Coolant Temperature Hack. Better MPGs!

[TheForce]

Originally Posted by JoesMorgue

I saw your vid. Is this an immediate thing, or does it take time for that to come up?

You control how fast or slow the temp rises or falls with the POT but as the coolant gets warmer the temp will rise unless you manually lower it.

Originally Posted by richard schumacher

Now, who can tell us why Toyota didn't design the car to do this automatically?

Because you can damage the engine? Because priority number 1 for the Prius is low emissions?

[JoesMorgue]

OK, I have little electrictical experience, can you explain how the POT controls the temp? Can the minimum temp be permanent setting?

Originally Posted by TheForce

You control how fast or slow the temp rises or falls with the POT but as the coolant gets warmer the temp will rise unless you manually lower it.



Because you can damage the engine? Because priority number 1 for the Prius is low emissions?

[KK6PD]

Originally Posted by JoesMorgue

OK, I have little electrictical experience, can you explain how the POT controls the temp? Can the minimum temp be permanent setting?

Easy
Basic Ohms Law.
You put 2 resistors in parallel, say 100 ohms each. Than the total net resistance for that circuit is 50 ohms.

In the case of the Prius heating circuit the Temp sensor is a Thermistor, that is a temperature sensative resistor that changes its resistance with a change in temp. If you start out cold and the thermistor reads, well lets say 10k ohm ( Just a number picked out of the air, but it will work for this example)as the temp heats up the thermistor resistance will either drop or increase depending on the thermistor type.

The Prius wants to see a specific value of resistance when warmed up. That indicates to the computer that all is correct and the ICE can now stop running just to heat uo the engine block and catalytic converter.

By adding the "POT" or variable resistor in parallel you can fake out the computer into seeing a FALSE resistance indication that the system is up to temp and it will shut off the ICE, thus saving you gas.

Tha problem, as indicated, as the engine really does warm up, the thermistor will still change and combined with the POT's value could add to a resistance value that completly fakes out the computer, and can shut you down, thinking that there is a overheating problem, when in reality its just running just fine, but the Thermistor data is grossly incorrect!

Simple, now lets put a man back on the moon!!

Hope this makes some sense!!!

73 de Pat KK6PD

[Flying White Dutchman]

NICE
I think i am going to have a try at this!

is there any damage that can happen when you go to S4 or S2 and skipp the startup warmup of the engine?....

[sandman]

is there any damage that can happen when you go to S4 or S2 and skipp the startup warmup of the engine?....

Correct me if I am wrong, but I don't think this is used to skip the initial startup warm up. I think it is used in his case (because he is Warp Strealthing so much with that extra battery) to keep the ice from coming on ..But I think it could benefit all drivers in keeping the ice from coming on during stops around town when the motor is warm already..Just my opinion of course..

[TheForce]

Well I should let you know on my way home I was able to get 212MPG compared to my 195MPG on my previous trips. I think this hack may help me stay above 200MPG if I'm lucky.

[MR.K]

Do you know what is the voltage @ 170 degrees....to use a pic chip that would be useful....also...................235 vs 377MPG.....is that per tank???

[ken1784]

Originally Posted by TheForce

One thing I noticed is that a good warp stealth temp seems to be between 160F and 170F. In between those temps I was able to draw about 50 amps off my Hymotion pack. If the temp was above about 170F I could only draw about 20 amps. I don't know if this is a temp related fact or if its related to how much juice is in the battery. I will have to do some more tests to find out.

It's an interesting observation.

The Prius thermostat starts to open at 82C(180F) and we see the typical temperature is approx 86C(187F) after complete warm-up and such temperature is used to be recognized as an optimum temperature.
The thermostat is closed at 170F, and it is still in a warm-up stage.

Ken@Japan

[JoesMorgue]

I personally am thinking of this because of the way my wife leaves my car after she drives it, usually green, if I can get into the stealth mode and run it down from the green instead of the car just burning it off.

Originally Posted by sandman

Correct me if I am wrong, but I don't think this is used to skip the initial startup warm up. I think it is used in his case (because he is Warp Strealthing so much with that extra battery) to keep the ice from coming on ..But I think it could benefit all drivers in keeping the ice from coming on during stops around town when the motor is warm already..Just my opinion of course..

[Bobwho]

Perhaps it has to do with EPA regs? Meeting California emissions?

Or just an engineering oversight? No one thought of it in the rush to get the car developed? This happens all of the time with sales asking for things and engineering getting bad information.