V6 Fan Temps in Conversion - Too Low?

[Thevanman]

Hi All,

Working through my cooling setup on a my Toyota Dyna 100 conversion.
Have done ~8000km since conversion without issue, just looking at towing etc.. now....

Setup is a aluminium radiator and single davies craig thermo.

Only mod to PCM so far was to remove VATS - but as I've been researching fan speeds/temps I noticed something non-standard in mine, seems to kick in at lower temps than discussed here....downloaded the BIN this morning for the first time from my truck and noticed the fan temps are set much lower than standard (based on The1's enhanced).
Low Enable/Disable - 95.75°/95 (vs 104°/99.5)
High Enable/Disable - 98°/97.25 (vs 107°/103.25)
My fan kicks in and out nicely at the lower temps, doesn't need to stay on for long (~90 sec) to rip the temp down and turn off.

My question is....given the thermostat only starts opening at 90deg, are these lower temps likely to be fighting the thermostat reaching full flow and therefore max ram air/natural cooling?
Ram air is a premium resource in my cab-over setup!

vanman

[immortality]

Not really. Stock thermostat should be a 195°F/90.5°C it will open and be flowing before then as it's designed to regulate the temp to 90.5°C. Basically a thermostat acts like a restriction in the cooling system to regulate the temperature and the reason why "high flow" thermostats are a marketing gimmick unless you have issues with overheating because you make much more power than stock.

[vlad01]

The switch off point should be about 4-5c above the thermostat temp. At least for 12P, the hysteresis is a hard coded 5c. Stock is 99c iirc, so on at 99, off at 94 or there abouts.

A common mistake I see if people install a 82c stat but do nothing in the tune or aren't able to/unaware of it. The the temps in slow speeds or traffic still remain the same 99~ peak and then only can drop to 94c when the fan kicks in.

Only on the high way with ample air flow does the engine drop down to 82. I adjusted mine to 90 or so, so the fan goes off 85c.

I found having a lower temp really helps with burst knock when moving slow behind grandpa traffic which heat soaked the engine and manifold, and the knock is eliminated or greatly reduced once you get an opportunity to overtake and blast past the lane hogs lol.

However, there are several temp dependent items in the tune that turn off or decay, or enable right around this 80-90c mark so you need to scale those down to suit.

An 82 stat counter intuitively helped my temps stay rock solid all year round. I found in winter the 91 stat just stayed closed and seemed to extend warmup time by at least 15min. Not sure why but my guess is having way less coolant flowing through the rad meant it was a res of stone cold coolant that took away the heat the engine was building up before the stat started finally opening, I could be way off on that but the 82c one starts to more evenly heat the cooling system sooner when it's ice cold, so I speculate there is less of a temp gradient from rad to block ?

I never had an issue with 91 stat being too hot, but rather couldn't warm up in winter. Having the 82 is where the engine and cooling system like it with my climate.

[immortality]

He's not on 11/12p as he mentions The1's enhanced tunes.

There are quite a few settings that need changing on the ecotec stuff too when going to a cooler 82° thermostat.

[antus]

What is efficiency like with the cooler temps? I thought the factory temps where to get everything up to an efficient operating temp, and those running 80 degree 'stats were running inefficiently and wasting fuel with an engine too cold? Not sure where I got that idea from, could be completely wrong. I know Vlad would know and I know he wouldn't take efficiency off the table.

[vlad01]

I didn't register any difference in warmer weather, slightly better in winter though. I speculate less parasitic losses since a colder stat allows some flow and load to be taken off the pump, where the higher one basically barely ever opened in winter. This might not be a thing in warmer climate, but where I live it's normally 2-7c throughout winter.

An engine will make more power, especially at the low end the colder the coolant, as long as the oil is hot (that's a factor of rpm more than anything). But too cold then there is poorer vaporization of the fuel and greater quench layer. At least for Buick, the sweet spot is 82.

Emissions is the main driving factor behind manufactures decisions as they must comply with ever tightening emissions laws. Economy is further down on the priority. Higher temps reduce HC and CO, but does increase NOx.

[immortality]

I thought I'd lost efficiency on the L67 with the cooler thermostat but since found a closed loop setting was wrong and then recently also a cracked exhaust manifold which was putting fuel trims out quite a bit on the passenger side bank however the variation wasn't consistent.

Not had it back on the road since but we just fitted pacemaker headers and will put in some extra O2 bungs so I can run WB sensors in both banks if need be.