Temperature control

[smithersoli]

What do you guys with more control over your engines temperature, choose to run it at?

I have a large Alloy radiator with two massive fans and an electric controller, ditching the otter switch etc.

I think mine is now a little on the cool side but haven't had an opportunity to fully test it (not road legal yet) but on my journey to the test centre and playing around with the carbs to get them balanced I struggled to get it over 85 and actually trigger the fans.

I think that cooler is better for power, but should I be trying to keep it a little warmer than that for efficiency (or wear considerations)

I have a water to oil cooler in there also which i haven't got around to checking out the efficiency there, but could I be keeping the oil too cool as well with this setup?

[Ozzy_UK]

mine always ran too cool... 79-82C

put in a dual fan controller and upped it to more like 85-90c stage 1, 95-100 stage 2...

Oz

[Lotus-e-Clan]

Your oil to water cooler will be sharing the heat load. In other words the heat from the cylinder jacket during the warm-up period will be dissipated through the radiator AND into the oil, whereas with an air to oil cooler the oil takes much longer to gain heat through direct contact with the engine internals alone (particularly cylinders and pistons). So basically the oil and water will warm-up together, which is better for engine life than you thinking the engine is fully warmed-up (oil & water) when it's only the water that's up to temperature.

The fan size and efficiency is totally irrelevant for normal running because they should not be on at all, especially in winter. They should only kick-in when the engine is fully heat soaked in high ambient temperatures in traffic etc.

Now then, if during winter your alum rad is over-cooling the system, it's basically telling you that you should be using a smaller radiator size to save weight and cut down aerodynamic drag! The original rad size chosen by Lotus was based on the efficiency of the original matrix material/design. With no cost constraints, they would have fitted a smaller, more efficient rad to give the same cooling capacity as the less efficient one fitted as std and gained a performance advantage.

The engine temp is set by the thermostat @ 82C. You don't want to increase that value because that's the best compromise between power and thermal efficiency without overheating the engine and causing a gasket failure.

Best thing to do now is to develop a system of radiator blinds that control the air flow through the rad so that the engine is working at the design temperature of 82C. You can have them fully open on your mid-summer continental holiday to take advantage your new-found increased cooling capacity, and have them part closed to control warm-up during winter. Or more cheaply for winter use , just block off part of the rad matrix with a board of some sort.

[smithersoli]

Actually now I have thought about it a bit more, my temperature sensor is in the back of the head (where it is most likely to demonstrate overheating problems), so the fact it never rose above that temperature does demonstrate that I have plenty of spare cooling capacity in the radiator and the thermostat is working !!

(Don't really want to swap out the rad as its a thing of beauty and probably cost the PO a bomb although I might consider removing one of the fans to save some weight if its never going to be needed (will test that in the summer once have got some decent road miles on her !)

Appreciated that the oil to water cooler was going to be sharing the heat, warming the oil up faster from cold and cooling it when needed, but I thought that once up to full running temperatures and engine bay heat soaked that the temp would creep up.
If the oil temperature is around the 80 degree mark is that going to mean it is causing extra drag within the engine? I did notice that with the oil to water cooler the oil pressure does seem to be higher across the range (although I did also smooth out some of the casting roughness in the oil pump galleries when I rebuilt it and put a restricter in the head as per lotusbits advice which will more likely be the cause)

I suppose my test conditions weren't particularly taxing, I observed all this when left idling after about an hours hard drive, but i did remove the bonnet so I could keep an eye on it and check for leaks etc.

Should I be thinking about moving the sensor to the top hose to keep an eye on the temps there? I still have the standard temp sensor wired up to the gauge in the dash, but I don't trust it!

[Lotus-e-Clan]

I've been running an oil temp gauge for a number of years and it's more likely that the running sump temp in normal part-throttle non-motorway driving is only 65C- 75C - the sump pan is air cooled and hardly needs an oil cooler for this type of driving.... and it takes a while for the sump pan to reach this low range without a heat exchanger. The oil temperature only rises significantly during hard full throttle, high revving, spirited A and B road driving and during sustained (after 20 min) part-throttle motorway driving @ 4000 rpm and above.

So your oil heat exchanger will help reduce drag during normal driving once it reaches water temp @ 80C - 82C. I've found the ideal oil temp operating range is between 75C and 95C and despite the claim on the oil can that the oil is capable of running at 120C (or higher) without film breakdown, your oil pressure will suffer when the oil goes way over 95C - not so much at higher revs, but when you are idling (immediately after spirited driving) and the pressure drops to 2 bar and below.

[smithersoli]

Hey guys, wondering if anyone had any thoughts on temperature range for a modified 912 engine. I inherited a rather large Aluminium radiator and 2 massive fans from the PO ( i suspect because he had silly ideas about what kind of engine he was going to be putting in the car and was overspecifying in order to make sure he had capacity. Anyway I have reverted to a modified 912 engine, fully gas flowed head, bigger valves, cams, balanced etc, to about stage 2 of Mike Taylors guidelines and I hope when it is run in and dynoed about 220hp.

Have been runnning it on the road for about a month now and I can't seem to get the temperature above about 75 degrees. I appreciate it is cold at the moment and I am not using it in heavy traffic on a summers day, but at the moment I can drive around for about 2 hours and the fans are not even kicking in (standalone temp controller tapped into the rear of the head) The main coolant gauge barely gets off cold!

The question is should I be worried I am overcooling the engine at the moment, should I be checking my thermostat again (it worked properly when I put it in), or is this just a function of the outside temperature and not working the engine too hard?

I need to check the valve clearances again and change the oil quickly before I start to really buzz it around the upper reaches of the rev range (I haven't even tested the rev limiter) but roughly how long do others cars take to reach the stage where pulling over and idling for a few minutes will kick in the fans?

One other thing which is relevant is that I have an oil to water cooler in the circuit which does seem to warm up the oil quicker now, but will that be affecting my temperatures to this degree?

[fueltheburn]

This is a point which I am currently looking at in relation to oil temperature, coolant, cooling and oil/water exchanger.

After sitting in traffic on the way to the NEC in Lola it was cringeworthy watching oil pressure drop as the oil heated up with no airflow over the cooler As a precaution to future proof I may add a small fan to the oil cooler which will be turned on in traffic.

On Ethel I have a large aluminium radiator so overcooling could potentially happen.
Hoping that a combination of the radiator, EWP and the oil/water cooler will maintain temperatures of both oil and coolant to between 75 and 85 degrees celcius with the added bonus of a fast warmup.

[AndyLotus]

After my engine rebuild I found that the temperature wasn't getting as high as I wanted.

It turned out that when 'glueing' the liners in place with the correct loctite the bit that exuded out at the bottom never went off, as the loctite only sets in the absence of air. Once filled with water/antifreeze some of this came adrift as small particles and stuck in the thermostat.

With the stat removed I could see the little flecks of white 'glue' were stopping the stat closing fully and therefore making the engine run cool. A new stat and a flush and no problems since.

Andy.

Fogot to mention, I fitted a stat to the standard oil cooler which helps to bring the engine temperature up quicker. In this cold weather the oil cooler stat sometimes doesn't even open. (This was after I sorted the cool running)