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Discussion Starter · #1 ·
A recent discussion about heat issues….. it’s worth noting that every internal combustion engine is only using a relatively small percentage of the heat generated by the fuel to turn the drive wheel. Wikipedia claims street cars are only about 20% efficient.

I’ve heard higher, on the order of 30%.

Even if that’s the case, that means you’re generating twice as much excess heat as you actually use. In simple numbers, 200 HP worth of heat in the form of burnt fuel is wasted, to get 100 at the crankshaft.

I’m not going to attempt the math. Hopefully someone else will chime in and educate me on the specifics.

Fuel is burnt, gasses expand, pistons move.

The relevant point from my perspective is that dumping all that waste heat occurs either into the exhaust gasses, or transferred through the metal into the water jacket.

From there, back to the atmosphere.

Radiators are sized for the needed level of cooling to keep the engine in its ‘happy place’ no matter what ambient temperatures may be.

Hardest work, hottest conditions are taken into account.
 

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So what you're saying is we should install tea kettles surrounded by a water jacket in line with the radiator so we can use more of the energy output productively. :unsure:

And we can put a little oven inside the muffler for our lunch.
 

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RJ,

Your numbers are in line with what I have always seen mentioned on the engineering side of things. Modern engines should give 30-35% thermal efficiencies. The wikipedia number may be based on real world performance that considers throttling losses, mechanical losses and other things that cost power in a real engine instead of a theoretical math model.

For Otto cycle engines the thermal efficiency is directly proportional to the compression ratio and nothing else (this is idealized based on a perfect cycle, but is close enough for our purposes). The higher the CR, the higher the efficiency. This means the biggest limiting factor is the knock resistance of our fuels. Fix that and you will find higher efficiency. A significantly higher CR is the major reason why diesels are more efficient than gasoline engines.


Mark
 
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Discussion Starter · #4 ·
So what you're saying is we should install tea kettles surrounded by a water jacket in line with the radiator so we can use more of the energy output productively. :unsure:

And we can put a little oven inside the muffler for our lunch.
More a matter of recognizing that there is a lot of waste heat coming off the engine system. Some folks seem surprised at that.

Mythbusters did an episode where they cooked a multi course meal in the engine bay of a V8 car while driving it around.

My first car, a clapped out 1963 VW bug used forced air to cool the cylinders. That heated air was then channeled into the unit body frame and was supplied to the cabin for heating. Hot enough to blister skin, even after traveling through the frame back to front on any winter’s day I could get it to run. Not too shabby for a 27HP car. Not quick by any stretch, but a great winter car.

Years ago I thought it would be a great idea to plumb the handlebars so you could scavenge some of that heat for the grips. The seat would be easier, as there would be fewer moving parts. it’s just a matter of getting the correct amount of flow. With modern plastic plumbing lines, it should be quite simple. Not really a sport bike thing, but that heat is going to get radiated off into the atmosphere eventually.

It’s even feasible to tap that coolant loop for heated clothing, although the potential downsides of a leak far outweigh the benefit.

Efficiency from changing forms of energy the least number of times possible. External combustion (steam engines) ECE are considerably more efficient than ICE because the combustion process just heats water to steam.

I don’t consider electric vehicles as especially efficient; the power required is initially generated by a form of steam engine, whether that’s coal, natural gas, or nuclear. The only upside is that the carbon emissions are generated in large volumes in a single location…. Economy of scale should reduce the emissions released , except for all those carbon credits the dirty power plants buy from the electric vehicle producers.

Fuel cell technology will bridge the gap more effectively, once someone admits cracking hydrocarbons to get the hydrogen is far more practical than setting up hydrogen fuel stations.

We can’t even get an upgraded power grid figured
 

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More a matter of recognizing that there is a lot of waste heat coming off the engine system. Some folks seem surprised at that.

Mythbusters did an episode where they cooked a multi course meal in the engine bay of a V8 car while driving it around.
This waste heat sure is useful for those of us in northern climes that see real winter. This is also a significant weakness of EV's for use in cold places. We heat the car interior essentially for free with ICE vehicles, but having to keep the occupants warm directly reduces EV range. There are a fair number of Teslas on the road up here, but I don't know anyone who owns one so I haven't heard how they do in cold weather.


We can’t even get an upgraded power grid figured
Some days we can't even keep what we have running, let alone upgrading it. The EV thing is going to run hard into this reality in the next 10-15 years. Up here our illustrious moron in chief has already started extending deadlines for industry carbon reductions and we have hardly begun with the bullshit. In another 5 years they will be spending more time stretching timelines, altering reduction targets and justifying why it isn't all working than anything else.


Mark
 

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The snow bike crowd taps the handle bars and uses coolant to heat. Also they make throttle body heaters and then slide plastic covers in front of the radiators to keep engine temps up, as the dirt bikes converted to snow machine use have excess cooling capacity often.

Now one major limiting factor in ICE efficiency is emissions. When compression ratio and temps get too high you end up with more Nox in the emissions. Hence VW diesel gate. You can have greater fuel economy but you’ll pollute more…
 

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you will notice lots of vehicles used to have thermostats of say.......... 156*

and now nearly every vehicle has a thermostat right around 200*

trying to squeeze out those mpg's and pass emissions standards..... I am not sure it makes the engine last any longer


As far as the tesla in winter comment about battery life, locals in Minneshithole say the few weeks in a row we do not ever see above 0*F-- battery life is sub 100miles on a full charge, when it is around 190 miles on a full charge in spring and fall (no heat and no AC use).......... brand new it used to be almost 240miles in those same "ideal" conditions".... says typical summer use with AC going all the time he can get 130-140 but it varies wildly between 120 and 170 most of the time (seems like garbage to me for a $70k bare bones base model car with only 80,000miles even if 6 years old... but it is a fat pig at well over 4600 lbs.... and the tires are kind of small imo)
and don't forget about the disappearing rear tire tread on summer only tires that cost about $750 to replace and barely last 15,000 miles........... more pollution and definitely not GREEN
or the cost of getting the right 230v into your garage so you can have 10hr charge times instead of 3 day charge times from a 115v outlet (unless you parasite from the few charging places)


and I once did the bake a potato on the exhuast manifold of a 3 cylinder subaru justy........ in winter drove from Minneshithole to shitcago (about 7 hrs drive time)........ it was bit burnt but edible........ just had to try it
fyi...for such a tiny shitbox of a car with zero power it sure didn't get good mpg at best I ever saw was 40, my gf's focus with twice the power, way more comfort, stopping power etc can get that.hell my Mustang with nearly quadruple the power and gets from 0-60 in about 1/4 the distance and time, can get real close to that (35mpg best I have accomplished but certainly not the norm--28mpg is my lifetime average in 16,000 miles)
 
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A recent discussion about heat issues….. it’s worth noting that every internal combustion engine is only using a relatively small percentage of the heat generated by the fuel to turn the drive wheel. Wikipedia claims street cars are only about 20% efficient.

I’ve heard higher, on the order of 30%.

Even if that’s the case, that means you’re generating twice as much excess heat as you actually use. In simple numbers, 200 HP worth of heat in the form of burnt fuel is wasted, to get 100 at the crankshaft.

I’m not going to attempt the math. Hopefully someone else will chime in and educate me on the specifics.

Fuel is burnt, gasses expand, pistons move.

The relevant point from my perspective is that dumping all that waste heat occurs either into the exhaust gasses, or transferred through the metal into the water jacket.

From there, back to the atmosphere.

Radiators are sized for the needed level of cooling to keep the engine in its ‘happy place’ no matter what ambient temperatures may be.

Hardest work, hottest conditions are taken into account.
Not everything is designed to be efficient. And great performance cost a lot of extra waste.

Not to mention aluminum is poor at thermal conductivity which is what our engines and radiators are made out of. Plus the fans are absolutely crap, they cover like 50% of the surface area on motorcycles.

I’m sure there are ways to improve the efficiency of how much cooling and engine could offer per how much fuel it is burning. But the cost and weight of improving this wouldn’t exactly make sense or it would be super expensive. Not to mention, when you look inside an engines cylinder walls where the coolant flows they don‘t really have much engineering going on that would promote great cooling.

I think an engine could be built to offer better performance than what you’ve mentioned. Bigger and thicker radiator with more surface area, fans that cover at least 80% of the radiator with blades shaped in a way that would generate better static pressure so air is pushed through the radiator easier. Then maybe take a look at how the block is designed promoting better heat extraction with the block where the coolant passages are at. I would think micro fins would help that connect the cylinder to the block and water passes through them. ^ Most of this does not make sense financially. But it could definitely be done better.
 

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you will notice lots of vehicles used to have thermostats of say.......... 156*

and now nearly every vehicle has a thermostat right around 200*
Higher coolant temps also increase the radiator cooling efficiency, which is driven by the temperature difference between the coolant and the air.


fyi...for such a tiny shitbox of a car with zero power it sure didn't get good mpg at best I ever saw was 40, my gf's focus with twice the power, way more comfort, stopping power etc can get that.hell my Mustang with nearly quadruple the power and gets from 0-60 in about 1/4 the distance and time, can get real close to that (35mpg best I have accomplished but certainly not the norm--28mpg is my lifetime average in 16,000 miles)
Mileage is mostly a function of driving habits and aero drag. Having lots of horsepower doesn't really matter unless you start hammering it. Puttering along at 60mph will give similar mileage results across a fairly wide range of cars as long as they are similar sized and have similar drag numbers. Engine size has almost no influence on it.

If the Justy was old enough to not have EFI and electronic engine management then it would be pretty easy to match or beat it with more modern vehicles that offer much better performance.


Mark
 

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Nice discussion you started @RJ2112. One advantage of EVs is the efficiencies of generating stations can be much higher than a car with an internal combustion engine. Last I saw combine cycle generating units running on natural gas were 65%+ efficient. All the engines discussed are carnot cycles and the bigger the difference between the input and output temperature the better the efficiency - as I remember from thermodynamics several decades ago. I'm an electrical engineer so don't ask me about stuff like that. That is why the coolant temperatures have gone up in recent years. Lots of simple techniques in the engines to reduce friction and pumping losses. 0W-20 oil for and better tolerances, using regeneration for braking means some of the energy is captured and able to be re-used. That's why hybrids do so well in city driving. Modern engines have lots of tricks to reduce friction and benefit from better materials and machining.

Something I never see discussed is all of the vehicles on the road burning fuel but only at maybe 30% efficiency with 70$ dumped as heat, well ultimately it all goes as heat. That has to have an impact on the environment and must raid the local temperature. I've been on Interstate 75 in Florida and noticed when running in a pack of cars my coolant temperature will go up a few degrees. If I get out in clear air it drops back down. That is just one indicator of the amount of heat pumped out by cars. Add to that the houses and industrial and commercial sources of heat. In cities there are vast areas which have swapped woods and fields for concrete and asphalt - heat islands.

Know there are lots of EVs in Minnesota but cannot figure out why. Here in the south where it doesn't get that cold - LOL 0F is something we see maybe once every 25 or 30 years! On the Bolt forum every winter that are folks who are shocked to find out their EV gets way less range in the winter and the heater kills range.
 

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Discussion Starter · #11 ·
The heat management for a car is a phenomenal thing, when you consider just how little of it anyone is exposed to.

That was my point at the start of this conversation..... My 2014 Corolla produces half again the peak hp my zx6 does, and as a result produces half again the wasted heat. To be injured by a hot part of the car, would probably be grounds for a lawsuit.

That level of insulation, isolation, and dare I say 'idiot proofing' has led to an ever increasing number of people who expect that level of performance with everything they interact with.

The whole concept of 'excess heat' coming out of the fairing is so profoundly flawed as to make it difficult to take seriously. Yet, here we are.....
 

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One advantage of EVs is the efficiencies of generating stations can be much higher than a car with an internal combustion engine. Last I saw combine cycle generating units running on natural gas were 65%+ efficient.
Yes, stationary power generation is much more efficient. The downside is you then eat a lot of transmission losses getting the power down the lines to the end user. It's all a game of trade offs and what works best for specific circumstances.


I've been on Interstate 75 in Florida and noticed when running in a pack of cars my coolant temperature will go up a few degrees. If I get out in clear air it drops back down.
I would suspect that is more because you are getting turbulent air into the rad when in traffic and then much cleaner airflow on your own. I agree a big pack of cars at rush hour heats things up a fair bit as well. I noticed that a lot in summer when I used to commute for work.


Mark
 

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Discussion Starter · #13 ·
^^ When in traffic, the train of vehicles has a much smaller pressure differential compared to the leading vehicle….. the pocket of low pressure works both ways. Less wind resistance & less radiator efficiency.
 

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^ also go next to any concrete jungle at dusk and then sprint to the grasslands or woodlands........

temp drops in the concrete jungle are slow as fuck overnight, sometime non existant

temp drops in the grasslands and woodlands drop like a fucking stone as soon as the sun gets low enough, even before sunset!


I just got back from sconieland, my car told me is was 93* there back at 5pm when the sun was still blasting, at 8:45pm coming home the car said it was 77* until I got back to the concrete burbs where it read 86*-89* depending on how much concrete/asphalt and buildings I was in........ downtown hastings (tons of buildings and nearly all hard surfaces) still said 90* when I came through
I am willing to bet had I driven up to actual downtown Murderapolis where you can barely find a blade of grass it would have still been in the 90's (a real concrete jungle of stupid)
I am only talking a gross distance travelled from the furthest point away of about 35 miles! so local weather and ambient high temps and humidities were nearly identical
 

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Discussion Starter · #15 · (Edited)
Not everything is designed to be efficient. And great performance cost a lot of extra waste.

Not to mention aluminum is poor at thermal conductivity which is what our engines and radiators are made out of. Plus the fans are absolutely crap, they cover like 50% of the surface area on motorcycles.

I’m sure there are ways to improve the efficiency of how much cooling and engine could offer per how much fuel it is burning. But the cost and weight of improving this wouldn’t exactly make sense or it would be super expensive. Not to mention, when you look inside an engines cylinder walls where the coolant flows they don‘t really have much engineering going on that would promote great cooling.

I think an engine could be built to offer better performance than what you’ve mentioned. Bigger and thicker radiator with more surface area, fans that cover at least 80% of the radiator with blades shaped in a way that would generate better static pressure so air is pushed through the radiator easier. Then maybe take a look at how the block is designed promoting better heat extraction with the block where the coolant passages are at. I would think micro fins would help that connect the cylinder to the block and water passes through them. ^ Most of this does not make sense financially. But it could definitely be done better.

Water cooling systems aren't meant to keep an engine cold..... They're designed to maintain a specific operating temperature, so all the different parts reach their desired dimensions quickly. Bronze bearings, steel rings, aluminum piston and silica impregnated cylinder bores all expand at different rates as they heat up. That's why cold engines produce more smog, and make less power. They leak more until they heat up enough to seal.

SR-71 Blackbirds were an extreme example of that. The fuel tanks leaked on the ground because the airframe expanded so much from aerodynamic heating that gaps had to be left in things to account for it. The pilots could not touch the canopy glass because of how hot it was in flight.

All of that, to say a bigger radiator, bigger more efficient fans have very little benefit towards improving performance. We think 212°F is a critical number, when it's really not. If you have an unpressurised cooling system, it absolutely is. We don't have that, so it's not. When water starts to boil, the bubbles that form sitting on the hot metal surface are the problem. Higher pressure, reduces the formation of bubbles.

Just like with foam insulation, those bubbles make a layer of insulation that slows the transfer of heat. Anything that causes turbulent flow in the coolant promotes bubble formation, which creates a localized hot spot. If the heating makes something expand more than expected..... (This is why using different chemistry coolants has to be approached with great care. When the two types mix and jell, how big of a hot spot does that make because that jell doesn't move with the flow? ) smooth surfaces with uniform flow work much better than fins or rough surfaces with turbulence.

Indicated coolant temperature is an at best average number. It certainly isn't a uniform value throughout the cooling system..... That temp indication simply allows you to monitor the trend. The fluid does shed heat more quickly than any of the metals in the engine...... But none of us can say exactly where the hottest points in the engine are without talking in generic terms. Obviously, the top of the cylinders are hotter than most other places. Heat 'soak' to other points depend on time and that conductivity you spoke of.

A few molecules above the top of the pistons are nearly the hottest points in the engine..... The exhaust valves and the valve seats are hotter. No one really cares how hot the headers are, on this first cut of heat 'management '.
 

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Discussion Starter · #16 · (Edited)
Yes, stationary power generation is much more efficient. The downside is you then eat a lot of transmission losses getting the power down the lines to the end user. It's all a game of trade offs and what works best for specific circumstances......
Mark
Transmission lines for power use really high voltage, to reduce the effect of line loss. Work is calculated in Watts, so that combination of current times voltage benefits from higher voltage.... line loss is the result of resistance which really only affects the flow of current. Many transmission lines are on the order of 4,000+ VAC, so on those 'long haul' lines between the point of generation and the transfer station the efficiency is quite high.

Superconductors will eventually increase that efficiency - but that will be another heat management scenario as almost all of this class of conductors require either near absolute zero, or the far less 'just' liquid nitrogen levels of cooling to work.

The biggest losses come from converting energy to be used from one form to another. The heater on an electric vehicle is a great example of blowing all the efficiency right out the vents (same as with the AC).

Having a hot water storage tank inside a house being cooled by AC, along with a refrigerator is another exercise in absurdity. The biggest consumption of power in a private dwelling comes from temperature management of the air within the house, or the production of hot water. Some work has been done on this in the form of both freezers and hot water tanks that are actually heat pumps that dump their scavenged heat into the appropriate climate to contribute rather than subtract from the required gradients.

Ground loop heat pumps are worlds more efficient than air loop systems..... why they are not more common is puzzling to me. I understand the need for the lines in the ground to be at a stable temperature point -- what I don't understand is why they need to be sunk in wells 300' deep. Me being on 24 acres of land, it would be simple to trench as much coolant loop as required some 10's of feet down and go horizontally.

The best solution of all is to reduce the need to heat or cool as much as possible..... super insulation is far and away the most efficient way to reduce power consumption.

Controlling solar loading is another hugely effective way to reduce the unintended heating of a home. Look at any farm house from times before networked power; they are always in an island of deciduous trees. Shade is a viable way to reduce heating. No leaves when it's cold.....more heat introduced to the house....
 
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