your engine warms up faster without heater??

[MrWideTires]

I wanna find out if this is true... as far as I know.. the heater in our cars does use the heat from the engine.

When my friend's 300k mile Civic Si tried to overheated.. we opened the windows and put the heater on max.. and it cooled down.
I also heard that there are some cars that you can put the heater on and the car WILL NOT let the heater work for at least 2 minutes to let the car warm up and then you can get heat.

This makes me think that if you wanna help your car warm up... it's best to not use the heater for the first 5 minutes or so.
Am I right? can someone add information, correct me, etc?

 

[demarpaint]

Yes running the heat too soon will slow the warming up process on anything I've ever owned. If you start over heating turning the heat on high and the blower on its highest setting can help cool things off. I leave the heat off until the thermostat is opened and the temp is in the normal range. If I can wait 10 minutes I'll sometimes do that.

 

[LS2JSTS]

I've had cars where the blower motor wont turn on until a certain coolant temp is reached.

It does make sense that the engine would warm up quicker with the heater off. But how much quicker? Probably not a lot quicker in my estimation.

 

[JHZR2]

Absolutely, I wait to apply half throttle until heat is halfway, and don't turn heat on until it is at full...

 

[Kaboomba]

Yes, you are right.

On pretty much every car I can think of, the heater core has engine coolant flowing trough it. A blower under the dash blows air over the hot heater core (which is basically a mini radiator) and into the cabin to give you heat. Naturally, blowing cold air over a hot heater core makes the air warmer and the heater core (and coolant) cooler.

So if you want your engine to warm up faster, leave the heater off.

Cars with climate control tend not to even begin blowing air until the coolant is up to 100-120F on the engine block.

 

[Quattro Pete]

Originally Posted By: MrWideTires
This makes me think that if you wanna help your car warm up... it's best to not use the heater for the first 5 minutes or so.
Am I right?

Certainly.

Honestly, even if you did try to use heat in those first minutes, you're not going to get much heat since everything is still cold.

 

[Bryanccfshr]

My morning routine includes starting the truck and turning the defrost on full blast and going inside and cooking and eating breakfast.
I have No room in the garage for the work truck and I need to be able to see real clearly when I leave the house. Morning lowes have been anywhere from 0 to 15 this week with ice and snow stuck to the vehicle this am.
After some scrambled eggs and toast the truck is ready to go and I have a clear view and warm cab.

My personal vehicles are garaged and are started and driven off immediately when needed.

 

[simple_gifts]

My !echo! has a 5 qt cooling capacity; pretty easy to tell the impact of running the heat on high on a 10F morning

 

[Quattro Pete]

Originally Posted By: Bryanccfshr
My morning routine includes starting the truck and turning the defrost on full blast and going inside and cooking and eating breakfast.

At 15F, I don't think my car's engine would actually warm up at all under such circumstances. It seems to need rpms higher than idle to warm up anything.

 

[Bryanccfshr]

Turning on THe AC compressor and the draw from the Alternator as I run all the lights gives my 5.4 Ford enough resistance to warm the coolant to temperature.

 

[crazyoildude]

the heater acts like another radiator... actually in some cases on most newer cars with electric fans if you turn on the air conditioner the other fan turns on and as long as there is coolant flow that will cool the engine off also

 

[Quattro Pete]

Originally Posted By: Bryanccfshr
Turning on THe AC compressor

Ah... good old manual AC. My compressor won't engage below about 30F.

 

[labman]

First of all, I hope you can run the defroster as soon as you start the engine on all cars. Most cars activate the A/C compressor as soon as you turn on the defroster.

You can run the heater as soon as you start the engine, but you won't get much heat until the coolant warms up, so at some point, having the heater on will rob the engine of heat while still doing you very little good.

I think it is the aluminum block, but my 02 Cavalier warms up faster than all the iron block things I ever owned.

 

[mechanicx]

I agree with running the heat slows engine warm up some. I think the biggest factor in warm up time is engine design and type of t-stat bypass but that is a set thing. Most cars, but certainly not all, have constant flow through the heater core and the fan and temperature can be directed for full heat so I imagine they do slow warm up somewhat. Many A/C systems come on in Defrost mode (full air to windsheild) and the Defog mode (air gets directed to windsheild and floor) if the temperature is above 40F, but not below that.

If a car is overheating the best thing to do is to shut it off immediately until it cools off some.

 

[Bamaro]

If you use recirculated air instead of outside air you will heat up a little quicker.

 

[brianl703]

Originally Posted By: Quattro Pete
Originally Posted By: Bryanccfshr
Turning on THe AC compressor

Ah... good old manual AC. My compressor won't engage below about 30F.


Even with manual AC the low-pressure cutoff will keep the compressor from engaging, should the temperature be low enough. The pressure in the system drops as the temperature does. The low-pressure cutoff exists primarily to keep the evaporator coil from freezing over, although it also serves a useful secondary purpose by keeping the compressor from operating if the refrigerant charge is low.

 

[Craig in Canada]

Originally Posted By: MrWideTires
I wanna find out if this is true... as far as I know.. the heater in our cars does use the heat from the engine.


It absolutely makes a difference. I've routinely taken that into account for years. When fairly cold weather sets in I will leave my (otherwise fully automatic) climate control set at a low fan speed unless I'm going on a "long" trip. The engine comes up to temp much faster, which helps mitigate "short tripping". There's little reduction in passenger comfort since we all have winter clothes on anyways and there's still enough air moving over the windows to keep them clear.

If I'm going on really short trips in the winter (ie. forced to go out just to return that rental DVD, just a little too far to walk in winter) I'll shut it the HVAC right off.

To all those "idle for 15 minute" warm up types: My engine (2.8L BMW M52) won't even come up to temperature in an infinite amount of time in sub-freezing temps if HVAC is on auto and it's doing nothing but idling. If I was partially warmed up and had to stop somewhere for the missus to dash in somewhere and leave the car running the warm up stops in its tracks and sometimes the engine temp goes down a bit if the heat is on. There's nothing wrong with my t-stat system, this is simply the low heat generation of idling combined with the heat sink from the HVAC heater. Two previous cars did the same thing.

I'm a "start it and drive gentle" guy, just like the owner's manual says to do. My UOAs are great (both wear and dilution scores) and the engine heats up in a couple of minutes with HVAC fans low and engine under load.

 

[Warstud]

Some cars have a Heater Control Valve which I believe is just another T-Stat to prevent coolant from reaching the Heater Core until a certain temp is reached.

 

[demarpaint]

Originally Posted By: brianl703
Originally Posted By: Quattro Pete
Originally Posted By: Bryanccfshr
Turning on THe AC compressor

Ah... good old manual AC. My compressor won't engage below about 30F.


Even with manual AC the low-pressure cutoff will keep the compressor from engaging, should the temperature be low enough. The pressure in the system drops as the temperature does. The low-pressure cutoff exists primarily to keep the evaporator coil from freezing over, although it also serves a useful secondary purpose by keeping the compressor from operating if the refrigerant charge is low.


That's how the system works. What I was always a little fuzzy on was why doesn't the low-pressure cut off keep the compressor from engaging when the defroster is on? The compressor is supposed to be engaged when the defroster is on, but is it really engaging in extreme cold?

 

[brianl703]

Originally Posted By: demarpaint
The compressor is supposed to be engaged when the defroster is on, but is it really engaging in extreme cold?


If it did, the evaporator coil would potentially freeze up. This happens with the evaporator (outdoor) coil on heat pumps and they have a defrost mode that temporarily reverses the cycle to deal with it.

If the evaporator coil froze up, there would be no airflow through it.

From what I have read on the subject, the compressor will not engage if the temperature of the evaporator coil is below 32F, and the temperature may need to be higher than this for it to engage.