sixshooter

iTrader: (12)

Regarding the thermostat, I agree with you that too many people have no clue how these things work. It's tiresome.

Padlock

to help educate those that may not know and to help spread proper information, I'll go on record here by saying the thermostat controls the powertrain temp minimum and NOT the temp maximum.

Helpful track example:
If your coolant temp is running at 230F on track and you have a 212F thermostat that many OEM's put in. Your thermostat is fully open at that operating temperature. You are pumping as much fluid through the open thermostat and into the radiator as you can to keep things cool. Putting in a lower temp thermostat (let's say a 180F one) won't do you any good because guess what? It'll also be open at that 230F operating temperature. Nothing fundamentally changes.

In fact, you could remove the thermostat in some applications and possibly see an improvement for track use because the thermostat itself acts as a flow restriction for your water pump. Remember what I said above? More flow generally = more heat rejection. Testing a thermostat removal in your application would be required to see if that thermostat restriction makes any notable impacts. Usually impacts are pretty small in my experience (a couple degrees), and not worth the tradeoffs. Keep in mind that it will take a lot longer for your engine to get to operating temp without one.

So then Matt, why do lower temp thermostats exist?
Let me start by saying that it isn't ironic that most OEM's use 212F (boiling point of water) as a common thermostat temp. You want your powertrain to achieve AT LEAST that temperature in a regulated manner so that any condensation or moisture in your oil boils off into vapor (extending oil and engine life). You see lower thermostats used in drag racing a lot because it gives you a little time to protect a less than capable cooling system from overheating during short bursts of heat input. I'll exaggerate here, but let's just say you add 50F worth of heat into a cooling system during a 1/4 mi pass with your drag car. If you start at 212F at the light with an OEM thermostat, then you'll be at 262F by the end of the run which may be closer to the boiling point than what you want depending on your pressure cap rating. If you start at 180F with an aftermarket thermostat, then adding that same 50F of energy gets you to a 230F temp, which is still a comfortable margin to boiling the fluid, but the downside there is your engine can be operating below the boiling point of water which you really don't want from an oil lubrication system perspective.

jedd

Spec Miata racer for twenty years here and even with the biggest baddest aluminum radiators, running nose to tail bumpdrafting for laps on end will raise the engine temps and turn your car into a turd (pulling timing). To get to or stay up front you always need a partner/teammate to draft with and to be effective you each take turns leading to get airflow through the radiator to cool down. In this situation while taking your turn leading, getting below operating temp buys time for when its your turn to drop back and do the pushing with minimal airflow through the nose. I would also hop out of the draft near the end of races and really focus on getting my car cool for that last lap drafting and last turn pass for the lead. This was always my theory for running with a lower thermostat and even running without one occasionally but who knows if it actually made a difference, winning those races always came down to luck and avoiding carnage mostly.

Gee Emm

Like others above, I have long been puzzled by statements around changing the thermostat to one of a different temperature setting.

If you haven't got the cooling capacity the thermostat becomes irrelevant, end-of-story (ok, apart from warm-up), it just opens and stays open, and your coolant temp just keeps on rising.. It will set the operating temperature when you do have the cooling capacity - balancing the radiator's cooling with the engine's heat input.- so in that situation the opening temperature of the thermostat makes a difference and becomes the de facto engine operating temperature. The drafting anecdata above illustrates that well, in that situation the thermostat sets the minimum temperature achievable, and a lower temp thermostat provides a tactical advantage giving more headroom (heatroom!?) for that final push. That's probably not relevant for most of us, we just want to run our cars hard in the hottest conditions we face, and hence the various cooling threads on here, which focus on radiator size, managing airflow so it goes through (not bypasses) the radiator, and venting hot radiator air.

sonofthehill

iTrader: (1)

What?
Here are a few data points for you guys.
I drag race my car... Regularly. I recently hot lapped 10 12 second passes in a row in 98°F heat. Plenty of cooling air at 116mph, my car didn't overheat. I run a 192 or 195° thermostat don't recall, but whatever a stock NB is supposed to have, and you want your car warmed up before you make a pass. Best thing I did to my cooling system with a crappy plastic tank radiator was put a real hose between the radiator and overflow tank. Hot lap in the heat, sit in traffic for hours, no track racing though, but I learned a few things from those guys too.
Intercooling... My polluted aluminum garbage $100 A2A intercooler only picks up 40 to 55°F max on any 11 or 12 second pass I have ever made under any conditions. I am looking to upgrade one day to a quality unit which will likely stabilize IAT's around 30°F above ambient.
Just sayin'