Possible improvement to the car for cooler areas?

1/ reservoir remains the same unless you increase the cooling system capacity
2/ The engine driven coolant pump circulates coolant around the engine to keep temperatures even through the engine, the thermostat prevents coolant flow in the radiator until it is needed. The engine never spins as fast as the same engine in a Yaris, it is quite slow reving, topping out at about 5000RPM so there is little danger of cavitation.
3/ The engine runs to replace heat lost not to pump coolant. The belt drive is more efficient than driving the generator then a motor through an inverter. Each process is about 90% - 95% efficient while the belt drive is also about 90% efficient so using about 15% less energy than electric.

The water pump and it bearings are proven reliable, and they are off the shelf parts used in other models so cheap to make. I stand to be corrected but I think the belt driven pump is fine.

 

interesting thought. it does bring to mind... exactly what is the mileage hit on a water pump?

 

Hi Pats...,

An electric motor can be shut down, or run at lower RPM/Power in cold weather. So even if the belt and generator/motor efficiency is the same or a little worse than a belt drive, the electric coolant pump can use less energy.

The electric coolant pump is also advantageous for those desert mountain climbs, as the electric coolant pump can run at a much higher RPM while the engine is under high toqure low RPM loads.

 

cmon man!!

high torque, low RPM???

we all know that Toyotas CVT will NEVER let that happen!!!

 

Belt-driven water pumps are by far the simplest, lowest maintenance and least-cost-to-replace-or-repair of options for water pumps. You want to heat the cabin quickly? You have a ~250 volt battery system with enormous capacity that you could use to heat a large set of electric coils with only one conversion - from electrical energy to heat energy - rather than the three required for using engine heat. Efficiency is already good the way the car is done.

One more electric motor is that many more parts to worry about, another electric circuit to fuss over, and many extra energy conversions that are unnecessary. A belt-driven system using pulleys or a chain-drive using sprockets can approach mechanical efficiencies of 98% and is among the highest-efficiency mechanical drive systems available on Earth today.

You do -not- want to have a variable-speed electrically controlled coolant pump in this car. It would decrease efficiencies and increase TCO (total cost of ownership). Think of it like a shadow tax.

I realize I'm duplicating someone else's post, but I feel it's necessary to drive the point home to Prius owners.

 

What exhaust heat would you get with the ICE down? I think very low, if any.
Maybe I am missing something.


I think that using the battery to power some kind of heating coil is a good idea for short periods of time (traffic lights).

 

Ok,

high power low-speed (low cooling air flow)...

 

What a great idea. I'm gonna run a hose from the exhaust to the cabin right away..

 

Folks,

The heat to keep the interior of the car warm has to come from somewhere, and in the Prius there's really only one place it can come from - the gas tank. Using the traction battery to heat the cabin (even with the AC acting as a heat pump) introduces far too much inefficiency as an earlier poster mentioned. Putting the waste heat of the ICE to use in keeping the cabin warm instead of throwing it away in the atmosphere is the best thing to do with it. There's a tradeoff, though, since the ICE needs to stay warm enough for good emissions, so reducing heat loss period is the best approach when it's cold outside. When it's cold, the ICE is not really running to circulate coolant to the cabin so much as it's running to generate heat.

The best approach (IMHO) would be better insulation for the cabin. I might be wrong, but I don't think the roof is insulated at all, and there's got to be a lot of heat loss there. That would help with AC in the summer as well. Another possibility could be a temperature controlled grill block-off door to keep the ICE from cooling off as fast in the winter.

Side note - the ICE water pump is the only thing driven by a belt on the Prius. Most engines with timing belts drive the water pump from the timing belt, and I think there are a few engines that drive it from the timing chain (GM Quad 4 comes to mind - not a great example though.) It seems to me that with a chain-driven ICE water pump in the Prius, you could eliminate the crankshaft pulley completely. There would be several advantages - no belt to replace, no moving parts on the front of the engine, no front main seal to leak, better lubrication for the pump, quieter operation, etc. I see two potential disadvantages - one (and it's a biggie right now) is that eliminating the crank pulley means that the engine front cover design would be specific to the Prius - every non-hybrid car has at least the AC and alternator driven by accessory belts. The other is that a seal leak could potentially be a larger problem than normal since it would leak water into the oil.
Just my gearhead side coming out...

-Ben

 

I thought the Prius already used an electric coolant pump, or is that just to cycle coolant to/from the thermos?

Prius has those puny 12 vdc PTC electric plenum heaters. I'm sure they work fine in tropical climates, but at -20 C and colder they don't do too much. Apparently, the new 2008 Ford Super Duty with the new PowerStroke offers electric supplemental cabin heat, folks who have one claim it works well

I would have liked to see the primary NiMH battery used to power supplemental electric heat. In winter the battery SOC is almost always green anyway, so there is plenty of spare charge to keep the footsies warm

The best mod any Prius driver in a cold climate can make is to fashion a "winter front" for the grille. The car warms up much faster and you will have a lot more heat

 

If I was a Toyota car designer (I'm not even equal to a Toyota designers toe nail) and I wanted to overcome this issue I'd go with reverse cycle air conditioning.

I think the roof has a thin layer of insulation from pictures I have seen.

How about an engine block heater and a small ceramic heater to preheat the cabin using household electricity?
Oh and a scan gauge and grill blocking would help too.

fruzzetti, thanks for your support.

 

Hi All,

The maintenance advantage of an electric coolant pump is that it there is no side load (as there is in a pully drive). Which will result in very long bearing and seal life.

Additionally, there might be away to do away with the shaft seal altogether, if bearings can be found that will run in coolant (hybrid ceramic ball bearings with stainless steel races are my guess). In which case the rotor magnet could couple to the drive from the coil through a thin wall of aluminum cast into the cover.

 

From my last post, you may have missed it.
2/ The engine driven coolant pump circulates coolant around the engine to keep temperatures even through the engine, the thermostat prevents coolant flow in the radiator until it is needed. The engine never spins as fast as the same engine in a Yaris, it is quite slow reving, topping out at about 5000RPM so there is little danger of cavitation.
Cavitation does occure in engines opperating over wide rev ranges. A rotary idles at 750rpm and revs to 7000rpm stock. The cooling system has a very high heat load to dump so flow rate needs to be high even at low revs. Cavitation is also caused by flow restriction when the thermostat is closed. The thermostat in a Prius and all modern Toyotas is the bypass type that allow coolant to flow around the engine (see above) when the passage to the radiator is blocked.
I say the Prius is a low reving engine compared to it's sister the Yaris which uses the same block and head castings. Prius idles at 950ish and tops out at 57kW @ 5000 where the yaris puts out 80kW @ 6000rpm the coolant pump is having a holiday in the Prius.
There would be limited gain grom being able to shut the coolant pump off unlike a thermostatic fan where vehicle movement moves air over the radiator fins when the coolant pumps stops there would be minimal flow causing heat stress in the engine due to uneven heating.
WHen the ICE runs just to heat the cabin it also charges the battery, heats the cat and maintains the cylinder head at the best running temperature. If an electric coolant pump was pumping heat out of a static ICE it would need to run an enriched mixture to run smooth while building the temperature up to ideal again.
Do you have a fan forced gas heater at home? try lighting the heater then turn off the gas but leave the fan on, wont heat for long and nor will your petrol driven heater in your Prius unless you feed it petrol.

 

Hi All,

I wonder if its possible to make an insulating blanket with magnets and stick it too the cabin ceiling ? Or if the present ceiling materials are too thick ?

 

Hi All,

Another thing one can do is modify the window to be double-pained. Stick-on Polycarbonate glazing might work. The inside rubber seal will need to be modified. The double stick tape would make an air gap. This would work for the rear window.

Only trick to it is forming the cast plastic sheet to the shape of the window.

This might even help with rear window fogging.

 

Hi folks,

Looking at craigk's sunroof install pictures, it doesn't look like there's any insulation on the roof. Of course, it might have been removed for the picture... A blanket of insulating material between the metal roof and the headliner might help a lot.

Didn't I read somewhere that the Prius has special thermal windows (low-e or something like that) already? Double glazing would be a real gain, though, as so much of the cabin is glass, and pretty easy for Toyota to do for the fixed windows like the hatch and windshield - they could be packaged, similar to house windows. Add-ons like donee mentioned would work too. The door windows would be trickier because of the exposed edges and the extra thickness.

Electric cooling pumps tend to have more issues than their pulley-driven counterparts, despite the lack of side load. How many of us have coolant transfer pump issues - and this pump doesn't run all of the time? VWs (bastions of quality that they are) have lots of issues with their electric coolant pumps also. The risk with a magnetically coupled pump impeller (VW does this) is that it can jam up internally and you won't notice until the car overheats.

-Ben

 

It's not exactly cost-effective to build vacuum-sealed, double-pane windows in a curved shape to fit the track of the car. I thought of this a while back, or using a similar idea with two separate rolling mechanisms - one for the glass itself and one for a very dark, opaque or mirrored tint (to use when parking on hot days). A car is very bad for acoustics and heat insulation. I think patsparks got it right, and I think the best way to do it is a multi-stage electric heater run by the big-boy batteries. Use a ceramic element and slate heat dissipators. It would work wonderfully and instantaneously and it would be cheap, both in terms of resources and expenditure.

~ dan ~