Odd behavior
#11
02-02-2010, 09:00 PM
Re: Odd behavior
When the passenger compartment heater is running, the hybrid system is more reluctant to shut off the engine. This is especially true of a partially warmed up engine that hasn't reached at least 164 degrees F coolant temperature. As the outside temperature gets colder, this effect becomes more pronounced.
Its a trade off between gas savings and your comfort. At least you can argue that in the winter, some of the 70% of the gasoline that is wasted by the engine as heat instead of mechanical energy is being reclaimed to heat up the passenger compartment instead of being dumped outside.
With outside temperatures above about 45-50 degrees F, the engine will stop when the vehicle stops if the coolant temperature is above 100 degrees F. When it is very cold, the engine will continue to run until the vehicle inside temperature approaches the climate control set point temperature. This means the engine runs much more often and shuts off much less negating the savings of the hybrid system.
To check this effect out, try driving in cold weather with the heater system turned to off. You will note that when stopped with an incompletely warmed up engine, the engine will stop more readily than with the heater on. Also cranking up the heater temperature several degrees is enough to get a stopped engine running again.
Note that the rear heater system is ignored by the hybrid system and does not keep the engine running as the front heater system does.
Its a trade off between gas savings and your comfort. At least you can argue that in the winter, some of the 70% of the gasoline that is wasted by the engine as heat instead of mechanical energy is being reclaimed to heat up the passenger compartment instead of being dumped outside.
With outside temperatures above about 45-50 degrees F, the engine will stop when the vehicle stops if the coolant temperature is above 100 degrees F. When it is very cold, the engine will continue to run until the vehicle inside temperature approaches the climate control set point temperature. This means the engine runs much more often and shuts off much less negating the savings of the hybrid system.
To check this effect out, try driving in cold weather with the heater system turned to off. You will note that when stopped with an incompletely warmed up engine, the engine will stop more readily than with the heater on. Also cranking up the heater temperature several degrees is enough to get a stopped engine running again.
Note that the rear heater system is ignored by the hybrid system and does not keep the engine running as the front heater system does.
#12
02-03-2010, 09:44 AM
Ridiculously Active Enthusiast
Join Date: Sep 2006
Location: Beautiful Pacific NW
Posts: 1,678
Re: Odd behavior
Ok, I'm back with more odd behavior. Up until it got very cold we were getting 24-27mpg on average. Our driving behavior has not changed. However, when it got cold (below freezing) our mileage dropped to less than 20mpg. This just does not sit with me.
Here are a few examples:
First, last night I drove the 08 HH on a drive that was part expressway and part city driving. It would not get above 30-40mpg on the readout screen (not tank average, but rather the live reading/average). The engine temp was almost at half (maybe 5-10 mins of driving), and I was literally coasting down a hill without touching the accelerator and it would not get above that value (battery was around 4 to 5 bars according to read out). This eventually improved but it took about 20 to 30 minutes. Now, why should that be the case when it is 36F? I was driving it lightly, only two people in the car, battery showed as being pretty near fully charged, and still had this trouble. I even stopped for a full 10+ seconds once as a previous poster noted. Our latest tankfull has us at 16.5mpg.
When its above 45 or 50F we have few problems and get about 26mpg. Once it gets anywhere near freezing the gas mileage falls through the floor.
I pay attention and try to do everything I can to maximize mileage short of car modifications or an engine block heater. This severe sensitivity to temperature seems out of hand to me. Its not like we live in Alaska (we live in Louisville, KY).
I guess I'm left wondering if this is jut the way it is or if there is something wrong with our car.
Here are a few examples:
First, last night I drove the 08 HH on a drive that was part expressway and part city driving. It would not get above 30-40mpg on the readout screen (not tank average, but rather the live reading/average). The engine temp was almost at half (maybe 5-10 mins of driving), and I was literally coasting down a hill without touching the accelerator and it would not get above that value (battery was around 4 to 5 bars according to read out). This eventually improved but it took about 20 to 30 minutes. Now, why should that be the case when it is 36F? I was driving it lightly, only two people in the car, battery showed as being pretty near fully charged, and still had this trouble. I even stopped for a full 10+ seconds once as a previous poster noted. Our latest tankfull has us at 16.5mpg.
When its above 45 or 50F we have few problems and get about 26mpg. Once it gets anywhere near freezing the gas mileage falls through the floor.
I pay attention and try to do everything I can to maximize mileage short of car modifications or an engine block heater. This severe sensitivity to temperature seems out of hand to me. Its not like we live in Alaska (we live in Louisville, KY).
I guess I'm left wondering if this is jut the way it is or if there is something wrong with our car.
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