You'll find this to be a very controversial issue--Many people disagree using lower temps and many agree---My personal opinion is that the only reason for high temps is to clean up emmisions--I have a racing background and have never heard of running hot for performace tuning--There are so many resons to run cooler--better city driving-longer lasting hoses-belt-rubber and plastic engine components-lower Iat temps--more accurate AFR tuning--less pre-ignition--more timing
As far as running hotter ?? The only reason I can think of is lower emissions-----Some will say that hot temps keep the engine oil at the proper running temperature---But I disagree there too--I have a 160* thermo--engine runs at 180* and the oil temp is STILL 200*--perfect So that agruement for low water temps causing low oil temps & sludge is not true in our cars---
I have a 178 degree stat and the ONLY code that I get is (cant remember the PCM code at the momemt) is one that states that the engine didnt warm up as the PCM expected it to. I get this code very infrequently and I just reset it.
Install the low temp stat and be done with it, I drive my car just about year round in the North East "CT" and do NOT have any issues with cabin heat at all!
I have a 178 degree stat and the ONLY code that I get is (cant remember the PCM code at the momemt) is one that states that the engine didnt warm up as the PCM expected it to. I get this code very infrequently and I just reset it.
Install the low temp stat and be done with it, I drive my car just about year round in the North East "CT" and do NOT have any issues with cabin heat at all!
No trouble codes for me with the 160* thermo---I have heard of an intermitent code like mentioned above but haven't seen it--If it keeps happening all you do it turn off the MIL.
I live in the Pacific Northwest, I run a 160° plus a Dewitts radiator and lower fan settings. Engine coolant temp stays in the low 170s' and I haven't seen any codes yet. Oil temp is still up above the recommended temp.
From what I have read, the motors these days run hotter than the older cars so they can burn more emissions. It was the only way the car manufactors could meet the strict goverment emission requirments.
Beginning in 2003 or 2004, federal emmissions laws require that a car engine warm up to operating temps in 4 minutes or less. Thats the reason for the code.
As far as best operating temps, it is more critical to maintain lower temps in an engine that has a metal intake manifold. The LS1 has a plastic intake manifold so engine temps arent AS critical. However, heat is a problem and it increases the chance of detonation. Normal temps in the LS1 wont have much effect on your oil since the LS1 uses synthetic oil and synth can withstand much more heat than conventional oil.
Last edited by leojnknsC5; 03-03-2007 at 07:20 PM.
Anyone have any dyno results between the factory 192 vs. 160 degree thermostat?
I am still learning about our cars so forgive me for what might seem simple questions.
Will a cooler thermostat change the A/F ratio? Which in turn will help the HP (or potential HP)? Or does it help you "tune" more performance without pinging or running too rich/lean?
I know many members are against changing the stat so I don’t want to get in a heated discussion I just want to know the “logic” or “theory” behind the lower thermostat (besides running cooler).
Will a cooler thermostat change the A/F ratio? Which in turn will help the HP (or potential HP)? Or does it help you "tune" more performance without pinging or running too rich/lean?
Engines with carburators on metal intake manifolds are affected by heat and cooler thermostats allow for more power if tuned properly. The LSx has a plastic intake manifold and the plastic doesnt get hot like a metal, aluminum, intake manifold so stat temps arent AS critical to incoming air charges. If your intake draws from a source of fresh cooler air instead of underhood air, the factory stat is not a problem. If you get into supercharging or turbos, you might want a lower stat for the peace of mind, insurance.
Thanks leojnknsc5, but that would also tell me that the throttle body bypass would work very well when many members state they are a waste of time. I can see both sides of the argument but I did a bypass anyways since I could not hurt.
formula for airflow is:
Airflow=Cyl# * RPM/120 * MAP * CylDisplacement * VE/ (120*Temp*SpecificGasConstantForAir)
Temp is in Kelvin, so the difference between running 20 and 40*C IAT's is going to
airflow1=X/(273.15+20)
airflow2=X/(273.15+40)
so 20*C of colder air is worth about 6.4%
remember that the temperature gets calculated as a blend of IAT and ECT, biased differently based on how much air you're pushing through. at airflows that matter, it's about 13% ECT and 87% IAT,
so between 180F and 200F, that's going to cause only about 1.5*C difference in aircharge temperature.
so if you're going to lower temperatures for performance, do it with IAT, not ECT, much bigger performance gain
Very true Marcin. I've never found it necessary to tamper with stock thermostats on any vehicle. The most I've done is trigger the cooling fans to operate a few degrees above highway cruising speeds so that I know the true closed/open value. On a stock C5, for example, it's 88*C. This keeps ECT relatively constant, and leaves erratic afr the result of incorrect IAT calculations (provided the VE table is accurate).
If you hold ECT constant, and accurately measure IAT inside the intake manifold, there should be no change to your AFR, provided your Charge Bias / Blending Table values are correct.
There are hundreds of posts on this issue. Some advocate ignoring IAT to eliminate one variable that causes AFR to drift with IAT. Others like EFILive have an additional IAT vs VE table that corrects the VE for the errors in the Charge Bias / Blending Table. Both depend on an accurate VE, though, derived from a wideband.
I'm still working on finding the near perfect solution. If anyone has already done so, I'm all ears.
EDIT: ... and finding the perfect solution is somewhat like a dog chasing its own tail. You have to set up the Bias table first, then re-tune the VE, then try and figure out whether the Bias table needs higher or lowest values to be less incorrect. Then repeat, etc.
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formula for airflow is:
Airflow=Cyl# * RPM/120 * MAP * CylDisplacement * VE/ (120*Temp*SpecificGasConstantForAir)
Temp is in Kelvin, so the difference between running 20 and 40*C IAT's is going to
airflow1=X/(273.15+20)
airflow2=X/(273.15+40)
so 20*C of colder air is worth about 6.4%
remember that the temperature gets calculated as a blend of IAT and ECT, biased differently based on how much air you're pushing through. at airflows that matter, it's about 13% ECT and 87% IAT,
so between 180F and 200F, that's going to cause only about 1.5*C difference in aircharge temperature.
so if you're going to lower temperatures for performance, do it with IAT, not ECT, much bigger performance gain
Well explained! And it shows why cold air induction of some sort seems to be a real popular mod. The stock airbox grabs essentially underhood temperature air, so you get both variability and the potential for HOT air if you live in a climate like ours here in the Sacramento Valley where we can get a string of days over 110F. Yikes!
I don't remember seeing it in the thread, so I'll mention that the reason this formula works is that colder air is denser air. When I was getting my pilot's license, long ago, we talked about density altitude. As it gets hotter, it's like adding altitude. To the point that aircraft manufacturers include density altitude tables in their weight and balance formulae, and if you ignore them, you getter hope you can still outclimb the terrain. Places like Lake Tahoe, where the base altitude is high and you add a lot of artificial altitude for heat in the summer, you can have problems. Same theory here - hotter air is thinner - less oxygen, so less power per cubic foot.
The Vararam, Honker, zip-tie mod, and others you can find on the forum will address the hot IAT issue. The hot (or variable) ECT can be stabilized with a tune that narrows the on/off range of the fans, as mentioned earlier in this thread.
I'm thinking about a 178F stat, just to open things up earlier on the hot days, but the Predator tune seems to keep me around 195F in traffic. That's down from about 220F stock.
As also mentioned earlier, cooler engine temps were important for the carb/iron manifold cars of yore. My '84 WS6 is running a 160F stat, which helps a lot. Now if only I could figure out how to program its fans to keep it under 200
Last edited by BowTieRocket; 03-04-2007 at 11:30 PM.
By the way I had been looking for the thermostats at a reasonable price and found em for 19.95 at mid america ....
So I bought a bunch of other odds and ends,,,, now I need to figure out which programmer i am going to buy so I can get the fans to come on earlier and CAGS garbage along with "CATS ignore" settings
I'm happy with the Diablosport Predator performance tune; you can make some additional mods with the handset, but it was okay for my purposes out of the box. Of course, I'm a geezer with a limited need for going scary fast. It tightened things up, and doesn't scare my wife too badly.
There are a ton of tuners out there, and a custom/dyno tune will probably get you better results. I just liked the combo of a performance tune and pretty good code read/reset capability. FWIW.
Corvette Store
lower temps more Horsepower?
Well explained! And it shows why cold air induction of some sort seems to be a real popular mod. The stock airbox grabs essentially underhood temperature air, so you get both variability and the potential for HOT air if you live in a climate like ours here in the Sacramento Valley 
Of course, I'm a geezer with a limited need for going scary fast. It tightened things up, and doesn't scare my wife too badly.
