Controlling and affecting proper operating temp

[jtsails]

Neil,
I like the study you posted.
As Ed pointed out, the key here is how much heat energy is removed from the hot side coolant as shown in the BTU numbers. Doubling the flow rate increased the heat energy removal by about 1/3.
Moreover, this same effect will apply to the engine side of the equation as well, higher flow rate will remove more heat energy from the engine.
Since our cooling system (when in good shape) is capable of removing more heat energy than the engine generates*, we need some kinda of a system that regulates the amount of coolant flow through the block. That system can be manual in the case of the bypass valve or automatic with a thermostat. The recirculation loop is simply an automatic system to regulate the efficiency of the heat exchanger by bypassing it. This allows full flow through the block at all times and therefore should result in better heat distribution in the block.


*Yes, I realize this is a simplification since the since the cooling system is an equilibrium system but it doesn't matter since our goal is to achieve a steady temperature.

James

[Dave Neptune]

fogitabout it

Neil, it is the diferances of opinion and various bits of information that make this forum work so well. And in agreement or disagremant I consider you an Aforinan friend and a wealth of marine and various pertinate information .
The above thought reminds me that one thing we should all consider is that there are many configurations that work on many many many different applications and they all seem to work in our individual applications. Like the PCV valve I am very pro and you are much against it however both engines (yours & mine) run great and we can offer our opinions to others. They can decide on what they will do from the information we all provide~ remember ~ opinions are like AH's we all have one to offer.

Dave Neptine

[ndutton]

All,

Please do not interpret my posts here as being against differing opinions. This is a good bunch and it would be pretty boring if we agreed all the time. Unlike other forums we can dig into this stuff without challenging each others ancestry or similar slurs. Gotta respect that.

Regarding this discussion, I'm done with it, presented my position, perfectly comfortable leaving it as it is.

[Ajax]

Hotter plugs means the plug tip runs hotter.Does not make the water hotter unless the motor was so rich and unable to fire on that cylinder, and make any HP or heat BTU's...

I think I was very near this point. The new plugs gave noticably more power, and I achieved a higher RPM. Still though, I take your point. I feel that more fine tuning of the fuel system is in order, to prevent fouling the plugs and return to a cooler plug tip like 12 or 8J's.

[Ajax]

Sony, don't run without a t'stat UNLESS you are using a restriction (valve) in the bypass line. You need to be assured that the water is actually going through the block and not just cooling the area around the housing where the sensor is. Also be sure your diverter inside is still functional,
I have run without one for over 26 years now and no troubles at all. Actually I never have used a t'stat in my engine since I have owned it. I removed it when I "un-siezed" my engine when I bought the boat. I did however have to replace 1 exhaust valve at that time.

Dave Neptune

I was not aware of this. Are you saying that ALL or most of my water is bypassing the block and going straight to the manifold and out the exhaust?

I think we're past the last freeze of the winter. I'll put the t-stat in, today.

[ILikeRust]

I was not aware of this. Are you saying that ALL or most of my water is bypassing the block and going straight to the manifold and out the exhaust?

Maybe not "all", but the water will flow more easily where there is less resistance. With no thermostat, and no restriction in the line from the T fitting to the thermostat housing, the water will preferentially flow across the t-state housing and out the manifold, with less water being forced through the block, because there is more resistance to flow going through the block than there is going across the top and out.

Which is why the Moyer kit has a little check valve that applies just a little back pressure, to help push some water that way, through the block, as well as a little ball valve, so the operator can provide even more back pressure to push more water through the block rather than just across the top and out.

[Dave Neptune]

Yep!

Ajax, yes a restriction is to force the flow (of your choice or need) through the block and the bypassed to the manifold. Otherwise yes most of the water will take the "straight shot" through the tee and the bypass line to go to the manifold and out, or "the path of least resistance". That same water will cool the area of the "sendor" and can give you a very false reading when not restricted.
A good check for non t'stat engines is to shut down a cruise rather abrubtly and let the beastie sit for a few minutes with the water in the block, then turn on the key and check the temp, it should rise a bit and will be a reading much closer to what the core of the engine is running at.

Dave Neptune

[hanleyclifford]

Principles

If we have learned anything from this thread it is a few principles that can be applied to either early or late. First and foremost; velocity of coolant yields temperature uniformity increases. To achieve this every restriction in a system should be scrutinized and this includes thermostats and check valves. Coolant will always flow preferentially thru a bypass and that is why the bypass shutoff valve is critical but at the same time no attempt should be made to stop or "dead head" a coolant system. Coolant should always be flowing at the pump's maximum potential, diverted not blocked.

[Dave Neptune]

Principals

Hanley, good point indeed. One of the most critical gages in many HP racing apps is the water preasure gage! I have one on all three of my river boats and am contimplating one on the A-4. They're just simple static reading gages, quick and easy to read. There is a lot of sand and silt in the Colorado and it chews up water pumps. I got tired of just replacing every few years and now I replace only when the preasure begins to drop, no temp gages at all!! If your preasure changes you know something is going amiss. I have no temp gages on them, 2 are big 6 cyl OB's and one 3 banger on the party barge.

Dave Neptune

[Mo]

Ajax,

I would like to offer another alternative...I'd put a by-valve in that hose just in front of the thermostat housing and don't put in a T stat. For a reference, I leave my valve open 1/2 . This provides a bit of restriction for water to be pushed through the block....and the head gets cooled as well. That what works for me and I have never overheated...a set of hotter running plugs, lean out the carb just right and you will have one fine running machine....and you will be able to push it also without temps rising to unacceptable levels.

[positron]

Is there another spot on the A4 that might give a more representative temperature reading? It sounds like if there was a clog in the cooling channels in the block you would never know it from the temp gauge. I am thinking of pulling out my thermostat (since my engine runs at 180-185 under load) but it sounds like another temp gauge would be prudent.

[hanleyclifford]

I have always found that I get the highest temperature reading with the sensor on the manifold as close to the UHS as possible. Avoid a "T" configuration; it will read a little cool. The best spot is the forward casting plug hole.

[Mo]

Positron...are you FWC or RWC? Mine is Raw water cooled....what I'm talking about here is not really indicated for FWC. I do agree, you need to drop out that temp a bit.

If you are RWC: remove the T-stat and put in a by-valve and then check the guage...she will probably be fine.

[positron]

Mine is RWC. What type/size valve do you use for the bypass throttle? Do you have a picture?

[Mo]

Should be a pic in my engine album...just click my name and have a look at the engine...it was easy.