I think that my MPG could be much better if I could tell the car how to operate. For example, when I am in a traffic jam, the gas engine shouldn't need to come on at all to inch along the road here and there. Is there an aftermarket switch that would allow you to turn off the engine when you know it is unecessary? My battery rarely has utilization high enough to get below half charge, which means that I'm not getting the full benefit.

 

Might be risky.

The operator would have to be skilled and trained and alert enough to not let the battery discharge all the way.
Also in an emergency you may want to gun it to accelerate out of an accident and wouldn't have the torque if the ICE was shut off.

Who knows what else?
Stuff usually seems simple in principal, but the devil's in the details.

 

Thanks - good points. I've heard that European Prius models come equipped with this functionality, though. Is that true? If so, how do they get around the problems you mentioned?

 

Prius uses the electric as the primary drive, rather than a torque booster like our Civic. I'm not sure that the EUR models have a switch to kill the electric, as it wouldn't really make sense for them. More likely they can inhibit the ICE from starting up, forcing EV-only operation.

 

I'd imagine they could design it to turn on the ICE if the accelerator was floored or if the battery got too low.

Those engineers can think of everything.

I think most designs are compromises reached in anticiaption of what they expect most people will want.

 

If you understand the Honda IMA system correctly, you know the engine crank shaft and the motor are connected together and motor can't run alone.

Ken@Japan

 

True, but the engine can still be off (valves closed, no fuel injection). With the low friction engine, it's ALMOST like having no engine running.

I've often thought of having this type of function. No reason to start the engine each time you have to creep forward a few feet in nasty traffic. I had one of "those" commutes last week. Five miles of zero to 6 mph traffic. I can handle the 10 -15 mph traffic just fine (often going into electric-only mode!)... but there's nothing you can do at 0 - 6 mph... except sit and watch your MPG fall. I lost 2 mph on that stupid commute!

From what I understand, if you run out of gas, the IMA motor will still propel the car. I'm wondering if a fuel cut switch could be added to temporarily enter this "mode" we're talking about.

Unfortunately, I'd never try it until the warranty was out... and that'll be MANY years from now!

 

This is one of the situations where an all-electric mode would be useful. If the battery charge became too low, it would be more efficient to run the engine in neutral at an efficient high loading to recharge the battery, than to leave the engine idling just to creep along.

This is a great exmaple of how hybrids could be dramatically improved by allowing the driver to control the electric assist/charging insdependently from the gasoline throttle. Another example is climbing a hill of known length, knowing just how much assist to use to get over the top without running out before the top, or without having excess unused capacity left over.

 

Creeping at 3 mph, you'll consume less than 300W to go foward and more than 1000W to rotate the crank shaft.
What a wasting energy!

Ken@Japan

 

I agree.

The current specifications & design of the HCH-II simply do not allow for such behavior. The HCH-II's electric motor and the existing battery capacity would not be able to facilitate (let alone sustain) such EV-mode as part of its regular operation.
It would indeed be a waste of energy... but a good exercise for 2nd year engineering undergrads.



Cheers;

MSantos