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Idle entry conditions 
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QFP80 - Contributor
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Joined: Thu Jun 20, 2013 4:24 pm
Posts: 86
Wich conditions have to exist that the EMS enters idle mode ?

So we got 3 reasonable values the EMS needs to determine a idle condition
- MAP
- RPM
- TPS

Code:
if (MAP < 40 && RPM < 1000 && TPS < 5)
    {
      set engine idle ;
    } 

But what if the ambient temperature is -10°C and the engine needs to idle at 1200rpm and 45kpa ?
So should MAP and RPM conditions for idle be based on a curve ?
Maybe something like this

Code:
 if (MAP < MAP_idle_condition && RPM < RPM_idle_condition && TPS < 5)
    {
      set engine idle ;
    }


A MAP_idle_condition curve could look like:

MAP | 45 45 40 40 35 35 | kPa
----|------------------|
CLT | -15 -5 10 40 60 90 | °C

A RPM_idle_condition curve could look like:

RPM | 1300 1100 1000 950 900 900 | rpm
----|——---————————————|
CLT | _-15__ -5 __ 10__40__60__ 90_ | °C


Sat Jun 21, 2014 11:45 am
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LQFP144 - On Top Of The Game
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Joined: Sun Jul 18, 2010 2:35 pm
Posts: 299
I personally don't think map is a good thing to use for idle.

I've seen a car idle around a map of 55kpa before, turbo 4 cylinder brand new car, with heater on and everything going. Idle with a lot of accessories can easily make pressure change a great bit.


Sat Jun 21, 2014 10:40 pm
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Joined: Tue Jan 15, 2008 2:31 pm
Posts: 14871
Location: Home sweet home!
I agree with Hentai, MAP is a function of load, and vice versa. It's an output condition of your airflow control (throttle and valve).

If this were actually code, I'd not want to see TPS anywhere in sight. I'd want to see "throttleClosed" as the condition. Whether that condition comes from a switch or TPS threshold is not relevant to idle or decel cut, and should not be in more than one place.

Also "set idle" needs some sort of definition. I'd want to see that control the closed loop stuff (for technical wind-up reasons only, the controller should have limited authority anyway), but for just base PWM/airflow I'd want a simpler control to *always* be active. IE, while (throttleClosed) look up idle airflow from RPM and coolant in some fashion, be it 3d or 2* 2d. Why? I want the valve closed on the overrun, or maybe the opposite, perhaps I want it wide open while in decel cut. User defined.

Fred.

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Sun Jun 22, 2014 12:21 am
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