1-25-14 later in the day 23F outdoors with strong winds, FWT 158 CHT 192 TAV 66 I go into EV. A few hours later with a shift of winds from the southwest to northwest brings dropping temperatures. 16F outdoors FWT 160, CHT 196 TAV 71, I can't get into EV. Braking down a long hill brings the SOC to 66.7 but still no EV at the bottom despite other parameters meeting EV requirements. It appears 20F outdoor temperature might the tripping point for allowing EV. I don't remember this as a trigger in the past and does this also relate to vehicles having more than 100,000 miles on them? More evidence that regenerative braking does not disappear when the outdoor temperature is 32F or below. Might be wise to plug in your FEH engine block heater immediately after work--if it has been sitting all day outdoors in cold winter weather--in an attempt to bring up its temperature and to improve those mpg. I'm running like E65 in my vehicle--mostly ethanol.

 

See my #10 post here ( https://www.greenhybrid.com/discuss/...uestion-29387/). I have seen these parameters in action recently around here.

 

Coasting down the hill means the ICE is not burning gas and so is generating no heat. I'd guess there's no ev mode at the bottom of the hill because it needs to heat up the engine, and/or heat up the catalytic converter. It's like a cold start. I'd guess ev mode came back after driving for a while on flat or uphill so things get warmed up.

 

Regarding cold and EV mode:

I've been in some really cold areas (-15F) back a few years ago and don't recall finding any cold EV cutoff.

Also let me ask you this: how does the car know the outside air temp?

I think it only knows (and cares) about intake air temp.
This is always 10 degrees above ambient at high RPM and 15-20, or more at idle when the amount of airflow is smaller and has more time to warm up under the hood.

John

 

The car does not know the outside air temperature. There is no sensor for this despite what some "self proclaimed Toyota engineer" claims. Bottom line, it takes longer.. to get into EV mode during true cold winter weather.

 

I don't like to be contradictory, but I know the '09 has an outside ("ambient") temperature sensor because mine was malfunctioning and I replaced it. The sensor is located in the front bumper.

The temperature readout on the dash was stuck at 10 degrees Centigrade, but worked fine after the repair. I also understand the engine computer uses this sensor to help determine when to allow ev mode, and it may also be involved in decisions by the automatic climate control.

 

At least for the first generation FEH, this is incorrect: a certain outdoor temperature and colder will prevent EV from occurring. The vehicle does not disable itself simply because the outside air temperature is .......(fill in the blank).

 

Check out the ScanGaugeIII if you have not already done so.

You can show 9 sensors per screen with 3 screens possible. 27 "favorites" can be shown.

Also wifi enabled.