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Old 01-22-2010, 08:11 PM   #21 (permalink)
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Holy Carp! The regular block heater takes about 400 W. Your 1,500 W. tank heater is about 4x that amount!

Ok the temperature hack link. The engine ECU is located between the glove compartment and the passenger side, outer shell. Some unpublished additions.

Part of the development was not only the early warm-up spoof but also handling the cool down:

For example, as soon at the coolant temperature reached 40C, the hack spoofed 70C so the car could go into Stage-4. As the engine warmed up, the PWM duration dropped off.

Around seconds 800, the ICE was off and started cooling down. So when it dropped below 70 C, the PWM cut in to keep the indicated temperature above 70C. Eventually around seconds 1200, it was so cool that the PWM pulses were not quite able to keep the temperature above 70C. Around seconds 1400, it failed to continue the spoof but the coolant temperature was too low and the ICE choked.

This detailed chart shows what I mean by PWM during cool down:

You can see how the hack kept the apparent ICE coolant high enough that the ICE stayed off. It turns out the ICE will start on its own in the 60-63 degree region. So by spoofing the ICE temperature, I could continue in EV mode, headed home. It was a brisk evening.

One of the earlier tests used a fixed resistor and diode:

The problem is it needs to trigger at a starting coolant temperature. Experimentally I found 30C was about as low as it could go w/o the ICE choking. Pragmatically, I used 40C to make sure there was a 'guard band.'

Here are some parametric curves that assumed a simple resistor, no diode, is used for biasing the coolant thermistor:

The problem with a fixed resistor is it doesn't shorten the 70C point that much but as the resistance goes down, it risks triggering a false, over temperature condition. This is why we use a silicon diode to gain the 1.2 V forward bias. As the coolant warms up, the voltage drops below 1.2 V and the diode-resistor network has an apparent rise in resistance. ... Kinda of stupid but effective hack.

When we were still looking at fixed resistors and hadn't considered the diode:

Ok, this was probably more information than you'd expected. But I had it handy.

WHY?

I warmed up our NHW11 in the driveway normally, until the first autostop:

From this systems analysis, we find:
  • 0.100 gallons burned just to reach warm-up temperature.
  • 0.320 gallons burned for 10 mile commute including warm-up
  • 1/3d of the gas just to reach Stage-4 temperature
The thermistor hack offers a potential savings of ~1/3d. So warm-up is a critical part of efficient, NHW11 operation.

I subsequently learned some 'tricks' that I can use due to the lucky geography of our home in Huntsville so I don't have to use the thermistor hack. But someone in a colder climate with less opportunity for coasting in "N" through their neighborhood needs the hack.

Bob Wilson

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Old 01-22-2010, 08:27 PM   #22 (permalink)
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If the fluid level is checked with a dipstick, maybe an oil-type dipstick heater is an option?

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Old 01-23-2010, 04:04 AM   #23 (permalink)
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Thanks for the info, Bob.

Quote:
Holy Carp! The regular block heater takes about 400 W. Your 1,500 W. tank heater is about 4x that amount!
True but you know how massive that tranny is. I figured it was roughly equal to an aluminum block V6 in mass. The 400 watt block heater in my Previa barely warms up the engine afetr a couple hours. having said that 500 to 750W would probably be fine.

Oil dipsticks are only a few watts so they won't fit the bill.
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Old 01-23-2010, 10:22 PM   #24 (permalink)
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Originally Posted by orange4boy View Post
True but you know how massive that tranny is. I figured it was roughly equal to an aluminum block V6 in mass.
Oh. My 5 speed weighs 50lbs and has no active cooling. Now that I know your tranny is a behemoth, the heater makes more sense.
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Old 01-24-2010, 12:20 AM   #25 (permalink)
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It's a monster all right. Have you seen the cutaways.

Copper windings, rare earth magnets, iron cores and steel gears dipped in aluminium.

It's like a white dwarf.

I think it has it's own gravitational field.

You can bend light by shining it tangentially to the case.

They don't call it a bell housing they call it a barbell housing.

Stop me.

Still, 1500 watts is overkill. 750 would be good.
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Old 01-24-2010, 12:27 AM   #26 (permalink)
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SO if it overheats, does it go SuperNova?
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Old 01-24-2010, 12:38 AM   #27 (permalink)
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It's working very well. Today engine was at 40˚C and the transaxle was at 50˚C when I unplugged. I was able to get into S4 earlier than ever and I got a 5.1 L/100 on both of my commutes.

Previously I got 5.3 on the same route and OAT.

I will do a run without heat again to see comparison tomorrow.

I think with a circulation heater on the motor I can get into S4 at the top of my driveway which means the engine will be off for 1/2 of the commute.
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Old 01-24-2010, 12:47 AM   #28 (permalink)
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Quote:
SO if it overheats, does it go SuperNova?
Hell yes!

Then it collapses into a black hole taking you all with me. BWAHAHAHA!!1!

Didn't you know the Prius is a doomsday device invented by Al Gore to destroy the world after the presidency was so cruelly stolen from him?

No?

Uh oh... here we go...
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Old 01-24-2010, 01:39 AM   #29 (permalink)
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Quote:
Originally Posted by orange4boy View Post
Uh oh... here we go...
Actually, our energy crisis would be solved!

To harness the immense amount of fusion energy produced, we'll need a specialized...

"Lock Box"
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Old 01-24-2010, 04:14 AM   #30 (permalink)
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Quote:
Originally Posted by orange4boy View Post
. . .

I think it has it's own gravitational field.

You can bend light by shining it tangentially to the case.
Shhhushh ... you don't want to let them know about the singularity overdrive.

Quote:
Originally Posted by orange4boy View Post
. . . Still, 1500 watts is overkill. 750 would be good.
Any photos? I'm interested in where you mounted the tank.

Is there an altitude drop down the driveway to the house that might put a final charge on the traction battery?

One thing I've speculated but not implemented is a plug-in lite ... topping the traction battery charge. This should provide an extra boost in the morning.

Are you able to use the ~45 seconds it takes for the cats to light off? At work, I'm able to gentle accelerate keeping the ICE at ~1,300 rpm and power is via traction battery while the ICE idles. I can often reach 35-38 mph on traction battery and if the traffic light is right, hit 40 MPG within the first mile.

Bob Wilson

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