I’ve driven gas cars for quite a while now, I’ve just bought a BMW with a Diesel (N47 2.0L). Engine is great and love the fuel economy (60+ MPG) but have noticed it takes twice as long to get heat in to the cabin! is This a trait of Diesel engines being more thermal efficient? After 20+ minutes at idle the engine is barely warm. Thought it might be an open thermostat but it’s fine.
Do diesels take longer to heat up?
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Maybe the block and cylinder head are much ticker than a modern gasoline engine. You must heat that metal mass before temperatures in the cooling system get any heat transfer.
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I always had to buy the auxiliary heater option on my big Ford diesels because in the winter you freeze to death. Took mine like 15 miles of highway running to put out heat.
Does your car have a frontal mask for the rad or it has louvers in the front that automatically close when starting and slowly open as the engine warms up?
Having had 2 diesel cars (TDI Golf and TDI Passat), and a diesel truck, this has been my experience that winters mean very long warm ups.
You can mitigate this with grille covers, and block heaters/coolant heaters. Seeing as you are in the UK, something like a Webasto or Espar may be a good option, as I believe they are far more affordable in Europe than they are in North America. These heaters are great, and use the vehicle's diesel fuel (along with the 12V battery for the controls), which then keep both the engine and the cabin of the vehicle nice and warm, and you are not restricted to where you can plug your vehicle in. I believe there are timer and remote control options for those.
You can mitigate this with grille covers, and block heaters/coolant heaters. Seeing as you are in the UK, something like a Webasto or Espar may be a good option, as I believe they are far more affordable in Europe than they are in North America. These heaters are great, and use the vehicle's diesel fuel (along with the 12V battery for the controls), which then keep both the engine and the cabin of the vehicle nice and warm, and you are not restricted to where you can plug your vehicle in. I believe there are timer and remote control options for those.
Diesels need a load to really get up to temp. A front cover is a must.
My 3500 does fine but I use the exhaust brake at idle. She shrieks to holy heII but heats up as fast as my gassers do.
My 3500 does fine but I use the exhaust brake at idle. She shrieks to holy heII but heats up as fast as my gassers do.
I wonder if this is related to efficiency. Diesels are more efficient, and theoretically, heat is energy that is wasted. If more of the combustion energy is transferred into mechanical motion, there would be less heat. Theoretically, all else equal.
This is exactly what I was taught in high school.
It's also the reason why diesel engine's are considered more efficient since less energy is "wasted" as heat.
Answer is yes. Typically BMW diesels contain an aux heater to help with in-cabin heat generation. Don't let them idle, just get in and drive off. It'll warm up faster.
Yes. Diesels won't warm up unless working. Low speeds and idling and they will take forever to warm up.
The engine in my Dodge Ram with Cummins diesel was 1000 lbs I believe. So engine is much heavier than gas. Longer warmup.
But my newer Ford PSD must have some electric heater assist since air from heater vents gets warm as fast or faster than gas car.
This in combination with diesel engines generally being more massive for the same displacement means not only less waste heat, but more time to heat the mass of the engine itself, meaning it takes longer for coolant to rise in temperature.
That all aluminum 4 cylinder gas engine will likely heat up pretty quickly. A diesel with an iron block and heads has more thermal mass.
I do realize that many/most light duty diesel engines are sleeved aluminum blocks and heads. Yet they are going to be heavier than a gas engine of the same displacement.
How much heavier? I cannot say. However, it probably plays into this as well.
How is that for a long, it depends
Yes they do, and they often have more thermal mass which doesn't help with the heating up. It was 5 degrees C when I headed home after work today, and it took nearly 10 miles for the engine to reach normal operating temp. I had a small downhill section before the engine hit normal temp and coasting down there the temp dropped 5 degrees again.
Once the cabin was fully heated and the fan calmed down, the engine got up to temp quickly.
Idling a diesel for heat is futile. Install a coolant heater (Webasto preferred) or start the car and drive normally in the cold to warm it up faster.
I have an electric coolant heater and a small space heater for the cabin. Both are on a timer and I walk out to a warm car with clear windows every morning.
You guys stated a few good points, but missed one...
Diesels are...
Every single intake stroke of a diesel engine takes in a maximum load of cold winter air. It is compressed and heated, but only enough to auto-ignite the diesel injection which is precisely the right amount to maintain the idle.
Every single intake stroke of a gas engine is metered...it only gets enough air to make the torque being requested. Low load means very low air flow through the engine.
So, not only are diesel engines more efficient...think of the thermal difference just in the amount of cold air flowing through it.
While I don't agree with "bro-pipes" on diesel trucks, they are bigger for a reason. There is no throttle, and that engine is taking in maximum (yes, I know a turbo changes the air charge with load) load of air on every single intake stroke.
Diesels are...
- larger and heavier and have more thermal mass
- more efficient, producing less heat to maintain idle and low loads
Every single intake stroke of a diesel engine takes in a maximum load of cold winter air. It is compressed and heated, but only enough to auto-ignite the diesel injection which is precisely the right amount to maintain the idle.
Every single intake stroke of a gas engine is metered...it only gets enough air to make the torque being requested. Low load means very low air flow through the engine.
So, not only are diesel engines more efficient...think of the thermal difference just in the amount of cold air flowing through it.
While I don't agree with "bro-pipes" on diesel trucks, they are bigger for a reason. There is no throttle, and that engine is taking in maximum (yes, I know a turbo changes the air charge with load) load of air on every single intake stroke.
Yes, diesels take longer to warm up. Increased efficiency means less heat is wasted to the cooling system.
My old 2006 Jetta TDI would drop the coolant temp quickly at idle just sitting at a red light per my ScanGauge, for the reasons mentioned above. On a winter trip to Wisconsin it wouldn’t even get really hot heat out of the vents at highway speed. I blocked the grill using black foam pipe insulation and that helped a ton during the winter.
Iron has a specific heat of about 0.11, vs. about 0.21 for aluminum. Therefore an iron block has more "thermal mass" than a corresponding aluminum block if (and only if) it has about twice the mass or more.
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