Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Radiator under heating!

Hi Everyone,

I had a spare piece of aluminium sheet so made a valance that fitted to the cowl box, was the width between the over riders and curled beneath the radiator. There are no holes or mesh in it, just a piece of bent sheet.

Went for a test run keeping an eye on the temperature gauge and expecting overheating problems but surprisingly, to me at least, found the temp gauge a few degrees lower.

I can only assume a lower pressure is being created between the radiator and valance resulting in hot air being sucked out by the under car air draught.

Any views/comments would be appreciated.

Regards

Geof

Geof,
I think you have correctly identified the reason your cowl box works to lower coolant temperature.
I presume you have the standard radiator.
My 2008 4/4 1.8 had to have a replacement radiator when the plastic inlet top pipe fractured. The new one is all aluminium by Mulfab and longer top to bottom. The lower edge comes about 5 inches lower than the original. I have taken temperature readings off the radiator and discovered that the lower 20% remains cold with normal driving. Spirited driving heats it more as you would expect but the electric fan rarely comes into operation. No cowl is fitted.

Geof,

it sounds plausible. Airflow management around radiators is a key part of modern cooling systems, a topic little understood when the Morgan Trad started its evolutionary journey!

Once the engine is warm the temperature is governed by the thermostat and measured usually in the engine block. Temperature gauges are crude instruments anyway.

Remove the thermostat then do two runs back to back with and without your add on.Make sure to measure ambient temperature and drive at the same speed

http://www.gomog.com/BLAIR/tech/cooling/art020.html

There's a clear explanation of what I think you are experiencing here.

Hi Geof. I can concur that blocking my rad also appears to aid cooling. I had some strange goings on in my coolant system. It could just all be conjecture but I put the cause down to the coolant flowing backwards in the Duratec compared to a normal engine.

Stumbled across this a while ago whilst trying to work out why my little engine with its big Plus 8/Roaster radiator ran so hot all the time. I had been scratching my head for ages trying to work out why the cooling fan was often running with the engine cooking yet my thermostat was closed with the bottom of the rad staying dead cold. Strangely this was more so in cold weather. Sometimes the stat would not open until the engine was way beyond 100C (reading from ECU not the useless dash ornament). I’m no auto expert but this is my attempt at an explanation ….

I’ve noticed that the thermostat on my Duratec doesn’t necessarily open at a fixed predefined engine temp. The point at which it opens is dynamic with respect to the cylinder head engine temp. This might have something to do with stat’s location and the fact that coolant flows in the opposite direction to a conventional engine that I am more used to. The dual valve stat is located down on the engine’s coolant input rather than at the top on the hot output (see below). There is both the hot bypass coolant and the cooled rad coolant flowing into the stat housing so the stat appears to be controlled by the combined heat from both.

Not my motor but here’s a pic of how the coolant paths converge at the stat housing



There is a kind of perverse inverse cooling relationship going on with this engine, I think… The lower the temp of the coolant exiting the rad, the higher the engine temp has to reach before the coolant in the stat housing is hot enough to open the stat. And what appears to makes the stat opening point so difficult to predict is that the rad temp is effected by at least 3 variables. The speed of the car or the air flow through the rad, the external ambient temp and efficiency of the rad. I suspect that for this system to work optimally there is fine balance and I think that my big ali rad was over cooling. My cooled coolant appeared to be inhibiting my stat causing it to open late.

In an attempt to open my stat sooner (or at a lower engine temp) I have de-rated my rad to raise the output temp of the cooled coolant exiting it. I have played with blocking off different amounts and now I think I have it optimised. After driving around for ages with a thermocouple stuck on the rad output and an OBD reader displaying the head temp it looks very well behaved. My Burton Power 82C stat (standard is 90C) is now opening and regulating the engine temp well in advance of the cooling fan cutting in. The ECU reports the engine temp now stays down in the mid 90’s with the occasional spike over 100C when the foot is hard down or belting up a hill. Last year’s 30C plus summer weather was a good test too as the engine temp stayed remarkably steady and consistent with out the rad fan kicking in despite the rad airflow restriction.


Here is my ‘run cooler’ baffle



Baffle sprung/fixed in position with PTFE feet. Air flow restricted at the top. The baffle is spaced off a little to allow the cooling fan to draw air through if required.


I apologise for the ramble

Interesting post. Thank you Roger

Doh! Just reading this again I should have said “flowing backward through the thermostat” rather than just “flowing backwards”.

Basically the stat is at the bottom of this engine so cooled coolant flows into the stat rather than uncooled as in a more conventional system. Normally it’s the uncooled coolant that regulates the stat or cooling system not the cooled as in the Duratec. I think that is right now if you get my drift…..

If you can get the air pressure lower behind the rad it encourages airflow through the rad. Hence the use of things like air dams to modify airflow under the car. Stopping air flowing UPWARDS to just behind the rad reduces the pressure there. Graham Bell describes it in his book on tuning with manometer results to show the effect. A well known tip for Morgans to improve airflow and reduce coolant temp is to block off gaps around the rad so air through the grill doesn’t bleed off round the sides. Similar with too many badges! The airdam effect is a relatively simple task using the cross brace to create the “suction effect” needed. The method described in the original post may be having a similar effect.
There is another effect caused by the windscreen....it creates a positive pressure just in front and down through the rearmost louvres, a possible aid to induction airflow/temp.
Ah...the mystique of aerodynamics...especially on a Morgan.

Roger, thank you for a very informative technical piece on the Duratec cooling system, very much appreciated.

And thanks to everyone for your comments which I have found to be most interesting.

Armed with this knowledge I will now do some "tweaking" until I find the sweet spot.

(And, I know realise just how the tiniest amount of bodywork alteration on an F1 car can have a dramatic effect!).

Thanks again

Geof