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  1. #1

    Question on Engine Kicking on

    I just got a used 2006 Mariner Hybrid. I love it! About 25.2 MPG for now, but climbing. The question i have is with the RPM's. I know that when the RPM's go down to zero I am travelling in electric mode, however, it seems like the engine kicks on and the RPM's go up to about 1 or 2 RPM's. I am assuming that it is the engine kicking on, but wanted to make sure, because sometimes I will be idleing in electric mode and for no reason the engine kicks on. Just want to get other owner's opinions!

    Happy Driving.

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  3. #2
    Let me try to help a bit here with this and your other posts. Hybrid technology is fairly simple but there is a lot of this simple stuff happening so it can be a bit tough to figure out what is happening and optimize for it.

    First of all, today’s hybrids have a gasoline Engine and and electric Motor each of which contributes to pushing the car along.
    The hybrid car uses gasoline to fuel the Engine and electricity from a battery to ‘fuel’ the Motor.
    The electric Motor is also a generator that is used to ‘add fuel’ to the battery.

    The Assist Gauge on the FEH (and I’m assuming the MMH) shows whether energy flows into the battery or out of the battery, indicating that the electric Motor is being used to assist the Engine or storing extra energy from the Engine. It deflects to the left to indicate energy is going to the battery (charging) and to the right indicating energy is coming from the battery (assisting).

    Most of the improved highway economy performance seen in today’s hybrid vehicles comes from the fact that a relatively weak gasoline Engine is used. The electric Motor us used to overcome the weakness of the gasoline Engine when it is needed such as when accelerating and climbing hills.

    Most of the improved city economy performance comes from the extra torque (force) that comes from the electric motor when starting and stopping. Some improvement also comes from shutting down the Engine when the car is stopped so it doesn’t waste gas just idling. Other improvement comes from Regenerative Braking, where the electric motor is configured as a generator taking mechanical (kinetic) energy from the wheels and converting it to electricity that is stored in the battery for use later. This Regenerative Braking both captures energy from a slowing car and it saves wear on the brake pads. You’ll notice regenerative braking as the Assist Gauge deflects to the left.

    There are 2 ways that the battery are charged on today’s hybrids:
    1. through regenerative braking as described above.
    2. when the Battery Management System (BMS), a computer that controls the battery and the electric Motor senses that the battery is running low, it ‘chooses’ to try to charge up the battery again. If the car is cruising easily and the Engine isn’t working too hard, it bleeds some of the energy from the motor to use to charge the battery. You’ll see a slight deflection to the left when this is happening.

    You’ll see the motor starting and stopping occasionally when driving on pure electric or when idling. There are several reasons this may happen:
    1. The battery charge gets below some point and the Engine needs to charge it again
    2.. When you get above a preset speed (about 35 mph) because the power splitter that connects the Motor and Engine to the drive shaft requires it. Some Engine ‘back pressure’ is required by the splitter at high speeds, hence the low RPM’s.
    3. When you try to accelerate more than the power splitter or the electric motor can handle
    4. When the catalytic converter gets too cool. If the converter gets too cool, the emissions from the tailpipe may exceed government standards so they start the Engine to so the exhaust heats it up (this makes sense to lawyers and bureaucrats but not to technical folks).

    Dealers probably can’t do much to improve gas mileage. They have the vehicle tuned to a point where emissions, performance, battery life, and fuel economy are kind of at a happy medium (if not happy, at least a grudging compromise level agreed upon by government regulators, and the car company’s marketing, maintenance, and engineering department’s). There are several ways to improve your economy that are discussed in depth elsewhere in this forum that range from over-filling your tires to driving techniques.

    Hope this helps. Others can probably weigh in with other good info.

  4. #3


    That is a great explanation. I appreciate the time you took to write this. I do try to keep the car in EV mode, but with the hills in Pittsburgh, even at about 15 mph the regualr engine kicks in. I am happy though I am at 25.5 mpg and climbing (second tank of gas so far!).

    Thanks again!

  5. #4

    Ok, but

    Thanks again, one more question. Does that mean that the electric engine is being used at the same time the ICE engine? Sorry if I am confused!


  6. #5
    Junior Member
    Join Date
    Oct 2006
    Quote Originally Posted by Labbett Family View Post
    Thanks again, one more question. Does that mean that the electric engine is being used at the same time the ICE engine? Sorry if I am confused!

    It's not an electric engine, it's an electric motor! Yes, it's used to assist the ICE with torque during acceleration. The motors can drive the vehicle or assist the engine during acceleration.


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