coolant flow - (follow up to cooling diagram)

[missfixit70]

From your earlier post: At that amount of lift does the cross sectional area of flow allowed in exceed the cross sectional area of the inlet pipe from the bottom hose & what effect might that have?

In short - NO
The areas are as follows:
inlet pipe diameter at stat =31mm, area = 755mm²
Mazda stat lift @ 95 deg.C = 9.5mm, which equates to a flow area of 497mm²
(Blueprint stat lift @ 95 deg.C = 8mm, which equates to a flow area of 439mm²)

Brains dead - can you think of effect?

I was just pondering on Mel's query earlier with that one really

The 94/95 that you are getting is flow from the primary circuit with a little help from the secondary that has a higher resistance so less flow until the bypass is fully closed and all the legs are balanced (have the same resistance). Is it possible that the continued opening of the stat at above that temp is panic mode passing as much coolant as possible through the rad in an attempt to contain an overheat?

I don't think it's "panic mode" as I'm pretty sure the fans haven't kicked in at that point as you'll only get full flow through the rad once the top disc shuts off the recirc flow, it's just the stage in between that point & the fan/s kicking in.

[mikexgough]

I think you may get temps that high from the rad returns if the system really isn't running right, but the fans kicked in on mine before the engine outlet/top hose/inlet to the rad got to upper 90's, with approx 15-20 degrees cooling on a static rad (while bleeding, depending on ambient temp & wind), I think the max rad outlet/bottom hose temp you'd get on a healthy system is @85 degrees before the fans kick in. The highest I managed to measure was 75 degrees.

Yep I agree with all that........

[widdowson2008]

the temperature test vehicle is progressing very well indeed. Not long before I get some results
I'm a happy bunny

[mikexgough]

the temperature test vehicle is progressing very well indeed. Not long before I get some results
I'm a happy bunny

Waiting with interest....... I assume it is the same vehicle we discussed when we were at Bakewell....

[widdowson2008]

the temperature test vehicle is progressing very well indeed. Not long before I get some results
I'm a happy bunny

Waiting with interest....... I assume it is the same vehicle we discussed when we were at Bakewell....

That's the one. Completely serviced cooing system, in A1 condition, sensors all over the place - ya wanna see the dash - covered in digital readouts and led's, rotary gauges, switches (there is space for an ejector seat button if its kept small) - run out of space so now utilising the window pillar

[widdowson2008]

the temperature test vehicle is progressing very well indeed. Not long before I get some results
I'm a happy bunny

Waiting with interest....... I assume it is the same vehicle we discussed when we were at Bakewell....

That's the one. Completely serviced cooing system, in A1 condition, sensors all over the place - ya wanna see the dash - covered in digital readouts and led's, rotary gauges, switches (there is space for an ejector seat button if its kept small) - run out of space so now utilising the window pillar

Found space (if Geoff comes up with the goods) - I have faith!!!!!!!! ............and a lot of hope
Cape Canaveral has got nothing on it

[sandstone]

The reason for holes on stats is usually:

1. To allow trapped air to circulate out of the system when filling.
2. To prevent a stagnant area of coolant between the engine's heat generating surfaces and the thermostat's wax capsule. A stagnant area would slow down the response of the thermostat and accuracy of control.

Item 2. above usually applies to engines with "constant outlet temperature" control where the thermostat is on the outlet, and responds to outlet temperature changes.

The Bongo engine uses a "constant inlet temperature" system, with the thermostat on the inlet. The wax capsule in the mixing chamber of the thermostat senses the temperature of the re-circ line. When this reaches 82 degsc the thermostat opens and cool fluid is admitted from the radiator circuit. A stagnant area is therefore avoided.

This initial opening of the thermostat after a system re-fill is also the point at which trapped air in the radiator/thermostat hose is released into the system, about which so much has been written on these pages. The bleeding procedure eliminates this air once it has been released from the hose. In other words when the thermostat opens and the hose get warm.

The "constant inlet temperature" system gives a tight temperature control on fluid entering the engine even with varying engine speed and changing ex-radiator coolant temperature. After warm-up, when the thermostat has taken control, the system can react quickly to inlet coolant temperature changes caused by surges of cold fluid such as when engine speed increases. An outlet control system can only sense the temperature of coolant after it has passed through the engine, when it is too late, with the resultant thermal shock to the engine. The Bongo system eliminates this.

The bleed pipe therefore performs two functions.

1. When initially filling it prevents air being trapped in the cylinder head.
2. When warming up it allows air released by the opening thermostat to exit the system.

[widdowson2008]

The "constant inlet temperature" system gives a tight temperature control on fluid entering the engine even with varying engine speed and changing ex-radiator coolant temperature. After warm-up, when the thermostat has taken control, the system can react quickly to inlet coolant temperature changes caused by surges of cold fluid such as when engine speed increases. .

Excellent description sandstone
Particularly agree with 'tight temperature control on fluid' - Very tight
Also 'react quickly' - very quickly indeed.
The only part I would query is '.....coolant after it has passed through the engine'.
My current thinking, (and heat tests about to commence will prove or disprove this) is that the Bongo stat configuration also senses the coolant temperature change AFTER it has passed through the engine.
The main reason for me thinking this is that if it took effect as the coolant from the rad entered the stat body, then the stat would close, ie-before the coolant had reached the engine.
I also think that in the case of a Bongo, from a temperature point of view, the controlling flow is from the heater circuit as this is the only circuit that is permanently flowing.

But again, I will only be absolutely sure when I start getting data from the tests.

[mikeonb4c]

Item 2 on sandstones list seems to make cmplete sense to me. However I can't see how the logic should be any different whether thermostat is on inlet or outlet. Either way, I'd have thought the idea is to ensure the wax is surrounded by the warming water (though I can see it might matter more where the stat needs to respond to water being heated around the head so maybe I do understand!).

[widdowson2008]

..........I'd have thought the idea is to ensure the wax is surrounded by the warming water (though I can see it might matter more where the stat needs to respond to water being heated around the head so maybe I do understand!).

I am of the same opinion, and the only flow that is CONSTANTLY present around the wax bulb ALL THE TIME is via the heater circuit.
If you examine the stat housing geometry, you will see that the flow from the heater circuit to the engine is virtualy a straight line, with the stat wax bulb sat directly on that line, whereas the flows from both head and rad are deflected by either valve or disc, so have very little effect on the stat wax bulb until first having passed through the engine.

[mikexgough]

The bleed pipe therefore performs two functions.

1. When initially filling it prevents air being trapped in the cylinder head.
2. When warming up it allows air released by the opening thermostat to exit the system.

and the 1st comment is the key technique for perfect bleeding.....

[The Great Pretender]

..........I'd have thought the idea is to ensure the wax is surrounded by the warming water (though I can see it might matter more where the stat needs to respond to water being heated around the head so maybe I do understand!).

I am of the same opinion, and the only flow that is CONSTANTLY present around the wax bulb ALL THE TIME is via the heater circuit.
If you examine the stat housing geometry, you will see that the flow from the heater circuit to the engine is virtualy a straight line, with the stat wax bulb sat directly on that line, whereas the flows from both head and rad are deflected by either valve or disc, so have very little effect on the stat wax bulb until first having passed through the engine.

Sandstone said 're-circ line' isn't that the same as the heater circuit?

[missfixit70]

I took recirc line to mean the recirc/bypass coming from the engine & going into the top of the stat. I wouldn't describe the heater circuit as recirc, it's the heater circuit.

[The Great Pretender]

I took recirc line to mean the recirc/bypass coming from the engine & going into the top of the stat. I wouldn't describe the heater circuit as recirc, it's the heater circuit.

That's the problem with definitions, lets let sandstone tell us what was meant.

[widdowson2008]

I took recirc line to mean the recirc/bypass coming from the engine & going into the top of the stat. I wouldn't describe the heater circuit as recirc, it's the heater circuit.

That's the problem with definitions, lets let sandstone tell us what was meant.

Clarification required sandstone, which line did you actually mean by re-circ? the heater return or the head return?