Technical The Winter Front Grille Thread

[jrkitching]

Teed off with the drastic mpg hit once the mercury drops below zero, and observing that the front grille is cunningly designed to ensure a continuous blast of icy cold air bathes the radiator & engine compartment, I'm looking at a little 'winter modification' .

Here's a picture of the Mk1 version, and the results of a 40 mile round trip to the shopping centre with a 4 hr stop, so essentially two cold starts & an OAT of around -1C.

Still a significant drop from the summer figures, but the temperature gauge didn't budge even a milllimetre above normal - so the experimentation will continue in the search for better economy.

 

[Most Easterly Pandas]

If your temp guage us fluctuating then you have a faulty thermostat which needs changing

The guage should rarely fluctuate in this weather with the possible exception of this being if running for a long distance on fuel shutoff, and even this shouldn't affect things by much.

 

[jrkitching]

If your temp guage us fluctuating then you have a faulty thermostat which needs changing

The guage should rarely fluctuate in this weather with the possible exception of this being if running for a long distance on fuel shutoff, and even this shouldn't affect things by much.

Exactly. The whole point of mentioning this was that I'd have expected to see it start rising if I'd 'overcooked' the blanking off - and I haven't (yet).

 

[Most Easterly Pandas]

Exactly. The whole point of mentioning this was that I'd have expected to see it start rising if I'd 'overcooked' the blanking off - and I haven't (yet).

But you shouldn't be needing to do any blanking off! And equally the change it causes to the cars aerodynamics could have a negative affect on the MPG as well.

 

[jrkitching]

But you shouldn't be needing to do any blanking off!

Fuel economy on the Euro4 engine takes a big hit until the engine reaches normal operating temperature (the Euro5 in my 500 is better at low temperatures), and with the standard grille, I felt it was taking too long to get there.

And equally the change it causes to the cars aerodynamics could have a negative affect on the MPG as well.

Highly doubtful - in fact, the opposite is more likely to be the case. I only managed 52.7 mpg from the last tankful, and today's numbers are at least a step in the right direction.

I can remember in the '60's (long before thermostatic radiator fans were commonplace), when these kinds of modifications were commonplace & you could buy adjustable blanking grilles in Halfords .

 

[David C]

But you shouldn't be needing to do any blanking off!

Exactly.
It is completely pointless on a car with an electric fan and a working thermostat.

 

[jrkitching]

Exactly.
It is completely pointless on a car with an electric fan and a working thermostat.

In your opinion.

If I get better mpg with the 'modification' than without, and get heat out of the heater sooner than I otherwise would, then it's not pointless to me.

Further testing will establish whether it is pointless or useful.

 

[Most Easterly Pandas]

Its not in David C's opinion, its fact. If the thermostat is working correctly blocking the radiator shouldn't make the heater start to work quicker. If it does then your thermostat is defective and needs changing, again this should improve the MPG.

 

[Matthen]

Exactly.
It is completely pointless on a car with an electric fan and a working thermostat.

Say that to the owners of diesel Multiplas... Blanking half the radaitor decreases the time for the heater to come on by a huge margin.

 

[Most Easterly Pandas]

Say that to the owners of diesel Multiplas... Blanking half the radaitor decreases the time for the heater to come on by a huge margin.

Which means they've more than likely got defective thermostats

 

[jrkitching]

Its not in David C's opinion, its fact. If the thermostat is working correctly blocking the radiator shouldn't make the heater start to work quicker. If it does then your thermostat is defective and needs changing, again this should improve the MPG.

There's nothing wrong with my thermostat - it's working just the way it should be.

I think you may be misunderstanding what I'm trying to do here - I'll try to explain a little better. It's not the radiator I'm trying to blank off, it's the front grille. I'm trying to reduce the forced cooling of the engine block during the warmup period. The radiator is a red herring - it shouldn't be doing anything at all until the engine is hot.

As you quite rightly say, the thermostat will take care of the coolant in the rad - it's not going to start circulating until it's needed. It's the cooling effect of the air over the rest of the engine that I'm trying to reduce here. Think of it this way - you'll be warmer if you fasten up your coat when you go out in a cold wind.

The second idea is that this will help on journeys with multiple stops. By keeping the engine bay warmer for longer after the car has stopped, the engine will get back up to temperature more quickly once it's been restarted.

Whether these factors turn out to be significant, or just trivial, I don't know yet, which is why I'm playing around with bits of cardboard.

 

[Most Easterly Pandas]

Fair play, I can see what your saying a bit more now, especially about the multiple stops.

 

[999auto]

Just as a 'bye-the-bye' here. It may interest some to know that various current Citroen and Peugeot models refer in their handbooks to a 'Very Cold Weather Shield' which clips on to the front grille. (This is of course available from the dealer at ridiculous prices!).
Interestingly, one is advised that this can be used at temperatures below 10 degC. - so not that cold really. So I think jrkitching is probably on to something!

 

[Popshot]

Those of us old enough to remember carbs and chokes will know it was all but mandatory to stick cardboard over half your grill in winters past.

 

[Most Easterly Pandas]

Those of us old enough to remember carbs and chokes will know it was all but mandatory to stick cardboard over half your grill in winters past.

That was to try and prevent carb icing though, different to this.

 

[trackdayqueen]

That was to try and prevent carb icing though, different to this.

Actually I did it more to allow the engine to get to running temperature as otherwise it wouldn't.

Never ever had trouble with carb icing tbh, I've had 5 or 6 cars with carbs.

 

[jrkitching]

That was to try and prevent carb icing though, different to this.

I'm very familiar with carb icing from my flying days. Carb icing is usually associated with warm, humid conditions - it's not a problem in very cold weather, as there's very little moisture in the air to freeze. Outside air temps around 15C & 90-100% humidity present the greatest risk.

Not, of course, a problem with a fuel-injected engine in any case.

[ame]http://en.wikipedia.org/wiki/Carburetor_heat[/ame]

 

[babbo_umbro]

I had carb icing issues many years ago with an an early Alfasud that had the single downdraught carb replaced by two crossdraft Dellortos; also hints of it on a Fiat Mirafirori Sport where I also had two big crossdraft Dellortos - as you say, cold dry air isn't the problem, the choke tubes suffer a dramatic loss of temperature where the air speeds up passing through the venturi and moist, cold(ish) air causes the problem

 

[Popshot]

That was to try and prevent carb icing though, different to this.

No, it was to get some heat into the engine. I don't recall ever having carb icing.

 

[Van Diemen]

It is also worth mentioning that a lot of thermostats also have a pressure relief element to them, and will open with rpm even when under temperature.