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#1
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Engine Temps
Anyone know the normal stock idle engine temp? Mine runs at about 87 C. I was thinking of replacing the thermostat with one that opens at 60 C instead of 70 C.
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Chuck D. 1992 Subaru SVX LS-L - Heavily modded turbo 2002 Subaru Impreza WRX- Turboxs stg3 & Susp. Mods |
#2
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( 87 C), 188.6 F sounds about right. I tried purchasing a lower thermostat at advance and autozone, but the lowest either had was 170, (stock).
Where did you find a stat that opens at 70 (158 F) and who is the manufacturer. I'd like something like this for winter months. I've removed mine completely for the summer. |
#3
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In reality, an automotive powerplant dumps so much energy into the cooling system that opening the thermostat earlier, or even dispensing with the thermostat entirely, is largely irrelevant. If the cooling system cannot keep up with the engine's rate of waste heat generation then the problem almost certainly lies within the radiator itself, or perhaps, the water pump's ability to transfer sufficient quantities of water from the engine to the radiator. If the radiator cannot keep up with the engine's "wasted" power output then fiddling with the thermostat might, at most, buy you another mile or so up the road until the radiator 'boils over" but it aint a permanent solution. |
#4
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Chuck D. 1992 Subaru SVX LS-L - Heavily modded turbo 2002 Subaru Impreza WRX- Turboxs stg3 & Susp. Mods |
#5
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Quite why anybody would want to do this intentionally is beyond me. The whole purpose of the thermostat is to ensure that the coolant temperature is raised to the minimum temperature at which the engine starts to operate somewhere near its optimum efficiency. The standard cooling system was designed to let the car run flat out in the hottest air temperatures imagineable. Under these conditions the water temperature may well be raised to over 100 C, which is why the system has a pressure cap! Under less stressful conditions, and certainly at idle, the cooling system should be more than adequate. If you do have cooling issues (and I'm not convinced that you do), then the first, and easiest, place to look might be the airflow through the radiator. Is it bunged up with dead flies, leaves, feathers etc.? If that's O.K, then are the fans and their shrouds undamaged? If all of that seems O.K. then perhaps the radiator itself is silted/furred up internally, or perhaps the water pump is on its last legs. |
#6
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Cooling systems
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I also would tend to agree with you that on a stock engine, the stock cooling system should be work fine to cool the engine, provided all of the parts are working. However, my engine is not stock, and I am expecting a bit more heat from my boosted cylinders. Eventually I would like to run an aftermarket aluminum radiator. I also have installed an external ATF air/oil cooler. This should reduce the heat applied to the radiator as well. If you have not already, read the vendor claims from the link and tell me what you think. I would be interested to hear what you think.
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Chuck D. 1992 Subaru SVX LS-L - Heavily modded turbo 2002 Subaru Impreza WRX- Turboxs stg3 & Susp. Mods |
#7
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I could never be as dogmatic about it all as they are, but then I have no axe to grind. But, as a general principle, reducing the thermostat temperature is just plain wrong!!!!! It's attacking the problem from the wrong end, and is an ineffective solution too! Let's assume that your turbo equipped car is dumping more waste heat into the cooling system. That is going to be undeniably true if you've got a lead foot. What the cooling system has to do is remove that waste heat from the coolant at a rate that is fast enough to prevent localised boiling of the coolant in the water passages in the cylinder head, which is a bad thing to happen. If the water does boil inside these water passages then the cooling system goes into catastrophic failure, things start to expand and warp, perhaps even seize up entirely. So what would an engineer do? Well several things, perhaps the most obvious thing is to size the radiator and/or water pump so that the heat generated from the engine can be effectively dispersed into the atmosphere. I don't know how much safety margin Subaru engineers designed into the SVX's cooling system, or how much extra heat your turbo set-up generates. Unfortunately the standard temperature gauge is not measuring the water temperature at any one of the six danger points in the cylinder head next to the combustion chambers, but merely at a point that is convenient to get access to, so this is not going to be much of a guide, merely a 'rule of thumb' kind of thing - you are on your own here Secondly, put additives in the coolant. You do, at least, have antifreeze in the coolant don't you? Even if there is no risk of frost, a good brand of antifreeze contains anti-corrosive agents and raises the boiling point of the coolant too. Some people swear by 'water wetting' agents too, they can do no harm. Thirdly, a higher rated pressure cap will raise the boiling point of the coolant by a few degrees. Lastly, try to improve the airflow through the radiator. The thermostat barely enters the equation at all, once the thermostat is open, it's open, it cannot magically supply more cooling than the system is designed to provide. Beware! Maths and physics beyond this point. The miniscule safety margin that a lower operating temperature can provide is derived from about 9 litres of water running 17 C lower in temperature, (and the associated thermal mass of the radiator too which I'll guess to be approximately the same) will mean that it takes 2x9x17 = 306 Calories of energy to heat up that thermal mass which equates to 4180x306 = 1,279,080 joules of energy. With me so far? O.K. Let's further assume that your turboed engine is putting out 200 kilowatts of power (nice job!) it would not be too unreasonable to assume that at least 50 kW is being dumped into the coolant - probably much more. Working the maths 1,279,080 / 50,000 = 25.6 seconds. So, at the penalty of running the car inefficiently most of the time you have bought less than thirty seconds of engine protection. It doesn't seem a particularly good deal to me. |
#8
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Thanks for the info cdigerlando. I'll check into the WRX stats. Use of practical experience along side technical knowledge will go a long way.
Measure engine temps in the middle of the summer on your SVX, stop and go traffic, 92+ F ambient temp and you'll quickly see that a perfectly functioning factory cooling system will keep your car around 200+ F. That's great if you're concerned with keeping your emissions down and gas mileage up. If you're more concerned with keeping your engine at optimal temp for performance and longevity, ~180F, then use whatever means you can, within reason, to solve your particular dilemma. Over cooling is bad, but persistent and subtle over heating is just as bad. Last edited by svxcuseme; 08-22-2006 at 10:11 AM. |
#9
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Thanks
I agree with everything you are saying. The only benifit I think that is gained is that if I run slightly lower temps, a sudden spike would be better absorbed due to the lower temp. Thus response would be improved and keep temps from spiking so high. Also these thermostats lock open in the event of an overheating event. They don't fail closed (that is the claim anyway). I found one for $40 on a group buy at nasoic. I'll probably give it a try.
I believe that my original overheating problem was caused by some sort of air lock. I'm hoping that cycling the heat cycles with the radiator off will help remedy that situation. Currenty my car idles in Florida (95F ambient) at about 87C. Does this sound reasonable? Also in the future I will probably be getting an aluminum aftermarket higher efficiency radiator. Anyone logged any engine temps using the new radiator?
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Chuck D. 1992 Subaru SVX LS-L - Heavily modded turbo 2002 Subaru Impreza WRX- Turboxs stg3 & Susp. Mods |
#10
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Matt Locker Link 2015 BRZ Limited 6MT 92 Ebony LS-L ECUtune Stage2av1, Z32 MAF, 370cc injectors, TomsSVX intake, BontragerWorks 22mm RSB #003, HID Hi and Lo beams, OT endlink and bushing mods, PWR Aluminum radiator, Harvey's QC shift kit, 2.5" flowmaster 80 exhaust, 17" Michelin Pilot Sport A/S, Poly sway bar bushings, Slotted Bradi rotors, AFBeefcake powdercoated calipers, 97 grill, and a huge set of air horns. 300,000 miles and counting 92 Ebony LS-L. ecutune stage1v4, motorsport 1pc pulley. Garage Queen - sold to Dad in upstate NY 155,000 miles 19 Subaru Ascent Premium - -Hers !. 89 DL 4x4 little red wagon - a.k.a. The immortal suby. 275k R.I.P. |
#11
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Another case of trying to be smarter than the engineers?
Leaving the 'stat at OE level and increasing the system's reserve ability is the answer. A $12 'stat seems like a cheap alternative to spending several hundred dollars to do it the correct way. But we all know you can't whip that dead horse hard enough to make it trot.
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ASE Certified Master Automotive Technician w/L1. ASE Certified Master Medium/Heavy Truck Technician. Certified EVT (Emergency Vehicle Technician) |
#12
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Reference to not failing closed, would probably indicate a closed position whereby it would form only a restriction leaving a bypass flow. This is quite a normal arrangement.
The thermostat regulates, fixes, establishes, maintains, a specified operating and minimum temperature, as is its normal and exact function. It can have no effect on temperatures above normal, unless it is faulty and does not open at the preset figure. Unless it is not to specification and does not afford the correct rate of flow. Only spikes shorter than the thermostat reaction time could occur and the time delay in opening is not excessive.
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Trevor, New Zealand. As a child, on cold mornings I gladly stood in cowpats to warm my bare feet, but I detest bull$hit! |
#13
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For less money than that thermostat costs at the site that you indicated, you can buy a higher pressure radiator cap, which should make a real difference in delaying boiling problems, and it will enable the radiator to radiate more energy too, because the coolant can get hotter before boiling - that's basic Newton's law of cooling. But higher temps and pressures mean you'd better have good hoses. But the real solution still lies in having a radiator and waterpump that can dump heat as fast, or faster, than the powerplant generates it. |
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