This is where my gage sits all the time http://s892.photobucket.com/user/RTE38/media/100_5455.jpg.html
If it takes more British Thermal Units before to raise the degree-temperature then the thermal capacity is increasing. As people have mentioned glycol is a poor choice of heat exchange medium, this is because it has a low heat capacity, much lower than water, you can see here http://www.engineeringtoolbox.com/ethylene-glycol-d_146.html that as glycol content increases heat capacity drops and they explain that this requires an increase in mass flow to pull the same amount of energy from the block. Similarly, hot oil will burn you much more easily than hot water because it has a high heat capacity it can transfer much more energy to your skin before it cools down. Viscosity and stickyness plus the higher boiling temperature contribute to how bad oil burns are too but even when they're controlled you'll still see a difference.
Dont EVER take a lot of notice of those stock guages M8. Every one of them more or less sits right there, anywhere from about 60 Deg.C thru to 100 Deg.C Mine does not move in this range of temp. The stock guage is little more than an indication that the engine is not cold and the cooling system has some water in it!!! E
At ok thx and I think I can see where I misunderstood their explanation. So efficiency DOES increase as the liquid becomes hotter?
Yes but it is truly an 'academic' difference, you'll only ever see it on paper. Also, there are lots of different efficiencies you can measure in a heat transfer system and the ones quoted will never be the total functional efficiency of the system because that varies all the time with temperature, humidity, airflow, load etc.. As Tas mentioned, unlike the heat capacity change, an increase in the delta T (difference in temperature) between two mediums will have significant efficiency improvements as the rate of transfer is greater with a larger difference. This is why a healthy car may heat up from 80 to 90 on a hot day but doesn't keep going, the thermostat is already fully open at 80 so there's nothing mechanical improving cooling (unless that's when thermos or a clutch fan kick in) but the car stabilises once it is able to expel the heat generated again. This is also why a low temp stat doesn't help on longer drives unless it is also reduces a flow restriction, and the system design is such that more flow actually helps.
Now, all we need is a few more to read this and some additional data on heat transfer thru different metals and the great ally radiator debate with have a definite "copper" colour to it... Hawhawhaw!!!!!! Ally, FTL! E
Here here..... I have a copper core and copper end tanks, no idea where it came from and have been told its definitely not standard but it works a treat. edit ** it also has all the plumbing for the auto ** and factory positioned mounting
Yeah it cools better, but you have solder issues on the joints and it's a fair bit heavier. And in todays prices, worth quite a bit!!
Not at all........this is a public forum....... I don't know whether they drive like a hoon or a grandma, live in in a desert oasis or the snowy mountains, have no coolant in their system or too much, have aftermarket parts, faulty thermostat, faulty pump, faulty radiator or even a faulty radiator cap or different cap pressure rating etc. What I do know, is that the engine was designed by Nissan to operate optimally under two thirds load / two thirds throttle at temperatures and not exceed 100c at normal operating temperatures/ and starting from atmospheric pressure. We don't pressurise the system for its ability to transfer heat. We pressurise the system only as a temporary place to store energy (a thermal protection buffer) We don't add coolant for its ability to transfer heat, we add coolant to temporarily store energy (another thermal protection buffer). We only use a pressure cap to stop the water from evaporating and to hold pressure as a temporary thermal energy storage device, not a permanent one. Using pressure we can get up to 10c more and 10c more from coolant but this is still only 20c combined against the thermal energy of water storing its energy from the ambient start point of anywhere between 0c and 40c on average up to 100C. Water is the cooling mechanism here........ not pressure or coolant! There are not three physical states but four Solid / Liquid/ Gas and Vapour. Vapour is the critical exchange temp between three physical states and all in 1degree difference. Vapour for water is 100c at 1 Bar approx. at sea level A coolant system will start with not less than 1 Bar thus the safe temp to quote on a forum is 100c or lower if that's the max operating temp. This is a critical figure! To advise someone to set a figure greater than 100C could mean disaster depending on their own circumstances and whether they even have faulty parts or systems or where they live etc..! I would rather err on a guaranteed safe level of max operating temp than have someone comeback and say later .........You ruined my motor because my radiator cap was faulty etc....... and you told me to set it higher than 100c. Driving full throttle like a hoon or sitting in a desert idling with air con on is also not normal. if your driving normally under normal operating conditions, you will never get above 100c at 1013 Bar at sea level 100C is a major thermal exchange point, as hot spots can develop with temps higher than that (as ROB260 points out) Heat travels to cold not the other way around...
The critical point of water is 374*C https://en.wikipedia.org/wiki/Supercritical_fluid Boiling point is relative to pressure up until that point, on Everest water boils at 70*C, at sea level on a still day it's 100*C, here in canberra it's 98 or something. None of those are the 'true' boiling point, they're the point where the liquid's vapour pressure overpowers the atmospheric pressure, the chemistry and physics of water do not change from 99 to 101 so long as it remains liquid.
105*C with the AC off apparently, https://z32.wikispaces.com/Auxiliary+Fan I wouldn't know though, A/C is for chumps Clutch fan is progressive but not sure what the temp curve is supposed to be.
According to the manual, coolant used in the engine should be ethylene glycol based. If the outside temperature is down to -30 degrees Centigrade, the mixture ratio is 50% antifreeze to 50% soft water. If it's down to -15 degrees Centigrade the mixture ratio is 30% antifreeze to 70% soft water. Lowest recorded temperature in Australia: Charlotte Pass, New South Wales -23.0 C (-9.4 F) on the 29th June, 1994. Adding antifreeze to water reduces cooling system performance. Antifreeze reduces thermal conductivity which reduces heat transfer efficiency. Perhaps of interest: http://rehermorrison.com/tech-talk-55-keeping-cool/
Re: Temperature gauge The owners manual indicates the normal operating range is the area marked on the gauge from the C to just below the H. Common sense would indicate if the outside temperature is below freezing & the gauge is in the upper section of the normal range, it is unlikely to be normal.
But your motor will be melted before it gets to 374c This is all true but its only pressure that holds the water as a liquid even though its still technically neither gas nor liquid at 1 Bar - as soon as you take your cap off - it will start vaporising We don't travel around with our radiator caps off, so why I am talking about 1 Bar/ 100C / sea level - only because its a well known reference point....nothing more............ I used to have a performance motor that sat on 105c all the time - not an issue ever - but this was not a stock system either A warning light at 99c / 100c gives you time to assess and rectify any fault safely - you can always adjust upwards later but setting above 100c and then having a fault may not give you enough time. Not many people drive around on Mt Everest and Canberra at 98 is quite fine - so quoting 1.013 Bar at sea level at 100c is not a bad reference point to start with. Your coolant system won't run less than 1 ATM unless its cooling down and sucking coolant back in from the overflow, so pressure can only go upwards from there. 100C is a safe figure to quote generally speaking - even if you lose your radiator cap, it will give you time to shut down and cool off slowly without fear of damage
Dude, your quoting mighty big figures and stuff here but the whole thing ASSUMES that this magical figure of 100c is the be all and end all of everything and is the lynchpin or your entire argument. What you are stating largely is personal speculation based on a few physical properties of water and pressure we already know about... at, or around seal level! I asked a question before about very high horsepower, high rpm large displacement V8 engines that turn primarily to the left for 500 miles at a time. They seem to have NO trouble whatsoever in allowing their engine coolant temps to climb to stupid figures up near 150deg C...... now why would that be? Oh...... pressurised cooling systems with NO pressure relief!!!!!!! Why run the cooling system unrelieved? So the temps are ABLE to climb that far with little worry about boiling over. Oil temps are a little different as the physical properties of oil go south quite quickly at elevated temps. The engines dont mysteriously melt into a big puddle of oily slush. nor do the instantly grenade. in fact, the build tolerances of these engines are not that far removed from the ones we use now yet they happily let them run hot enough to peel paint. Water properties, as near as f**ck is to swearing, remain the same up to some stupid temperatures if pressurised as mentioned. The properties more or less simply more along the scale to the right!!! If you could keep your oil within its operating characteristics at temps of circa 375 degrees then there is NO reason an engine cannot run there. Especially when you are speaking of EGT's circa 1500Deg.F. It wouldnt "melt". That temp is a fair and resonable to see for prolonged periods of time and already is far higher than the liquid point of aluminium alloy, and THATS what ya pistons are made of. Next, idling in the desert for days on end with the AC running flat out is EXACTLY what the manufacturers do. i know they do. its handy having a M8 who is a long time engineer and works in the R & D department of GHM!!! They have to build sufficient headroom into the different systems of the car to account for fearfully extreme outside temps that a car is expected to reliably operate in. Think about it, idling for hours in the desert is not near as stressful on the car as interminable idling on hot day stuck in traffic where a black road will absorb enough heat to liquify the tar, depending on the road wering course contruction, this can be in the vicinity of 80 degrees C. The AC system is producing gas temps proportional with its discharge pressure in psi (150psi is normal) and every car for many meters in front of you is adding additional heat out and under their own cars adding to the firestorm your fan is eating. So are you seriously asking anyone here to believe that 100deg.C, which is a nice uniform figure in your mind, is all that a cooling system will be asked to deal with in its ordinary working life and a pressurised system is ONLY there to account for a few extra precious few degrees as headroom? The HOTTER you can run the system, the more efficient the system becomes. You cannot get around that fact. The ONLY time i concern myself with anything at all is if the engine actually BOILS over which means temps must have exceeded 120 odd degrees C. I have NEVER damaged an engine as a result of boiling. My VG30det in my ute was boiled dry dozens of times in its early development. So what? It boiled....meh!!! If i drove it dry forever then id expect something to fail but a simple boiling case will not hurt the engine one iota. The fact that ANY car can withstand this kind of abuse, even on a shorter term such as a traffic snarl, is testament to the guys who designed and tested these systems to within an inch of the cars lives. So its fair to say that your magic figure of 100deg.C is actually a normal operating condition in hotter climes!!!!! These guys didnt just guess 105.C as a fan switch on point. to be honest, Id just connect a warning LED to the fan circuit PRIOR to the relay and let the ECU tell me its warming up!!!!! E
If your built your cooling system to maintain the higher pressures, ie not rubber hoses and worm clamps, then it'd be fine. Oil is another kettle of fish, but you want that hot enough to burn off any moisture from the combustion process, but you really have up to 170+ before a good oil starts to break down, around 375 Fahrenheit or somesuch. When I tracked ze zed I was seeing around 100 on the coolant temps and about 115 on the oil temps. Got up there pretty quick and stayed there. This was with electric fan as well, so lay it on me...
Hey E Sorry about the figures... figured SH might be useful to know offhand since we don't really see the unusual strange properties of water (water doesn't make sense in chemistry terms and there is nothing simple about it -lol) 100C is only a reference point for a start point not the not a magic figure for any car. The Z is not a nascar - having so much air flow at high speeds even on a hot ambient day is not really comparable nor is their cooling system. Nascars don't sit on idle for long periods. With the technology behind them, I would'nt even be surprised if they run radiator heaters with paraffin wax for coolant- lol Its true that engines can run at higher temps if the oil is cooler, but oil is also assisted in cooling by the strategically placed water jackets, but seals /bushes can all be affected at higher temps as rob pointed out - even if the alloy block won't melt into a puddle. I agree that they test in all conditions and certainly don't believe the coolant system is limited to 100C or even just above that - I was pointing out the fact that temperature can surge quickly above that temp because the bonds holding it as a liquid have been broken and energy is no longer absorbed as a result of it turning to the phsyical state of vapour. This is why temps can quickly escalate out of control once very high. The Higher the temp also means the higher chance of detonation, so a higher temp is not necessarily more effecient if your engine fails. What temp does detonation occur at? Its a variable answer but the cooler it runs the less chance. I have also boiled engines before myself with no problems, but I have also seen others boil engines and suffer damage as a result such as the engine seizing when cooling etc. There may well have been other issues, but the problems showed as a result of boiling over. If you think engines are hardy enough to run without water or boil over all the time, why do you even put water in your radiator, given its waste of time? There was no magic point I quoted, it was a start point at the max operating temp (if lower than 99c) or set to 100c and adjusting from there. Its not about the temp figures being the be all and end all, its about recognising that your system is having an an issue with cooling and understanding why and having time to rectify. Generally speaking thats the point where car is above what it is generally speaking, so if your car sits on 91 and never gets to 92, then 92 would be a good guide to say "somethings different - keep an eye on me", if its 98 then 99 would be a good setting, if its 105 then 106 etc etc. The 100C is just a start point not the end figure that you end up at. Why start at 100C as your possible max start point? Because from there temps can accelerate rapidly now that the water has turned to vapour and the bonds no longer require energy as they are broken. You cannot rebreak a broken bond without given off energy (i.e. reducing temp to 99c) Pressure or temps above 100C do not reattach the bonds, it merely compresses the molecules together to the point it may flow like water, it may even act to some degree like water, but unlike water, it is not as a liquid has its bonds intact. Its actually now just vapour/ steam under compression/ pressure. I'm happy to be corrected here given I am not a chemistry professor but technically speaking Super Heated Water or water above 100C doesn't exist - its not water but vapour or steam with a different physical state to water or gas. We only use the term water to indicate its orignal H20 constiuent and becuase it can display an illusion of acting like water when we pressurise it, but it is vapour and the bonds remain broken. A warning light is not designed to tell you anything, its merely designed to draw your attention to the fact that something is wrong/ abnormal / or different and then let you assess the situation in time. Its not a bad thing if it goes off early as long as its not normal becuase it can give you more time. Your magic figure of 105C for all situations / conditions/ systems/ cars is actually only 5C off my 100c (or lower max operating temp but mine was dependant on your personal situation), so I don't see how your figure is correct but mine is wrong being only 5C off? Yours is basing the figure off the fan kicking in becuase its struggling whereas mine was based at the point in where your water is no longer effective in taking energy on board due to the bonds being broken (the water/ vapour component of the cooling mechanism is is struggling). One point is just when its starts to struggle, the other is when the situation is already struggling, so the fan kicks in. I believe there is no actual correct figure though.....becuase all situations/ pressures/systems are different........ But someone asked for a figure...and as hard as it is to give one size shoe to fit all, 100C seemed appropriate as it's a well known thermal exchange point and a reference start point that could be adjusted as the situation dictates. Its not just an another increment on a gauge but a point at which the thermal saturation point of water has been achieved and that the molecules are excited and freely able to change between the three physical states of liquid(bonds intact)/ vapour (bonds broken but the medium is trapped) and a gas (where the bonds are broken and the gas is allowed to escape free) If you think 100C is too low - then some of the other recommendations here will shock you - lol. If you want to advise to set higher temps up to 150C - that's your call. I sincerely appreciate your response and always find your posts interesting and insightful to say the least. I just beg to differ by about 5C on a start point in which to adjust from - lol Regards as always...... er..............Dude JC
