Help me understand lower temp thermostats

[markmurfie]

What exactly is the major downside of a lower temperature thermostat and lots of street driving? I'm not clear on that.
I've had the 170* one in my car for nearly the entire time I've had it, 60k + miles, most of that was NA. It was seriously easy to change out 30-45 minutes. not once have I seen any thing which made me think about going back to the higher temperature one. If you say warm up time on cold winter mornings, you are BSing me and every one else with subjective perception of the passing of time. If you say carbon build up, that's not true as well, at least not because of the thermostat temperature.

Change your thermostat to a lower one. Run your coolant water mix as water biased as possible as the season allows.

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[EFI]

What exactly is the major downside of a lower temperature thermostat and lots of street driving? I'm not clear on that.

Mainly increased engine wear, but at how much is highly subjective.

These engines were designed with an operating temperature of ~212*, and that includes both the hard parts and fluids. When you run the engine at a temperature vastly different than that then you stand to encounter more wear (especially when it's on the colder side) as component clearances are tighter running at 170*.

As stated before, exactly how much extra wear is added is hard to say, but it's there. There's a reason why you want to get the car up to temperature as quick as possible and why it's recommended before driving hard.

 

[Avispa]

The major downside is that these engines use a lot of hydraulic control and have tight tolerances. Ford designed them for a specific range of oil viscosities, and those are based on expected operating temperatures. Maybe 195 degrees was chosen for other purposes, like emissions requirements, but everything that's viscosity dependent will be based on that. I'm not in a position to second guess the factory engineers.

 

[markmurfie]

You countered your own argument. More wear is done during warm up then the entire time operating 20* cooler.

Engine oil hmm, some cars have oil coolers, others don't. Is there no difference in warranty or maintenance interval between them?

 

[sigintel]

What you said makes perfect sense to me...regularly hitting 215+ also seems like very sound advice.

I guess what I don’t understand is why people say that they have lower engine operating temps after installing a lower temp thermostat..when at normal operating temps, I would assume both the stock and lower temp stat would both be fully open.

Does the increased flow really account for that much change?

I think I can see how sitting at idle with the tune altered for increased fan activity would yield lower temps but outside of that, it seems like little difference should be noticeable.

I’m in AZ, so with ambient temps consistently reaching over 115, I feel like I’m most likely maxing out the thermal capacity of the cooling system itself, not the thermostat.

Let me know if any of my thinking is wrong.

Thanks again!

Thermostat might not always be fully open or always fully closed.
Some of us paranoid idiots actually still test with a thermometer and pan on the stove, you can measure the temp/opening curve. Much cheaper to check operation in kitchen, vs reassembly cooling system and go to track and find you have a binding/wonky cheap tstat (learned hardway once before, ugg).
Keep in mind the flow is non linear with position/opening as well.

In the end, you'll find the result is more of a flow curve, so an oversized 170 stat is cracked open at 165-180, flowing moderately at 215, pinned hard wide open at 230.
A stock sized 180 is similar but opening is shifted up 10F and max flow is slightly lower.
There is a stock sized 160, but Id call it more of a 168 and its flow maxes out and I could not use it for road course work on the Whippled 2015.

Note the Reische 170 is higher flow@all positions due to larger geometry.

I also tested a stock OEM tstat w 6 bypass holes drilled. It was mehh compared to $50 for the 170.

 

[Bmaughan]

sorry to bump this thread but i had another thought...really its more of a question:
Just to be clear, i really have no idea what I'm talking about....this is just me thinking out loud and pure speculation....

What do you guys think are the chances that some the ring land issues people have had on these cars are due to running at lower than optimal temps?

I know overly rich situations can cause detonation from within the ring land itself but outside of that issue.. I've heard/seen very tightly gapped rings from the factory, and being that the pistons are hypereutectic and have high silicon content, i wouldn't think they are capable much thermal expansion to begin with...
so it just makes me wonder if the block isn't expanding to its expected size, could the gaps be closing under high boost situations?

again, all speculation...i would love to hear your thoughts!

 

[sigintel]

sorry to bump this thread but i had another thought...really its more of a question:
Just to be clear, i really have no idea what I'm talking about....this is just me thinking out loud and pure speculation....
What do you guys think are the chances that some the ring land issues people have had on these cars are due to running at lower than optimal temps?
I know overly rich situations can cause detonation from within the ring land itself but outside of that issue.. I've heard/seen very tightly gapped rings from the factory, and being that the pistons are hypereutectic and have high silicon content, i wouldn't think they are capable much thermal expansion to begin with...
so it just makes me wonder if the block isn't expanding to its expected size, could the gaps be closing under high boost situations?
again, all speculation...i would love to hear your thoughts!

Interesting thought!
Yeay, going full pull on a cold motor 180 CHT or less should theoretically bind a ring up sooner than if the CHT is 235-245.
But even with the cooler tstats, on road courses I would still get 240CHT. With stock tstat temps would keep going higher to where some oil is 265++ and oil is smoking out the filler cap even once off track.
How much more heat/WHP you can risk by running 185 CHT vs 205 CHT at cruise is likely not much.

I would guess the peak ring temperature is driven mostly by the peak combustion gas temperature and flow rate around the ring.
The ring land failures likely occur during peak combustion temp and pressure. I assume they effectively try to expand while being overly constrained and the drag force against the cylinder wall eventually results in all out bind and the piston pops apart trying to go down with ring bound during power stroke.
Combustion gas temps around top ring might be 1400-1550F+ ?
Oil squirting on bottom of piston is like 240-270F (breaking down during peak temp)?
Piston temp is what? 260 - 700F from top to bottom?
Top ring itself bouncing between 500-1000F?
So how much more does the bore grow from CHT 185 to 205? And what amount of extra HP can you generate with that slight bore increase?

This could be analogy/speculation. But I seem to hear more people breaking ring lands going straight to 700+ on low mileage motors.
Seems to be others that start out with less HP and beat the crap out of the motor before going up in power, and they end up at 800 WHP+ on stock motor going up 50HP at a time and pushing it hard on street and track. It might sound counter intuitive, but unless you opened the motor to open the stock gaps, you might be better off starting at 650 wheel and pushing it hard for several months/2500 miles before upping it 50 more HP. You might even be able to see the metallurgy in used oil analysis?

 

[Bmaughan]

This could be analogy/speculation. But I seem to hear more people breaking ring lands going straight to 700+ on low mileage motors.
Seems to be others that start out with less HP and beat the crap out of the motor before going up in power, and they end up at 800 WHP+ on stock motor going up 50HP at a time and pushing it hard on street and track. It might sound counter intuitive, but unless you opened the motor to open the stock gaps, you might be better off starting at 650 wheel and pushing it hard for several months/2500 miles before upping it 50 more HP. You might even be able to see the metallurgy in used oil analysis?

I've been at about 530whp for around 16k miles, just recently upped it to around 750whp. I should be good if your theory has merit ;)

 

[Bmaughan]

Will cross fingers for you.
If you really want to know. Used Oil Analysis will probably show you.
Ring wear on cylinder wall should go exponential due to any binding.
It is likely a fine line between "self clearancing" and destructive ring land binding.

Yeah... so far so good! That’s why I’m a little nervous to change anything... running to motor a little warmer and running things a little looser seems like a good idea. It could be just to satisfy my ocd... but thinking for that reason I’m not going to end up installing this reische tstat. I’m on e85 so there’s little chance of detonation due to heat... I’m only at 11-12lbs of boost.

 

[Bmaughan]

If you work CHT above 235, consider running at least 5W30.
If you hit 245-250, definitely 5w50 and consider GT350/PP radiator, 170 tstat, easier airflow mods

That’s great advice! Yes I actually just switched to amsoil ss 5w-30 for a little more headroom since it’s starting to warm up here in Az. If I’m street driving with 5-30 stock t-stat should be good right? I just want to make sure I’m thinking about it right.

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