Prius, "oil thermos"

bob_ninja · Jan 13, 2006

A friend drove me in a Prius the other day. When we parked and he stopped the car there was a sound like a small pump. He said that the car has a "thermos" (well insulated container of some sort) into which oil is moved while engine is not working. That way the oil keeps most of the heat and the next time you start the car oil is already warm/hot (sent back into the engine of course).

Is this true? Are there articles some place on this topic? What do you think? Would this reduce/eliminate cold starts damage? Comments.

shanneba · Jan 13, 2006

A qiuck search on Yahoo for "Prius oil thermos"
turned these up:

Prius Chat Coolant thermos
What is that sound I hear when I turn off the Pirus?

simple_gifts · Jan 13, 2006

It is a coolant thermos.

Tosh · Jan 15, 2006

From the second link above:
"This thermos-type container stores three liters of coolant at close to boiling temperature for up to three days. When the Power button is pressed, hot coolant is injected into the engine coolant passages, avoiding a cold start. This reduces emissions at startup, as well as wear and tear on the engine."

From my internal dialogue:
"Just when I thought the hybrid drivetrain itself was too complex."
"Hmm, three liters of close-to-boiling coolant. I wonder if that wouldn't be useful on my car?"
"Extra valves, pump, plumbing, sensors, thermos...."

moribundman · Jan 15, 2006

Is the Prius gas engine very small in size?

bob_ninja · Jan 15, 2006

shanneba,
Thanks for the links. I was looking for something more detailed, a tech article from an expert.

Tosh,
From the diagram it doesn't appear to complicate the design that much. It is just one more hose and a container.
On the other hand, the benefit could be substantial, depends on several things. Here in Canada, we have low temperatures (sub zero C) half a year. The driving pattern for many people is short distance with many stops. People tend to drop by to different shopping centers for stuff which tends to result in many short trips sepearted by 1-2 hours. Therefore, the thermos keeping coolant warm can keep the engine block near the operating temperature all day long. That in turn can dramatically reduce damage from cold starts as well as improve fuel efficiency.

Anyway, these are just my thoughts and I was looking for an expert analysis.

Of course, in warmer climates (southern US for instance) it is not as useful.

simple_gifts · Jan 15, 2006

The Prius engine is 1500 CC and uses the atkinson cycle. It is NOT the same engine as the echo; the block my be the same, but the cr is much higher.

FYI, if the cooling system is similar to the echo, it holds a whopping 5 qts.

Pablo · Jan 15, 2006

pretty cool, IMHO.

Bryanccfshr · Jan 15, 2006

I think it's a great idea. Lower emissions, less wear andinstant heat in the winter.

rpn453 · Jan 15, 2006

Definitely an interesting concept. I like the idea! I wonder if an economic analysis would prove it to actually be worthwhile though, since the Prius isn't much more than a technological showcase at the moment? I guess we'll find out in a few years if it becomes common.

Vstrom · Jan 15, 2006

I suppose Toyota figured on what happens when you inject hot coolant suddenly into a very very cold block...cause we all know what can happen when you dump cold coolant into a very hot block....CRACK or WARP

PS- Toyota usually does their homework, except for their sludging engines

oilyriser · Jan 15, 2006

This preheat could allow 100% un-dehydrated ethanol (moonshine) as fuel. For the extreme north you could put a tiny block heater inside the thermos to keep it hot.

bob_ninja · Jan 16, 2006

Vstrom,
Good point. What is the evidence so far? Are there many damaged engines due to temp difference?
During winter here engine block can go down to about -25C, while the coolant is near 100C, so 125C difference.

steveh · Jan 17, 2006

I just can't imagine the cost of maintaining a hybrid when the warranty expires.

pa04prius · Jan 17, 2006

I haven't heard any reports of damaged engines from even Alaska and northern Canada. Remember that there is only 1 liter of hot coolant and at best it tempers the remaining coolant on start up. The car doesn't seem to warm up any faster than any other, but there are small electric heaters that help clear the windshield faster when starting out.
The cost of maintaining the hybrid will pretty much depend on the quality of the build from the factory. I would not buy a hybrid from a domestic manufacturer since they are not noted for long-term reliability. Toyota is, and I believe they put some extra effort into the Prius just to prove that it's a long-term system. Time will tell, but with almost 46k miles on mine, I haven't had a bit of trouble.

rpn453 · Jan 17, 2006

I don't think the thermal shock is going to be an issue. Manufacturers usually do some pretty serious testing cycling from very low temperature coolant to high temperature coolant while running at full power to make sure it won't cause failure.

eljefino · Jan 17, 2006

I wonder what would happen if they just insulated the block itself with some type of foam?

The thermostat should keep the cool radiator coolant out, somewhat.

I figure the future is near-- and not just for hybrids-- for electric water pumps and computer-driven solenoids replacing "dumb" thermostats. Imagine running a few degrees warmer at interstate cruise for that last MPG.

oilyriser · Jan 17, 2006

I wish Toyota would make a non hybrid version, or give the Corolla the same aerodynamic shape. You'd get 50 mpg on the highway without the extra hybrid costs.

stringsattached · Jan 17, 2006

PZEV's are required by law to have a 15 year/150,00 mile warranty on all emissions control systems. http://www.driveclean.ca.gov/en/gv/faq/index.asp#13

If something was going to fall apart on these cars, I would bet it won't be the thermos thingy. Sounds like a great idea; I wonder how expensive they are/if people in colder climates would be willing to pay more for it as an option on a non-hybrid.

quote:

I suppose Toyota figured on what happens when you inject hot coolant suddenly into a very very cold block...cause we all know what can happen when you dump cold coolant into a very hot block....CRACK or WARP

I'm sure their company "strongly considered" the risk.

rpn453 · Jan 18, 2006

quote:

I wonder what would happen if they just insulated the block itself with some type of foam?

It would probably be similar to my old Grand Am, which was insulated by a thick layer of sludgy oil from a valve cover leak that must have been there for quite a while. I never bothered cleaning it. If I plugged it in (450W block heater), it would remain at near-operating temperature and blow hot air right when I started it. Great for winter, but might not be so great in a really warm climate?

quote:

I wish Toyota would make a non hybrid version

Me too!

Prius, "oil thermos"

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