it is about 210 degrees.

2nd - the PCM has monitors ( software routines) that demand for a valid warmup cycle to reach 200 degrees. If that is not met, any type of error has a rule to maintain in the system for 40 to 80 trips ( certain functions reaching a set spec value as per EPA/OBD-II mandates).
Thus if the temps are maintained too low, it takes much more time and trips to clear DTC codes or PCM to relearn if it has been cleared either by erasing DTCs or PCM losing power for a period of time.

Three - if your engine makeup is keeping fuel trims to be on the rich side, making engine cooler only makes AFR worse which would cause lower timing ( esp at WOT).
Imagine if engine temps are too cool for summer how much worse it would be with winter temps.

ZR1, It sounds from you post you know much more than I do about the effects the computer programing has. But I run a 160 and rarely does it see 200 except in heavy traffic,never at the track. I haven't seen any codes and the car runs faster than any other Z06 I have run into. So at lest in my cars case if what your saying is fact it does not make sence to me. Can you help me to understand what the differance is? Thanks, Ric


 
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EPA/G.M warmup cycle

Runing colder would not trigger errors by itself but if errors were triggered for any reason, EPA mandates to be sure error has been resolved those codes must reside in PCM memory for XX amount of trips the following is G.Ms procedure to comply with OBD-II mandates :

The main intention of the GM OBD-II cycle is to run the OBD-II Main Monitors in order to determine the status of the I/M readiness tests and to have the PCM relearn after a low of power or Keep Alive Memory and errors lost.
The drive cycle can also be used to assist in identifiying any OBD-II concerns that exist by running all of the monitors.
A cold start is a necessary step in preparation to run a complete OBD-II compliant drive cycle.

If a car is driven under the correct coditions, all of the OBD-II monitors will run their various tests, and if a test fails, set a "pending" or hardcode (MIL is llluminated).
Differences in how each monitor runs a test define the type of TRIP needed to run that monitor.
Some monitors are run only on cold engine startup, some only on a highway cruise speed with the TCC off and others at idle speed with A/C off.
Some tests will not run until a car is driven in a drive pattern that meets all of its enable criteria.

Valid Drive cycle table Requirments( total time - 12 minutes)


Cold startup ( coolant temperatre less then 122 degrees)

Idle 2.5 minutes in "D" or "N". A/C & defogger "off"

A/C "off", accelerate to 55 MPH at 1/2 throttle

Steady state Cruise at 55 MPH for 3 minutes

M/T clutch engaged, no braking, Decel to 20 MPH

Accelerate to 55-60 MPH at 3/4 throttle

Steady state Cruise at 55-60 MPH for 5 minutes

Decelerate without braking
End of valid drive cycle.

For PCM to know the position of crank position sensor, PCM must see 5,120 RPMS within drive cycle after power to PCM has been lost.
Note: Specific engine warmup conditions must be met in order to complete all OBD-II tests.

Once an error is triggered under the regulations it must be stored in memory for some timeframe, even when the error has been resolved.
To clear that error, X amount of TRIPS must occur before that error will be erased by the PCM.

OBD-II Warmup cycle

To complete an OBD-II warmup cycle, the engine must reach 160 degrees and achieve a temperature rise of at least 40 degrees from the initial startup engine temperature.

For example a engine could start at 120 and rise to 210 degrees and achieve over a 40 degree change, in this case, the warmup cycle conditions would be met.

However, if a engine started at 150 and rose to 180 degrees, a 40 degree change in engine temps would not have occurred.
In this case, the warmup criteria would not be present and some OBD-II diagnostic tests would not be run.

Thus if you were to install a lower degree thermostat that prevented the 160/200 degree rule, it would take much longer a time period for PCM to relearn and to clear errors stored for XX amount of trips which can be as high a 40 trips.

Keep in mind that there also is a re-learn process that needs to be done for correct idle.
In most cases you would for a MN6 based C5:


Cold start and idle for 5 minutes ( all power functions are off)

Turn on A/C only and continue to idle for aother 5 minutes

Turn A/C off, continue to idle for 5 minutes

Also keep in mind I/M tests which must be in a complete state when you go in for the newer smog tests. If popwer has been lost to PCM or the error codes were erased, the I/M test flags will be set to "not complete" and with a colder engine setup it will take much longer for those tests to get completed.
Without using a PCM scanner you would not know what state the I/M states are and if your state requires I/M testing, you would be rejected in smog testing due to I/M tests never getting to a complete state.
 

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TeamZR1, Thanks for the imfo. I will be geting some new tires mounted this week and will have them hook up the scaner to see if anything is stored. Ric
 

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I think C4C5 is on the mark. Here are a couple of things to consider:

CAGS is not enabled until the coolant temperature reaches 169 degrees. I assume they do this so that cats reach their operating temps faster and that lugging the engine in fourth while cold isn't a good thing.

My experience with the stock 195 degree thermostat is that on warm days on the highway, the car stays at almost precisely 196 degrees while cruising (80 MPH).

The last few days have been in the upper fifties here and my coolant temps have stayed between 192-194 at cruise, note my heater core is removing some engine heat.

IMHO a 178 degree thermostat would be perfect along with turning the fans on at 195. If you can keep the coolant temps at 195 and below your doing very good. I wish the fans would turn on at 195, but keeping the AC compressor on at the lights keeps the coolant from getting in the 200s. In my experience, if your coolant temps are at 200, your losing performance, and 210 and above your losing a lot of performance.
 

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Just installed the 172 thermo and fan kit purchased from Nick at Extreme. Nice kit, good quality, wiring hrness was essentially a plug-in - good price. Car was averaging 215-218 sittin in traffic, now seems to be averaging about 20 degrees cooler. On the road, preliminary temps are in the mid to upper 180's.

So far I am very pleased with the early results...

Guess we will see what temps are like in a few months, although i do not do much driving in the winter.
 
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