Cooling too efficient 😄

[Patrick Taylor]

My car has over-cooled for years, ever since I put a full width rad on it. It rarely gets to halfway, even in the summer. I've just fitted a 91 degree stat, and that gives a needle bang on halfway and a toasty heater. I don't see why it would need the mixture and/or the timing adjusting as it is running at what is, presumably, the correct temperature. I'll have to swap it back again come warmer weather. 

[Iain T]

16 minutes ago, Patrick Taylor said:

I don't see why it would need the mixture and/or the timing adjusting as

Cold air is more dense so in theory requires more fuel to maintain the correct air/fuel ratio. Modern cars do this by an array of sensors, fuel injection and magic. We, again in theory, have to tweek the carbs but in practice no one does. 

Iain 

[johny]

6 minutes ago, Iain T said:

Cold air is more dense so in theory requires more fuel to maintain the correct air/fuel ratio. Modern cars do this by an array of sensors, fuel injection and magic. We, again in theory, have to tweek the carbs but in practice no one does. 

Iain 

Is that what waxstats are intended to do?

[Iain T]

Only on start up? Changes in ambient temp, humidity is why our cars run so differently even when warmed up. 

Iain 

[johny]

Never had SUs but I think they still have a choke for cold starting and the waxstat like the bimetallic system on later Stromberg is just for running in different ambient temperatures. Certainly need something cos as you say it makes a big different to the mixture and some cars even had a air intake position changeover system so for winter you took it from near the exhaust....

[Pete Lewis]

temperature  compensators on strombergs allow air to bypass the throttle plates and increase the idle in hotter conditions 

waxstats on SU raise or lower the jet ass as temperatures change to modify the mixture settings

air cleaners with manual or a Thermac valve and vacuum operated flaps control the incoming air to a steady 70F

by mixing air from the exhaust manifold and fresh air 

so there are a number of emission helping ideas over the years 

pete

[Iain T]

2 hours ago, johny said:

waxstat like the bimetallic system on later Stromberg is just for running in different ambient temperatures

I didn't know that was the reason for the waxstat. I only had my Spitfire 1500 with SUs for 6 months and never played with it. 

[johny]

1 hour ago, Pete Lewis said:

air cleaners with manual or a Thermac valve and vacuum operated flaps control the incoming air to a steady 70F

by mixing air from the exhaust manifold and fresh air 

so there are a number of emission helping ideas over the years 

pete

I suppose a manumatic system I could use on the Vitesse is just to disconnect the aircleaner hoses in winter😁

[Wagger]

I am very lucky in that I was able to keep much of my 'Kit' when I retired. I have a digital thermocouple meter which allows me to insert the probe into hoses by simply slackening the clips and re clamping. I go for a run and can read he temperature in the car.

Some on this forum have even later devices that can just be pointed at a surface etc.

It does save unnecessary work and worry to have these aids.

[Peter Truman]

10 hours ago, johny said:

I suppose a manumatic system I could use on the Vitesse is just to disconnect the aircleaner hoses in winter😁

If I remember correctly some cars in the 60's had an air filter inlet trumpet which was and recommended to be rotated to different positions for summer and winter to optimise the combustion air temperature.

I remember cold foggy nights driving home across the York moors and the car ran beautifully with the dense air.

[cliff.b]

1 hour ago, Peter Truman said:

If I remember correctly some cars in the 60's had an air filter inlet trumpet which was and recommended to be rotated to different positions for summer and winter to optimise the combustion air temperature.

I remember cold foggy nights driving home across the York moors and the car ran beautifully with the dense air.

Yes, despite not getting very warm my Spit was running beautifully on Sunday in the cold 5C air. Certainly seemed to be pulling well.

[cliff.b]

On 16/01/2024 at 20:48, johny said:

Is that what waxstats are intended to do?

I assumed they would adjust relative to engine running temp, not ambient temp. Certainly they won't be exposed to ambient temp once the engine is running.

[GrahamB]

I once had a problem with a car which I had fitted with a Weber carb. On cold damp days after travelling for about 10 miles, the engine would lack power and drink fuel.  I finally realised that it was icing  of the jets.  This was cured by constructing a shroud to direct air from above the exhaust manifold towards the air filter.  During my investigation of the cause, I used a thermocouple to measure the under bonnet temperature.  Whilst driving along, the temperature was close to ambient but as soon as I had to stop in traffic, the temperature rose by more than 20 degrees and any ice promptly melted.

[PeteH]

8 hours ago, GrahamB said:

I finally realised that it was icing  of the jets.

Interesting point made there. As the Freezing point of Petrol, dependant on grade and octane rating, is in the region of -50C. The likely hood is that the fuel contained Moisture (water specifically). More likely these days to be found in Bio-Fuels/Ethanol additives than straight Dinasour juice. I`ve had Diesel lines freeze in the past, But even that is not usual, as the suppliers normally put a preventative additive in the bulk fuel between October and April. In the UK petrol freezing is highly unlikely, as the lowest Temperature ever recorded was above -25C. (according to The Met Office?). I did have the Steam Heating on the Fuel Tanks of a small sulphur carrying Tanker in the Baltic one year, even then we struggled to pump the "Heavy" Fuel to the Daily Tanks, and it was touch and go as to wether we ran on the light, and substantially more expensive, "Gas Oil", normally reserved for the Generator sets.

Pete

[johny]

yes that used to be a big problem on motorcycle carbs and they eventually went to electrical heaters to stop them freezing...

[cliff.b]

8 hours ago, GrahamB said:

I once had a problem with a car which I had fitted with a Weber carb. On cold damp days after travelling for about 10 miles, the engine would lack power and drink fuel.  I finally realised that it was icing  of the jets.  This was cured by constructing a shroud to direct air from above the exhaust manifold towards the air filter.  During my investigation of the cause, I used a thermocouple to measure the under bonnet temperature.  Whilst driving along, the temperature was close to ambient but as soon as I had to stop in traffic, the temperature rose by more than 20 degrees and any ice promptly melted.

That's interesting as I have tried to keep exhaust heat away from the carbs by lagging the downpipes and extending the heat shield to curve under the carbs & encourage a flow of cooler air past them. Seems to work well at stopping problems when the weather is hot but never considered any possible consequences in the cold. But then I don't expect I will drive it much in the cold.

Saying that, it's -6C outside at the moment but it's sunny and the roads look dry👍

Edited January 18 by cliff.b
Spelling

[Wagger]

I had cables and throttle slides freeze up with condensation on motorcycles. With old cars, I have had fuel boiling off when stuck in traffic making re-starting impossible. That is one reason why Triumph decided to heat/cool the inlet manifold.

[Pete Lewis]

heating the manifold after the carbs does aid mixture atomising 

icing is caused by the vaporising reducing temperatures , 

on oldies the exhaust was circulated  around the inlet .    known as a Hot Spot .

some were constant others may have had a bimetal coil to try and control a often  seized up flap 

Pete

 

[PeteH]

Carb; Icing, is a function, not of the fuel, per se, but the relationship between External Air temperature and Relative humidity.

There is a useful, Article Here, Curtesy of Wiki:- https://en.wikipedia.org/wiki/Carburetor_icing

Note it`s  main thrust is toward Small Arcraft engines, which can suffer more.

Pete

[SpitFire6]

Hi,
Try closing the flow of coolant to the heater matrix. It will raise the engine coolant temperature.
Cheer,
Iain.