I've been a happy RX450h owner for the past year. Educated as an engineer, I've been fascinated by the design of the powertrain. On the highway, fuel economy is somewhat improved due to the Atkinson-cycle engine design. Around town, economy is dramatically improved by the engine being shut down while under light load (when it would be most inefficient from a mileage standpoint). BUT the one regime where the engine is extremely inefficient is in the warmup phase. The computer needs to bring the engine up to temperature and also typically needs to heat the passenger compartment. As a retired home-based investor I often make short trips several times a day. Under this scenario I can see mileage since last fill-up plummet to 15 or 16mpg, as much of the fuel is "wasted" in just heating the system up.

So I wonder: why not insulate the engine block? I've read that about 1/3 of the fuel energy goes out the tailpipe as waste heat, and 1/3 goes to the radiator as waste heat, while the remaining 1/3 does useful work turning the crank. I imagine under driving conditions very little of the total heat dissipation comes off the block directly. So by insulating the block we don't tax the radiator system very much, while allowing a warm engine to stay warm for hours. My city trips would probably go from 16mpg to the high 20's.

Hybrids are a relatively recent technology, but our friends in frozen climes have had to worry about cold engines for many decades. Block heaters are common, but have any auto manufacturers gone further and put insulation around the block? It would seem to be an obvious next step for hybrid engines. It would not boost EPA estimates because I assume those numbers are derived from warmed-up engines, but it WOULD boost real-world mileage because we all frequently use our cars for short trips.

 

Sounds like this would be useful in a very niche market, where temps are consistently below freezing. But, in most areas, I would think running an engine block heater in the colder months would be a better compromise.

Now, when you are describing the "warmup phase", are you idling during this time? Or, are you actually moving? Waiting for the engine to heat up would surely hurt your fuel economy.

 

On the truck forums I visit, a lot of the diesel guys in cold climates (Canada, Alaska, etc) will put covers over their grilles to help warm up their engines and keep them warm. That makes sense because diesels take longer to warm up and sometimes have difficulty staying warm enough to heat the cabin.

 

https://www.clublexus.com/forums/rx-...r-weather.html

 

"Northerners" install a block heater, which is basically a heating element that replaces one of the frost plugs on block, close to the engine coolant. Just plug it in when the temp dips below a certain point and engine will crank in the morning. Covering the grills to restrict air flow to the radiator is also done, but that is not good for city, stop and go drives, works better on the highway.

https://en.wikipedia.org/wiki/Block_heater

 

Just do a search on engine heaters, and pick the one that fits your needs. There's many different types, not just the freeze plug kind .

 

I don't see where blocking off part of the radiator will make the engine warm up any quicker. If the thermostat is working properly (and, on most modern vehicles, it is set to about 195-200 degrees F), the anti-freeze coolant won't flow through the radiator at all until it reaches that temperature and the thermostat opens up, allowing it to be exposed to the cooling flow of air through the radiator vanes and the engine-fan. Before that, the coolant simply circulates through the block, no matter how much of the radiator is covered up. What determines how fast an engine actually warms up is two things...First, how much heat is actually produced inside the cylinders and how rapidly that heat is absorbed by the coolant, and, Second, whether you have your heater on or not. If the heater (or heater-defroster) is on during warm-up, some of the warm coolant is diverted into the heater core inside the cabin (which is actually a small radiator), where it will delay full engine warm-up by transferring some of the heat from underhood into the cabin and defroster. So, in general, the less you use the heater inside while the engine is warming up, the faster it WILL warm up. You can actually watch that for yourselves on the temperature gauge if you tun the heater up or down...turning the heater up will delay the rise of the needle. Once the engine is fully warm (around 200 degrees), it has much less of an effect, and then you don't notice it.

Once the engine is fully-warm, however, covering part of the radiator will probably help to keep it that way by doing the obvious...restricting the amount of cooling air flowing through it. But, again, that doesn't necessarily help with warm-up...it only prevents heat loss through the radiator once the engine is warm and the thermostat opens.

 

You would only want the engine to be insulated during the warm-up phase. After that you do not because you do not want the engine block to overheat. That is why they recommend that you turn your cabin heat on high if you notice your engine overheating.

I do not know of anybody here in Canada who insulates their engine block. But engine block heaters (on a timer) are prevalent and residential area parking lots (I saw in Northern Alberta) have an electrical outlet at every parking spot so that you can plug the car in overnight.

 

How would that work while the thermostat is still closed (as is typical during the warm-up phase)? No matter how much of the radiator is covered, the coolant never actually gets past the thermostat, to the radiator itself (it merely circulates around the block) until it reaches around 195 degrees and the thermostat opens.

 

That's a great explanation. Essentially the engine block is the insulator of the coolant when it is cold but then when it is up to operating temps and is shut down, it also is designed to cool the engine. That's what you want. To speed up the cold start process, manufacturers provide the engine block heater which keeps the coolant warmed up through an electrical outlet.

Yes, this is how it has been done for decades across the prairies and up north. Engine block heaters and gentle driving to start the trip so that the engine warms up under load. Seat heaters actually do a great job of making sure you stay reasonably warm while avoiding trying to blast heat from a partially warmed up engine. That's how I do it.

15-16 mpg sounds low even for that generation of RX on short trips. I would look at the gasoline side and see about maintenance items. Plugs, coolant flush/fill etc. The only other option would be to get a much smaller vehicle with a 4 cylinder for those types of trips. There are various oil heaters or other types of devices but the good old reliable block heater is the best. If you need to have a warm car, the other hack is to add a cabin heater on the same circuit as the block heater. This keeps the inside nice and toasty when you're ready to go.

I didn't think Oregon gets that cold.

 

The coldest areas have engine block heaters all over the place. Shopping malls, home, hockey areas wherever. Usually that does the job.

 

No, I'm not talking about using an engine block heater. That would certainly be useful if the car is cold-soaked overnight in very cold weather--and if a power cord were nearby.

What I wonder is why the hybrid maker couldn't fabricate a thin block-hugging insulating blanket so that the block would be very slow to cool down once the engine was turned off. Up here in Oregon right now it's perhaps 40 degrees Fahrenheit during the day. Say I drive to get a haircut, the engine almost reaches operating temperature by the time I get there. I come out 30 minutes later and the temperature gauge is back on "C." With insulation it would probably have dropped only one notch or even less, and I'd be getting 30mpg on the drive home. Plus, instant cabin heat.

Yes, adding a blanket would not allow the block to radiate heat, but I have a suspicion that block cooling is only a few percent of the total heat exchange, something the radiator could easily take up.

Anyway, just a thought, but I won't be surprised to see this as standard practice on hybrids (perhaps even non-hybrids, though the gain would be less) five years from now.

 

I think you would need to talk to an car engineer. I don't see a block wrap keeping much heat in so that you could then save on emissions or EPA. All of your other components need to be up to operating temp to work. Your idea is exactly what an engine block heater would do in very cold areas in the West and up in Western Canada.

 

A few ideas on this topic....I am that driver who feels annoyed when a hybrid driver is keeping his vehicle in electric mode but not keeping up with traffic lol I merely feel we should be considerate whether it's gas, diesel, hybrid, or electric...

Are northerners different than northeasterners...I've experienced about 6F, which is cold but granted not cold cold, no issues starting non-garaged vehicles. The BMW has full heat by the time I reach the end of the driveway, and I don't live at Southfork (short driveway). It by design also has heat when the motor is not running, a feature I have only used 2X, but it works well. After about 30 min. without running the motor, it does start to get cold. Thought it was pretty clever of engineers to do that, but Germans are against idling motors and remote starting from what I understand...I see people do it all the time here in the states, summer or winter...

Where Germans need to improve is yes they provided heated nozzles for the windshield washers since the 80's, but if you don't use factory authorized washer fluid (that's what BMW says), then your washer pump may become clogged and pressure drops. They feel a need to install a filtering screen that is not accessible without removing the right front tire and fender liner! My Nissan does a lot of sitting, yet the thing starts up first try and windshield washer jets have stayed very strong for 19 years!

 

There is a reason OEM's haven't insulated the engine block, it needs to breathe, aka radiate heat when it gets up to temp.

I remember watching Ice Road Truckers a few years ago, up there in places like Fairbanks, Nome, Prudehoe Bay, where it stays below 0F most of the winter, they never shut off their diesel trucks and a lot of them have a blanket over the radiator grill. Its a miracle if they can get a piece of unused equipment/truck/generator that has been sitting outside to start as well, a lot of times it involved them plugging in a block heater or moving the piece of equipment/truck inside to their garage for 24 hours, squirting ether into the air intake, it was a real PITA. Then they'd have water in the air lines that would freeze, just a really harsh environment on their equipment.