MikeCapon
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| posted on 9/2/12 at 01:07 PM |
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Underheating
Just bear with me if you would. I may just be a rambling old loon but would be happy to know if anyone else follows this logic.
Cars not being able to get up to temperature in cold (its -10 here) conditions seem to be a recurring problem.
Cold engine = poor fuel consumption and increased engine wear.
To the point that some manufacturers (like VW) have added diesel burners to their cars to artificially create heat and speed the warming up
process.
Which costs money and ruins fuel consumption.
Back in the mists of time we used to blank off the grill to speed warm up and (although we didn't realise at the time) improve Cd.
So why, instead of burning extra fuel to warm up, don't the manufacturers use a variable grill to do the same job without burning extra fuel and
make the car slippier in the process.
Mike
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wylliezx9r
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| posted on 9/2/12 at 01:14 PM |
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quote:
Originally posted by MikeCapon
Just bear with me if you would. I may just be a rambling old loon but would be happy to know if anyone else follows this logic.
Cars not being able to get up to temperature in cold (its -10 here) conditions seem to be a recurring problem.
Cold engine = poor fuel consumption and increased engine wear.
To the point that some manufacturers (like VW) have added diesel burners to their cars to artificially create heat and speed the warming up
process.
Which costs money and ruins fuel consumption.
Back in the mists of time we used to blank off the grill to speed warm up and (although we didn't realise at the time) improve Cd.
So why, instead of burning extra fuel to warm up, don't the manufacturers use a variable grill to do the same job without burning extra fuel and
make the car slippier in the process.
Mike
I think you'll find that the new Ford Focus does.
I spent a lot of money on booze, birds and fast cars. The rest I just squandered.
George Best
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MakeEverything
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| posted on 9/2/12 at 01:14 PM |
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I seem to remember that there's a new car out that does have an automatic grille for exactly these reasons.
I forget which one though. Peugeot?
Kindest Regards,
Richard.
...You can make it foolProof, but youll never make it Idiot Proof!...
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Dingz
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| posted on 9/2/12 at 01:16 PM |
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You mean just like the air cooled citroens where you got a plastic gumshield to put in the grill?
Phoned the local ramblers club today, but the bloke who answered just
went on and on.
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loggyboy
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| posted on 9/2/12 at 01:22 PM |
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But the thermostat does that job. A radiator with no flowing water wont cool an engine. Pass Air cooling the engine bay has a minimal effect.
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balidey
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| posted on 9/2/12 at 01:24 PM |
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Remember when you used to swap the summer thermostat for the winter 'stat?
Dutch bears have terrible skin due to their clogged paws
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MikeCapon
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| posted on 9/2/12 at 01:25 PM |
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quote:
Originally posted by Dingz
You mean just like the air cooled citroens where you got a plastic gumshield to put in the grill?
My Ami 8, now the property of Dave Ashurst on here, had one. But what I'd be imagining for a modern car is some sort of variable aperture,
controlled by the ECU...
I'm tempted to block off the grill on my VW and the Audi (same 1.9TDI motor) but I don't want to have to stop on the motorway for example
to unblock it in the case of overheating. Or to be honest I'm probably more worried about SWMBO driving the car and noticing nothing until the
engine melts.....
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jossey
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| posted on 9/2/12 at 01:26 PM |
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My BMW does that. Closes off when it's Cold and opens if it's too hot or the air con is on.
Thanks
David Johnson
Building my tiger avon slowly but surely.
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MakeEverything
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| posted on 9/2/12 at 01:48 PM |
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quote:
Originally posted by loggyboy
But the thermostat does that job. A radiator with no flowing water wont cool an engine. Pass Air cooling the engine bay has a minimal effect.
But the cold ambient -15 (wind chill factor) into the engine bay will,have a similar effect.
Kindest Regards,
Richard.
...You can make it foolProof, but youll never make it Idiot Proof!...
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cliftyhanger
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| posted on 9/2/12 at 01:55 PM |
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I have experimented with my older cars, and blocking th eradiator (tinfoil) does raise the temp. I am not sure exactly why, as the thermostats work as
they should, but maybe enough water gets by to keep the engine cold? I know blanking shouldn't make a difference, but it just does! Never tried
it on a modern car though, it may be different?
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Confused but excited.
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| posted on 9/2/12 at 01:57 PM |
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Rollers have had thermostatically operated radiator grills for donkey's years.
Tell them about the bent treacle edges!
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MikeCapon
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| posted on 9/2/12 at 02:05 PM |
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quote:
Originally posted by Confused but excited.
Rollers have had thermostatically operated radiator grills for donkey's years.
I seem to remember that someone (Kenlowe?) sold radiator blinds you could control from inside the car?
Which would be good right now but my original point still stands. Why burn extra fuel when you could get the same similar) result from a presumably
cheaper and more ecological means.....
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coyoteboy
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| posted on 9/2/12 at 02:11 PM |
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You can't. That's why they use heaters - they're not stupid and do generally have a team of engineers doing the calcs on these
things. The effect of wind chill into the engine bay will be negligible (a few hundred watts lost at most when at full temp, especially on a car with
full under-trays). Rad curtains make no sense at all.
Most of the cars that use variable rad blinds these days do so for aerodynamics, not for warm-up - they only open when the static rad can't deal
with the heat it needs to shed.
[Edited on 9/2/12 by coyoteboy]
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nick205
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| posted on 9/2/12 at 02:25 PM |
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Fuel economy on my Passat has dropped badly in these low temps which is annoying. It doesn't half warm up quick though 2-3 miles and it's
bang on 90 degrees with hot air aplenty! The pre-heater on SWMBOs Alhambra doesn't work and it takes an age to warm up.
Concurring with the OP it seems a poor design approach to burn extra fuel when passive measures could overcome the issue.
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MikeRJ
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| posted on 9/2/12 at 02:39 PM |
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quote:
Originally posted by cliftyhanger
I have experimented with my older cars, and blocking th eradiator (tinfoil) does raise the temp. I am not sure exactly why, as the thermostats work as
they should, but maybe enough water gets by to keep the engine cold?
A wax thermostat is a very crude control system. The movement of the thermostat is only proportional to temperature e.g. if the engine is running too
hot the thermostat will open a little in response. A simple proportional control system like this is not capable of removing all error, i.e. the
amount the stat opens won't perfectly correct the error (if it did it would simply close back down again). This is why a radiator blind can
make a significant difference to the engines running temperature in extreme cold conditions. Some modern cars have the thermostats controlled by the
ECU which can implement a much more sophisticated control scheme and hence regulate temperature more accurately, so radiator blinds would be less
useful.
The diesel burners mentioned by the OP are usually for heating the cabin space, not the engine. Because diesel engines are quite efficient these
days, they have less waste heat so they naturally warm up more slowly. A diesel engine is typically more robustly built than a petrol as well, so
there is a greater thermal mass to heat.
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MakeEverything
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| posted on 9/2/12 at 02:50 PM |
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quote:
Originally posted by coyoteboy
The effect of wind chill into the engine bay will be negligible (a few hundred watts lost at most when at full temp,
[Edited on 9/2/12 by coyoteboy]
The original point was that the cars couldn't get up to temperature though. If the wind chill effects through the grille and a cold radiator
(closed stat) are negligible, then where does the cold air go once passed through the rad? It might not be too windy in there (negative pressure
though), but it will still be chilled by the colder (positive pressure) air in front of the car.
Kindest Regards,
Richard.
...You can make it foolProof, but youll never make it Idiot Proof!...
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designer
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| posted on 9/2/12 at 02:54 PM |
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Of it's really cold and I am poodling about locally, I put a sheet of cardboard in front of the radiator which had holes in it so that it is
just reducing the exposed area of the radiator..
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MakeEverything
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| posted on 9/2/12 at 03:01 PM |
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quote:
Originally posted by designer
Of it's really cold and I am poodling about locally, I put a sheet of cardboard in front of the radiator which had holes in it so that it is
just reducing the exposed area of the radiator..
That's what the black cabbies do, and it seems to work well. They have a sheet of laminated A3 paper in the front.
Kindest Regards,
Richard.
...You can make it foolProof, but youll never make it Idiot Proof!...
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fesycresy
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| posted on 9/2/12 at 03:32 PM |
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quote:
Originally posted by balidey
Remember when you used to swap the summer thermostat for the winter 'stat?
No?
Did you have crank handles to start the car 
-----------------------------------------------------------------------------------------------------
The sooner you fall behind, the more time you'll have to catch up.
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coyoteboy
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| posted on 9/2/12 at 04:12 PM |
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quote:
The original point was that the cars couldn't get up to temperature though. If the wind chill effects through the grille and a cold radiator
(closed stat) are negligible, then where does the cold air go once passed through the rad? It might not be too windy in there (negative pressure
though), but it will still be chilled by the colder (positive pressure) air in front of the car.
Just seems unlikely that your engine is so over-cooled that it effectively needs wrapping up to let it get warm. With a stat in place there's
sweet FA flow through the rad, so the only cooling it's getting is to ambient and through the heater matrix. Often people run the heaters on
full and it takes ages to get up to temp, naturally. The other point is the stat may be partially stuck open. But if the engine puts out so little
heat that stopping the airflow over its surface means it gets up to operating temp I'd suggest they've created one of the most thermally
efficient engines known to man.
Warmup just takes longer in winter due to the colder block starting temp and the fact that people put heaters on full chat, airflow and ambient air
will have a much lower effect in the pecking order.
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steve m
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| posted on 9/2/12 at 05:18 PM |
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To add to this "winter problem"
we used to have airfilters that could move from winter to summer, to aid in the running
and presumabley stop carb icing
Steve
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coyoteboy
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| posted on 9/2/12 at 05:25 PM |
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Do you mean the old settings that used to suck air from over the exhaust manifold? Died out in the early 80-90s about when injection became a norm
IIRC?
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steve m
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| posted on 9/2/12 at 05:31 PM |
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Thats the one m8, i certainly had it fitted on one of my earlier cars, cant remember which though!
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PSpirine
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| posted on 9/2/12 at 05:47 PM |
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quote:
Originally posted by coyoteboy
You can't. That's why they use heaters - they're not stupid and do generally have a team of engineers doing the calcs on these
things. The effect of wind chill into the engine bay will be negligible (a few hundred watts lost at most when at full temp, especially on a car with
full under-trays). Rad curtains make no sense at all.
Most of the cars that use variable rad blinds these days do so for aerodynamics, not for warm-up - they only open when the static rad can't deal
with the heat it needs to shed.
[Edited on 9/2/12 by coyoteboy]
That's spot on. Active vanes as they're called are done for aero reasons, and nothing to do with increasing engine temps - they close on
motorways and open in traffic.
The reason for fuel-fired heaters is twofold. Firstly it's to heat up the cabin, and secondly it's so the engine warms up QUICKLY to
reduce consumption and emissions, and let the catalyst work (they don't work when they're cold). The effect of blanking out the grille
would do very little to speed up warm up in most people's conditions (first couple of miles tend not to be motorway miles anyway), and after
that point you're sitting at thermostat level anyway.
If you're struggling to get up to temperature at our sort of "cold" of -10, I'd suggest your thermostat is knackered, as even
my 90hp TDi Passat (which is a silly efficient engine) gets to 90 degrees eventually with an open grille and a missing undertray.
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Ninehigh
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| posted on 9/2/12 at 06:28 PM |
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Just a thought, would an engine be using more fuel than normal if it's moving? I know it revs a little higher at idle but when driving does that
actually make a difference these days?
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