I've been using a 160 degree thermostat in conjunction with a modified fan setting for a couple of years without incident. My friends in my Corvette club say thats too low to go and I might be doing some damage to the system. Is this possible? My coolant temperatures on a hot day might reach 182, but under normal conditions it stays about 174. I don't use the car in the winter. Thanx. :seeya :seeya

 

Your computer won't close loop till 176, leave well enough alone.

 

What happens when it goes into closed loop? :confused:

 

The PCM for a C5 requires 3 or 4 things to happen before it goes into closed loop, but the temperature required is only 135, not 176. :cheers:

As for harming your engine, no, it won't. You may see earlier oil changes suggested from the DIC due to lower oil temps, but most people change oil sooner anyway. :cool:

 

My car usually runs between 174-192 or so, which I think is perfect. No harm will be done at all running these temperatures. :cheers:

 

I'd leave it just the way it is! Mine runs at 190 degrees consistently and I'm going to have it tuned to run closer to what you're running. The cooler the engine, the better power it'll make.

 

Not true, got dyno sheets to prove it also watch NASCAR and what they run for temps. This topic has been beet to death for 3 years check all the old posts and as I said leave well enough alone and be happy, believe it or not GM and the millions they spent aren't to far off compared to some backyard tuner and an ego...


[Modified by jimman, 2:06 AM 7/23/2002]

 

GM runs the motors hot for emissions control, not power. LS1's will generate more power if you run them a little cooler. Comparing LS1'S to NASCAR motors is apples and oranges, we aren't running leaded race gas through hand massaged mega dollar heads being rebuilt every 500 miles. We're forced to run goat **** gas through heads compromised for power, mileage, and emissions, which build up carbon from thousands of miles of running. Running OUR motors a little cooler will keep them out of detonation, allowing the PCM to run max timing. :cool:

 

160 is the temp when the thermostat opens...the car will, of course, run warmer than that. If you are looking for a relationship between temp and "harm", look at the oil temperature. In cars that seldom see oil temps over 212, there is the risk on contamination due to condensation of water in the engine. Most Vettes run hard enough to get to this temp though.... :jester

 

6speeder, Just finished dyno runs again, for the 6th time and again I say more hp at 200 then 170. I'll send the sheets and you can confirm with the other 40 guys that all dynoed on those days. Low temp isn't cutten it dude.

 

Low temperature thermostats can harm your engine. In the first place, they only produce more horsepower by fooling your computer into thinking the engine is not warmed up, thus it sets a richer fuel mixture (i.e. more gas), much like running with a choke on.

It's bad for your engine in several ways: 1) running rich can flush lubricant from cylinder walls, resulting in poor lubrication, 2) current oils are meant to run hot, 220 F and more, so they burn off any fuel/other impurities, lower thermostats will not let you burn off these, this results in poor lubrication, 3) engines are designed to run at certain temperatures, with tolorances, running at other temperatures is not optimum (especially true with an aluminum engine), this is one reason they tell you to wait until your car is warmed up before "getting on it", with a lower thermostat you're never warmed up, 4) varible weight oils (i.e. 10W-30, thicken as the temperature rises, run them cooler and they are thinner, with less protection.

Of course running more horsepower with less lubrication is a prescription for trouble.

 

I'm with oldvetter. Your Vette reaches maximum performance at a peak operating temperature, which, as done in a comparison test in an article I read in GM High Tech Performance mag was 178 degrees. :yesnod:

 

Higher temps will give you more 'peaky' HP on a dyno, but will be a more jagged powerband with possible minor detonation/KR.

Lower temps, but above 160 should give you a better average power rating with a smoother power curve.

I prefer the lower temps. Better for the engine too.

 

Sorry dude, my data (accelerometer AND at the track) shows more HP at 180 Vs. 205. 2 MPH faster and 2 tenths quicker at 180. Same night, one hour apart, only diff was coolant temp. All I can say is try it at the track, you'll see. :seeya

 

Let's solve this myth of closed loop temperature on the LS1 for good ;)

in the 2000 Corvette (Y-Platform) service manual: Volume 2, page 6-560
Under: Conditons for Setting the DTC (this is for related diagnostics when looking for Engine Coolant Temperature (ETC) Excessive Time to Closed Loop Fuel Control). "The Closed Loop coolant temperature of 34 degrees C (93 degrees F) is not reached in a predetermined time" (referring to when it sets the DTC code) The normal time from a cold start to closed loop temperature is 5 minutes, less when the engine is already warmed up some...


So if you are driving a C5 with the LS1 engine the 160 degree t-stat will not prevent closed loop when closed loop temp is reached at 93 degrees...
'nuff said

:cheers:

 

I think you need to finish the read, check your idle reset procedure they mention close loop at 176 water temp.

As far as the strip is concerned to many variables to make any acurate analysis, like track conditions, tire temps, shift points, the list goes on. I ran six runs last month and there was delta of .6 seconds between them. The dyno run was within minutes and no variables other than temp. I guess I've been an engineer to long, I'm just stuck on controled tests and there results vs a lets give it another shot.


[Modified by jimman, 1:07 AM 7/25/2002]

 

Another engineer (like myself) talking about controlled tests!! I like it. I agree, it's hard to control all variables but one. That's why I didn't talk much about the G-Tech data, which showed the same increase in HP at cooler temps, even thou I strived for constant conditions.

Did you REALLY do SIX dyno runs with the ONLY variable being the coolant temp? :eek: If so, what did they show? How much HP change did you see? Was the change in HP above or below the accuracy level of the equipment? Did you order the tests properly (hot, cold, hot, cold, hot, cold) and did you get repeatability of the data? I'm not gonna throw the BS flag, but you're the first I've seen to claim to test this (hopefully) the right way. :cool:

 

Charlie Hoyt sets up dyno days in Gardena CA, http://forums.corvetteforum.com/zerothread?id=304821

He has a web site that he posts the results. We get a ton of guys and it's quite informative. The hp gain or loss is really insignificant when the temps are varied. What is interesting is the erratic nature of the curve at cold temps. It takes the 3rd pull to get a clean line when you go in with a room temp car. We all now prewarm to get the best performance. My 00 was best over 200. I just did my 02 and I just now run the temp up so I dont waste a pull, His web site is, http://forums.corvetteforum.com/zerothread?id=304821

I would post the graphs but I can't even get the web site to do my sig photo let alone anything else.

 

I took your suggestion and continued to read my service manual. Here is what I've found to document my original opinion again:
From the same service manual, volume 2, page 6-1207
"Run Mode:
The run mode has 2 conditions called Open Loop and Closed Loop. When the engine is first started, and the engine speed is above a predetermined RPM, the system begins Open Loop operation. The PCM ignores the signal from the HO2S and calculates the air/fuel ratio based on the inputs from the ECT, MAF, MAP, and TP sensors. The system stays in Open Loop until meeting the following conditions:
*Both HO2S have varying voltage output, showing that they are hot enough to operate properly. This depends upon the engine temperature.
*The ECT sensor is above a specified temperature.
*A specific amount of time has elapsed after starting the engine.
Specific values for the above conditions exist for each different engine, and are stored in the electrically erasable programmable read only memory (EEPROM). The system begins Closed Loop operation after reaching these values. In Closed Loop, the PCM calculates the air/fuel ratio (injector on-time) based on the signal from various sensors, but mainly from the HO2S. This allows the air/fuel ratio to stay very close to 14.7:1."

Now if I'm not mistaken, my first quote included the reference to the ECT (Engine Coolant Temperature). Being that this is one of the criteria listed above, and that closed loop coolant temperature is (34 degrees C) or (93 degrees F), I don't know why you fail to see the association.

Now, at your suggestion, I have tried to continue to research this issue, and nowhere can I find a reference to idle reset procdure and closed or open loop.

I'm not an engineer but I do own my own business and in my world you provide resource data to back up what you say as fact. I have provided you with two references for my data. Could you point me in the correct direction to support your claim of 176 degrees F being the Closed Loop temperature because of the idle reset procedure???? :confused:
I'll withhold my use of :bs until I see you don't provide the requested information.
Thanks in advance.

 

I dyno'd yesterday.

At <225° temp, the pulls were 361, 359. When the coolant reached 225° the HP dropped DURING the dyno run like a switch was thrown, and achieved 343hp. The 359 pull was first, then the 343, last the 361. The 359 and 361 pulls were started at the same water temp and air temp.

This is bone stock.

I did alot of dyno testing on my LS1 engine. What I found: Water temps between 174-200 had little effect on output. Above that, and below that effects the output. Over 225 CREAMS it. This is the range that a 160° therm puts you in. ALWAYS thrash on your car prior to tieing down. Get up to operating temp, then go WOT several times. Then tie down. This adjusts your PCM for maximum performance. Don't believe it? Try it.