Hot or Cold

LR1796 said:

Dearot - I drilled the stat ring as you probably noticed on other threads,6 holes at 4mm is an extra 75.36 mm2 of surface area. On a hot blazing day coming out of work, sitting in traffic the temperature takes a little longer to rise but only goes to about a third of the temp gauge. Before I drilled the stat the gauge was always at just under half way.

I dont have any thermocouples to probe the coolant system with so dont know what the temp of the coolant is in real terms(oC).

However, as soon as I get out of town and hit 50mph on a B road the temp on the gauge drops. On cold mornings when driving at 50mph it can go from third of the temp gauge to the two whites lines on the base of the gauge . So efficiency of rad, coolant system is dependent on ambient air temperature and air flow over the rad and engine etc.

Only drill one or two 4mm holes in the stat ring. I have another spare stat ring to mess about with, going to drill either side of the two supports, hoping this will channel the cooler water around the stat and not through it.

The holes dont increase flow rate (velocity) so to speak but they increase 'throughput' of the volume of coolant. Does that make sense? Pump speed has not changed but volume has.


I have some links (courtesy of MHM, will supply them if you need) about guys modding the coolant system on the MGF and Lotus Elise, I dont subscribe to the gradual/ambient temp variation on the engine causing hgf, more so the initial opening of the stat from cold (initial shock). The MGF cup cars never had a stat fitted and they didnt suffer from hgf until very high mileage. The only reason they failed is because the red elastomeric compound on the OE gasket is crap!!
So if the MGF cup cars had the stat removed, temp fluctuations must have been over a wide range. So howcome they never had hgf until old age?

Have even read that one tech guru reckons that the cooling efficiency of the Rad in the MGF is far greater than what is required of the k-series engine. The Rad in the freelander is twice the size of that in the MGF so does that make it even more OTT????

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whats your fuel cosumption after drilling the holes? I am curious because you said temp gauge on goes down to the two whites lines on the base of the gauge when run 50 mph.
How does it run? that means I think the car never reach its operating temp, right?

I think you are right, two holes are enough. in KV6, maybe I should make the bypass hose from 22.4mm down to 4 -8mm.

LR1796 said:

On the heat soak issue? the EWP is the way to go.

Query - On the KV6 is the outlet from the cylinder block higher or lower than the inlet of the radiator.

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yes I agree with EWP.

I would say it is lower. MHM can you confirm this?

sorry guys - i dont have my hippoo any more - i saw the light (and the bank balance) and got a slitty

dearot said:

whats your fuel cosumption after drilling the holes? I am curious because you said temp gauge on goes down to the two whites lines on the base of the gauge when run 50 mph.
How does it run? that means I think the car never reach its operating temp, right?

I think you are right, two holes are enough. in KV6, maybe I should make the bypass hose from 22.4mm down to 4 -8mm.

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Fuel consumption is greater only because idle is around 1150-1300rpm on the cold mornings, when the sun is splitting the trees I have barely noticed a difference in fuel consumpion.
As already mentioned, as soon as I come to a traffic jam the car is stationary temp comes up rapidly and idle goes down to 750rpm again.......going to change the stat at the weekend.

The 1.8 runs well at the lower temp, although 6 holes would be more suited for our Aussie counterparts with their blistering heat.

The Mad Hat Man said:

"water wetter" is one of the additives. Meant to be good stuff.

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I read alot of articles about this and most of them are happy with it. If it does work as describe on redline website, I think it will also reduce the htermal shock issue as the temp of the engine and the coolant will be closer (at least by 10 degree). As the coolant will absorb more of the heat from the engine.

I think it has been discussed before here in this forum but could not find the threads.

QUOTE: Engines run much more efficiently when cold. Excessive heat can cause expansion and eventually warping, etc in places you don't want it.
Unquote

That is pure nonsense.
ALL our engines, petrol or diesel, are HEAT engines, and the hotter they run the more efficiently they perform. Getting cooler air into these engines is another matter entirely, but the ideal would be ramming lots of very cold air into a very hot engine.

One day someone will work out some sort of compressor, maybe driven by the otherwise wasted energy in the exhaust, which compresses the inlet air. Of course this would heat the inlet air up but it could be sent through an air-to-air cooler before it was fed into the engine. The bigger the MASS of air sent IN to the engine, the more fuel can be utilised, and in a diesel especially, the higher the efficiency will be. But, Alas, Dream on .....

The limits for heat in engines are several.
1. when the oil vaporises and ceases to act as a lube and probably explodes in the sump.
2. when the white-metal bearings melt and solder the con-rods to the crankshaft
3. when the alloy pistons melt and collapse due to heat
and things like that.

Too hot is actually VERY hot.

We use WATER as our coolant. This is because water is cheap and easy to get, and has a HUGE specific heat capacity, far more than any other useable substance. But water boils at 100 degrees unless it is pressurised .... so add a radiator cap that pressurises to 15 psi and Caramba! Boiling point is now nearly 110 degrees.

Actually, for safety reasons private vehicle engine coolants are usually kept to just under 100 degrees, but remember this - all the working parts, pistons, cylinders, valves, head and so on MUST be a whole lot HOTTER than the water.

As to "wetter water" additives for cooling systems, surely no-one on this forum doesn't know to put a few drops of Fairy Liquid into their radiator tank once in a while? This wets the water, eliminates "hot spots" and helps prevent traces of oils making hot spots. Basically your cooling system runs cleaner and that's good. About half a teaspoonful would start you off.

CharlesY

One purpose of drilling a few wee holes in the rim of a thermostat is to induce hot water to pass the bulb of the thermostat sooner or more effectively, thus getting the stat to open more reliably.

Over and above that, there will always be some coolant flow through the radiator which will send the same amount of cool water out of the other end of the radiator and that will mix with the by-pass flow coming from the waterpump, and help to some extent to reduce the thermal shock effect.

I would think three or four 5mm holes would do the trick to start with.

CharlesY

CharlesY said:

One purpose of drilling a few wee holes in the rim of a thermostat is to induce hot water to pass the bulb of the thermostat sooner or more effectively, thus getting the stat to open more reliably.

Over and above that, there will always be some coolant flow through the radiator which will mix with the by-pass flow coming from the waterpump, and help to some extent to reduce the thermal shock effect.

I would think three or four 5mm holes would do the trick to start with.

CharlesY

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Isnt four 5mm holes the same as five 4mm holes.

Working on the basic sums - 1.8 stat opening size, 28.5mm diameter by 5mm aperature is approx equates to 637.6 mm2.

The six 4mm holes that I drilled is an extra 75.4 mm2, thats only an extra 11.8% increase. It was still considerable to lengthen warm up times.

I was considering was shortening the spring on the stat to increase opening aperture.

The problem with the stat on the inlet is that when it just starts to open the aperture is narrow, therefore pressure jet into the block is high.

I have sleepless nights wondering how far the jet of very cold water ventures into to block , where's the thermodynamicist when you need emm

The stat bulb was moulded to facilitate this pressure jet, but the dynamics just dont seem to be right.

The MGF cup cars never had a stat installed and yet no hgf until later in life. I'm still making enquiries to Techspeed who built the MGF cup cars as to whether the coolant system had standard hose fittings etc

LR1796 said:

Isnt four 5mm holes the same as five 4mm holes.

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NO
Pi * (2.5 squared) * 4 = 78.5 sqmm
Pi * (2 squared) * 5 = 62.8 sqmm

Treworgey 90 said:

NO
Pi * (2.5 squared) * 4 = 78.5 sqmm
Pi * (2 squared) * 5 = 62.8 sqmm

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Yep thanks Treworgey, I knew that... but what I meant was it would have the same effect on the warm up times

LR1796 what kind of thermostat do you have? normal or the external one?

aussielander said:

LR1796 what kind of thermostat do you have? normal or the external one?

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Its the standard wax stat (88oC) Part No. PEL 10016, see pics attached in post 17 of this thread

The Pressure Release Thermostat is the way to go but at prices from £50 and upwards it could be an expensive item that may fail.

Some of the guys on MG-Rover.org do not rate the low load spring on the PRT, they say the spring is too soft. Many of them use the remote stat. This is basically a standard stat only placed on the outlet hose with its own housing and bypass.

Dearot is tinkering with some ideas for the KV6 on a similar thread

You are failing to see the point of drilling those holes.

The point is this - the drilled extra holes are always open, and always allowing HOT water to pass over the thermostat bulb and then through to the radiator, to get cooled, and sent back towards the engine and be mixed with the coolant being sent in to the bottom of the block again.

This has a dramatic effect on cooling systems in general, and on dreadful one like these it may make the difference between system failure and engine survival.

a 4mm diameter hole is 12.5 sq mm so 5 of those is 62.5 sq mm
a 5mm diameter hole is 19.6 sq mm so 4 of those is 78.4 sq mm

In practical terms there is no difference because of the way water flows through holes. It does not flow in strict proportion to the size of the hole.

Bigger holes allow proportionately MORE flow for several reasons.

Despite that the difference between 5 x 4mm holes and 4 x 5mm holes is of no matter.

CharlesY said:

You are failing to see the point of drilling those holes.

The point is this - the drilled extra holes are always open, and always allowing HOT water to pass over the thermostat bulb and then through to the radiator, to get cooled, and sent back towards the engine and be mixed with the coolant being sent in to the bottom of the block again.

This has a dramatic effect on cooling systems in general, and on dreadful one like these it may make the difference between system failure and engine survival.

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CharlesY - I WAS IN AGREEMENT WITH YOU! relax!

My point is.... the stat bulb on the inlet was supposedly 'balanced' between the bypass from the heater matrix (according to the workshop manual for the MGF).

By drilling the six holes in the stat ring (pics in post 17) this has shifted the equilibrium between heat efficiency of the rad and heat output of the cylinders 1.8.

Hence, far longer warm up times and lower running temp when driving at 50mph (2250 -2500rpm)

CharlesY said:

a 4mm diameter hole is 12.5 sq mm so 5 of those is 62.5 sq mm
a 5mm diameter hole is 19.6 sq mm so 4 of those is 78.4 sq mm

In practical terms there is no difference because of the way water flows through holes. It does not flow in strict proportion to the size of the hole.

Bigger holes allow proportionately MORE flow for several reasons.

Despite that the difference between 5 x 4mm holes and 4 x 5mm holes is of no matter.

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Yes thanks for clarifying that,

Would you care to elaborate on why bigger holes allow proportionately MORE flow?

Plus can the temperature differential across the block inlet and outlet be reduced by increasing the pressure of the jet of cold water and not just the throughput of the coolant?

Theories have been proposed for cavitation from the water pump.

LR1796 said:

CharlesY - I WAS IN AGREEMENT WITH YOU! relax!

My point is.... the stat bulb on the inlet was supposedly 'balanced' between the bypass from the heater matrix (according to the workshop manual for the MGF).

By drilling the six holes in the stat ring (pics in post 17) this has shifted the equilibrium between heat efficiency of the rad and heat output of the cylinders 1.8.

Hence, far longer warm up times and lower running temp when driving at 50mph (2250 -2500rpm)

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Your deductions are not justified by your stated case, nor by experience in practice. Drilling a few small holes in a thermostat will not cause a lower running temperature because those holes CAN NOT allow enough coolant through to cool the engine, and so the water temp WILL exceed the temp that opens the stat, and that's the temp it would have reached sooner anyway. All the wee holes does is flatten out the temp / time curve and pass warm water a bit.


Believe me - I've been doing it for well over 40 years ... and even on competition engines, never mind ordinary ones.

If the thermostat jammed wide open then the engine would probably over cool, and that would be bad all round.

Interestingly, in many engines the removal of the thermostat may cause OVER-heating due to the coolant circulating so quickly it gets back out of the radiator before it has time to cool down. Some old Minis were very prone to this and also a lot of others.

CharlesY

Would you care to elaborate on why bigger holes allow proportionately MORE flow?

It's a fact of hydrodynamics.
It seems all to do with friction on the surfaces of the pipe and in a short sharp hole such as we have, the way turbulences affect flow.

In a bigger hole there is less "edges" in proportion to area of hole - that's a fact. So one BIG hole of 100 sq mm will pass heaps more water than 100 small holes each of 1 sq mm at the same pressure.

I am told that friction in water pipes is a BIG problem, and the solution is to use bigger pipes, as these have a lower surface area of pipe for any given cross-sectional area. hence a lot less friction.

Flow through holes in plates is very complex. In fact, as I believe it is easier to "suck it and see" by experiment than to try to work it out.

After drilling the holes in the stat, say 4 small ones, de-burr them carefully. A sharp knife will do it nicely. The flow will be greatly enhanced.

CharlesY

CharlesY said:

Your deductions are not justified by your stated case, nor by experience in practice. Drilling a few small holes in a thermostat will not cause a lower running temperature because those holes CAN NOT allow enough coolant through to cool the engine, and so the water temp WILL exceed the temp that opens the stat, and that's the temp it would have reached sooner anyway. All the wee holes does is flatten out the temp / time curve and pass warm water a bit.


Believe me - I've been doing it for well over 40 years ... and even on competition engines, never mind ordinary ones.

If the thermostat jammed wide open then the engine would probably over cool, and that would be bad all round.

Interestingly, in many engines the removal of the thermostat may cause OVER-heating due to the coolant circulating so quickly it gets back out of the radiator before it has time to cool down. Some old Minis were very prone to this and also a lot of others.

CharlesY

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CharlesY - on the personal note,
I am not trying to undermine your experience or knowledge in this area, equally you should assume ones experience, as a competent scientist I have simply commented on the mods that I have done. It was changing one variable at a time.

I have simply drilled six 4mm holes, this prolongs warm up time (as expected and reported from Lotus Elise guys) and causes the 1.8 engine in my Freelander to run at a lower temperature when travelling at 50mph. No other mods were on the engine or cooling system when making this observation.

If you dont believe me I will send the stat to you (which is now removed from the system).

The mini with the A-series engine is a different system, many a time I threw an egg into the radiator to block the leaks, sometimes more than one egg, never really made any difference to the cooling really.

Wouldnt a mini with a k-series be a better comparison?

I am surprised that you say 6 x 4mm holes causes over-cooling in an engine like that.

I am not doubting it - I have no evidence to do so - but I remain surprised.

So next time maybe three or four would be plenty?

Doesn't the stat have two valves, upper and lower?

If so, during the time the stat is CLOSED, the stat's lower valve plate should be wide open allowing the pump to shove the coolant down the by-pass which is a lower resistance parallel shorter route than through 6 wee holes in the stat's rim and the radiator. Hence I am surprised it has that much effect.

CharlesY