Coolant Temperature Hack. Better MPGs!

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i am using it now for some while and did not yet get any trouble code's using this hack.
i dont let the car warmup but go to 80 celcius the moment i put the car in ready mode
then when the car wants to start the ice because the battery is LOW i pur the temp hack down to 40celcius and the ice runts nice ( when i let the car stay in a higher fake temp the ice is not running smooth ) after a while the real temp of the ice is higher and i shutoff the temp hack.

this is with a oudside temp of not less then 15 celcius. and not more yet then 22 celcius

 

Two heads are better than one even if one is a goat head

 

Precisely: you are getting slightly better MPGs by creating more air pollution. Thank You Very Much. You should have bought a VW TDI instead.

 

no because i am driving a plugin so i dont let the ice warmup until the battery soc is down to a point where i need to start the ice
and then i lett it warmup.

sorry:cheer2:

 

Awwww come on Prius's don't pollute much....even with a hack ! ..On the other hand Al Gore's jet does..............

 

Today I completed a Thermo Hack switch for a friend, mine is working great since few months now and with out a problem, 5K pot and 470 drop resistor and an enable/disable switch.
This one is a little more compact and refined.
I'm including pictures of the dash panel mounting plate with the components including a 4 pin socket for the wires harness.

Rear view


Front view with LED


Have a Happy PHEVing

 

Update for my past post.
Upon installation of the dash plate with the components and internal wiring to the ECU, I realized that the values used for this Temperature Hack Switch are no correct for my friend's 2007 Prius.
I can only assume that the "thermocouple or thermistor" used in my 2004 are not equal to my friend's 2007 or mine are out of tolerance, I'm leaning more toward different production components.
I replaced the Potentiometer to 1K Ohms and the drop resistor to 270 Ohms and theses new values give me a range of 95 to 185 F to fool the engine temperature, just what I was looking to start in full EV mode for her short commutes with out starting the ICE

 

nice work
where is the voltage coming from for the led?

 

I'm taping into the "remote engine start" constant +12V I had install in the vehicle, but any auxiliary power will do.

 

I realize that the reason the car insists on warming up is something to do with emission laws, but I dis-agreee temp spoofing increases polution.

Temp spoofing allows the car to enter into its hybrid modes before it is fully warmed up, and in doing so, it turns off the engine and stops poluting.

If it takes 5min to warm up the car, then the car will polute for 5min until it reaches warm up. Temp spoofing deons't change this, it just spreads the warm up phase out, over periods when we want to accelerate, thus not wasting gas, and poluting needlessly.

If we temp spoof, and then break up the warm up time of the engine into 10 30sec bursts over the course of a 15 min drive, the car is still essentially doing the same warm-up, with the same polution, except spread out over time. HOWEVER, if we arrive at our destination in only 10min, then the car is only 2/3 of the way through its warm up, and has produced far less polutants.

Pre-hack, there was nothing more frustrating than watching my engine racing away to warm itself up, only to finish warming up just in time to park and turn it off. Its a clear waste of gas, and that warm-up phase wasn't needed, nor polution free.

After hack, I arrive at destination, engine hasn't run enough to have fully warmed up, less gas used, less polution created.

 

Not all engine time is created equal. An engine under load produces different emissions than one that is not. A cold engine under load produces the most emissions, especially HC. A cold cat does not convert NOx to N2, does not convert CO to CO2, and does not convert HC to CO2.

We do know that the warm-up cycle is specifically designed for that purpose, and minimizes engine load until proper operating temperature is reached (within the bounds of what is commanded by the throttle).

In your scenario, you are ideally using the engine only under load. While vehicle emissions at speed are lower than emissions at 'idle' on a distance basis (g/mi), they are higher on a time basis (g/hr). i.e., 5 minutes of emissions under load are almost always higher than 5 minutes of emissions at idle. As an example from a recent project, one hour of a gasoline vehicle at 10 mph was estimated to produce 5.11 g of NOx. One hour of idling produced 1.88 g. (These numbers are based on the 2015 estimated vehicle fleet. Also, idling and 2.5 mph are considered equal for purposes of emission estimates)

In certain scenarios, such as very short trips, I could imagine your conclusion is correct. But generally, I do not believe so.

One piece of data that is missing, imo, is whether running under load only decreases the overall warm-up time (likely), and whether that decrease in warm-up time offsets the higher emissions described above.

 

politburo.
you compare a 1 hour at 10mph with a 1 hour of idling.
but after a idle warmup you need to do a drive or else this moment of idle was a total wast of petrol.
what are the total numbers if you first idle the car to a warmup and then drive 10 min or start the 10 min direct and do not warmup.
maybe 0,094 for warmup of 3 min and 0,85 for the drive of 10min for a total of 0.944
or
0 for warming up and +0,85 for a 10min drive?

 

FWD - Unfortunately the model does not support such an analysis. The numbers I provided were just an example to demonstrate how emissions at speed are greater (on a time basis). The model only calculates numbers for the whole universe of gasoline vehicles, and there is no way to get model-specific emission estimates.

 

ok.. because with the prius when its warmed up it wil also shutdown the ice.
this wil mean that idling will not be possible and with a 1hour standing still ( same as idling with a normal car ) the prius wil emit far less then when driving only because the ice is shutdown.
just like what also happens after the temp hack.
i think it al depens with the prius and the temp hack what you driving distance is etc etc etc
and i also think this will work a lot better in e PHEV where you dont need to have the ice to warmup when you drive a distance that is well within the range of the PHEV electric range.
then warming up is only a wast of energy.

 

I agree with some of politburo's comments, but not all.
Definitly the cold engine, especially spoofed, (which alters the fuel mix & timing from ideal) is not as efficient as when warm. And the cat converter doesn't work when cold.

That said, here are my calcs, in line with what I have observed in real life on my car. These numbers are estimates/guesses only, and they are for a hybrid hylander not a prius (sorry), but they give numbers in line with my experience.

Just to prove a point i am going to greatly penalise the engine performance when cold, and asume the cat converter is all or nothing, ie perfect when warm and useless when cold.

L/Accel: 0.03 warm, 0.04 cold (I haven't actually noticed a diff, but lets assume a 30% inefficiency)
2 accels per km average. (gives 6 & 8L/100km warm & cold)
L/hr idle: 3 (on a hihi, about) in city av of 30Km/hr = 0.1L/km

Compare an aprox 20min 10K drive: wholly spoofed, and the same drive assuming 10m warming up, 10min warm.

Let's assume the cat converter is completely useless until fully warm, (wich it would not be)

The car uses 0.8L with spoofing, using the engine only durring the accels. And produces 0.8Lworth of polution.

Driving withought spoofing, warm up phase (1st half of trip)
The car uses 0.4L for accels, and 0.5L idling. The car produces 0.9Lworth gas, and 0.9L worth of polution
The next half of the trip, the car uses 0.3L of fuel for accels, none for idling, and with the cat converter now working produces no polution. (in reality it would still produce some)
Total for regular warm up trip: 1.2L fuel, 0.9L worth of polution.

So the car used more fuel and poluted more, even with completely unrealistic assumptions for the cat converter, and a trip that was long enough to fully warm the engine.

The difference would of course be more striking, (as it is for me) for trips that are too short to fully warm the car.

 

Coming with ICE ECU tuning backgound, the following is a fair assumption:
- The ECT resistor is part of a voltage divider where +5V is divided between an (1K likely) resistor and the ECT sensor resistor. This divived voltage is then detected by engine ECU (MCU) for ECT information
- ECT information is most likley used for three purposes:
1) To detect when additional startup enrichment is needed for engine startup
2) To detect when engine can run closed loop, i.e. using oxy sensor information
3) To detect when engine is too hot and hence adding fuel and possibly retarding ignition

A question: Has anyone tried a simple clamping zener or diodes to keep the voltage divider voltage under a certain threshold ?

In practise we could set a limit to keep always the engine temperature over e.g. 70C when the hack circuit is on and never be worried about getting too warm engine condition error codes. As when using clamping, then the voltage would be dropping below the threshold voltage and the engine would be detecting the temperature correctly ?

 

How can burning less gas cause more pollution????

 

It's easy. Your gas lawn mower probably burns 1 gal of gas a year. But, it may produce as much HC (hydrocarbon) as your Prius does in 2 or 3 months.

 

Thanks for the apples to oranges comparison but, you don't get off the hook that easy. If I could hack that same lawnmower to only burn .8 gal of gas a year, would it not produce less emissions?