Cooling Systems
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From: Ball Ground, GA
Cooling Systems
I have a friend who is one of the top engineers in a highly respected engineering company that specializes in building high-end test cells and systems for major manufacturers. I recently asked Scott what he remembers from some cooling system testing a few years ago. This is his reply...
"I did a lot of cooling system testing for Ford in the late 80’s & early 90’s mostly in their climate controlled wind tunnels along with some track testing. Most of this was to validate new vehicle designs before production. I’ll let you know what I vaguely remember.
The maximum heat rise through the engine is usually 15-20°F. This is at maximum power output. I confirmed this in a book Engine Testing by Martyr & Plint, which says to limit the temperature rise through the water jacket to 10°C.
Typical rise in steady state highway cruising is more like 5°F. There are a lot of factors that will affect this: Thermostat rating, water flow rate, engine speed, gear ratio, AC compressor load and other accessory loads, etc. A typical road car only needs about 10-12 hp to cruise at 50 mph. (There are formulas to calculate this if you know your car’s frontal area and drag coefficient.) If the engine is only producing 10-12 hp while cruising it is obvious that it will only need a fraction of the cooling system’s capacity.
Car manufacturers do a lot of highly controlled testing to optimize the cooling system to work over the widest range of conditions the car could ever see. We ran cold wind tunnel tests at -50°F at 80 mph. The Hot test was at +115°F, simulating a fully loaded vehicle pulling a maximum rated trailer load up a 15% grade at 20 mph. This requires near full throttle in 1st gear on most vehicles. This condition is held for an hour followed by an hour of idling with max AC.
The point is, if you start changing things like the thermostat rating, using a “high flow” water pump or a larger radiator, you will have tradeoffs in some part of the performance spectrum. There is a misconception that doing things to make the engine run cooler is a good thing. Modern engines (<15 yrs old) operate at higher temperatures by design in order to get higher fuel efficiency and lower emissions.
Performance upgrades to an engine don’t necessarily require increased cooling capacity. Often a performance upgrade only increases maximum power output. Street cars rarely operate at max power for more than a few seconds. Many performance upgrades improve an engine’s efficiency which means it makes more power from the same amount of fuel. In this case it makes less heat as well.
If someone is having cooling problems it is usually because there is some faulty part and not a design issue. It’s better to diagnose the problem and correct it than to change to “high performance” parts to overcome the issue.
Common problems are leaking or incorrect radiator caps, clogged radiator cores, faulty or incorrect thermostat.
This is probably more information than you asked for.
Scott"
"I did a lot of cooling system testing for Ford in the late 80’s & early 90’s mostly in their climate controlled wind tunnels along with some track testing. Most of this was to validate new vehicle designs before production. I’ll let you know what I vaguely remember.
The maximum heat rise through the engine is usually 15-20°F. This is at maximum power output. I confirmed this in a book Engine Testing by Martyr & Plint, which says to limit the temperature rise through the water jacket to 10°C.
Typical rise in steady state highway cruising is more like 5°F. There are a lot of factors that will affect this: Thermostat rating, water flow rate, engine speed, gear ratio, AC compressor load and other accessory loads, etc. A typical road car only needs about 10-12 hp to cruise at 50 mph. (There are formulas to calculate this if you know your car’s frontal area and drag coefficient.) If the engine is only producing 10-12 hp while cruising it is obvious that it will only need a fraction of the cooling system’s capacity.
Car manufacturers do a lot of highly controlled testing to optimize the cooling system to work over the widest range of conditions the car could ever see. We ran cold wind tunnel tests at -50°F at 80 mph. The Hot test was at +115°F, simulating a fully loaded vehicle pulling a maximum rated trailer load up a 15% grade at 20 mph. This requires near full throttle in 1st gear on most vehicles. This condition is held for an hour followed by an hour of idling with max AC.
The point is, if you start changing things like the thermostat rating, using a “high flow” water pump or a larger radiator, you will have tradeoffs in some part of the performance spectrum. There is a misconception that doing things to make the engine run cooler is a good thing. Modern engines (<15 yrs old) operate at higher temperatures by design in order to get higher fuel efficiency and lower emissions.
Performance upgrades to an engine don’t necessarily require increased cooling capacity. Often a performance upgrade only increases maximum power output. Street cars rarely operate at max power for more than a few seconds. Many performance upgrades improve an engine’s efficiency which means it makes more power from the same amount of fuel. In this case it makes less heat as well.
If someone is having cooling problems it is usually because there is some faulty part and not a design issue. It’s better to diagnose the problem and correct it than to change to “high performance” parts to overcome the issue.
Common problems are leaking or incorrect radiator caps, clogged radiator cores, faulty or incorrect thermostat.
This is probably more information than you asked for.
Scott"
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Joined: Feb 2003
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From: saratoga, ca
Ive seen only clogged radiators and bubbles in the systems from not being burped properly, which caused t-stats to not work properly with our 928s.
Good points! probably why going up near 100hp in our 928s is never an issue with our stock 928 radiators, when they are functioning properly.
Good points! probably why going up near 100hp in our 928s is never an issue with our stock 928 radiators, when they are functioning properly.
I have a friend who is one of the top engineers in a highly respected engineering company that specializes in building high-end test cells and systems for major manufacturers. I recently asked Scott what he remembers from some cooling system testing a few years ago. This is his reply...
"I did a lot of cooling system testing for Ford in the late 80’s & early 90’s mostly in their climate controlled wind tunnels along with some track testing. Most of this was to validate new vehicle designs before production. I’ll let you know what I vaguely remember.
The maximum heat rise through the engine is usually 15-20°F. This is at maximum power output. I confirmed this in a book Engine Testing by Martyr & Plint, which says to limit the temperature rise through the water jacket to 10°C.
Typical rise in steady state highway cruising is more like 5°F. There are a lot of factors that will affect this: Thermostat rating, water flow rate, engine speed, gear ratio, AC compressor load and other accessory loads, etc. A typical road car only needs about 10-12 hp to cruise at 50 mph. (There are formulas to calculate this if you know your car’s frontal area and drag coefficient.) If the engine is only producing 10-12 hp while cruising it is obvious that it will only need a fraction of the cooling system’s capacity.
Car manufacturers do a lot of highly controlled testing to optimize the cooling system to work over the widest range of conditions the car could ever see. We ran cold wind tunnel tests at -50°F at 80 mph. The Hot test was at +115°F, simulating a fully loaded vehicle pulling a maximum rated trailer load up a 15% grade at 20 mph. This requires near full throttle in 1st gear on most vehicles. This condition is held for an hour followed by an hour of idling with max AC.
The point is, if you start changing things like the thermostat rating, using a “high flow” water pump or a larger radiator, you will have tradeoffs in some part of the performance spectrum. There is a misconception that doing things to make the engine run cooler is a good thing. Modern engines (<15 yrs old) operate at higher temperatures by design in order to get higher fuel efficiency and lower emissions.
Performance upgrades to an engine don’t necessarily require increased cooling capacity. Often a performance upgrade only increases maximum power output. Street cars rarely operate at max power for more than a few seconds. Many performance upgrades improve an engine’s efficiency which means it makes more power from the same amount of fuel. In this case it makes less heat as well.
If someone is having cooling problems it is usually because there is some faulty part and not a design issue. It’s better to diagnose the problem and correct it than to change to “high performance” parts to overcome the issue.
Common problems are leaking or incorrect radiator caps, clogged radiator cores, faulty or incorrect thermostat.
This is probably more information than you asked for.
Scott"
"I did a lot of cooling system testing for Ford in the late 80’s & early 90’s mostly in their climate controlled wind tunnels along with some track testing. Most of this was to validate new vehicle designs before production. I’ll let you know what I vaguely remember.
The maximum heat rise through the engine is usually 15-20°F. This is at maximum power output. I confirmed this in a book Engine Testing by Martyr & Plint, which says to limit the temperature rise through the water jacket to 10°C.
Typical rise in steady state highway cruising is more like 5°F. There are a lot of factors that will affect this: Thermostat rating, water flow rate, engine speed, gear ratio, AC compressor load and other accessory loads, etc. A typical road car only needs about 10-12 hp to cruise at 50 mph. (There are formulas to calculate this if you know your car’s frontal area and drag coefficient.) If the engine is only producing 10-12 hp while cruising it is obvious that it will only need a fraction of the cooling system’s capacity.
Car manufacturers do a lot of highly controlled testing to optimize the cooling system to work over the widest range of conditions the car could ever see. We ran cold wind tunnel tests at -50°F at 80 mph. The Hot test was at +115°F, simulating a fully loaded vehicle pulling a maximum rated trailer load up a 15% grade at 20 mph. This requires near full throttle in 1st gear on most vehicles. This condition is held for an hour followed by an hour of idling with max AC.
The point is, if you start changing things like the thermostat rating, using a “high flow” water pump or a larger radiator, you will have tradeoffs in some part of the performance spectrum. There is a misconception that doing things to make the engine run cooler is a good thing. Modern engines (<15 yrs old) operate at higher temperatures by design in order to get higher fuel efficiency and lower emissions.
Performance upgrades to an engine don’t necessarily require increased cooling capacity. Often a performance upgrade only increases maximum power output. Street cars rarely operate at max power for more than a few seconds. Many performance upgrades improve an engine’s efficiency which means it makes more power from the same amount of fuel. In this case it makes less heat as well.
If someone is having cooling problems it is usually because there is some faulty part and not a design issue. It’s better to diagnose the problem and correct it than to change to “high performance” parts to overcome the issue.
Common problems are leaking or incorrect radiator caps, clogged radiator cores, faulty or incorrect thermostat.
This is probably more information than you asked for.
Scott"
