I have already posted that increased air inlet density (from lower temp air) increases horsepower. And I have already posted that this is one of many effects on hp production from different coolant temps. The largest losses in an IC engine is the loss of energy into the coolant which far exceeds the increase in hp due to lower temp inlet air.

 

Then I guess we agree

 

Me too!!

 

the 175 -180 range seems to be where my temps stay around while i was driving my car. my car has the 160*thermostat and a 185 on and 175 off switch for the fan. i dont think seeing 160* in my car is verry likely without some work so when i put in an hd radiator which i plan on doing hopefully this summer i may switch to a 180* stat. im just unsure how that stat is going to work with the switch i have in my car at the moment for the fans. i just dont see the point in the lower t-stat if it just stays open all the time. i think it did get under 160* but verry breafly. if i do go to the 180* thermostat would it be okay to keep the fan at 185 on and 175 off without too much adverse problems?

 

They route it through the TB on L-98s as well. Even if they didn't, coolent temp does have an effect on intake temps, because it has an effect on the heads and block. Those parts are connected physically to the intake, and physical thermal conduction causes heat from the rest of the engine to affect the temp of the intake.

In my opinion, a couple of "facts" believed by some has caused them to misinterpret a basic priniple of combustion. Proper internal engine combustion is a rapid burning of the fuel mixture along a single flame front. This process is not an "explosion" as previously mentioned. An explosion in the combustion chamber is detonation, which quickly destroys an engine. As the fuel mixture rapidy burns, the resultant burned gaseous mixture heats up and the gas pressure in the cylinder rises. It is this increase in pressure which is the force that is applied to the piston crown that causes the piston to go down and turn the crank. Engine HP comes soley from gas expansion force on the pistons. The greater the force, the greater the resulting HP. The force of the gas pressure is directly proportional to the heat temperature (energy) of the individual gas molecules.

Assume that after the fuel burned, we could instantaneously remove all of the combustion heat from the burned gas mixture before the piston had moved from TDC. The gas molecules would have no heat energy creating the pressure to push on the piston. No hot gas molecles = no force = no HP.

Now, we cannot instantaneously remove all of the heat, but as each molecule impacts with the sides of the cylinder and the piston it transfers some of its energy as heat to those parts. This energy transfer lessens the energy of the gas molecule, lessening the pressure of the gas overall. As the cylinder walls heat up, the rest of the engine heats up. The gas molecules cannot transfer out more heat energy and raise the cylinder wall temp higher than their own temp, so as the engine parts heat up closer to the gas temp, the temperature differential becomes less. With hotter cylinder components, the hot gas molecules transfer less heat at impact to the cylinder walls and the gas stays hot longer, producing a higher pressure for a longer time. The additional heat energy retained by the gas molecules keeps the pressure higher so it maintains a greater force on the pistion. Greater force = greater HP.

However, we cannot allow the cylinder walls and piston to reach the same temp as the burned gas mixture if we want to avoid having them structurally fail. We need coolant to keep the cylinder walls and piston from heating up to that point. Once we begin to use coolant to extract heat energy from the the cylinder walls and piston, then the temperature differential between those parts and the gas becomes greater. They now absorb more energy from the gas molecules that are impacting them, which in turn reduces the gas pressure. Less pressure = less HP.

Don't cool enough and you destroy an engine. Cool too much and you lose HP. The ideal is to keep the engine as hot as possible without causing structural failure to the engine components. The SBC is designed to work at 190-220*F. Kool88Vette's post concerning the Felpro site confirms that about 190-220*F is "normal". Not too hot, "normal". The factory thermotat at 195*F is set to help achieve "normal". Run too far below that temp and you are costing yourself HP, longer warm-up times, and longevity. This is America, it's your car, do with it as you see fit.

In the old days due to cost and lessor manufatcuring capability, cylinders were cross-hatch honed like a steel file so that the rings and cylinder walls would file themsleves down to match. That is why there was a lengthy break-in period to let things 'seat'. Unfortunately, people often went too easy and didn't seat the parts as well as needed, or were too rough and caused the honed ridges to break off instead of wear in, so in both cases performance was less than optimal. The BMW motorcycle racing team researched this wear-in process extensively in the 80's. No modern engine manufacturer hones the cylinder walls like they did in the old days. That is why there is now either minimal or no break-in period recommended for new vehicles.

As to running an engine and later finding hone marks in the cylinder bore. That is a poorly broken in engine. Probably out of round as well. What are hone marks? They are physical gouges cut into the cylinder wall large enough to be visible to the naked eye. Since air molecules are generally not visible to the naked eye and are MUCH smaller than the visible gouges of the hone, is it possible that air molecules under high pressure will travel a path along those gouges and bypass the rings? You bet. Loss of compression. Not complete failure loss of compression, but definately less than optimal. Not questioning anyone's general mechanical ability, but I would NEVER rebuild an engine using a mechanic who thought that hone marks in the cylinder walls after break-in was a good thing.

 

Scooter, even the aftermarket high capacity radiators cannot get rid of heat fast enough to let your engine coolant run 160 F in the summer. With a 180 stat and new radiator, your 185 on and 175 off fan will be on all the time because your coolant will likely exceed 185 while stopped and never get below 175. The only adverse thing that would happen is that you will be replacing alternators and fan motors more frequently. The fan motor has brushes which eventually wear out and draws 14 amps which will be supplied by the alternator which is an additional load.

 

This was the posters original question: anybody know when my fans are supposed to come on in my 85? i put a new switch in and it went to 215 and they didnt come on. it was rigged up when i got it so i dunno where to start troubleshooting. 215 seems way to hot to me for them to come on shouldnt it be around 200


This was your response:

We all agree now that the normal operating temps are 190-220 degrees F. The fans in a 85 C4 come on when the engine is already running too hot at 228 degrees F. The aux fan comes on within 12 degrees F of oil breakdown which is 250 degrees F. You said a ccouple of posts later : You don't need to tune the fans or have them come on any differently than GM designed them to. One thing you have to get used to in modern cars is the fact that their cooling sytems run at a higher temperature and that it isn't harmful to the engine!!!! All of my previous vettes (I own an 87) had a 180 thermostat, a larger radiator, and a mechanical fan and the coolant stayed at 180 once the thermostat opened. The temps you see make you nervous because your previous cars would have been spouting steam at the side of the road. GM says to shut the engine off and let it cool down if it gets to 260 F. I drive my 87 everyday and for 18 years now and I have never ever seen 260 F. You should keep your radiator clean, as debris catches in them and reduces airflow. I'm lazy and instead of taking the radiator out, I blast water from my garden hose backwards through the radiator several times a year. Look at the a/c condenser radiator too and clean debris and straighten the bent fins. You can see it from below the front of the car. This is why I got upset with you. You are advising members to do things that will blow an engine. If the poster takes your advise he will keep driving until his Vette hits 260 degrees F. I'm sure you have driven around with temps in the 240 to 250 degree F range for a few hours. You said you changed your head gasket at least one time, maybe more. Maybe now you will see what your doing wrong. When you ran out of argument you changed the topic. You argued that a hot engine generates more HP than a cool engine and that your HP goes into the radiator via the coolant. What good is HP in an engine with a blown head gasket? Maybe now you will agree that the C4 cooling system is inadequate and the C4 is made to run too hot in order to control emissions. That was the original argument. No one cares about loosing a few ponies if it will cost them an engine. On the original argument by your own admissions and statements you are giving out advise that leads to destroying an engine. Why not play it safe? Keep you car on the low normal end. Have it run so that it averages between 190 and 200 degrees F. Save your engine and PLEASE never take JFB's advise.

 

Are you kidding?

"Heat is removed so the engine metal doesn't melt AND it removes horsepower at the same time. I cannot help you, you are too ignorant!
Does your mommy know you are up this late and on an adult website? "

When your view was challenged, you restorted to adding in personal attacks to your position.

 

indeed. as have i... on IC engines in general anyway...


well, while certainly not one of the best things you can do to one, IMO,
there are many far worse things you can do to one...
i wasnt trying to justify it, just pointing out that right or wrong, the engines continue long lives after its done, thats all...

its been my experience that any engine that shows that much cylinder wear, suffered from problems other than overcooling...

i understand about increasing charge density, but you are incorrect about block temps not affecting charge density.
cylinder wall and combustion chamber, (as well as piston surface temps)
play an even bigger role in charge heating than the intake does.
all the way up until the intake valve closes some time after BDC...

these parts have far more surface area than the intake manifold does, from the TB, to the intake valve. and these surfaces are considerably hotter than the intake is...

and even though the actual total ammount of intake charge that enters the cylinder, and is sealed in by the closing of the intake valve is fixed after that point, regardless of its density,
any further heat absorption from the piston/wall/chamber, and thus expansion, by the charge during the compression stroke, raises cylinder pressure slightly more during the stroke. thus increasing resistance to the pistons upward travel...

 

i understand (and agree) with the concept just fine...
but its only one componet of several at work on the engine.
a point that you dont seem to be grasping here... your dwelling on only one piece of a much bigger puzzle.

from a power production standpoint, on typical, production engines, icreasing thermodynamic efficency, (higher engine operating temps) and any ever so slight increase in fuel atomization that may result from it, are in direct competition with the reduction in intake charge density and increased compressoin stroke pressure rise mentioned in my previous post.

not to mention the increased risk of detonation that higher operating temps put many high output engines at risk of... and the possible tuning compromises that may have to be made to avoid it, or the use of much more expensive higher octane racing fuels.

in a typical automotive engine, from a power output standpoint, take a guess which factor outweighs the other???

lets be honest here. how much more heat energy do you really think that an air/fuel mixture burning at over 2500 deg. is going to loose to an engine operating at 160, compared to one operating at say, 220 deg.? hmmm?

now, how much heat gain, (and thus density loss) is an incoming air/fuel charge, at say 70 deg. going to pick up passing through all the parts of an engine operating at 160 vs. one at 220 again???

see the difference in the scale of the temps here?

the simple fact is, if you want a really significant increase in the thermodynamic efficiency of an IC engine, you are giong to have to increase operating temps WELL beyond a mere 60 deg.

well beyond the temps that aluminum, iron, and steel can be reliably and safely operated at.... thats why someone mentioned ceramic engine components.
they are the only materials capable of handling the super high operating temps needed, to make a truly meaningful gain in engine therodynamic efficiency....
these materials also have the properties needed to insulate the the incoming intake charge from exessive heat absorption as well..

i expect that electric vehicles will become predominant before the practical use of ceramics for high effiency IC engines ever hits mass production...

 

You are correct. The performance gain would be between miniscule to none. Simply put,with the exception of emissions control. There is no legitmate reason to run an IC engine at higher than normal temps. I think that around 190-200 degrees F is a good range with synthetic oil. Maybe a little higher for conventional oil. JFB mentioned the ceramic coated engine that operates at 4000 degrees F. He thought it made sense. I would not want to drive around with a blast furnace all day long during summer.

 

Kool88, why in the world are you still posting in this thread? You said, and I quote: "This is the end of this discussion". Why don't you keep your word and end it? You also admitted, and I quote: "I admit I don't know much about cars". That statement was unnecessary, your posts told us that from the very first one. If you don't know much about cars, then why do you continue to post about C4's running too high a coolant temperature? GM put 195 thermostats in every year they made L98 engines AND they made the statement to NOT put 160 thermostats in those engines. They put 190 F thermostats in C5's and the current C6 Corvettes and those cars run 190 to 200 F. Go look at all the current automobiles, they all run near 200 F all the time with no harm. If you admit you don't know much about automobiles, then why are you insist that you know more than automotive engineers? You also said in response to Uralman's post that his 87 runs 180 to 200 F, and I quote: "Thats about perfect". My 87 Corvette has always had a 195 stat and it runs 180 to 200, so by your own admission, "Thats about perfect", so why are you still posting that C4's run too hot?
By the way, GM doesn't say to shut the engine off at 260 F because motor oil boils, motor oil boils at about 600 F. Look it up!


I think you are psychotic and I hope you get some help. I am no longer going to try to educate you, its impossible. I am going to take CFI-EFI's recommendation which I quote here:
It is pretty evident that jfb and I are talking to a brick wall. You don't want to be confused by the facts, because your mind is made up. You don't know what an explosion is, you don't realize that the heat produced by the engine is converted to the rotational forces at the crank shaft that power the car. Ignorance is a lack of knowledge. To refer to you as ignorant on the subjects necessary to understand the help that is being provided isn't "name calling" so much as it is an accurate assessment of the situation. Do some studying on the subject and come back with some intelligent, informed, discussion, rather than arguing principles you don't grasp.

 

Kool, I think you have your oils backwards, dino oil is good to around 250, synthetic is good to aroun 300. Of course no one want there engines to come close to these temps.

 

`nuff said...

 

oh, BTW, just a little FYI, i`m experimenting with a 140 deg. thermostat in my 2000 GMC...

"oh no! the sky is falling!"

 

Having read some posts in other topics, I knew this was coming. Still, there is some really nice information here!

 

As I said before you are a very sick man.

 

come to Florida, get stuck in traffic for about 20-30 minutes and you will see 260 in a hurry.

 

Not if you keep your cooling system properly maintained. Plus Florida is not the hottest spot this forum reaches.

RACE ON!!!

 

There is something wrong if your getting that temp.