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 Should I replace my OEM thermostat?

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AA
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PostSubject: Should I replace my OEM thermostat?   Mon Jan 15, 2007 8:39 pm

For thermostat write-up: http://rivperformance.editboard.com/t3484p15-write-up-thermostat-installation#41776


Replace the thermostat? For supercharged engines, the short answer is yes.

Changing the stock thermostat to a 180F unit will slightly lower the engine block temperatures by opening sooner (at a lower temperature). This helps to fight spark knock, which enables the engine to generate more power. A 180 unit will not interfere with the ability to heat the car in winter. 180 units can be purchased through most auto parts stores, or at any of the online 3800 V-6 vendors for around $5-10.

160F thermostats are also available, but understand that there are issues related to the engine running too cool that make the 160 unit undesirable in most daily driving situations, especially in cooler weather. For racing purposes, or in very hot climates, it may make more sense.

Results of installing an aftermarket thermostat in '98 Riviera

One concern when modding the L67 is how to rid the combustion chambers of excess heat. The easiest way to help lower engine block temps is to install a thermostat that opens at a lower temperature and flows more coolant than the stock unit.

Here is a graph showing two separate scans of my car, one with the stock thermostat and another with an INTENSE high-flow 160F unit installed. The tests were done on a 40F day over a span of less than 10 minutes, most of the time cruising at 65mph:



As you can see, the aftermarket 160 t-stat does its job quite well. After opening at 155F, the unit lets temps fall to as low as 140F, and it stays open after the engine completely warms up, keeping the engine at a sustained 145F operating temp at freeway speeds on a cool day. Note that 145 is much too cold for practical daily driving, and the 160 unit was removed after this test. But it shows its effectiveness.

In contrast, the factory (195) unit lets the engine heat up to ~200F and then allows temps to fluctuate up and down within a tight 10 degree window as it opens and closes about once per minute. As far as I can tell, it does this continuously at freeway speeds, especially in colder weather.

Not exactly a ground-breaking study, but it's interesting to see how each t-stat operates. The end result is a considerable lowering of engine temps - an average of 50 degrees - a bit more than I had expected.

Caution: it has been determined that using a 160 t-stat can be dangerous for our engines in colder weather. The Riviera's PCM comes programmed with a setting called "KR activation temp". This setting is a specific engine coolant temperature value (158F), above which the engine's knock sensors will be activated and "listening for knock". Below this point, the sensors are ignored by the PCM, and the engine will likely knock (audibly) if pushed to WOT. For this reason, it would be unwise to run a 160 unit in ambient temps much cooler than 65F, as engine coolant temps will drop below the KR activation threshold.

Through the use of a PCM programmer like the DHP PowrTuner software, the KR activation temp can be set to a lower value (-40F) so that the knock sensors are "listening" at all times. However, it is suspected that running with an engine's coolant temps much lower than 180F can cause excessive engine wear over time, so it may not be a good idea to run a 160 except for racing applications. On the other hand, there are those who feel running cold is of not as much concern. Run the 160 t-stat at your own risk. A 180 unit is safer choice until it is known for sure how badly our engines wear at lower temperatures.


After this test, it was decided to use a 180F thermostat for the best balance of cooling performance, knock reduction, fuel economy, interior heating, and engine longevity.

_________________
'98 SC Riviera 268k miles 298 HP/370 TQ 0-60: 5.79s ET: 13.97 @ 99.28 4087 lb 20.1 avg MPG Nelson Ledges Lap: 1:30
3.4" pulley AL104 plugs 180 t-stat FWI w/K&N 1.9:1 rockers OR pushrods LS6 valve springs SLP headers ZZP fuel rails
KYB GR2 struts MaxAir shocks Addco sway bars UMI bushings GM STB Enkei 18" EV5s w/ Dunlop DZ101s F-body calipers
EBC bluestuff/Hawk HP plus SS lines Brembo slotted discs DHP tuned Aeroforce Hidden Hitch


'05 GTO 49k miles 0-60: 4.8s 16.9 avg MPG Nelson Ledges Lap: 1:26
Because fun


Last edited by AA on Sat Dec 31, 2011 4:47 pm; edited 3 times in total
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PostSubject: Re: Should I replace my OEM thermostat?   Thu Feb 01, 2007 1:06 am

I thought I saw somewhere some modular type system or something. I don;t know, all I remember is you could change the temp yourself via a wired digital remote/display unit
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PostSubject: Re: Should I replace my OEM thermostat?   Thu Feb 01, 2007 1:35 pm

why would you want to? for that +1 mpg fuel econ lol
i really didnt see any drop in fuel when i switched to the 180*

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PostSubject: Re: Should I replace my OEM thermostat?   Thu Feb 01, 2007 3:23 pm

No, it was in order to change the temp on the fly. So if you are driving around town you could keep it around 180* or whatever you want, then at the racetrack it could be easily set to 160*. Then when you are done back to 180*
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PostSubject: Re: Should I replace my OEM thermostat?   Tue Mar 20, 2007 8:53 pm

i just put in a new radiator today and a 180* thermostat. the thermostat opened at a/b 185 but the fans did not come on until a/b 210 does anyone no why does it have to do with the computer or something.??
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PostSubject: Re: Should I replace my OEM thermostat?   Tue Mar 20, 2007 9:47 pm

robertwolf86 wrote:
i just put in a new radiator today and a 180* thermostat. the thermostat opened at a/b 185 but the fans did not come on until a/b 210 does anyone no why does it have to do with the computer or something.??

Yes that is what they are programmed to do.
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PostSubject: Re: Should I replace my OEM thermostat?   Tue Mar 20, 2007 11:00 pm


_________________
'98 SC Riviera 268k miles 298 HP/370 TQ 0-60: 5.79s ET: 13.97 @ 99.28 4087 lb 20.1 avg MPG Nelson Ledges Lap: 1:30
3.4" pulley AL104 plugs 180 t-stat FWI w/K&N 1.9:1 rockers OR pushrods LS6 valve springs SLP headers ZZP fuel rails
KYB GR2 struts MaxAir shocks Addco sway bars UMI bushings GM STB Enkei 18" EV5s w/ Dunlop DZ101s F-body calipers
EBC bluestuff/Hawk HP plus SS lines Brembo slotted discs DHP tuned Aeroforce Hidden Hitch


'05 GTO 49k miles 0-60: 4.8s 16.9 avg MPG Nelson Ledges Lap: 1:26
Because fun
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PostSubject: Re: Should I replace my OEM thermostat?   Sun Aug 10, 2008 12:55 pm

Tired of watching my gauge sit a little over 200. Just picked up a 180 T-stat.
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PostSubject: Re: Should I replace my OEM thermostat?   Sun Aug 10, 2008 1:32 pm

That will help when the car is moving, but sitting in traffic you will still see climbing temps, unless you have modified fan turn-on settings.
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PostSubject: Re: Should I replace my OEM thermostat?   Sun Aug 10, 2008 1:37 pm

1998 Riv wrote:
That will help when the car is moving, but sitting in traffic you will still see climbing temps, unless you have modified fan turn-on settings.

Taking a long trip to TN tomorrow and I am hoping for slightly lower temps. Gonna have to research the fan settings.
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PostSubject: Re: Should I replace my OEM thermostat?   Sun Aug 10, 2008 1:38 pm

It will certainly help on the hwy. What year is your Riv? That will determine if you'll be able to modify the fan settings. Please take some time and add basic car info to your default sig in the Profile section.
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PostSubject: Re: Should I replace my OEM thermostat?   Sun Aug 10, 2008 2:13 pm

1998 Riv wrote:
It will certainly help on the hwy. What year is your Riv? That will determine if you'll be able to modify the fan settings. Please take some time and add basic car info to your default sig in the Profile section.

I'll do that now. It's a 97 SC. The T-stat replacement was amazingly easy.
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PostSubject: 160 vs 180stats   Sat Aug 16, 2008 9:16 pm

Im not driving the Rivi in the winter time at all, i have a heated storage facility i used to work at to keep the car there for the winter, i know that a 180 stats is better for cooling, so 160 has to even better right, if im only driving the Riv in the warmer months, is the 160 a better idea?

also, i noticed when i baught the car that coolant overflow tank is full of a brownish colored liquid im imaginig is that DEX-COOL Crap, or some mixture of coolant and stop leak mabey, anyone else ever experience this?
i syphoned it out and put new coolant in but its back, im hoping its not pulling oil from somewhere through the system, im hoping that a radiator flush will do the trick. Any Ideas?????


scratch
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AA
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PostSubject: Re: Should I replace my OEM thermostat?   Sat Aug 16, 2008 9:29 pm

Scroll up to 2nd post from top.

_________________
'98 SC Riviera 268k miles 298 HP/370 TQ 0-60: 5.79s ET: 13.97 @ 99.28 4087 lb 20.1 avg MPG Nelson Ledges Lap: 1:30
3.4" pulley AL104 plugs 180 t-stat FWI w/K&N 1.9:1 rockers OR pushrods LS6 valve springs SLP headers ZZP fuel rails
KYB GR2 struts MaxAir shocks Addco sway bars UMI bushings GM STB Enkei 18" EV5s w/ Dunlop DZ101s F-body calipers
EBC bluestuff/Hawk HP plus SS lines Brembo slotted discs DHP tuned Aeroforce Hidden Hitch


'05 GTO 49k miles 0-60: 4.8s 16.9 avg MPG Nelson Ledges Lap: 1:26
Because fun
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http://www.cardomain.com/ride/657082/4
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PostSubject: Re: Should I replace my OEM thermostat?   Sat Aug 16, 2008 9:31 pm

THX
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