RWC Engine temperature question

[romantic comedy]

Some of us run with FWC and a t stat. Some dont. Mine runs at 180 pretty steady. Maybe hits 190 on occasion. I have the original t stat in. I do have a valve in the by pass, just in case.

[nyiftos]

The by pass valve is, in effect, a thermostat - utilizing human brain and dexterity as opposed to spring and lump of metal.

Very interesting thread.
I ran the engine without a thermostat for as long as I can remember.
Late model, A-4 RWC.
This summer I installed a by-pass valve in order to bring the temp. to a hotter range.
Well without the thermo. and without the valve, temp. was never over 120F.
With the bypass valve wide open I still cannot go over 120F.
Any ideas why?

[joe_db]

Sure. The bypass valve forces water through the engine.
The thermostat forces water to go around the engine.
If the thermostat is defective or the surface it sits on is eroded it will be unable to divert enough water to warm the engine up much. I may have this issue myself, I have to run about full power for a while to see the gauge get over 120.
Now if you don't even HAVE a thermostat, the bypass valve will vary the temperature from cold to really cold.

Very interesting thread.
I ran the engine without a thermostat for as long as I can remember.
Late model, A-4 RWC.
This summer I installed a by-pass valve in order to bring the temp. to a hotter range.
Well without the thermo. and without the valve, temp. was never over 120F.
With the bypass valve wide open I still cannot go over 120F.
Any ideas why?

[nyiftos]

If I got it right, without the thermostat, my bypass valve is pretty much useless for varying the temperature.

[Ajax]

A further question-

When shooting the engine with an IR thermometer to compare readings with the engine temp. gauge, exactly *where* are the best places to take your readings?

My understanding is that the temp. sender located in the front of the cylinder head isn't necessarily a true representation of whole engine temperature.

[nyiftos]

On the issue of the IR thermometer, check on the cyl. head just under the thermo. housing and on the head same spot but at the rear, say right next to the coil mounting. I believe that comparing those 2 should give you a good idea as to the whole temp. situation. Now if space permits, taking four readings on the top side of the head, say 1 for every cyl. should give you a different reading but a nice clue as to the combustion performance of every cyl. individually. I hope this makes sense.

[hanleyclifford]

Very interesting thread.
I ran the engine without a thermostat for as long as I can remember.
Late model, A-4 RWC.
This summer I installed a by-pass valve in order to bring the temp. to a hotter range.
Well without the thermo. and without the valve, temp. was never over 120F.
With the bypass valve wide open I still cannot go over 120F.
Any ideas why?

Yes. The standard by pass valve is only a restrictor of the by pass loop. Opening it up cannot in and of itself create a preferential flow thru the by pass loop. To do it you need to create an external by pass with a three way valve that will divert the flow away from the main loop while increasing flow thru the by pass loop.

[hanleyclifford]

Like this:

[Ajax]

So with just the ball valve, I will continue to run cool. The only thing the ball valve does for me, is allow me to prefer water to the block -if- I start running hot due to say, ambient water temperature and heavy loading.

The fun thing about this, is if you have an exhaust manifold restriction, the ball valve does not help this, because -all- of the water remains in the engine block for too long.

[hanleyclifford]

So with just the ball valve, I will continue to run cool. The only thing the ball valve does for me, is allow me to prefer water to the block -if- I start running hot due to say, ambient water temperature and heavy loading.

The fun thing about this, is if you have an exhaust manifold restriction, the ball valve does not help this, because -all- of the water remains in the engine block for too long.

A restriction in the manifold should tend to make the engine run hotter. The larger issue is: why allow restrictions to develop anywhere in the castings? The value of the three way valve, quite apart from it's positive preferential path selection, is that it allows total flow in the system to remain unchanged whereas the thermostat is a net restrictor.

[JOHN COOKSON]

To Summarize A Bit......

So with just the ball valve, I will continue to run cool. The only thing the ball valve does for me, is allow me to prefer water to the block -if- I start running hot due to say, ambient water temperature and heavy loading.

One more if.................
If total water flow through the (RWC) cooling system is suddenly reduced due to say a sudden partial blockage of the inlet, a vane on the impeller breaking, or whatever, restricting the bypass will divert water from flowing around the engine to more water flowing through the engine. This is the idea behind reserve cooling capacity.
As we all know restricting the bypass will result in a (RWC) engine running cooler. If the engine is running too cool one needs to restrict the amount of water flowing through the engine with a thermostat or a diverter arrangement. (Good idea Hanley)

TRUE GRIT

[nyiftos]

Like this:

Ok, let's see what we have here.
Is this a late A-4 or the older one.?
Where is your by-pass hose coming from?
Is your engine RWC or FWC ?
And the ball valve is a 2 way or 3 way? If it is 3 way where does the 3rd way lead to?

[hanleyclifford]

Ok, let's see what we have here.
Is this a late A-4 or the older one.?
Where is your by-pass hose coming from?
Is your engine RWC or FWC ?
And the ball valve is a 2 way or 3 way? If it is 3 way where does the 3rd way lead to?

Good questions. My cylinder head is the early model. The bypass flow where you see it labeled goes to the pump inlet (which it shares with the inlet from the exchangers). My engine is FWC. Note, however, that the 3 way valve (having one inlet and two discharges) is mounted on the manifold which is the same for early and late. The coolant comes up out of the manifold and is divided to the exchangers or the pump inlet. The flow is never restricted, only divided.