Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) +4 GDI Air Temps

Update.

I fitted a Bypass valve to the Heater, see

https://www.talkmorgan.com/ubbthreads.php/topics/795722/gdi-heater-bypass-fitted#Post795722

I retested the air temps as before and it does improve things but it's not the result I was hoping for. It's obvious the bypass leaks and there is still heat getting into the Heater Box.

The best result achieved is to get air 10.5 degrees above Ambient into the cabin, this is with the heater bypassed and the flap within the heater set to Cold. This is hardly what you want when waiting to get on a Ferry with the outside temp in the 20's.

When the flap is set to Hot then the air temp going to the cabin is warmed by 17.7 degrees.

Alternatives?

Other bypass valves that may or may not work. I have seen a Brass one but it couldn't be switched remotely.

fit a simple straight through connector in place of the Bypass and have no water going into the heater at all. More chance of working but a pain to switch between bypassed and not.

Stop Valves in an arrangement of T's and Hoses, should stop the hot water getting to the heater but switching between the two states will be manual.

Some more thought me thinks.

I can understand your disappointment Mark but given the very low price of valve maybe to be expected. Having said that the four way electrically operated valve John V6 suggested in your other thread (linked below) is cheap enough to try your luck with. You would just need to confirm the hose unions work with the standard 16mm i/d heater hoses.



Hoses hopefully would swap straight over then a fused power feed operated by toggle switch added.

A hair-brained thought…

Given the design of the valve and the high temp of the coolant in the valve after exiting the cylinder head, even when that diverter plate is closed, there will be some parasitic heat conducted out along both the in & out coolant paths into to the heater matrix.

If the issue is just the heat from the heater matrix heating the cockpit or soaking into the cockpit on a hot day, perhaps you could engineer the system to also work in reverse. Maybe mount a couple of large fans (larger than shown) on a manifold plate in the space above the heater box, one either side (or even a bank of smaller fans). Then with the heater flaps open you could draw ambient cabin air back through the matrix, taking the heat up and away out through the bonnet louvers.

Obviously you couldn’t use both fans together.

A good though Rog. My guess (yes, guess) is that a couple of those fans (scavenged from an old desktop PC?) might be needed to give sufficient airflow. Back pressure from the louvres near the windscreen might be a problem with insufficient fan piwer.
As another off the wall thought....
Is it pissible to reverse the heater fan to suck air instead of blow?would a polarity swop of the piwer work?

That would be good but I don’t think that is possible on a centrifugal fan unfortunately

Mark.

Since you have some straight metal tube to slip inside the rubber tubes, so that you can revert the system, you could try linking the input and output tubes together to completely isolate the heater box. In this case you could establish if the heat is coming from elsewhere other than the heater box matrix.

Don't forget that you are testing with a stationary car so you are not benefiting from an unheated flow of air. The very design of the Morgan including the louvres above the engine in front of the cabin ventilation intake louvres make it difficult to separate hot engine bay air from the, hopefully; cooler environmental air.

In a perfect setup the temperature of the air coming in to the cabin should be very close external air temperature.

HI All,

I added an elastic band to the Valve lever to keep it more firmly closed and retested.

It made little difference!

The difference between Entry and Cabin temps show that the heater box is warming up the air a minimum of 6 degrees and when passing the air over the Hot part adds another 3 degrees.

The Entry temp is by far the biggest issue still, it increased steadily through the testing and It increased faster when the Fan was switched on, so pulling hot air into the box from the engine bay.

I had assumed the remaining heating of the air was from the Hot Water going through the heater matrix. I now think the Bypass has reduced this and now adds only a few degrees.

The much bigger issue is the very high temp of the Engine Bay, after the test I opened the bonnet and burnt my fingers on the stays!. This sort of temp has a few impacts
- It warms the whole Heater Box.
- It warms the Hoses going to/from the Heater Box and therefore the water within.
- It passes hot air into the Heater box through any gaps in the foam around the top and through 6x drain holes that exit in the Engine Bay.

Hi Peter, I accept that while the car is moving the results would be very different, but you also have the ability to get air into the cabin by putting the hood down or opening a window. The only time I really needed some fresh air in the cabin was while stuck in standing traffic so that's what I'm trying to simulate.

I have got to a point where I think it's impossible to get Ambient air into the Cabin through the Heater Box while stationary.

Rogers idea makes sense, extract the warm air from the Cabin, as long as it's not replaced via the Heater Box it should work. Something to work on another time perhaps.

What the Morgan lacks, which most cars have, is a cabin air recirculation system. This is not important in the case where the car is not fitted with aircon but with aircon a recirculation system would allow air that has already been cooled to pass the cooling system again thereby increasing the cooling.

Perhaps what we are seeing here is something along the lines of previous discussions for cool engine air intake where it is necessary to duct air from a cool place to the cabin air intake.

Just a thought

I think you have hit the nail on the head Peter, re the cabin recirculation system.

With the best possible endeavors the air sucked in through the current design will always be above ambient or warm to some extent. The engine heat is always going to warm the heater box air paths, and then there is that heater matrix to deal with. And it’s not going to be possible so get sub-ambient air without a cooling device either.

But another thought...

Howerver it might just be possible to recirculated ambient air within the cabin, if you were prepared to sacrifice the radio space. You could always mount a bank of PC fans across the radio aperture to stir the air. That would pull in ambient cabin air from the existing heater box outlets and blow it forward. Little risk of warm air being pulled through the heater matrix as it would most probably just short circuit, pulling air from the least line of resistance through those outlet vents.

You might even be able to mount something like this in the radio aperture, although might not be so powerful.



PS – Do you really need a radio in a Morgan. I’ve never ever used mine

Mark

If I understand your test results correctly it seems that fitting the bypass only improves the situation by a couple of degrees. That is to say that with the fan on and the heater off, with the bypass valve closed the cabin temperature is only about 2°C less than when the bypass is open (feeding hot water to the heater element).
Also you have arrived at the conclusion that the major source of un desired heat is hot engine bay air????

This would seem to indicate that it is most important to limit the entry of hot engine bay air. A second slight improvement can be made using the bypass valve.

Having said all that the reduction of only 2°C on a hot day is still significant.

I still remain somewhat undecided as to whether or not it is worth fitting the bypass valve.