I noticed today that while driving in stop and go traffic, my coolant temperature gauge would go from 190 to 225 withing minutes. Once out of traffic, it would remain between 190-200. Is this normal? The evening was approximately 89 degrees and my AC was not on.

 

Yes, this is normal. Our temperature sensors are more sensitive than those in most other vehicles, so temperature drops due to fan actuation are fairly rapid - likewise for rising temps during slow-moving conditions.

 

ECM turns the fans on around 220 - 225 degrees. A lot of the reprogramming setups change that to a cooler thermostat and lower fan on degrees. [8D]

 

Coolant temperature will fluctuate widely and rapidly.

The digital display under the speedo can be cycled through various things (Gauge button) to show oil temperature, which I have found is a more stable indicator or how hot the engine is and how hard it is working. I generally leave mine on oil temp all the time to get a good idea of the real operating temperature swings of the engine. Coolant will fluctuate up and down depoending on fan operation, etc., but oil will stay about the same -- unless I am running the engine hard, then it climbs quickly and stay there, cooling down slowly once we stop tunning hard.

 

since we're on the topic.... is there an optimal temperature range for the motor's performance? i know too hot is a bad thing, but too cold is just as bad, if not worse.

 

Engineer told me in some distant seminar way back that if they could find a way to run your engine @ 300 degrees they would, because the hotter you run it, the more effecient the combustion is. But, unfortunately, current metalurgy only allows so much. Nost factory fuel injected systems run around average of 190 - 200 degrees. [8D]

 

well, obviously, we should all just have a fire pit in the engine bay.... anything other than that and we get heat losses. but, you know, the whole limits of internal combustion and man's attempt to control fire, etc... [sm=badbadbad.gif]

 

The engineer was talking theory, the Carnot cycle: absolutely correct thermodynamic theory (a law of nature) that overall operating efficiency is equal to (operating temp - ambient temp )/ambient temp, with all measured from absolute zero (Celcuis degrees) ----> the hotter you run the engine the more power you potentially can get out of the fuel. What he was saying is that if you could run your engine hotter, it would be more efficient - produce more power from the same fuel and/or the same displacement. running at 300 degrees coolant temp versus around 200 would give you about 10-15% more power. True in theory

But in the real world the engine has been designed as a compromise asnd you really do not want to try to run a standard car engine "hot" unless you have done a lot of re-engineering (and I mean a whole lot - re-engineered everything). Realistically, the thing to do on any street engine is to keep the incoming air, and the coolant, as cool as possible, and keep the exhaust as hot as possible (wrap the the headers or at least keep the heat inside the pipes and flowing out the exhaust).

I generally want coolant temp above 165 and below about 210 degrees, perferring 175-180 degrees, and oil temp above 180 under 220 when fully warmed up -- I prefer 175/195 degrees respectively, however, both shoot way up on high-power runs of even half a minute, and a minute of spirited driving in my vette, on a hot (100 def. F) day, can shoot water tem, to 210 and oil to 225, respectively, despite oversize radiators and oil coolers. I run exhaust pyrometers to measure exhaust temp (which is what really matters) around town just loafing the engine does an exhaust temp or around 600-700 deg., at full thorttle on a standing start mile run (about 25-28 seconds to 185) it peaks at about 950.

 

LOL, that's why I work on them, not engineer them. I have enough trouble keeping up with current technology diagnosing them instead of engineering them. []

 

hey guys, i picked up a 97 corvette today, silver, T-TOP, Silver Leather, 6 Speed Manual

im new to the whole corvette scene, so i ask that you please dont flame me.

ok, basically heres my question, if the temp gauge goes to 225, is it normal i noticed it was doing it only while idle, and in traffic, i had a 91 acura legend coupe before and it was always like a quarter of the way, anymore meant bad news, im not saying it should be like that, but some advice would greatly be appriciated!