Coolant Temperature Hack. Better MPGs!

[Flying White Dutchman]

when i pres the EV button right after hitting the power button it Will not start warming up
only after the SOC drops below 45 or something then it starts and begins to warm up
at that point i can shorten that startup with this mod..

[carz89]

Originally Posted by 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.

You gotta be kidding me! Over what distance, terrain and driving conditions did you achieve that? If one can consistently achieve 200 mpg in a Prius simply by falsifying the engine coolant temperature, then I would presume this would grossly outweigh the environmental advantage of keeping the catalytic converter hot to reduce emissions.

Thus, I'm skeptical you could consistently achieve even half of that mpg (100mpg) with this mod under typical driving distances and conditions. Perhaps you could significantly boost your MPG this way if your commute was very short. But why go through all the trouble, when an engine block heater would provide the same benefit for a couple pennies on the mile?

Those engineers at Toyota are a pretty smart bunch, and I'm sure they experimented with different thresholds of temperature control before arriving at the present system.

I'm very interested in this entire issue of temperature control and modes. My own commute is just 4 miles of flat terrain with about 10 stop signs or traffic lights, speed limit 30mph (which I exceed a bit in order to pulse and glide, when possible). Before my scangauge, I would average about 48mpg. With the scangauge, which provides me better awareness of engine status and modes, I now average about 53 mpg. My coolant temperature doesn't achieve the target 185 degrees until the end of my 4 mile commute. Last night I did a simple experiment --- I drove to work, then turned right around and came back. With the engine completely warmed up and in Stage 4, I achieved 85 mpg on the return trip. Based on that experience there is absolute no way I could achieve even over 100 mpg with either a truly warmed up engine, or a faked-out coolant temperature.

[JimboK]

Originally Posted by carz89

You gotta be kidding me! Over what distance, terrain and driving conditions did you achieve that? If one can consistently achieve 200 mpg in a Prius simply by falsifying the engine coolant temperature, ....

Well, there's a little more to the story. He also recently had installed a plug-in conversion with an additional battery, described in this thread. That's where most of the improvement over the fuel economy achieved by us mere mortals comes from. The hack helps more fully exploit the conversion's capabilities.

[DaveinOlyWA]

cool mod, but since i did not buy the Prius to reduce my gas bill. i will pass.

this just makes the Pri pollute like a reg gas car until warmed up.

[Flying White Dutchman]

old cars did not run with higher fuel to warmup faster so maybe this hack/mod is not that bad for the prius engine?

[DaveinOlyWA]

not bad for engine im guessing since engines have run this way for years and still do. just bad for environment. so what is worse? lower gas mileage or slightly more pollution?

if there are independent sensors in the exhaust stream, it might not be so bad after all, as the car may still be able to sense unburnt fuel and be able to recycle it anyway

[TheForce]

The past few times I tried to instantly get into WS have failed. There must be some other variable that says its OK for WS besides completing S1 and coolant temp above 157F. I can however get the GPH to drop to .2 or .1GPH which is still good but its still no WS. I will continue to monitor this and see if I can find out whats going on.

[TheForce]

Here is something new. The car gave me some codes.

P0111 Intake Air Temperature Circuit Range/Performance Problem???
P1600 ECM BATT Malfunction????
P0000 Null???

I don't think I did anything to cause it but I'm not sure. Its something that I will continue to look into and to also warn others to look out for.

[Flying White Dutchman]

sure your not going to contact Hymotion? P1600??

[TheForce]

Originally Posted by Flying White Dutchman

sure your not going to contact Hymotion? P1600??

From what I read I think it might be referring to the 12v battery.