Controlling and affecting proper operating temp

[ILikeRust]

Thought I'd start a new thread on this, rather than hijack Marian Clare's thread...

All this talk of flow and heat exchange reminded me - when I brought my boat back to her slip last weekend, I noticed that the temp never got much above 150 on the gauge. Now I never ran her hard, but I would have thought that even just running along at around 1200-1400 RPM would have made the engine get up to full operating temp. So if that is the case, then it would seem that "full operating temp" in this case was only 150.

I'm thinking I'm going to need to play around with the bypass valve to see what effect it has when I slightly open or slightly close it.

What about slightly hotter plugs? The engine was a little hard to start, to my surprise. I am using the plugs that were in it when I took it out, because they seemed to be fine. But I could easily decided to yank them out and put new ones in.

I also don't know if maybe I need to to a little tinkering with the carb. I kinda don't want to.

[Marian Claire]

Rust: I look at the water temp as a guide. A warning of to hot or to cold. What I do check is the condition of the plugs. If they are staying clean then the running temp must be close IMO. Dan S/V Marian Claire

[Mo]

different.

Bill,
150 for temp...nothing wrong with that. Might be hard to start if the carb is leaned out a bit too much.

As for plugs, I use NGK XR4'S. Nova Automotive suggested them and I've had them in since last spring. Nova automotive does A4 rebuilding here in the area, they rebuild just about any engine. My engine never ran as good since I started running with those.

That said, Dave Neptune thought they were too much for that engine and he has some sound reasoning for his opinion. I respected Daves opinion so much that I went back to Nova Automotive to double check. They told me NGK will help the engine perform better. Phil said that they will keep the combustion chamber cleaner. They run hotter and are a bit deeper in the combustion chamber...they said they've never seen damage related to it...they told me to run them and see for myself. All I can say is that the engine has never run as smooth or as well. I have the carb leaned out nicely and my fuel consumption is right in the ballpark.

Please note I don't use a T-stat and my operating temp is always low side...around 130-140 if pushing it. Engine doesn't use oil to speak of and the plugs are consistently clean don`t leave much residue in the combustion chamber.

So basically, I'm FWC no T-stat, by-valve open about 1/2, and hotter plugs maintaining clean combustion chamber.

[hanleyclifford]

So, to continue the discussion, have we established that faster flow rate tends to more uniform temperatures throughout the system? This, of course, applys only to FWC.

[ILikeRust]

I had understood that a more optimal operating temp, with FWC, was 180 F, and that running too cool will lead to fouling on the valves.

[hanleyclifford]

I had understood that a more optimal operating temp, with FWC, was 180 F, and that running too cool will lead to fouling on the valves.

I think for those who run their A4 mostly to get in and out of the harbor 180 is good; but for sustained long range running I have found that 165 or so with FWC is better. What concerns me is that looking at the gauge, what you see may not really be what you get. I have been toying with the idea of installing a sensor where the coolant should be the coolest, and then switching between the other sensor, where the coolant should be hottest, and monitoring the differential.

[Dave Neptune]

Cool!

I have been thinking of the electric conversion for my beastie so I am very interested in this thread. I have run at 130~140 as Mo for 26 years now and no stuck valves (I have filled the crankcase with saltwater too many times tough) and very clean J8 plugs. I will say I am a bit of a carb nut and the carb is very close to spot on. I don't feel that there are any real adverse issues running "cool" albeit cooler running can increase wear on rotating parts., however once the "operating temp" is achieved the wear factor pretty much becomes a non factor.

Mo, I'm a bit intrigued by the plugs you are trying out. The extended tip is a must for some applications and I am a bit suprised that they are working better. Did they state the heat range comparisons with what you were running?

Bill, it should be a bit hard to start if the idle is correct. Didn't you say you were fouling plugs before?
And yes the valve adjusting makes a differance however it will take more than a few minutes for temps to settle. I suggest if you are going to "set" the temp you do so just above your "max crusing speed", take your time and enjoy some liquid bread. After setting like that you will notice the temp will rise only as the load increases and idle warm up will be slow and and drop to around 100+ degrees in 50 degree water. After running and the engine has set for about 5 minutes switch on the ign and see what the core of the beastie was running, it will usually rise around 20 degrees because the heat can radciate into the block and not be carried away by the cooling fluid.

Dave Neptune

[ILikeRust]

Bill, it should be a bit hard to start if the idle is correct. Didn't you say you were fouling plugs before?

No. I owned the boat only for about 5 months before I pulled the engine out, and probably put only a few hours on the engine during that time. The plugs were a little dirty when I pulled them out for the overhaul, but nothing I would consider "fouling."

I'm thinking I need to take a careful look at the idle setting on the carb. I fiddled with the screw last time I was out there, and it didn't seem to have much effect until I got to one extreme end of travel or the other. So I probably need to start over - although it seemed to be idling pretty well.

I also lowered the idle speed, because it was idling a bit too high. It always was that way since I got the boat, though. I don't know if the P.O. purposely set the idle at that level or just didn't understand that it wasn't necessary to have the engine idling at 1,000 or 1,100 RPM.

Another factor of course is that my temperature observations were made cruising through water that probably was around 40 degrees or so. It will be interesting to see what the engine temp does when cruising later this year, when the water temps will be up around 70.

[ILikeRust]

Another thing - the valves did have a bunch of baked-on crud around their necks.

[Marian Claire]

FWIW: I have been running my FWC at the same temp as I did my RWC, 140-150 F. My thoughts are, same temp sensor location, same 100% flow thru the block and head, same valve in the recirculating loop to control the mix of cooled and un cooled liquid entering the pump. The only thing that has changed is the type of fluid running thru that loop. Am I missing something here? Dan S/V Marian Claire

[ndutton]

Moved here from "Under-propped"

Running coolant faster lowers it's temperature and increases the heat transfer rate.

How does solely running coolant faster lower its temperature? Does running hot coolant faster make it cooler? Using another thought experiment of an extreme example, could we run the coolant fast enough to eliminate the need for a heat exchanger??

Without consideration of the variables of exchange efficiency, heat exchanger capacity, raw water temperature and raw water flow rate, inside the heat exchanger the longer the coolant remains there the more heat is extracted and the cooler it is delivered to the block until it reaches equilibrium with the raw water. I agree that beyond that point more time is meaningless. The delicate balance in the entire system (block and heat exchanger) comes from a corresponding lower flow rate in the block heating the coolant up more.

With a massive HX this topic isn't an issue. With a smaller or marginal HX due to space constraints, the idea of balance comes into play and flow rate is but one of several factors acting in concert.

The positive effect of faster coolant flow in the block is a negative in the heat exchanger and as I offered in the original post, within limitations.

[Ball Racing]

In the same waters as Bill just cruised thru, my engine at cruise Never comes off 100, (the lowest mark on the gauge)
I have to run at full WOT for at least 10-15 minutes to go to 130.
If you lift off the throttle at all back to dead cold.

I have RWC and a thick shoe in the water pump.

[Dave Neptune]

Hmm

Daniel, are you using a valve in the bypass or is it blocked off? You may want to try the smaller shoe.

Dave Neptune

[sastanley]

Daniel, in the cooler months mine runs cold too. I remember the first winter I had the boat, we motored it down to the marina to haul out in late November. I was a little worried that the water temp would not come up barely above the bottom of the gauge @ 100, but I also didn't want to mess with it because it was colder than crap and raining (of course!) and I just needed to get to the marina. This was stock cooling config...202m3, OEM Holley t-stat and failing original t-stat housing, so I was still getting a lot of bypass leaking & had no valve. I also have no idea in what condition the cooling passages were or when the last acid flush had been.

Once the Bay is up to 60F or so, I run 160-170 RWC..Below 60 at creek cruise RPM (1,500 or so) it stays down below that..120-140..but 2,000 RPM or greater it will come up to 160. Tied to the dock at a high idle it also barely gets above 140 unless the creek water is 65+F. I have to run WOT at the dock to get 160F.

Just some comparison numbers for you.

[hanleyclifford]

Back at it...

How does solely running coolant faster lower its temperature? Does running hot coolant faster make it cooler? Using another thought experiment of an extreme example, could we run the coolant fast enough to eliminate the need for a heat exchanger??

Without consideration of the variables of exchange efficiency, heat exchanger capacity, raw water temperature and raw water flow rate, inside the heat exchanger the longer the coolant remains there the more heat is extracted and the cooler it is delivered to the block until it reaches equilibrium with the raw water. I agree that beyond that point more time is meaningless. The delicate balance in the entire system (block and heat exchanger) comes from a corresponding lower flow rate in the block heating the coolant up more.

With a massive HX this topic isn't an issue. With a smaller or marginal HX due to space constraints, the idea of balance comes into play and flow rate is but one of several factors acting in concert.

The positive effect of faster coolant flow in the block is a negative in the heat exchanger and as I offered in the original post, within limitations.

The point here is that the temperature of the block, not the coolant, is the issue. Certainly by slowing the coolant in the exchanger we can extract more heat and deliver a cooler product to the block. But while this is occuring the block is heating up at different rates at various points in the block. The question then becomes; can we achieve a lower and more uniform average temperature throughout the block, notwithstanding we are injecting coolant at a hotter temp than is potentially available?