My race car has an S52 out of an M3. It has no heater box, no external plumbing except for the radiator and after one hot lap I cannot imagine a scenario where it would be closing to maintain 160F.
I can, however, imagine a scenario where it fails to open and causes me a DNF.
My gut says leave it out.
Cold engines don't run efficiently...between poor combustion efficiency, thick oil causing excessive oil pump power draw, and sometimes poor driveability due to open-loop operation of the ECM. I like my engines warmed up before I start to hammer on them. There are a lot of reasons to have a thermostat and very few to leave it out. If you're concerned about reliability, get a new OEM-sold unit and replace the t-stat. If you want to be extra conservative, drill a few holes in it to allow more bypass flow and prevent short-term catastrophic failure if it gets stuck mid-race.
Bryce
If you are going to leave it out, at least install a restrictor. I like to install a disc with a hole about the size of a quarter where the tstat goes. If the coolant moves too fast, it won't be in the engine long enough to absorb enough heat. You need at least a 20 degree difference between coolant temps going in and out of the radiator. This can't happen if the flow is too fast. I also like to grind off half of the water pump impellers as well to cut down on cavitation. Little pockets of hot air in a cooling system can be killers.
i read about a guy in a jeep cherokee, in arizona or texas i believe that constantly had overheating problems and he put a ball valve inline to the radiator inlet to restrict flow depending on conditions. he said it worked fantastic. another guy turned a chunk of delrin down with a fixed oriface (i forget the diameter, looked around 5/8-3/4" or so) and put that inline with the upper hose with good results.
tr8todd wrote: If you are going to leave it out, at least install a restrictor. ... .You need at least a 20 degree difference between coolant temps going in and out of the radiator. This can't happen if the flow is too fast.
See, this is why I post this stuff here. That is a tidbit I was not thinking of. I assumed I'd be helping by getting rid of the restriction but it makes sense that if it flies thru the head less transfer would occur and then the water flies thru rad too quickly to drop off the heat enroute. You end up just swishing hot water around in circles.
I think, I'll use a factory t-stat with the flapper removed. That should provide the same restriction as the original engineers planned. I have no trouble getting it warm before heading out because there is no mech fan & the elec only runs when I turn it on or above 230F.
You end up just swishing hot water around in circles.
ed-zachary.
im 18 and have virtually no racing experience, so that being said, it seems like there should be such a thing as an aftermarket thermostat thats extra reliable; or an electroncally controlled one that doesnt rely on thermal expansion of rubber/wax/whateveringodsnamethatstuffis. am i completely off base?
Giant Purple Snorklewacker wrote: I think, I'll use a factory t-stat with the flapper removed. That should provide the same restriction as the original engineers planned. I have no trouble getting it warm before heading out because there is no mech fan & the elec only runs when I turn it on or above 230F.
So what keeps it at normal operating temp once you're out on the track? I'm not sure what type of racing you're doing, but keep in mind that with a lap or two of yellow flag driving on a cool day will drop the engine temp very quickly. Have you had a really big problem with stuck thermostats? It seems like the failure rate of a new, high quality unit is pretty low, in my opinion.
Bryce
Nashco wrote: So what keeps it at normal operating temp once you're out on the track?
WOT. I've never seen it below 200F on track and if a prolonged reason to slow down presents itself... I can turn the fan on/off but... running cold or in open loop, etc are not real concerns for me. Its not a street legal car and it is only driven at less than 4000 rpms in pit lane. If it open loops the ECM in the pits I don't care.
Nashco wrote: Have you had a really big problem with stuck thermostats? It seems like the failure rate of a new, high quality unit is pretty low, in my opinion.
No, not really. I have had one stick closed on me but thats a single example in over 20yrs of driving. I have a very minimalist attitude I guess. If its not necessary I'd rather not have it. The engine is out right now and I spent last evening removing every flange, bolt, hose, pulley and so on that didn't have a purpose. Things that aren't there can't surprise you with new ways to fail or open a 3" gash in your arm when you stick your hand under the intake.
In the case of the t-stat I just couldn't think of a reason I needed to spend $30 to buy one. So... I'm going to rip the baffle out of the old one and put the "restriction" back in the hole. It made for a good discussion so I'm atleast doing it with my own informed consent.
Giant Purple Snorklewacker wrote:tr8todd wrote: If you are going to leave it out, at least install a restrictor. ... .You need at least a 20 degree difference between coolant temps going in and out of the radiator. This can't happen if the flow is too fast.See, this is why I post this stuff here. That is a tidbit I was not thinking of. I assumed I'd be helping by getting rid of the restriction but it makes sense that if it flies thru the head less transfer would occur and then the water flies thru rad too quickly to drop off the heat enroute. You end up just swishing hot water around in circles. I think, I'll use a factory t-stat with the flapper removed. That should provide the same restriction as the original engineers planned. I have no trouble getting it warm before heading out because there is no mech fan & the elec only runs when I turn it on or above 230F.
Though it's false science.
First, heat flow is related to temperature difference. The greater the difference, the greater the heat flow. It does not turn off when the difference is 20 degres or less.
Second, the time fast moving water spends in the radiator is offset by the time spent in the engine. Yes, each gram of water carries less heat in a fast moving coolant. There are more grams of water going by, so it's more than offset.
Third, the real problem with excessive speed is cavitation. And it's not always in the water pump. Some engine passages are such that fast moving water cavitates away from the backside of curves, letting the metal get real hot. Not good. Slowing down the water in these cases helps the heat get into the water instead of just staying in the metal. These are the engines that a restrictor plate actually works on. It's not all engines, just some engines.
grimmelshanks wrote: im 18 and have virtually no racing experience, so that being said, it seems like there should be such a thing as an aftermarket thermostat thats extra reliable; or an electroncally controlled one that doesnt rely on thermal expansion of rubber/wax/whateveringodsnamethatstuffis. am i completely off base?
Well...the factory thermostats are designed to outlive a warranty. So it would stand to reason that they would be about as reliable as you can get.
Goo (rubber/wax)? There's not any goo in there to my knowledge. They're a bi-metallic thermostat, I think. Maybe I'm out off base here though as I haven't disected one lately.
But anyway, you can't get much simpler than basic physical principles controlling the thermostat (like in an OE mechanical unit). I mean...those are laws that we cannot break (notice, phycics doesn't have a political lobby).
In general, I don't think you'll get much more reliable than a factory OEM mechanical thermostat. Replace them on a factory service interval and you're set.
That's my opinion...
Clem
foxtrapper wrote: Though it's false science. First, heat flow is related to temperature difference. The greater the difference, the greater the heat flow. It does not turn off when the difference is 20 degres or less.
Yeah, I get that. Its a tradeoff that is possibly a non-issue but since the open t-stat was enough, then I shouldn't hurt anything by leaving the restriction - even if removing it wouldn't hurt anything either. My guess is it wouldn't - because the radiator is an extra core, gallon, and many square inches larger than the stock one so if anything it will travel further thru the radiator (and even traveling faster it will spend more percentage of distance there).
foxtrapper wrote: Third, the real problem with excessive speed is cavitation. And it's not always in the water pump. Some engine passages are such that fast moving water cavitates away from the backside of curves, letting the metal get real hot. Not good. Slowing down the water in these cases helps the heat get into the water instead of just staying in the metal. These are the engines that a restrictor plate actually works on. It's not all engines, just some engines.
The head is not known for hot-spotting but the pump on these is a source of cavitation issues - I could oversize the pulley to slow it down but I've not really had issues to warrant it provided it was carefully bled. I'm pretty sure putting a new t-stat, gutting the old one and/or going with none would have no discernable effect but I'll take the logical approach and assume if it was fine with the restriction and with the t-stat open then a gutted one is functionally equivalent, will never fail and is free. A Winner.
I am going to go hotlink some stuff, safe in the knowledge that I've got a plan and I learned something new.
lol, i wasnt making any reference to goo, i was talking about the little rubber deely that expands causing the valve to open. other people were expressing concern over these failing to open or failing to close, and my question was if a system exists where a sensor reads temp and operates a solenoid alowing water to go to the radiator.
I chased overheating issues with my Saab oval track car for atleast 3 or 4 weeks. I put a stock thermostat in and most of the issues went away. That and gettin the electric fans to stay running.
I'd keep the thermostat in it. Maybe buy one of those fail-safe ones that stick open instead of closed.
grimmelshanks wrote: lol, i wasnt making any reference to goo, i was talking about the little rubber deely that expands causing the valve to open. other people were expressing concern over these failing to open or failing to close, and my question was if a system exists where a sensor reads temp and operates a solenoid alowing water to go to the radiator.
Every BMW since the E46 has a variable electric thermostat.
grimmelshanks wrote: lol, i wasnt making any reference to goo, i was talking about the little rubber deely that expands causing the valve to open. other people were expressing concern over these failing to open or failing to close, and my question was if a system exists where a sensor reads temp and operates a solenoid alowing water to go to the radiator.
I still prefer good old metal expansion rates to electronic gizmo-ry for reliability 
so the electronic ones are more finicky huh? now i know! C:
grimmelshanks wrote: im 18 and have virtually no racing experience, so that being said, it seems like there should be such a thing as an aftermarket thermostat thats extra reliable; or an electroncally controlled one that doesnt rely on thermal expansion of rubber/wax/whateveringodsnamethatstuffis. am i completely off base?
Check out failsafe thermostats. They fail in the open position and save the engine.
neat
tr8todd wrote: . If the coolant moves too fast, it won't be in the engine long enough to absorb enough heat. You need at least a 20 degree difference between coolant temps going in and out of the radiator. This can't happen if the flow is too fast.
No! Negatory! Not true! False! Negative! No!
The problem is not that "the coolant moves too fast" if there is no thermostat.
Ideally, the coolant would move as fast as possible to minimize the temperature difference between the radiator inlet and the radiator outlet. That way the radiator has the highest temperature differential between the coolant and the airflow, from top to bottom.
Thought exercise: If the coolant moved slowly enough that the coolant got down to ambient temperature by the time it got to the bottom, are the bottom fins actually doing anything to reject heat?
So why then do many engines overheat if they have no thermostat? Hint: some water pumps create up to 50psi of water pressure in the block, over and above what the radiator cap adds! That pressure is necessary to prevent localized film boiling at the hottest points in the engine, usually near the spark plugs and exhaust ports. If there's localized film boiling, the layer of steam acts as a great insulator and prevents heat from being transferred to the coolant. The water temp gauged shows that everything is hunky-dory but the engine is overheating. You don't get to find out until the overheating is bad enough that the heat spreads by conduction to the rest of the block, or you shut the engine off and it starts boiling over.
Remember there is no such thing as moving the coolant too fast!
There's a lot of text; did anyone mention oil possibly not getting to temp reliably and the issues with condensation & contamination from running "cold" oil through an engine?
pres589 wrote: There's a lot of text; did anyone mention oil possibly not getting to temp reliably and the issues with condensation & contamination from running "cold" oil through an engine?
Nope. Its a race car. Its going to idle until the water temp is 160 and the oil temp starts to move. Then its going to do a warm up lap under 5k and then its ballz out for the rest of the day. The oil will be up to temp by lap 2. Usually around 250F (which is a little high but... oil changes are frequent and oil cooler fitment is a difficult problem on my car right now).
I dunno if you can find a racing specific one. I know for the honda crowd I believe mugen makes a thermostat that breaks in the open position.
Andrew
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