Just been having a discussion with some friends about what is the ideal temperature for an engine to run at…
I reckon around 88 - 90 degrees - any colder and it is detrimental…
Anyone care to comment, technical or otherwise ??
I alwasy thought it was part of the engine design and spec. i.e. the clever beardy engineer types know why it’s gotta run at a certain temp…
For example the K at ~90C has expanded enough with all the sandwich sections to mate 100%…
I know older toyota engine run very hot compared to most other engines hence why lots of condensation from the exhaust in the winter…
Race bikes run around 60 - 70C…
So I think anywhere between 60C and 120C
I thought they run the Motorsport Elises and B&C’s Exige racer in the 70s.
Ian
IDG
I think 90C is supposed to be the ideal… i can’t imagine they run race-cars cooler ??
Rox,
If it was a full blown race car you may want to skim the head quite a bit to up the CR then really you’d want a lower temp just to avoid any possibility of pre det / dieseling from too high a CR IYSWIM… Lots of variables to consider
That’s just one (possible) scenario where you may want a lower temp…
yeh but RL
why would you run a water temp of 70C ?? this wouldn’t stop pre-det… would it?? … you would do that by playing with ignition timing and fuel and spark-plug ratings and piston/bore materials an stuff… no??
I honestly have no idea Rox!
But to my thinking, if you skim the head a lot to get a higher compression ratio, well to the best point, then you get exponetially more heat generated by increasing the pressure in the bore…
And if it get’s too hot will the mix ignite before the spark… Maybe, this bit’s pure speculation So therefore pre det?
Plus running hotter fuel in a “full blown” race car, to my thinking you’d just want everything that bit cooler
well
i see what you are saying but in a racecar, although they might want to stop melt-down, if they can get it to run at 90C i think they’d be happy…
also - the fuel/air mix in the cylinder will burn most efficiently at a certain specific temperature and if the cylinder walls are too cool then you won’t reach maximum efficiency and hence you won’t burn ALL the fuel and so power will be down and emmissions up etc etc…
Also i think the fuel and air mix best at specific temp and so if you are too cool, again, you don’t get the 14.7:1 AFR and, again, lose power and increase unburnt fuel emmissions etc…
Yep, I do agree with all of that
Really tho, I have no idea… All I know is that older Toyota engine definatly “run hot” compared to other engines…
And that the race bikes (the team my dad works for, they’r in the full BSB next year!!! MSS Kawasaki, keep an eye on 'em ) run with a 70 deg thermostat… I remember my dad being quite shocked that it started life with an 88deg thermostat
I was just quoting from memory, I may have got it wrong, they may have got it wrong, I’m certainly no engine expert.
Ian
Ian, I think that’s OK
But looking from the coolant thread, that NPG stuff…
Evans NPG Coolant is 100% inhibited Propylene Glycol. It can maintain substantially vapor free, liquid - to - metal contact at all coolant temperature and engine loads. By bathing the entire combustion chamber with coolant 100% of the time, metal temperatures are controlled to such an extent that critical levels of detonation and pre-ignition are never reached.
I’m no expert, but heard that the reason the Exige 190 kit includes a lower temp thermostat is (allegedly) because a lower temperature is good for making power whereas a higher temp is better for economy and emmisions. This may be just a specific case for this particular engine, or it might just be a load of arse!
Well that’s what I (a self confessing non-expert) thought too Brendan.
Ian
I’m no expert, but heard that the reason the Exige 190 kit includes a lower temp thermostat is (allegedly) because a lower temperature is good for making power whereas a higher temp is better for economy and emmisions. This may be just a specific case for this particular engine, or it might just be a load of arse!
Brendan
If it makes more power… it generates more heat… yeh… ? so…
My guess would be that with the distance to the radiator and with the stat in the position where it aint sending coolant up to the very long line to radiator then you have a very small closed loop for the coolant to flow in… in addition to that, our engine is in the back so free air cooling is also limited… yeh ? So as a protection it would be prudent to open the stat earlier (82 instead of 89) so that you use the radiator earlier and dump that extra heat from all those extra ponies before its too late…
I don’t think the ideal temp for power and/or economy/emissions will be any different… at the end of the day for power, economy and emissions you want to burn ALL the fuel (but not the Nitrogen content) perfectly… and this will happen best at a specific temperature.
If the cylinder walls are ‘too’ cool then the flame won’t burn as well there as it does in the centre of the cylinder and you will get a higher level of unburnt fuel… so power loss, increased emmissions etc etc… no ??
RemarkLima
I guess the same for bikes… they have a very small coolant loop so probably send it to the radiator earlier because of the low volume? but i guess yer Da will know?
I was just quoting from memory, I may have got it wrong, they may have got it wrong,
Ian
IDG
doesn’t matter a toss me old fruit… it leads to good discussion and making us think about ‘what if?’… etc etc…
“What if?”… Honda
I’ll ask my dad about it, see if they have any reason other than everyone’s always done it
RoxTeddy, Your argument makes a lot of sense. I was thinking when I wrote that, that the best power should come when the fuel’s being burnt most efficiently. Somebody must know the true answer.