I've only had my Prius C for a few days. I'd like to know more about how the ICE shuts on and off efficiently. As a teenager, I was told it was a waste of time to turn a car's engine on and off to save gas. Now, I've got a car that turns its ICE off every minute or two! I did some searching on YouTube, but couldn't find anything that talked about this. I suspect there is some special injection scheme to pull this off. Can someone explain this, or point me a video on the subject? Thanks, Mark
Mark_ - Whoever told you “it was a waste of time to turn a car's engine on and off to save gas” was wrong. Think about it… Engine OFF means you are burning ZERO fuel. If you are moving and burning ZERO Fuel you are getting “INFINITE Instantaneous MPG.” As I write in my Ten Tips Guide related to the Prius Hybrid, “H. ‘INFINITE’ INSTANTANEOUS MPG-FE: Whenever the Gasoline Engine (ICE) IS NOT RUNNING and you are moving down the road, you are getting over 99.9+ MPG (i.e. ‘Infinite’ Instantaneous MPG). When the ICE IS RUNNING and you are moving, you are getting ~30-35 MPG.” I invite you to give my Ten Tips Guide a studied read. It will help you with your “Can someone explain this, or point me a video on the subject?” question, with respect to how Toyota’s Hybrid “Gremlins” operate your new c(cee) to cause it to deliver Maximum MPG, and how you and your throttle pedal foot fit into the picture.
Some (most, all?) regular cars do a higher idle/warm up every time you turn it on with the key. It usually varies with how hot the engine is, but its still a little higher fuel usage than idle. However, I've read that its only equivalent to 5-10 seconds of idling, so turning your car off at a long light or a train crossing usually helps. The Prius on the other hand is in control of turning the ICE off and on and doesn't use any extra fuel when turning it back on (unless the coolant temp has dropped enough). Another reason people say not to turn off your car at a light is starter wear and wear on the engine. The motor the Prius uses to start the ICE is much more powerful than a regular starter and it spins the ICE up to operational speed almost instantly, unlike a conventional starter that spins the ICE at a few hundred RPM. It also waits until the oil pressure is built up before injecting fuel. So in the end, a Prius ICE that is turning off and on all day is probably much happier than an ICE in a regular car that is only turned on a few times a day. Also, killing the ICE at a stop is only part of the magic. Like catgic said, when you're moving with the ICE off, you're getting infinite MPGs during that time. No reason to have the ICE burning fuel when coasting up to a stop.
Most if not all car manufacturers are adopting/using this technology. Chevy, Jaguar, BMW to name a few.
The generator also acts as a starter. With 28 hp from HV battery, it can rev up the engine to 1,000 rpm very quickly. The combustion begins after that "gentle" start. I don't think there is special fuel/air mixture. That's the beauty of a hybrid. Only the initial warm up use special ignition timing. It operates to produce the most heat producing very little power and torque. HV battery plays much bigger supportive role during that time. If you don't take it easy, you will see a big swing in battery state charge.
Once the engine is warm on any modern fuel injected automotive engine, only a very small amount of additional fuel is used during starting. We're talking about less than the total amount used during a couple of seconds of idling. Some engines require zero additional fuel to start. It has little to do with "starting", and more to do with the intake manifold being at ambient pressure. The engine can take a big gulp of air for the first few revolutions, and therefore needs fuel to match. I used to do engine mapping for high performance engines. Now, studying the super-complex mapping of modern cars is a hobby. For kicks, maybe I'll put the scope on the Aqua and see if there's any additional fuel added during starting vs. idling. With the engine speed attainable with MG1 before fuel is idded, I seriously doubt it, though. It's fun watching modern technology put to bed a lot of old wives tales.
This sounds like that old tip people would sometimes give you, which is to not waste energy turning a light off and then back on, but to leave it on because it uses so much energy being turned on, that it equates being on for a long time. The engine does not consume a large amount of fuel when it is turned on each time. If it did, then turning it on and off may be a waste. It's always more efficient to just turn it off when you don't need it. In all my non-hybrid cars without start stop tech, especially my V8 Mustang, I always turn the engine off at drive-thrus or long traffic lights, or anything similar.
