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Old 09-16-2013, 08:21 AM
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Pros and Cons: 165 Coolant vs 180

I have enough radiator to keep the coolant at 165 degrees, even on the hottest summer days. Is there an advantage? What are the disadvantages? This is verified (measured) temp with an IR gun at the thermostat housing.

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Old 09-16-2013, 08:48 AM
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Advantage of 165º coolant temp. would allow more agressive timing/fueling curves.

180º
Will have less cylinder bore wear. There is a chart floating around on teh interwebs that shows bore wear vs. coolant temp.

I run a 160º thermostat in my 1997 rcsb L31 Vortec 350 and get coolant temps of about 170º in the winter I run a 195º as I prefer the extra heat for cabin heating.

If you are running iron heads, and a carb, I doubt there would be much difference between 165º or 180º coolant temps. Unless you are running on the very ragged edge of detonation at 165º coolant temps.

peace
Hog
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Old 09-16-2013, 09:59 AM
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Quote:
Originally Posted by 1965tripleblack View Post
I have enough radiator to keep the coolant at 165 degrees, even on the hottest summer days. Is there an advantage? What are the disadvantages? This is verified (measured) temp with an IR gun at the thermostat housing.
It is well documented that fuel efficiency, emission reduction, oil contamination from the chemistry of blow-by which includes a lot of waters of combustion and un-burnt to partially burnt fuel and engine life are all greatly improved running the engine hotter. The military back in WW II was attempting to run liquid cooled engines at 300- 350 degree coolant temps. Something Smokey Yunick also advocated. Problem with those temps is the cost of exotic materials required.

Power comes from a thing called Delta Temperature (Delta T) this is the difference between intake mixture temp at the intake valve and the temperature to which it is raised in the combustion process. The greater Delta T the more expansion of the gasses occurs which applies more force to the piston. To an extent that incoming air is heated by the engine surfaces it touches some Delta T is lost. But when you consider the intake air is say 160 degrees and the combustion temp is 2000 degrees, one can see that playing with the intake air temp is just messing around on the edges of what can be done.

Living in New Jersey your biggest problem is winter operation where fuel would rather remain liquid at winter temps which cause several problems.

1) The carb or injection has to put in more fuel to arrive at a percentage of that which evaporates from the total will be enough to sustain combustion, which makes the second big problem.

2) Fuel that does not evaporate in time to burn is forced around the ring package which destroys the already pretty marginal upper cylinder lubrication which then results with increased cylinder wall, piston ring, and piston ring groove and skirt wear.

3) The next headache is unburnt and partially burnt fuel and the waters from combustion which are by weight of the burning air and fuel are 50 percent of what went in, which is a pretty big number. This stuff has a lot of acidic components that etch the metals and some non-metals. Extraction form the oil first depends on getting the oil hot enough to force the evaporation of this stuff so the PCV system can remove it from the crankcase that takes something in the order of 190 to 220 degrees oil temp. In winter getting the oil that hot requires a lot of long distance driving at freeway speed or engine oil to coolant heat exchanger in the radiator. Short and slow trips don’t get the oil hot enough and this will be reflected in engine life. A help is to run the engine hotter to force the bad stuff out and running it hotter requires less time running rich fuel mixtures, so the contamination amounts are reduced.

Bogie
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Old 09-17-2013, 08:24 AM
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Originally Posted by oldbogie View Post
Power comes from a thing called Delta Temperature (Delta T) this is the difference between intake mixture temp at the intake valve and the temperature to which it is raised in the combustion process. The greater Delta T the more expansion of the gasses occurs which applies more force to the piston. To an extent that incoming air is heated by the engine surfaces it touches some Delta T is lost. But when you consider the intake air is say 160 degrees and the combustion temp is 2000 degrees, one can see that playing with the intake air temp is just messing around on the edges of what can be done.


Bogie
This is why Direct Injection works so well, it cools the intake charge, instead of cooling the intake valve and cylinder/chamber wall like Port Fuel Injection does.

I remember reading about Smokey's hot engine testing. IIRC he would even heat the fuel before it was used.

peace
Hog
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Old 09-17-2013, 08:48 AM
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Originally Posted by Hogg View Post
This is why Direct Injection works so well, it cools the intake charge, instead of cooling the intake valve and cylinder/chamber wall like Port Fuel Injection does.

I remember reading about Smokey's hot engine testing. IIRC he would even heat the fuel before it was used.

peace
Hog
so.. it works better when you heat the fuel, but it works better when you keep it cool... Very interesting.


Regarding operating temps, If you want to run a cool thermostat then I would do a partial block fill prior to your machining. This will cause the cylinders to run hotter, stabilize them, and keep your oil hot while your coolant and heads are cool.

If you're not building a new engine I would leave the thermostat alone unless you're having other issues.
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Old 09-17-2013, 10:24 AM
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Originally Posted by ap72 View Post
so.. it works better when you heat the fuel, but it works better when you keep it cool... Very interesting.


Regarding operating temps, If you want to run a cool thermostat then I would do a partial block fill prior to your machining. This will cause the cylinders to run hotter, stabilize them, and keep your oil hot while your coolant and heads are cool.

If you're not building a new engine I would leave the thermostat alone unless you're having other issues.
When I built the engine, I filled the block 3/4 with Hard Blok. This took an enormous amount of heat load off of the original radiator (brand new reproduction DeWitts 1965 Corvette Harrison aluminum), which is marginal to begin with, even when brand new. I installed an oil cooler and regulate the oil temp as close to 200-210 degrees as my patience allows. If I leave the heat exchanger completely uncovered, it will cool the oil to 160. It's a stacked plate cooler. Very expensive. I keep it 3/4 blocked in cool temps and about 1/2 blocked in summer temps. I bought too much cooler, but nice to know I have plenty excess capacity.

As far as the coolant goes, this is why I can run such cool intake manifold temps. If I remove the tstat completely, the coolant will run about 150 degrees. With the tstat in place, it stays pegged at about 165, regardless of ambient temperatures. I don't know whether I'm on the ragged edge of detonation, or not. The heads are aluminum. Dynamic compression is 8.6:1 (static is 11.35:1). Timing is very aggressive at 20 initial plus 16 all in by 2200, plus 14 vacuum advance. Engine runs great on 93 octane. It is very loud so can't readily detect detonation, although when driving next to concrete lane barricades and/or neighboring vehicles, I don't hear any detonation in the reflected exhaust sound.
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Old 09-17-2013, 12:03 PM
How fast is fast enough?
 
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Quote:
Originally Posted by 1965tripleblack View Post
When I built the engine, I filled the block 3/4 with Hard Blok. This took an enormous amount of heat load off of the original radiator (brand new reproduction DeWitts 1965 Corvette Harrison aluminum), which is marginal to begin with, even when brand new. I installed an oil cooler and regulate the oil temp as close to 200-210 degrees as my patience allows. If I leave the heat exchanger completely uncovered, it will cool the oil to 160. It's a stacked plate cooler. Very expensive. I keep it 3/4 blocked in cool temps and about 1/2 blocked in summer temps. I bought too much cooler, but nice to know I have plenty excess capacity.

As far as the coolant goes, this is why I can run such cool intake manifold temps. If I remove the tstat completely, the coolant will run about 150 degrees. With the tstat in place, it stays pegged at about 165, regardless of ambient temperatures. I don't know whether I'm on the ragged edge of detonation, or not. The heads are aluminum. Dynamic compression is 8.6:1 (static is 11.35:1). Timing is very aggressive at 20 initial plus 16 all in by 2200, plus 14 vacuum advance. Engine runs great on 93 octane. It is very loud so can't readily detect detonation, although when driving next to concrete lane barricades and/or neighboring vehicles, I don't hear any detonation in the reflected exhaust sound.
11.3:1 is a lot for 93 octane on a sbc. I'd leave it at 165 in that case. and increase your oil temps to about 220-230.
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Old 09-18-2013, 04:32 PM
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Originally Posted by ap72 View Post
so.. it works better when you heat the fuel, but it works better when you keep it cool... Very interesting.

Smokey Yunick did some hot engine, hot fuel testing. IIRC he ran gas through a cool can, but he had something hot in it instead of water/ice, salt/ice, or alcohol/dry ice mixtures..

I was merely stating testing that was done back in the day and what has been proven to work today. I didnt say that heating fuel works better. Not sure what required. "rolling eyes"?


1965tripleblack-here is the graph that I was speaking of with engine wear in ches plated against engine coolant temp in degrees F.


peace
Hog
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Old 09-18-2013, 04:34 PM
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Originally Posted by ap72 View Post
so.. it works better when you heat the fuel, but it works better when you keep it cool... Very interesting.


.

Smokey Yunick did some hot engine, hot fuel testing. IIRC he ran gas through a cool can, but he had something hot in it instead of water/ice, salt/ice, or alcohol/dry ice mixtures..

I was merely stating testing that was done back in the day and what has been proven to work today. I didnt say that heating fuel. Not sure what required. "rolling eyes"?


1965tripleblack-here is the graph that I was speaking of with engine wear in ches plated against engine coolant temp in degrees F.


peace
Hog
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Old 09-18-2013, 04:47 PM
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What can we learn from the test that was done to produce that coolant temp chart?
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Old 09-18-2013, 05:05 PM
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Quote:
Originally Posted by Hogg View Post
Smokey Yunick did some hot engine, hot fuel testing. IIRC he ran gas through a cool can, but he had something hot in it instead of water/ice, salt/ice, or alcohol/dry ice mixtures..

I was merely stating testing that was done back in the day and what has been proven to work today. I didnt say that heating fuel. Not sure what required. "rolling eyes"?


1965tripleblack-here is the graph that I was speaking of with engine wear in ches plated against engine coolant temp in degrees F.


peace
Hog
Was this test done with a filled block? Don't know.
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Old 09-18-2013, 08:39 PM
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Don't know anything about the test, renders it close to useless. Unfortunate too as the idea is worth something.
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Old 09-19-2013, 07:59 AM
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With a filled block, I believe that the wear issue becomes moot for 2 reasons:
1. The Piston to bore clearance should already be wider than normal
2. The cylinder bore temp is regulated by the oil temp, not the coolant temp


Forgetting the wear aspect for now, let's look at DENSITY as the major power producer, since the air-fuel mixture is entering at a slightly cooler temp, so it's denser. The "delta T" argument presented earlier by Bogie only shows a very small part of the story; it's from a thermodynamics viewpoint and contributes almost nothing. It's the DENSITY component that contributes more significantly, I would think. More density means more O2 molecules; same reason an engine makes more power on a cool, dry day.
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Old 09-19-2013, 08:54 AM
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NASCAR engines are set to run at 200+ degrees because that is where they make the most power. my 2013 silverado runs at 210 degrees. lower intake charge temp raises the HP not lower coolant temp. for every 10 degrees you lower the intake charge temp you raise the HP !%
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Old 09-19-2013, 10:27 AM
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NASCAR engines are set to run at 200+ degrees because that is where they make the most power. my 2013 silverado runs at 210 degrees. lower intake charge temp raises the HP not lower coolant temp. for every 10 degrees you lower the intake charge temp you raise the HP !%
Thanks Clem. I figure that lowering the intake manifold temp is one way to lower the charge temp. Don't forget, my engine, although 3/4 filled, has coolant circulating in the upper 1 -2 inches of the block, as well as the entire cylinder head and intake manifold castings. Are you thinking that cooler running cylinder heads are a power robber, or adder. Do NASCAR engines run filled blocks? If not, then I wonder wheather your argument "holds water" (pun intended).
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