Automatic Coolant Temp Hack for Better MPGs

I'm no longer selling these because I ran out of parts. So if you want one your going to have to build your own.

If you have any questions about the ACTH or its use just ask.

JeffreyDV has confirmed that this design works for the 2004 Prius.

Hurray !!!:cheer2:
One more in the road.

This is probably a dumb question and I may be crazy, but why couldn't someone just locate the coolant temperature sensor and measure its cold resistance and resistance when the ICE comes up to temp of say 180 degrees. Then rig a switch in the coolant temperature sensor circuit to swap the sensor out for the calibrated 180 degree resistor for ICE temperature spoof. Maybe the coolant temperature sensor is not a variable resistance type sensor?

I think what you describe has been done.

The one on the right.


The problem with that is that you cant monitor the real temp at the same time. The reason you want to monitor the real temp while faking is so you dont have overheat condition or a too cold condition. If the real temp is below 100F and your faking at 170F and the engine wants to start it will stutter and possibly give you some error lights and codes. Also with switching over the fake temp like the pic on the right you might get codes just by the switching process.


I have been working with Bob Wilson on his micro controller controlled hack that has hot and cold protection. I have not been successful yet because I dont understand the MSP430 micro controller and how he is using it to figure out why its not working for me.

I am however working on an Arduino version based on Bob's version. I hope to duplicate what Bob has done but also to include a real time adjustable settings so you can set your start and fake temps.

I will post about my Arduino temp hack as soon as I get it working.

Though I am a welder I am not worth a d**mn at soldering nor would I know what to buy in order to build my own .I have read all the conflicting ideas to your mod., but I want one .Please don't give up on such a good Idea What can I do or say to get you to build another?

Sorry but I'm no longer building the ACTH because I don't have any more parts.

That's too bad. This looks like something I could use for my very short commute in cold weather. Many times I it seems to stay in the low 150's 'F and it may not get to 157'F until I'm already at work. To be always in S3 for the one nice downhill on my commute would be great.

I could buy the parts and do it myself since you have the whole schematic shown, but I don't trust my soldering skills. If plugging in my EBH longer doesn't solve the temperature problem, I'll have to rethink that.

To anyone wanting to build this I would wait until in get the Arduino version working as it will have more features. Or at least I hope it will have features. One thing the Arduino version will do is have cold protection as well as hot protection. Plus the Arduino version will be much simpler in design.

This is an interesting hack. The intent of the OP is to save fuel.
Thinking on this the other day, I was starting out on a cold day with a cold car and a short trip.
I started playing with the Auto A/C. If I turn the Auto off when I am at a stop light or gliding, the engine did shut down to 0 rpm even when cold. When I started moving again, just flipped the Auto back on for heat. Im sure I was past S1, but not even sure where the stages are after that. It did seem to help on the consumption overall.

Kind of does the same thing as the hack, allowing fuel saving when cold and the engine is not needed for power or charging.

Just wanted to toss this in. Seems to to a similar job, with a manual flick of my left thumb.

ACTH can be used to hack Prius Gen3?

If you where I can connect the pin 18.

Thanks

See this for Gen3.
http://priuschat.com/forums/gen-iii...s/76906-yet-another-thermistor-hack-gen3.html


And for the current Arduino controlled version of the hack see here.
http://priuschat.com/forums/gen-ii-...-automatic-coolant-temp-hack-better-mpgs.html

I do not know how to program Arduino.
I wanted to build this thermistor hack because it has protection for warm ice.
In pin18 I think there is 5V DC?

I dont know where there is 5v for the Gen3. You will have to look at a wiring diagram to find that.

If you can build this you could build the Arduino version. You dont have to program anything. I have the source code posted for it. Just use the Arduino software to upload the source code to the Arduino board. Its that easy.

But if you dont need cold protection then building this version would be cheaper. But the start temp and fake temp are effected by the ambient temp. This is because the transistors are temperature sensitive.

I am interested in fixing the temperature to 70C for make full use of the EV mode.
If I use a voltage regulator for the 5V, is ok?

I'm no electrical engineer but I think it should work.