Cold -vs- warm engine horsepower

[LMPerformance]

probably already known but at colder temps the computer will advance timing a little too.

[strange_trp]

<blockquote>quote:</font><hr>Originally posted by Shadly:
Is there a way to keep it open-loop all the time, or is this bad?<hr></blockquote>

sure there are several ways to keep the pcm in open loop but its not recommended.. anyway, the pcm will go into driver-commanded open loop at WOT. it will automatically go into power enrichment mode as well, where it changes desired air:fuel ratio.


&lt;quote&gt;
probably already known but at colder temps the computer will advance timing a little too.
&lt;end&gt;

yep pcm will command more ign timing advanvce when cold but potential durability issues negate the feasibility of running too cold all the time. not enough benefit for the risk....

[TurboKillaZ]

of course a colder engine will run better,take a pc cpu cold vs hot :D

[nikon]

OK I think the exact opposite is correct...sometimes...in older engines yes, they should be colder, its how they were designed...but the hotter an engine can get without the water boiling, the better and faster it'll go according to my grandpa who has a stock car...our cars have 18lb or 20lb pressure caps I believe...I forget...but thats what makes the coolant not boil...I need to ask my grandpa a few mroe things....maybee someone can add to this statement?

[Dojo2000]

There has been an argument that running an engine at too cold a temp is bad. Its been shown that as the engine heats up HP tends to go down. But it hasn't been proven that a low engine temp is harmful. I'm sticking with my 180* thermo, instead of 160*, just in case though [img]tongue.gif[/img]
I say research it more and make your own choice.


P.S. Where the hell is strange_trp?

[ November 23, 2002: Message edited by: Dojo2000 ]</p>

[Slow-N-ugly]

Water boils at something like 212 at I think sea level, but is has to do with atmospheric pressure. Your right Nikon about the caps. A "pressurized" cap will actually make the boiling point higher. It seems like I read somewhere that an engine needs to be at operating temperature to run optimal and I think it was because of the cylinder walls not being a true round or something. I have been up entirely to long. I mean why would every car manufacture in the world put a thermostat in their cars to try and keep it at a optimal temp? If the colder an engine was the better it ran, then it would seem like there would be 140 or 120 thermostats right. I think there is a gray area or a safe area. I know you shouldn't rev your motor when its cold, but I get nervous when the gauge shows 200.

[nikon]

I run at 210, constantly....but I also live in florida ;)

[zccop2001]

Id have to agree that driving a freezing cold engine hard isnt good.. Think of it, go freeze your hand in the freezer, then get out and make fists REALLY fast.. like 5000 crunches a minute.. ull see how it could be bad for an engine..

i hope someone really trys this, and reports their findings... [img]graemlins/rofl.gif[/img] [img]graemlins/rofl.gif[/img]

[V6Bob]

"OK I think the exact opposite is correct...sometimes...in older engines yes, they should be colder, its how they were designed...but the hotter an engine can get without the water boiling, the better and faster it'll go according to my grandpa who has a stock car..."

It's complicated. There are a number of things going on here.

1. Cold air in is denser, makes more power.

2. The computer richens mixture and may advance timing if the engine is cooler.

3. Hot engines make more power.

I think number 2 is what people notice most, but who knows for sure? Clearly the best setup for a race car is cold air into a hot engine with a fuel system designed for maximum power.

[Dominic]

So much said thats wrong, so many dilusions and wrong analogies... oh my gosh...

First off... water boils in one atmosphere at 212degF. Add in the fact we pressurize our radiators to 15psi over atmospheric and we usually run 50/50 mix glycol in our coolant, the real boiling temp is more like 250-260degF. Without the glycol the liquid phase of water is far too small, and you would end up running over 50psi of pressure to keep it from hotspot boiling as it passes through the hot heads.

Yes, 50° air is denser than 120° air, but the idea behind cooling the heads is to reduce detonation. Optimal running temperature for power varies from engine to engine because of what metals they're made of, their displacement, their water jacket size, etc. Our engines are IRON, top to bottom, and they retain heat extremely well. LS1s are aluminum, they don't retain heat well at all. I'll explain how this comes into play in a minute.

The theory for making power is yes you want the cyls and oil properly heated, but you want cool heads - a trully cold engine (top to bottom) will not make good power and will harm itself when run hard.

Because our engines are iron, heads and block, the cyls retain heat very well to begin with. The whole bottom half of the engine holds the heat well and running a 160 thermo doesn't hardly make much of a lick of difference down there at all (I've zapped mine with a temp gauge a few times, same temp once the engine is fully warm regardless of the thermo... even the oil maintains the same proper temp).

Now, keeping the coolant cooler allows the heads to run cooler. Cooler heads = more power = less likely chance to blow a headgasket = denser intake air = less cyl expansion and more compression ratio. Running the heads too cold will cause serious carbon buildup inside the cyls, on the plugs, and everywhere else it ought not to be.

On an LS1 aluminum block/headed engine it is probably for the better to run them at least at 180° Coolant since the heads release so much heat naturally regardless of the coolant. Our engines don't want to let go of this heat though and running the coolant 10-20degrees cooler allows us to get the efficiency of an aluminum engine running that 180 stat.

The purpose of the coolant passing through the block is so that its preheated to a proper temperature before hitting the heads, again you don't want to overcool anything. GM engineers ran 180° and above thermostats in reverse-flow LT1 cars (and rightly so) because the cold coolant from the radiator would hit those heads first... put a 160 in an LT1 and you're just asking for bad carbon build up and plug fouling [img]smile.gif[/img]

Now back to our cars.
#1 - They're all IRON and they retain heat VERY well
#2 - They use a conventional preheated by the block coolant system, so that there is hardly a chance of overcooling the coolant.
#3 - There is no stock oil cooler, so the oil is almost independant in temp from the coolant, hence it runs a normal 200-210°F regardless of the coolant varying from 160-210°F.

There are only 2 reasons that GM runs a hotter stat in the newer 3800-II. One is to achieve lower NOx emissions to satisify the ULEV rating of the EPA. The second is the car is built in CANADA, designed in Michigan, and the people up there wan't their HEAT! If you run a 160 stat in a vehicle when its -20F outside, you'll notice that you can't half get any heat into the car for over 30 minutes... This to me would be unacceptable if I lived somewhere that got that cold. The simple fix is of course to run a 180 stat in those cars.

I apologize for any spelling or grammatical errors if you find any.

[ November 25, 2002: Message edited by: Dominic ]</p>

[Slow-N-ugly]

All of that and you still didn’t give your opinion on the hot/cold why subject of this topic.

[Dominic]

My personal opinion is that 195 stats are not suited for our cars. 180s are fine, but 160s are a little better. I don't feel the 160 is too cold unless you need the heater, and living in FL I rarely need the heater. When its 32F outside I still get plenty of heat and its available soon enough, no problems [img]smile.gif[/img]

With reprogrammed fans and my 160, I'm a happy camper. For 2001-2002s I know the fix.

For those of you who feel it lowers thermal efficiency I ask "Then why do I get significantly better fuel economy with the 160?" [img]smile.gif[/img]