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Rear Seat Delete Builder
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Discussion Starter #1
Is it that important to change to a 160 stat when I do my tune? Im in california and winter is coming where the avg temp will be around 60-65 daily.
Ive read where some guys are running 180's only with a tune.
Any thoghts?
 

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May I quote you on that?
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180 is best bet for staying out of the "controversy zone" There is a body of evidence that cylinder wall lubrication efficiency begins to decline below 180, and 160 might upset the PCM into going open loop. The greater sin is how high the PCM lets the temps get before kicking on the fans.
 

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No More GTO!!!!
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I have a 160 and with my fans reprogrammed the way I like it sticks right at 174 all the time.
 

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Rear Seat Delete Builder
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Discussion Starter #6
So keep the 180 and set the fans to come on a bit earlier?
 

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May I quote you on that?
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I would. I suspect the only SES probs with 160 might be in very cold climates at high speed.
 

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The Anti Dyno Racer
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Blitzu, I agree with everything you said. I ran a 160 in the Vette all year, including the below freezing temperatures. It obviously didn't hurt anything, looking at the ETs I got with a stock motor :D
 

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Wooohooo
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Blitzu said:
Stock is 186 so a 180 would be pointless in my opinion. I run a 160 year round.... I justr adjust my fan temps through the computer.
Stock is a 195 not 186.
 

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13 year owner
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16,379 Posts
The problem with a 160* T-Stat on a stock headed, stock cammed motor, is that it'll run too cool which may put the PCM into a "reduced power mode". A DTC which triggers your check engine light isn't going to happen.

On 80* days here, cruising, with the 160* stat in, mine would run about 172* That is simply too cool. 180* is optimum. So I put the stocker back in which ran at about 184*. Much better!

So unless you're running around with heads and cam, S/C or something else, a 160* simply isn't needed.
 

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The Anti Dyno Racer
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CMNT, 172 is not too cool. I liked to run with my coolant in the low 170s and oil temp of 150 - 180. The car always got a few hundredths better ET this way, on a stock heads/cam LS1 with bolt-ons. I got the C5 with the stock internals LS1 down to [email protected], so it obviously wasn't too cool, and never ran too cool before tuning. If I was in "reduced power" mode the track times don't show it.
 

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13 year owner
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I think it's too cool regardless. Mine never have run that well cold and I actually think that was part of my power loss reasons that I suffered from this summer. After I went back to the stock T-stat, the car came alive again.

I don't know for sure if our PCM's have this feature, but I honestly think it went into a safety "reduced power mode".

If yours ran well at that, fine, but I think you're the anomoly.
 

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'05 GTO Nationals - St. Louis
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Baaa said:
Stock is a 195 not 186.
Are you sure about this?... I think I read in my FSM that the stock thermostat is in the 180º range. I'll have to check tonight when I get home.
 

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13 year owner
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Most factory t-stats are 195+ for emissions purposes. The only way to truly tell is to dump the stocker in 180* pot of water and see if it pops. If it doesn't, it's not a 180* stat.
 

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No More GTO!!!!
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The PCM reduces timing before 176 degrees and after 212 degrees on a stock tune.It varies amount of timing on engine load.In HP Tuners the in the timing advance section you can edit the timing under ECT Correction tab.I just zeroed out the retard over 160 and left 212 and above in place.So CMT is correct about losing power but I wouldn't call it power reduction mode.It is just not adding the timing that is given at the other temps.
Anthony
 

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Wooohooo
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Blitzu said:
Stock thermostat-

Looks like 186 to me.
Not the greatest picture. It is difficult to get a good angle on it.
I thought someone else on here posted a pic of one that said 195. Hmm is it also possible they changed to a different t stat sometime like they seem to ahve done with some other items?
 

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Been here for a long time...
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Mine says 86 C which comes out to 186 F
 

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Wooohooo
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Rob said:
Mine says 86 C which comes out to 186 F
Then 160 is not that much cooler and should run just fine. I know my car runs the best and def feels the strongest about halfway up the coolant gauge before normal operating temps. Prob 150 or so.
 

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13 year owner
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Bone said:
The PCM reduces timing before 176 degrees and after 212 degrees on a stock tune.It varies amount of timing on engine load.In HP Tuners the in the timing advance section you can edit the timing under ECT Correction tab.I just zeroed out the retard over 160 and left 212 and above in place.So CMT is correct about losing power but I wouldn't call it power reduction mode.It is just not adding the timing that is given at the other temps.
Anthony
Oh good. So I was onto something then. :D I went back to my stock T-Stat and run 183 - 186 now. Optimum.
 

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May I quote you on that?
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I take the writing on the thermostat with a grain of salt, metric or otherwise. The ECT at speed on a cool day is the bottom line. Fans can be reprogrammed to keep you closer to the thermostat set point, if you don't mind additional fan activity. I get 191-192 at speed, but idling or in traffic it climbs to 228+ before the fans come on. That's too high for me.
 
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