Keeping Engine Coolant Hot
 

I read somewhere a while back that the Prius or Insight uses a special canister that stores the engine coolant after the car shuts down. It keeps the coolant super-insulated so that it stays hot longer, even overnight.

I'm wondering if there's a $5 mod that would make much difference -- installing ducting insulation wrap around the coolant reservoir.

It might not keep the coolant hot overnight, but it would keep it hotter if you leave the car for 2-3 hours.

Question about this is, would that also make the coolant hotter while running?

I looked into replicating Toyota's design over this past winter. Its a fairly complex setup with sensors and an automated valve and pump that controls flow to the thermos. Their setup is really ideal, and also not easy to replicate. Its also really the only way that is worth while IMO.

Insulating a coolant reservoire in most cases is going to do nothing. Reservoires are usually outside of the normal coolant loop so they never heat up (there are exceptions of course). In that case, insulating the reservoire still will not really not help much. If the reservoire is after the radiator then the coolant in the reservoire is already going to be cooled down. If its before (and I'd tend to think this isn't the case just due to plastics and their vulnerability to heat) the radiator then you may see a small benefit, but still not much. This is because when the engine warms up the thermostat is closed and the coolant circulates only inside the engine block and head until it is up to temperature. At this point the thermostat opens and lets cool coolant into the engine to cool it down. If the tank was insulated it would simply flow the warm coolant through until it got cool coolant again.

I have a possible solution that may only work during the day.

I have used ambient temperature plates in my refrigerated keg setup for some time now. Basically they are plates that when powered will either maintain a 20 degree cooler air temp or 20 degree hotter air temp depending on which way its switched. I would suggest gutting a couple of those coolers and attaching those plates to the sides of your radiator and powering it with solar panels, unless you want it to draw power from your battery all the time.

Just an idea to spark further investigation ...

I can see it now... hood/roof mounted passive solar coolant heaters...

http://www.builditsolar.com/Projects...g/PipeCoil.jpg

Why not!?
 

It'd be a good use for those fancy clear hoods all those tweaker rice burner drivers install.

Hi,

This is something that all car makers should be doing. Quicker warm up is a good thing!

You could maybe do a custom metal tube lines in place of the radiator hoses (I used to have pics of a setup on a straight-6 67 C10 that had this) with rubber joints for the bends and where it connected to the radiator and engine. Then grab some exhaust wrap and wrap the inlets and outlets from the radiator and engine... Possibly wrap the side tanks on the radiator too. All the cooling action happens in the fins so it shouldn't effect cooling. Maybe have a display reading trans temp since it's cooler is typically inside the radiator tanks on a typical car.

Not sure if that's totally what your looking for, but that's about as much as I'd want to insulate the cooling system on the car.

The reservoir's main goal is to collect coolant that flows out as the engine heats up (typically in an over heating situation) and the coolant expands in volume. Older cars used to just dump it on the ground via a rubber line that ran down under the car.


::edit::
Two examples of metal ratiator lines:
http://i42.photobucket.com/albums/e3...5/DSC01030.jpg
Straight metal pipes


http://i42.photobucket.com/albums/e3...6024Custom.jpg
Universal metal bendy hoses

There is a seperate thermos type resivoir on the prius, and when the car is shut off they pump it full of hot coolant. So when the car is restarted they put the hot coolant back in to the main system and "preheat" the engine a bit without wasting hardly any energy to do so.

I see what you mean.. Maybe use a 2nd reserve tank (junk yard hunt) with a small electric pump that can pull a gallon or so of coolant out of the system, and have it heated by a small electric coil. Start the engine, reverse the pump, and back into the system it goes. Though it would have to be manually controlled.

This is not a worthwhile mod guys, just slap on a oil pan heater (use block heater too) and plug your car in 30min-1hour before you are going to use it.

The issue with that is, you have to wait 30 min - 1 hr before driving. The Prius' system is instant. Adding a block heater as well will defintely help considerably, though, especially with engine wear and drag created by thick oil.

The easiest way I can think of for an instant system is to tap the coolant drain plug on the block and run a braided line to an accumulator. These are usually made for oil for prelube purposes, but should also be able to use coolant. It's a piston inside a chamber that will release and collect fluid depending on pressure, or by using a hand operated valve. Just insulate it, open the valve to collect hot coolant (pressure is much higher when hot), close the valve and shut the car off. Get back in later, open the valve to release the warm/hot coolant, and start the car. There are even remote mount electronically controlled valves if you don't want to mount the accumulator in the cabin.

The only issue I see here is with the capacity of the system. The largest normal oil accumulators I've seen are 3qt, but it's possible they may be produced in larger sizes. Does anyone know how much coolant the Prius collects?

The Prius uses a 3L "thermos" reservoir.

It's called an accusump.

Canton Racing Products

1, 2 & 3 quart accumulators. You would have to insulate it yourself. Electric valves are available.

Normally they are used with drysump oil systems with a large resovoir. The small cooling resovoir may present a problem. There may not be enough volume to empty the accusump.

A system with a pressurized "overflow" bottle may be the way to go. You could increase the size of it with an auxillary tank with an upper & lower hoses. You need to make sure the tank has air in it.

Don

You can't always heat the coolant or the oil except with propane type heaters.

I was looking through old PopSci magazines and I found an article about using a thermos with molten salt to keep the engine's heat (Popular Science, June 1994, p.38).
It's called a Schatz heat battery and was apparently available in 1994 VW Golfs and Jettas. I wonder how well this system worked, and if it can still be found in junk yards?

Awesome idea. Use the phase change of the material to hold much more energy. I know I've read about it before, just not related to cars. Its really a great idea I think.

Unless you live in a climate that is extremely cold and has inexpensive electric rates, it usually doesn't pay to do this either. The small amount of gas you save is offset by the cost of the heater itself plus the cost of operating it.

Here's another PopSci: Popular Science, June1990, p.29.
I also found this link on the Schatz heat battery: Engine waste-heat storage.
600Wh is about the same as what you'd get from a block/coolant heater, but it's free and remote, and lasts for a few days.

This article said the melting temperature of barium hydroxide is 75*C, Wikipedia states 78*C. That may be a little high. My coolant temp hardly ever exceeds 78*C (during winter only on long uphills), and there are more efficient turbodiesels than mine (like 1.2TDi, of VW Lupo and Audi A2 fame), which have even lower temps, so the medium may never melt. On the other hand, any thermal help for a cold engine is good.

I googled around, but it seems that this in the news in the early '90's, VW and Saab fooled around with it, and then Hush! I wonder why it never went mainstream? Cheap oil, like usual?

Insulation technology has come a long way in recent years. I just finished up work on a Can-Am Commander 1000 X.

Installed a heater and insulated the interior panels around the engine and floor under the seats, both to reduce noise and to keep heat out of the interior in summer and hold heat in the interior in winter. (The rig has a Mammoth Skins rear panel and side curtains, BRP factory plastic roof and windshield option.)

I used two different materials. One is a non-woven fabric, about 1/4" thick with aluminized plastic on both sides, reinforced with a mesh, probably fiberglass. Supposed to withstand very high non-contact temperature. The other is Hushmat, a black, tarlike substance with heavy gauge aluminum foil on one side. Somewhat less expensive than DynaMat.

What might work well for insulating a hot coolant tank or PCM heat storage is cast in place foam. Smooth-On has silicone and urethane foams in a range of density and hardness. A low density, rigid foam would be what you'd want for stopping convection and radiation heat transfer.