Coolant Temperature

[Scotty]

You are likely seeing the effect of the water pump spinning a little faster and the load on the engine being a little less.

But, I have to ask, so what?? So what if it runs 196 instead of 203..?? The engine is perfectly happy either way so what is the rational for changing/redesigning/redeveloping the water pump drive and what do you expect to gain?? Lower observed operating temps have NOTHING to do with measuring or assessing cooling system capacity when the thermostat is regulating. Nothing.

Under the conditions you are describing the engine is at such low load that it is just laofing along and the same is true for the cooling system. It is not operating anywhere NEAR capacity. The temperature you are observing is controled by the thermostat plain and simple. By increasing RPM and water pump speed the flow thru the engine is increased and the stat operates closer to it's true control point.

If you put your stat in a pan of water and boil it you will probably see it open right around 195 or so. When the stat is in the engine the wax motor controlling the stat operation is in the mixed flow path of hot water being recirculated thru the engine (the bypass flow) and the "cold" water from the radiator. The stat will bias a little to the warmer side in this condition. As the pump RPM picks up the bypass flow rate changes due to the pump speed and internal hydrostatic pressure and the state starts to sense more of the bypass flow....so it opens a little sooner as it is "seeing" more of the hot water from the bypass.

The drive ratio of the water pump is set up for idle speed circulation (sufficient heater flow for warmup and windshield defrost primarily) at the one end of the spectrum. At the other end, the pump drive ratio is set up for maximum engine speed operation so that the pump cavitation characteristics at high speed are taken into account.

If you choose to change the water pump drive ratio remember that you have only looked at one small operating point. The engine/cooling system has PLENTY of capacity in the 1800/2500 RPM range you describe so it is not really considered critical to the system design or definition. Remember that when you focus on that specific area. The high speed operation is more critical as the water pump is designed to operate up to the 6500 RPM operation point without severe cavitation using the production drive ratio. If you speed up the water pump with a different pulley for more flow at 2500 you are going to be in trouble for cavitation with the pump at 6000 RPM. The pump WILL cavitate at high engine speeds if overdriven and cooling flow will drop off significantly when this happens. Make sure your vapor bypass line is clear and open so the pump can clear itself of vapor when this happens with your faster drive ratio....LOL LOL. You really do not want to do this as you will hurt the flow at higher speeds when the engine/cooling system REALLY needs it only to pick up flow at the lower speeds where it could care less due to the low demand on the system.

You guys are WAY too fixated on the coolant temperature....LOL LOL

Thanks Guru you set me staight again! You and I have this coolant temp discussion every summer! I will relax about it...lol

[up2ng]

Guru,

What about coolant temp that goes below 195 ?

I replaced my radiator & thermostat and I noticed that the temp will drop to 192-190 on occasion and has gone as low as 188. I know you are going to say don't look at it but I was just curious shouldn't it stay above 195 ? at all time after the motor is warm ?

[Scotty]

Guru,

What about coolant temp that goes below 195 ?

I replaced my radiator & thermostat and I noticed that the temp will drop to 192-190 on occasion and has gone as low as 188. I know you are going to say don't look at it but I was just curious shouldn't it stay above 195 ? at all time after the motor is warm ?

WOW, I would love to have my engine run that cool..... Are you sure that a 190 degree stat was not used by accident? The 195 degree stat should cause a system to have at least a 195 degree baseline temp, IMHO, I am not sure how it could be cooler than 195 degrees unless its stuck wide open, and then it would be unable to regulate the temp upward by closing itself to maintain 195... I am curious what others have to say about this.

How was your heat in the winter or did you do this work since the cold weather?

[Scotty]

How about this Guru, a variable speed electric motor, controlled by the CPU to run optimally so that at 1000 RPM in traffic it is commanded to run fast, and at highway speeds, it runs slower but at the most efficient speed to produce the best flow without cavitating. As this design were to develop you could design cavitation detectors and run it up just short of cavitation at all RPMS. WHat do you think? This would eliminate the parasitic drain of the pump on the engine (which with the pulley system may not be much) and lessen noise. Is this too much draw for the electrical system? How much HP does it take to turn the water pump? Today's motors can have a lot of torque. If we are worried about the motor crapping out, how about the belt? Why wouldnt this be considered? Electronics is to a point of this being very easy to do and porting this to the NS via an algorithm or sensors should be cake walk.

I think we had this discussion once on the old board and if I recall we concluded that there was nothing to be gained. However what I think can be gained is very efficient coolant flow at all RPMs... What do you think

[JimD]

Guru,

What about coolant temp that goes below 195 ?

I replaced my radiator & thermostat and I noticed that the temp will drop to 192-190 on occasion and has gone as low as 188. I know you are going to say don't look at it but I was just curious shouldn't it stay above 195 ? at all time after the motor is warm ?

Causes me to ask: what variable controls the logic switch from open-loop to closed-loop fuel trim, if not coolant temp.?

If it is coolant temp., you would want to see a coolant temp. at least as high as the thermostat specification. No?

[up2ng]

Causes me to ask: what variable controls the logic switch from open-loop to closed-loop fuel trim, if not coolant temp.?

If it is coolant temp., you would want to see a coolant temp. at least as high as the thermostat specification. No?

That is the whole reson I ask ! I can't complain about gas mileage (400 miles on 17.6 gals with mixed driving)

The stat is a delco 195, 60/40 dex-cool. if i leave the car idleing the temp will fluctuate between 203-228/230 with the A/C on it wont make it past 220.

Scotty, my heat is kick *smurf* and the car over the winter warms up within 2-4 minutes the heat starts @ about 1 1/2 mins. It was pretty cold here in NY as you know.

[Scotty]

When did you replace the radiator and stat?

[Ranger]

Scotty,

If heat is a concern for you, why not just hard wire the fans on all the time or wire in a toggle switch to turn them on selectively when you want them and the are not already on. Wouldn't that be easier and just as effective?

[up2ng]

When did you replace the radiator and stat?

1st week of January, the old one had cracks in the endcaps

[JimD]

I will plead to going way off topic.

But, since the advent of digital control of many functions, I have asked myself why auto makers (and Cadillac specifically) have so far failed to disable any cooling fan operation at vehicle speeds greater than ~~ 45 MPH.

[Scotty]

I will plead to going way off topic.

But, since the advent of digital control of many functions, I have asked myself why auto makers (and Cadillac specifically) have so far failed to disable any cooling fan operation at vehicle speeds greater than ~~ 45 MPH.

Thats not off topic given my electric motor suggestion...

It would be easy to do also, but isnt it done already. With the AC on the caddy fans are on 100% of the time? But is it true that if the AC is off, the caddy fans will be off below 222? So while we are driving any speed with the AC off if the temp is below 222 aren't the fans off?

[JimD]

I will plead to going way off topic.

But, since the advent of digital control of many functions, I have asked myself why auto makers (and Cadillac specifically) have so far failed to disable any cooling fan operation at vehicle speeds greater than ~~ 45 MPH.

Thats not off topic given my electric motor suggestion...

It would be easy to do also, but isnt it done already. With the AC on the caddy fans are on 100% of the time? But is it true that if the AC is off, the caddy fans will be off below 222? So while we are driving any speed with the AC off if the temp is below 222 aren't the fans off?

According to my '98 Service Manual (have not drilled down this deep into my '04 books) both engine coolant system fans are commanded ON whenever A/C is enabled. And the reason for that is obvious in stop-go traffic.

With A/C OFF, the airflow at highway speeds allows the wet thermostat to control coolant temperature and the fans should not be needed (normally).

But: Why run ANY fans for engine cooling or A/C condenser at highway speeds? And I cannot see any digital logic that would disable the fans (with A/C ON) as a function of vehicle speed.

Hoping to be corrected......

[Scotty]

I agree with you, with the AC on, the fans will run, and you are right, with computer control, and coolant temp monitoring this could be done really easy... maybe our thinking is picky and asking for too much and it doesn't matter if they stay on as there is no harm done, but the system could be designed to:

Greater than 45 MPH, turn fan off,

Greater than 45 MPH, and temp increases to 222 turn fan on (this should be rare and should set a code). However there are times, like the ride I took from Phoenix to Sedona where there is a LONG uphill climb, where they instruct you to turn off your AC. In that instance, the fans would turn on assuming you did not turn your AC off

less than 45 turn fan on

Are you trying to redesign the "system" Jim, or just tweaking it?

[JimD]

Tweaking is all. Any electrical load translates to fuel required to supply the energy.

[Scotty]

Tweaking is all. Any electrical load translates to fuel required to supply the energy.

Hmm I never thought of it that way. So my electric water pump idea would consume fuel? I was thinking that it would decrease fuel consumption..

[JasonA]

But: Why run ANY fans for engine cooling or A/C condenser at highway speeds? And I cannot see any digital logic that would disable the fans (with A/C ON) as a function of vehicle speed.

Jim, I've thought about that before. I'm sure there's a certain speed where ram air forces more air through the radiator than the fans do. At 20 mph, certainly you'd think the fans can draw more air than ambient. At 45 mph...eh...I don't know. At 80 mph, you'd certainly think the electric fans get in the way more than they help.

Scotty, any electrical accessory consumes energy. It all comes from somewhere. In the case of an electric water pump, you're just changing the order of the energy (from liquid fuel to electrical via the alternator). For something as small as the water pump on a Northstar, I doubt you'd see any fuel economy improvement by changing it to an electric pump. I don't think electric pumps are very streetable. They're mostly found on drag cars I understand. Even NASCAR engines use mechanical water pumps (at least I believe they do).

[Scotty]

But: Why run ANY fans for engine cooling or A/C condenser at highway speeds?  And I cannot see any digital logic that would disable the fans (with A/C ON) as a function of vehicle speed.

Jim, I've thought about that before. I'm sure there's a certain speed where ram air forces more air through the radiator than the fans do. At 20 mph, certainly you'd think the fans can draw more air than ambient. At 45 mph...eh...I don't know. At 80 mph, you'd certainly think the electric fans get in the way more than they help.

Scotty, any electrical accessory consumes energy. It all comes from somewhere. In the case of an electric water pump, you're just changing the order of the energy (from liquid fuel to electrical via the alternator). For something as small as the water pump on a Northstar, I doubt you'd see any fuel economy improvement by changing it to an electric pump. I don't think electric pumps are very streetable. They're mostly found on drag cars I understand. Even NASCAR engines use mechanical water pumps (at least I believe they do).

Yes but the reason I was saying to use and electric water pump was because at low speeds they could run at a higher speed to promote better cooling... and at high speed they could be commanded to slow down..

I am curious what Guru thinks.. I am sure they have put a lot of time into calibrating the water pump for all RPMs. I would like to see the impact of running the water pump at higher speeds in heavy traffic however.

[JimD]

Another thought:

Build the cooling fan motors as a motor / generator.

That could 'generate' electrical energy from the air flow at some vehicle speed (> 45 MPH?) and reduce the parasitic engine load from the belt driven generator.

Small things add up when amortized over several million vehicles traveling many million miles per year. I recall someone inferring that powertrain engineers would trade their sister for a 1 MPG fuel economy increase! (OK, probably not.)

[Scotty]

Oh well...Thanks

[adallak]

Guru,

What about coolant temp that goes below 195 ?

I replaced my radiator & thermostat and I noticed that the temp will drop to 192-190 on occasion and has gone as low as 188. I know you are going to say don't look at it but I was just curious shouldn't it stay above 195 ? at all time after the motor is warm ?

Could you swap stats with Scotty....???

Sounds like that stat is on the low side...it happens sometimes I guess.

Is replacing 195 stat with say, 180 one hard on the water pump?

[adallak]

Scotty,

At highway speeds in the summer time your temperature will be controlled with your stat (say 195), but in stop and go traffic your stat (no matter 180 or195) will be open all the time because of lack of "fresh air" and the temp will be controlled rather with your PCM by means of fans (210-230). And your concern is mostly low speed driving in summer as far as I understood.

[up2ng]

Guru,

What about coolant temp that goes below 195 ?

I replaced my radiator & thermostat and I noticed that the temp will drop to 192-190 on occasion and has gone as low as 188. I know you are going to say don't look at it but I was just curious shouldn't it stay above 195 ? at all time after the motor is warm ?

Could you swap stats with Scotty....???

Sounds like that stat is on the low side...it happens sometimes I guess.

Could it cause any problems with open/closed loop operation or water burn off in oil ?

[JasonA]

up2ng, when I replaced my water pump and thermostat a few years ago, I got one that was on the "low side" of the acceptable tolerance. Average running temperature is dead on 190. On hot days with the A/C on, with moderate traffic, it'll hang out anywhere in the 190s. Heavy traffic will push it over 200. I've never had it to run more than about 215 with the A/C on. On the other side of the spectrum, coasting down a long Interstate hill in the winter time can drop the temperatures to the high 170s. 178 was the lowest "engine warm" temperature I've ever seen. 235 was the highest temperature I've ever seen.

[Scotty]

Guru,

What about coolant temp that goes below 195 ?

I replaced my radiator & thermostat and I noticed that the temp will drop to 192-190 on occasion and has gone as low as 188. I know you are going to say don't look at it but I was just curious shouldn't it stay above 195 ? at all time after the motor is warm ?

Could you swap stats with Scotty....???

Sounds like that stat is on the low side...it happens sometimes I guess.

Guru you read my mind! I would love that!

[Oldgamer]

Mike:

1. In my experience the engine temperature is very stable. It stays between 198 and 203 when I drive and I think THIS IS AMASINGLY STABLE. Yes, in traffic it can go up a bit, so what a big deal? This engine WAS DESIGNED TO HAVE THIS TEMPERATURE.

We just still under this old thought that "temperature of the engine should not be higher than temperature of the boiling water". We do not have these engines anymore. I assume you still warming up the engine 15 min before drive. My neighbor does. He start the car at 6:30 AM and drove at 6:45 AM.

2. Like Guru said, the water pump takes up to 7! HP. Now, take in attention that electric motor efficiency around 60-70% for this size. The alternator efficiency around 60-70% too. So, a whole thing will have 49% efficiency in the best case scenario. It means this electric water pump will take up to 14 HP. Plus believe me, electronic switch will not make the car any cheapper. Then, the alternator and electric water pump will require a better cooling themself. Just imagine what size and cost this 7HP electric water pump will be.

3. Existing system controls fans independently of the speed. And this is good. Why we should make additional variable (speed of the car) to that function? It works fine now and turn fans on if temperature is too high. Can't see any point, sorry.

Why you don't consider the idea to make water pump blades angle adjustable so you can change it perfomance?

JimD:

To make fans work like generators we should add the electrical switch too. And more: more efficient generator will take more cooling air off radiator. Yes, it's possible the fan is parasitic on a highway speeds. If fan will generate electricity it's spin will lower (under load) and it will even more parasitic. In reality the power of these fans working like generators will not be enough even to light the interior lights.

Cheers,