Crazy idea....electric thermostat, will this work?

[Jonny Hotnuts]

Firstly, does running the engine at colder temps affect HP? (bad, good or other)

Secondly....I am not running a thermostat and using electric water pumps to a coolant tank. These pumps flow a poop load through the block. I am wondering what would happen if I were to use a a temp. electric fan relay:

http://www.jegs.com/i/Altronics/030/ST/10002/-1?parentProductId=1127496

with the sensor in the water jacket sensor port of the block and use the relay to turn on and off the water pumps.
At least in my mind the pumps would only run when the temp came up and would shut off when the cool water entered the block basically making an electric thermostat set to whatever the temp is on the sensor.

I have noticed that even after a run my coolant temp is still relatively low.

Any thoughts/comments?

[manta22]

JH;

The coolant in your block should be around 190F. Your idea should work; just make sure you use a relay with high enough amperage to turn your pump on.

Neil   Tucson, AZ

[Dean Los Angeles]

Heat makes the whole horsepower thing happen. Ideally you would not run any cooling and insulate the engine so that there would be no heat loss.

Sadly, we haven't figured out how to keep things from melting. So we have to remove heat, and water is the best method to do that.

If your coolant temps are low then so's the HP. Turning the pumps on and off is going to cause heat cycling. Consistent flow would be preferable.

[hotrod]

Firstly, does running the engine at colder temps affect HP? (bad, good or other)

Depends on which part of the engine is hot or cold.

High temperatures increase the thermal efficiency of the engine, better fuel vaporization, less loss of combustion heat to the cooling system cylinder walls.
High temperatures increase likelihood of detonation, and reduce the volumetric efficiency of the engine (lower density intake air charge).
High temperatures in the intake increase the speed of sound in the intake air, which slightly delays onset of choke flow in the intake ports, since that is tied directly to the speed of sound in the intake mixture.

High temperatures lower viscosity of the engine oil reducing pumping losses in the oil system, but it also increases friction due to thermal expansion of parts (piston side clearance drops as the piston gets hotter).

In short it depends on which effect you want to maximize and if the engine can tolerate the change. A rule of thumb developed by NACA during research on high performance aircraft engines is that power increases at the square root of the change in intake air absolute temperature. Cooler intake air charges producing more power than hot intake air charges, but you are in a running battle with friction losses and pumping losses of both intake air and oil windage, so to a point high temperatures reduce those losses. Cold engines are much harder to crank than hot engines due to thick oil and as the oil heats up power losses go down until you reach an ideal temperature then begin to go back up.

Ideal oil temps seem to be around 210 Deg F, and ideal coolant temps are typically near 180-200 degrees but each engine has its own sweet spot for both values.

I would not want to completely stop pumping coolant to avoid development of hot spots in the head and local boiling of the coolant.

Your idea has merit if you set it up with double water pumps and if the engine gets too cool one of the pumps shuts off to keep from over cooling it. If I were you I would run some sort of thermostat, perhaps only a 160 deg F but it will help even out the temperature. It also helps the water pumps develop hydrostatic pressure in the cooling system to help suppress boiling, since the pumps are moving the water through a resistance rather than wide open with no back pressure. Too low of a pressure at the pump can also lead to cavitation.

Years ago I found my 392 Chrysler Hemi gave me best times at the drags if I idled it just long enough that it was difficult to hold my hand against the front of the cylinder head prior to staging. This gave a water temp at staging of about 140-150 degrees. By the time I was staged the water temp was around 170 and I would trap at 180-190 deg F. That worked for me and that particular engine. You need to find what temps your engine wants to run at with the oil you use and your running clearances.

(something to test on a dyno)

Larry

[Jonny Hotnuts]

.....ok, let me throw another wrench in these gears.

It also helps the water pumps develop hydrostatic pressure in the cooling system to help suppress boiling,

I have done a fair amount of research about this....and consulted the engineers at Meziere pumps: http://www.meziere.com/

Basically from what I understand a closed system, once up to temp the hot water generates its own pressure regardless of head pressure in a system with restriction and lowers the boiling point.

I know after a run my system is under pressure and can push water past the 14 psi cap to the res..

[kiwi belly tank]

Johnny,
   I have a street legal belly tank with a 650 horse turbo'd 401 in the back & I run this type of system on it. I have the Meziere pump mounted beside the engine due to a space issue but run it via a 180 temp switch on top of the thermostat housing via a 50 amp relay. (over kill on the relay) When the thermostat opens, the pump runs. The cooling fan is run the same way via a switch at the rad outlet. The only issue I have is lack of air flow at low speed. The rad is buried behind the passenger seat & gets it's air from under the nose that is ducted under the floor. After 40mph & beyond 150 it's just fine in the summer heat.
I'm doing the same type of system in my liner with the rad in a water tank.
The system in the tank seemed to work better with a thermostat than without.
& no, I haven't had a ticket yet.
  Sid

[SPARKY]

be aware that it will continue to run afterwards if you don't put a switch on it.  We went back to making the water pump part of closing the canopy drill---not done by the

("MONKEY" That is the term DD uses for the drivers because acording to him that is about how reliable they are lol on performing tasks or giving reliable feed back)

whos is riding in the seat

[kiwi belly tank]

 PS.  I have the tank system wired through the ignition switch accessory circuit so I can turn it off or go to accessory & let it cycle down.
  Sid.

[Rex Schimmer]

JHN,
I think that you are looking to kill your engine by going with what you are proposing. Your motor is turbocharged which means the area around the exhaust valves is very critical for cooling and you need to have lots of water at a high rate of flow and high pressure moving in the coolant areas around the exhaust valves or you are looking at trouble. You need to have both high system pressure, i.e. a 30 psi coolant cap (or higher) plus any additional pump provided pressure to keep the water around the exhaust valves from boiling. If you actually stop the water from flowing and are sensing the water temp from the standard water jacket temp connection, by the time that gets to a temp that your system decides to turn the water pump back on the coolant by the exhaust valves will have already boiled away the water and started to melt. It happens in milliseconds!. I would suggest using the BMW 320 I, 3 port thermostat with a 180 deg. temp setting and keeping your pump running continually. The 3 port thermostat maintains circulation of the water through the engine at all times and when you reach the set temp it then will modulate the cooling water from your tank through the engine to maintain the 180 temp. Turning the pump off and on is not a good idea in my opinion.

Rex

[donpearsall]

I agree with Rex. It seems to me that you do need a constant flow of water through the jacket. With a hot engine at boost, It will not take long for the engine jacket water to get too  hot. When the pump relay finally responds to the fast temp spike, and considering the delay to get the pump starting flowing water, it may be way too late.

But I like you thinking out of the box for things like this.
Don

[johnneilson]

I did some work like this on a dyno for testing, electric thermostats and thermocouples tied into PLC controllers etc.

The best, most relaible system was turning on the pump(s) and using theromstats in the return lines to the coolant tank and or radiator.

You need to have water flow past the thermos when closed, 1/8" to 1/4" dia bypass. And have the thermos as close to the head as possible, if not in the head.

One detail about having the pump run continously was that it keeps the pressure on the water jacket and the water moving.

J

[SPARKY]

In '01 steam bubbles killed a set of Brodix heads in '01 without a pressure system--  nosed over on the backup---no hat 2.5 mph short

[manta22]

You are describing a simple "band-bang" control system-- heat source (cylinder), coolant, sensor (thermostat), and pump. The coolant flow is either on or off-- just like the thermostat that controls your furnace or air conditioner. These types of control systems are very simple but not very accurate. The biggest problem with getting them to control accurately and respond fast is the long transport delay between a temperature rise and the time it takes for the sensor to know that it happened and therefore take corrective action.
With the pump shup off, it is going to take a long time before your thermostat senses that it needs to open (or turn on the pump) to cool things down-- this will cause wild fluctuations in the temperature.
A better system is going to a proportional control system-- sense the temperature with a thermistor and use that signal to control the speed of the pump. This will give far better temperature control and response time ("transient response").
A simple system where you don't shut off the pump entirely but let it still circulate some coolant even when your thermostat is off will reduce the transport delay and improve the simple on-off "bang-bang" control system.

Regards, Neil  Tucson, AZ

[gas pumper]

I think what Rex mentioned about a multiple thermost bypass system will be the most reliable. You do want water circulation going on before you reach operating temps of the overheat thermostats.

GM Diesel, years ago on the inline engines had a system where a normally open thermostat passed water from the thermostsat housing out a water line to the inlet of the water pump to allow for circulation of water during engine warm up and when the engine was not up to operating temps (During winter this was very important as they were very cool running when the intake air is cold).

As the temp of the water went up the regular thermostat would start to open as the bypass would start to close. So there was always flow thru the pump and engine. Circulating water all the time to even out the internal water temps.

This system worked really well and was carried over to the V engines by using a thermostat that had a skirt that moved up and down in a bore with a seal ring that diverted the water to the bypass or the radiator hose variably by the position of the skirt. Providing full flow all the time thru the block and heads.

Frank

[robfrey]

I agree with Rex whole heartedly!
I would keep the speed of the water through the block and heads a fast a possible then only divert it to the rad or coolant tank whenever it reaches operating temp. This keeps the the block and heads a uniform temp which is good especially when you start "getting after it".
Again, I like your out of the box thinking though. Keep it up!