What is the optimal running temp for our motor

[slacker69]

Well i was at the track last week fri when i ran my new best time and it was cold outside. And from what i know an engine likes to run cold. Well i ran my 14.345 at around 160-170 degrees. I later let the car sit untill 125 degrees and pushed it up to the line and ran it and ran somethin like a 14.48 i didnt change anything on the car the 60 foots were roughly the same 1.866 and same amount of knock through both runs is there a point where being to cold will slow the motor down or is the a tempture i should try to reach for optimal performance.

[navyblue2000]

i think it's around 165 degrees. Don't quote me on it, but I do believe it is the best when it's just warm enough to go into closed loop operating mode. A colder engine will pull timing too if I'm not mistaken. Go start your car cold in 30 degree weather and take it 0-60. it won't pull in the top end

[Dominic]

Yeah 165-170 is about optimal for power.

[MoreThanAV6]

Lower temps make more power, cause more engine wear and worse gas millage.

[phoenix64]

My uncle who works on bush cars gave me **** for running a 160 degree thermo, b/c his engines make more power at 180, b/c the combustion chamber is more efficent. The reason we see gains, is because the intake charge is cooler, at 160 so you get more o2 into the engine, the colder it is. the trade off is that the combustion process is less efficent, which is why you get worse gas milage. You just have to find a balance. My uncle stacks ice on the intake of the bush car engine, and then puts a probe in the oil pan to keep the 180 degrees inside the engine, while waiting to qualify.
I apologize for babling I just wrote a 7 page term paper, so I doubt I'm making much sense.

[Dominic]

Worse fuel economy? ha!
90mph with 160 = 32mpg
90mph with 180 = 29mpg
90mph with 195 = 27.2mpg

Thats my fuel economy on the interstate running those thermos... Ive yet to see a decrease in fuel economy running a 160 [img]smile.gif[/img]

[ravenp]

Engine temp is important, but I've noticed that the really cold air temps made a HUGE difference for me. Harder to get traction on the cold track but i was still pulling my best times.

That said, the manual fan switch was the best mod i did to my car this year...and for less than $20 [img]smile.gif[/img]

[Magnus]

aonther huge reason we see gains at 160 compared to 180 is because timing is higher at cooler engine coolant temps..

I graphed it out a while back.

[navyblue2000]

<blockquote>quote:</font><hr>Originally posted by Dominic:
Worse fuel economy? ha!
90mph with 160 = 32mpg
90mph with 180 = 29mpg
90mph with 195 = 27.2mpg

Thats my fuel economy on the interstate running those thermos... Ive yet to see a decrease in fuel economy running a 160 [img]smile.gif[/img] <hr></blockquote>

dom, that's because it was in the middle of summer...and you live in a tropical climate anyway [img]tongue.gif[/img] (fla and ca).
for us where it actually gets BELOW 50 degrees, you can lose gas mileage when it gets cold. the motor stays cold...the intake stays cold, more cold air = more fuel = bad gas mileage. the ONLY thing i've done from last winter to this is the 180* thermo. and during this winter I've lost 3-4 mpg since last winter. Summer mpg is great though

[Cruzin]

Phenox has the right idea. The more heat in the combustion chamber the more power you can make. The limiting factor is when it gets soo hot that detonation occurs. The reason you all see track gains is because the intake is cooler causing a cooler intake charge. Basically a motor is turning fuel air mix to heat, more heat more power. (untill detonation)

[John_D.]

<blockquote>quote:</font><hr>Originally posted by Cruzin:
The more heat in the combustion chamber the more power you can make... The reason you all see track gains is because the intake is cooler causing a cooler intake charge. Basically a motor is turning fuel air mix to heat, more heat more power.<hr></blockquote>

Not true. You can run an engine very lean and make tremendous heat, enough to melt the top of the piston. Running lean does not produce more power.

You can retard the ignition timing and run very hot, because you are running inefficiently and the combustion process is happening too late, wasting fuel and creating excess heat. This does not produce more power.

You can overheat the car, and power will drop off very noticeably, well before you get detonation or damage. Clearances start tightening up and things don't move as easily.

The more fuel you can burn, the more power you can make. The more fuel you can burn completely that is. Cooler air is more air. More air means you can add more fuel. And that means more power.

The more efficiently the internals of the engine operate, the more power you can make. Getting the engine up into its designed operating temperature gets all the clearances to their intended levels for best internal efficiency.

The better the fuel atomizes, the more power you can make. Until the engine heats up to a certain point, fuel doesn't atomize very well. After it reaches that point, additional heat doesn't really aid the process any further.

Rather than the intent being turning fuel into heat, the intent is to turning fuel into a controlled explosion with high pressure being generated against the top of the piston. Whatever energy that gets converted to heat is actually wasted energy.

[Cruzin]

Listen to what you are saying. Running lean, Retarding timing, overheating. You are creating a malfunction.

With everything being equal a cast iron head will out perform a aluminum head because it holds more heat in the combustion chamber.

What do you think a/an explosion is? It is heat. more heat more explosion more power.

Now i am not talking about the temp of the air charge or water temp.

I have lost my article on this subject if i find it i will post it for ya to read.

[John_D.]

<blockquote>quote:</font><hr>Originally posted by Cruzin:
Listen to what you are saying. Running lean, Retarding timing, overheating. You are creating a malfunction.

What do you think a/an explosion is? It is heat. more heat more explosion more power.

Now i am not talking about the temp of the air charge or water temp.

I have lost my article on this subject if i find it i will post it for ya to read.<hr></blockquote>

Not so much a malfunction... It's all tuning.

What is the optimal a/f ratio for power? (richer) For emissions? (leaner) Optimal ignition timing? (and so on...) Optimal coolant temp?

These are all variables that we adjust through tuning and testing for different results. Coolant temperature isn't any more unique than any other operating parameter we can vary within a reasonable range.

I think an explosion in the cylinder is the sudden ignition of a flammable mixture, creating a large pressure wave very suddenly to push the piston down. I think intense heat is produced more effectively by a blowtorch, but I don't think that would push a piston down very effectively. An empty grain silo can explode very violently, and not produce much heat as a byproduct. That's what I think is the difference between heat and an explosion anyway.

I am curious about your reference(s) about the effects of a head retaining heat. Whether it is better for atomization, lighting off the mixture better, or what.

Actually, I thought this thread was about the overall engine and coolant temp, rather than the cylinder head temp specifically. Slacker's original question anyways.

[Cruzin]

Right i was just trying to enlighten the forum.

If i find the article i will post it.

The reason a piston goes down is because things expand when they burn, like air. Hot air takes up more space than cool. That is why your tires have less psi during winter and why a cooler air charge has more air.

anyway forget it.... i'll let ya know if i find the article.

[phoenix64]

You guys need to read others posts. Anyway corret me if I'm wrong, but detonation is an explosion, but normal combustion is more of a controlled burn.