Me and my bro were chillin hard tonight, tippin back a few Natty Ice's, and we started gettin all technical and ****. Long story short; what effect do higher/lower ECT's have on HP and gas mileage? Higher being the stock tstat, lower being a 160* tstat.

Thanks d00dz.

 

I'm in for this. I do know E85 likes heat.

 

where's all the gurus at to answer this question? it's actually an interesting topic

 

do you really want a lower temp if the pistons expand during a run? i want the smart guys to answer this.

 

If you change temps much, what about oil? Thought recommended oil was for pressure and flow at about 210-220?

 

empirical data is needed to draw any meaningful conclusions from this discussion. otherwise it's just speculation. hopefully some of the "gurus" have some of this data floating around...

 

well, as a gas (gas like air, not gasoline) gets colder, it increases in density.

1 CFM of high density air will contain more oxygen molecules than 1 CFM of lower density air so you have to deliver more fuel with higher density air to acheive any given air/fuel ratio.

So generally speaking, colder temps (more dense air) would be better for power, but not economy.

Higher temps (less dense air) would be better for economy, but you make less power.

You can't really make a direct correlation to ECT though, because your ECT in winter could be 160 deg, while your IAT is only 32 deg.

Vs. a summer situation where your ECT cuold be the same 160 degrees, but your IAT is 90 or 100 degrees (much less air density, less fuel, less power).

 

So, is the optimal ECT about 210 and cooling is only if you are pushing higher? Given reasonable cool and dense air, is there a gain to lower ECT below 210? Is lower hard on the motor unless you adjust oil viscosity for pressure and flow?

 

I'm guessing more "guru's" didn't chime in because this topic is a can of worms...

Every engine is different and will have a different temperature for optimal combustion. This is dependant on many factors (displacement, compression, combustion chamber shape, VE, etc...).

Generally speaking again, I'd say lowering your ECT is beneficial up to the point that you go under the minimum temp. for optimum combustion. I haven't studied oil or lubrication enough to give an honest & educated answer, but I'd be shocked if someone suggested you change oil viscosities due to 30 degrees less ECT.

 

Definitely no guru here, just questions. I thought that most street cars unmodded ran at about 210. I can't answer the viscosity question, but from this quick chart it is not linear. Found this interesting chart (Hass oil article). About 100 degree change from 104 - 212 the change is 90, and 212 to 302, 7

"30 grade oil (often referred to as a 30 “weight” oil):

Temperature ( F )....Thickness

302...........................3
212..........................10
104..........................100
32..........................250 (rough estimate)

The automotive designers usually call for their engines to run at 212 F oil and water temperature with an oil thickness of 10."

 

ECT isn't as important in tuning as IAT.

ECT sets the standard on combustion though, it is a can of worms thats why nobody has really responded.. i just thought i'd throw this out there.

This is why , in tuning programs you have compensation tables for things like this..

Ever get into your car in the morning, let it warm up a bit(not all the way) and drive. Ever notice the car feels "stronger" and responds better to throttle? Because its a cooler motor, and the compensation really isn't in full effect like it would be on a fully warmed motor.

for a honda, opitumal temp is around 180-190 - IAT's should be around anywhere in the 80-110 range.. i know here in louisiana, we've had some close to 100 days..real 100's.
My ECT is around 188 and my IAT is around 110ish..maybe more.. car doesn't "feel" as fast as it would when its 80 outside compared to 98.

 

This probably could be proven one way or the other with a dyno and controlled temperatures. Noting the above chart, if oil thickness changes from 10 to 20, or perhaps, 15, that should change pressure (up), but flow down. If the quoted statement is true, "The automotive designers usually call for their engines to run at 212 F oil and water temperature with an oil thickness of 10," then it seems oil viscosity needs to be something that will give 10 at the 180-190, and good flow.

 

I know if I drive my car when it is at full operating temp it is much smoother than when the temp gauge is just registering off of C. I won't drive my car until it registers and raises about the C on the stock cluster. I notice a huge difference in power though from day to night. Mind you day time it is nearing 100 degrees fahrenheit with 80% humidity and at night it will be 70 degrees fahrenheit and even with the same 80% humidity the car feels so much different. It pulls strong and is so responsive! I think heat soak is the biggest factor in that. In the day the intake manifold will be hot! At night it will be warm where you could hold your hand on there and wouldn't have to pull it away. Now I don't have a temp gauge to truly tell what ECT's are both night and day but the gauge never moves from normal operating temp once warmed up. I know you can make an engine too cold and sometimes too hot, I see this when people completely remove the thermostat and don't even put in a restrictor. The coolant would flow so well through everything it took forever to warm up, then once warm it didn't have enough time to really cool down since it was a quick in and out of the radiator.

 

Not sure how IATs came into the scenario. It is different from ECT. The engine is designed to run at a specific operating temperature. Everything from oil viscosity, fuel atomization, injector PW and so on will likely be negatively affected. You will gain nothing and likely lose something from lowering ECT temperatures. Dont believe the hype....

 

There is no "optimal" ECT. Optimal is whatever the engine is designed to run at. That being said, the range is usually between 180-220, depending on the engine. again IAT's have nothing to do with ECT. There is no bearing on the intake charge with regards to ECT's.

 

"The automotive designers usually call for their engines to run at 212 F oil and water temperature with an oil thickness of 10."

I quoted that from a Hass oil article. I thought that Hondas were about 210 from the factory, thus the "optimal." Showing my lack of knowledge, but are many brands not 210?

My question stemmed from IAT statement above. "ECT isn't as important in tuning as IAT." IAT and ETC are not related directly to each other, but it was suggested that both relate to power. I wonder if for stable IAT, with cool and dense air, about lowering ECT. I was trying to get at the original question about ECT and how that affects not only hp, and gas mileage, but add in oil viscosity and wear.

 

I dont know who or what Hass is, but the info is incorrect. Again operating temp varies between engine and evn make of vehicles.
IAT is the "intake air temperature" it has NOTHING to do with the vehicles operating temperature.Lowering or raising the vehicles operating temperature is not going to affect the vehicles incoming air charge, at all. Only negative effects will occur from altering the operating temperature unless other parameters are altered to compensate. There is nothing gained from lowering ECT. Period. People think that making the car run cooler will make it run better, they are mistaken....

I suggest this book.
http://www.amazon.com/Internal-Combu.../dp/007028637X
It is the definitive answer to the workings of the ICE. There is no other author more renowned or better qualified than Heywood. It is considered the "bible" in the automotive world. It is pricey, but a must read if you wish to truly understand the ICE. Ya dont know who Heywood is? A little info.....
http://meche.mit.edu/people/?id=43

There are a lot of "gurus" in the automotive world. Most of them are jokers. Heywood is the real deal.

 

"IAT is the "intake air temperature" it has NOTHING to do with the vehicles operating temperature.Lowering or raising the vehicles operating temperature is not going to affect the vehicles incoming air charge, at all. Only negative effects will occur from altering the operating temperature unless other parameters are altered to compensate. There is nothing gained from lowering ECT. Period. People think that making the car run cooler will make it run better, they are mistaken...."

Thanks, that is what I thought, but did not know and was trying to get a conclusion from the thread. I was thrown off by this quote:

"Ever get into your car in the morning, let it warm up a bit(not all the way) and drive. Ever notice the car feels "stronger" and responds better to throttle? Because its a cooler motor, and the compensation really isn't in full effect like it would be on a fully warmed motor.

"for a honda, opitumal temp is around 180-190 - IAT's should be around anywhere in the 80-110 range.. i know here in louisiana, we've had some close to 100 days..real 100's.
My ECT is around 188 and my IAT is around 110ish..maybe more.. car doesn't "feel" as fast as it would when its 80 outside compared to 98."

My thought was eliminate IAT, "cool dense and stable air," variation and talk about ECT as the variable. I am aware what IAT is. The Hass oil article is a good basic oil article, but gave the generality that most street cars operate at 210-212. Hass article:

http://ferrarichat.com/forum/faq.php...tor_oil_basics

Actually I was trying to get a good discussion about cooling an engine and good and bad affects. I think you answered that. I am still not very clear who/brand that does not operate at about 210, again my lack of knowledge.

 

Ah yes Dr. Haas. He is a medical doctor with zero automotive training or back ground. Much of that article has been debunked on BITOG. That article is probably around 10 years old or so and riddled with inaccuracies. I wouldnt bother reading anymore of it.

 

Again, thanks. I knew who he was. I think that the viscosity part of the article, relating to temperature, pressure, and flow are a reasonably understandable. I thought that part of the article was based on measured numbers. I got the suggestion from the article that cooling an engine below its normal ECT would not be good for oil flow, and therefore not good for the engine.
I have tried to search ECT, and the generalities on the internet suggest that todays cars mostly run aroung 200-210, and that older cars used to run cooler. Computers and sensors eliminate some of the risk of running hot by adjusting for predetonation and the relative high temps are good to feed the catalytic converters.
The discussion was to try to obtain answers, not debate or disagree. My take from the beginning was that it was not good to lower a normal ECT, but only inferred from oil articles, Hass and others.

 

It does not. Though it is a major input.

This is incorrect.

This has nothing to do with the ECT being high. Ambient temperatures have very little, if any, affect on ECT's, on a vehicle that is temperature controlled.

 

The PCM will think the car is in open loop and the vehicle will get poor gas milage and lose HP.

 

Can of worms. I'm on my phone so I can't respond to explain..this thread is just one you walk away from