vtechtuning
Posts: 64
Joined: Wed Dec 16, 2015 7:16 am
Location: Krakow, Poland
Contact: Website

Let's stop ICEheat, when cold...

Fri Mar 18, 2016 1:35 pm

As you know some of my ideas/developments from "Let's go pure EV" thread, I promised to focus on gasoline engine heating function control.
I'm still not sure about exact algorythm of ICE start (and I cannot read AC-control ecu to check the algo just in code), I decided to check it step by step and look for a non-intrusive method of influence to it. I have some success (video in 2 hours, when it will be colder - now it is +4 and +7 in the car and I'm not sure, if it is cold enough to proove that partial success).

What I have now:

- gasoline engine is controlled not only by difference of temperatures (set and real) inside, nor ambient to internal difference. Algorythm is more sophisticated for sure (depends on actual load, delta of actual load (especially kick-down impulse prohibits gasoline engine to be used/started as heater - sounds ridiculous, because kick-down forces ICE start and driving with gasoline engine is a source of heat - but I have already found, that it is managed and handled totally separately). It depends on ambient to internal-set temperature, internal-set to internal-actual temperature and actual level of electric heating. I have no signs from my tests that it is dependent on battery temperature, or SOC.
- I have added such functionality to the PHEV box (pure EV mode box - for those who did not read "Let's go pure EV" thread) that box can simulate ultra short kick-down behaviour, that is not considered at all by PHEV ECU as kick down (as this function has a time delay and integration of signal hard coded) but PHEV ECU puts appropiate information to CAN (once) and this prohibits (or better to say - reduces importancy of gasoline engine start demand. Luckily such trigger has it's own delay in AC-control ecu (so for few seconds gasoline engine start by demand of heating is blocked or exactly - has lower priority).

Finally we can highly reduce gasoline engine start-for-heating reason and importancy and even started - it stops much faster. This is proven.

Box must have one additional line with reference temperature signal (internal temp signal) to know (estimate) what is actual probable demand due to internal temperature. To calculate total demand I need 2 more temperatures for sure, but signals are not available (at least - not easy available, without car alteration). I need to produce one plug for that, but hardware in the box is ready now. For tests I have soldered one signal line to temp sensor, so box knows internal temperature, and installed additional chinese thermometer with out and in temperatures, just for me, to monitor temps.

What do you think? Any more info about AC-ECU algo for heating?

https://youtu.be/xpp6i_ebVnM

I did two starts - first with box on, second - off. +4,5 C outside, similar cold inside (I first declared to do one test and second one after 1 hour, but I thought that during second start it is even warmer inside & gasoline engine is warmer - so for sure it should work shorter or max same time than in first try.
Observations:
- engine starts in both cases.
- with box on engine works 30 seconds, then stop
- then restarted (car off, car on) with box off - engine works for more than 3 minutes 15 seconds (then I switched it off manually as I want to cool down the car again and re-test).

I still do not understand fully why it starts it (for sure these complicated dependencies cause that, for instance outside temperature) but I have reduced it's working time more than 6 times in the first try (in both cases electric heating works same, 100% of heating power).
Alcohol won't solve your problems. On the other hand, milk won't solve them either...
Outlander PHEV & Nissan Leaf tuning http://evtun.com

Tipper
Posts: 324
Joined: Mon Sep 07, 2015 2:34 pm
Location: Devon UK

Re: Let's stop ICEheat, when cold...

Fri Mar 18, 2016 4:07 pm

My observation is that ICE starts on 'start-up' if the external temperature is less than 10C and the heater is selected on.
2015 GX4hs - Glacier Blue

vtechtuning
Posts: 64
Joined: Wed Dec 16, 2015 7:16 am
Location: Krakow, Poland
Contact: Website

Re: Let's stop ICEheat, when cold...

Fri Mar 18, 2016 9:54 pm

Tipper wrote:My observation is that ICE starts on 'start-up' if the external temperature is less than 10C and the heater is selected on.
Ok, thx, I consider this to be a part of the "heating algo".

It seems to me basically such algo:

Treshold_of_ICE_start = - k1*(temp_outside - 10) + k2*(temp_inside_set - temp_inside_measured) - k3*temp_of_engine - k4*(other_power_demand) - k5*(electric_heater_level)

k1...k5 are various coefficients. If sum is higher than treshold, ICE starts. Some coefficients must have big value (like k3 - that is logical, or k4 - that I have proven by tests). But nothing is sure, these are my observations & prediction, how it may work. For sure it is not dependent on one temperature (or temperatures only).

5:30 in the morning, - 0,4 C outside (below 0 C). I tested my ICEheater stop plugin for my box switched on (so box can increase k4 coefficient influence), video uploading. Next test in 1-2 hours. But it looks not bad :) It seems problem of ICEheating is 90% solved :)

https://youtu.be/WHBbMcTxV98

ICE worked 1:01 (61 seconds).

Parameters: - 0,4 C outside, 2,1 C inside (chinese thermometer ;) , 20 C set, fan set to 50%, battery full, car was whole night outside, connected to charger. 5:30 in the morning (dawn here).
Alcohol won't solve your problems. On the other hand, milk won't solve them either...
Outlander PHEV & Nissan Leaf tuning http://evtun.com

anko
Posts: 3405
Joined: Mon Dec 01, 2014 11:30 am
Location: Netherlands, Utrecht area

Re: Let's stop ICEheat, when cold...

Sun Mar 20, 2016 8:44 am

To me it also seems very strange that starting the engine for heating purposes depends on power demand for driving. Unless the "start engine" request from the A/C specifically tells the engine to run "low".

Behaviour of engine start caused by A/C (compared to engine start by pressing Save or Charge button) are:
- The engine will generate as much power as needed for driving but no access power will be produced for charging the battery. When parked, the engine effectively idles (until you hit Save or Charge)
- The engine will not engage in parallel drive at 40+ MPH (until you hit Save or Charge)
- The engine will start when fuel level is very low (which it will not do when you hit Save or Charge)
- The engine will start at very high SOC (which it for most of us will not do when you hit Save or Charge)

When you start the car with the heater turned up, the engine will start. When you immediately turn off the heater, the engine will keep running for a little while, I assume to prevent excessive wear and such. 30 seconds as a minimal sounds about right. I can imagine that the duration of this will depend on the ambient temperature and more parameters and could indeed be 90 seconds in colder environments.

It appears as if the result you got in your tests are consistent with blocking the "engine start" request from the A/C just a little too late: the engine was started and as soon as your device kicks in, the engine is allowed to stop again. But it will only do softer 30 - 90 seconds. I think the same may have happened when you had turned down the heater, directly after starting the car.

I wonder, what happens when you start the car with the device active and the heater turned off and then, after a few seconds, turn on the heater? Will the engine run for 30 - 90 seconds? Or not at all?

Altogether, this is a good result, as it allows youth use the electrical heater rather than the engine for heating (after 30 - 90 seconds) on short trips. But I am still hoping to get rid of that first burst. A couple of times this winter, the engine of my car started when I had to move my car from a non charging parking bay into a charging parking bay or vice versa, a distance of 20 meters or so. Only because I forgot to switch off the heater when I parked the car.

Oh and another question: why would you need ambient temperature feed to your device? Why not let the device do it's thing with the "ultra short kick down" always? Until you switch it off?

ClasseClas
Posts: 108
Joined: Sun Nov 09, 2014 4:47 am
Location: Sollentuna, Sweden

Re: Let's stop ICEheat, when cold...

Sun Mar 20, 2016 3:16 pm

Tipper wrote:My observation is that ICE starts on 'start-up' if the external temperature is less than 10C and the heater is selected on.
I have noted that also. If no preheating then ICE will start if ambient is below 10C.

ClasseClas
Posts: 108
Joined: Sun Nov 09, 2014 4:47 am
Location: Sollentuna, Sweden

Re: Let's stop ICEheat, when cold...

Sun Mar 20, 2016 3:38 pm

I am very glad that you vtechtuning work on cracking the algorithm for this! :-)

Your assumption on algorithm looks reasonable. It is a bit hard to give you exact information about own experiences as they are based on own views and conclusions and not based on exact measurements.

However, my view is that the algorithm is dead stupid. Here is the use case;
-Temp below 10C (rather below 0C). I preheat the car for 30 minutes. Thus coupe temperature is so high that ICE will not start. Fully charged battery minus preheating.
-I drive 10 minutes to the store.
-I go shopping for say 10 minutes.
-When I return to my car and start it ICE will engage. Most likely the trigger for this is only 1) low temp and 2) low coupe temp. It seems that it does not know anything about possible residual heat in the electrical heater that would inhibit start of ICE. I guess that there is no temp sensor in the electrical heater (similar to an engine heater temp sensor). Given this situation at idle when ICE starts there is relatively low power demand. Car stands still.

Please also look into this thread with some observations,
http://www.myoutlanderphev.com/forum/vi ... 251#p24251
1) It is possible to set AC in manual mode in MMCS (turn off "snowflake") resulting in lower power consumption
2) It is possible to set "economy" ACC mode in MMCS (engaged by the ECO mode button) resulting in lower power consumption
3) Battery temperature may have an impact on ICE start

anko
Posts: 3405
Joined: Mon Dec 01, 2014 11:30 am
Location: Netherlands, Utrecht area

Re: Let's stop ICEheat, when cold...

Mon Mar 21, 2016 10:51 am

ClasseClas wrote:It seems that it does not know anything about possible residual heat in the electrical heater that would inhibit start of ICE. I guess that there is no temp sensor in the electrical heater (similar to an engine heater temp sensor).
Not quite. There are two temp sensor, one for the inlet and one for the outlet of the electrical heater. But do not forget, the water temperature in the electric heater will drop much, much faster than that of the engine coolant:
- there is very little fluid involved
- there is no large heavy massive solid body that can hold the heat (engine)

anko
Posts: 3405
Joined: Mon Dec 01, 2014 11:30 am
Location: Netherlands, Utrecht area

Re: Let's stop ICEheat, when cold...

Mon Mar 21, 2016 10:53 am

Tipper wrote:My observation is that ICE starts on 'start-up' if the external temperature is less than 10C and the heater is selected on.
May I suggest to rephrase this into:
ICE does not start on 'start-up' if the external temperature is more than 10C
Also I think the 10 deg C border is not solid. I have been able to drive away at 7 deg C and use the heater without the engine starting up. But not always.

ClasseClas
Posts: 108
Joined: Sun Nov 09, 2014 4:47 am
Location: Sollentuna, Sweden

Re: Let's stop ICEheat, when cold...

Mon Mar 21, 2016 3:09 pm

anko wrote:
ClasseClas wrote:It seems that it does not know anything about possible residual heat in the electrical heater that would inhibit start of ICE. I guess that there is no temp sensor in the electrical heater (similar to an engine heater temp sensor).
Not quite. There are two temp sensor, one for the inlet and one for the outlet of the electrical heater. But do not forget, the water temperature in the electric heater will drop much, much faster than that of the engine coolant:
- there is very little fluid involved
- there is no large heavy massive solid body that can hold the heat (engine)
Thanks for the info! As I wrote earlier it is easy to draw conclusions based on assumptions which are not fact based.

Now, as the electric heater is faster to heat the cabin than the ICE given above reasoning, it would be the first choice to deploy rather than the slower ICE heating. Still, this is not the case. Then the question is why? Maybe it is about the max power available from the batteries which set the limits here. The algorithm of vtechtuning with "k4*(other_power_demand)" may come in strongly as the main limiting factor.

A side comment: On Toyota Prius gen 4 there is now a PTC heater available which will provide even faster heating and also reduce the ICE usage for heating.

anko
Posts: 3405
Joined: Mon Dec 01, 2014 11:30 am
Location: Netherlands, Utrecht area

Re: Let's stop ICEheat, when cold...

Mon Mar 21, 2016 3:14 pm

The electric heater throws in 4 kW max. The engine roughly 70% (heat losses) of the energy in the fuel burned during heating. Or even more when the engine is not contributing to driving. That is an awful lot of heat.

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