Can starting in EV mode be dangerous?

I certainly wouldn't use EV mode that way. I only use it to relocate the car when I know I won't be needing the ICE at all - like moving the car in or out of the garage. I'd also use it when pulling away from somebody if I didn't want to leave them in a cloud of my offal. But I wouldn't use it to get all the way up to speed with a cold ICE.

 

No the HV system will not let you harm the car! It will cut in the ICE to Charge the Battery. The three laws of robotics apply.
Woo I don't believe I had that idea. It may well be that the "zeroth" law applies as well!

 

(don't mean to be ignoring the good I, Robot humor....)


Yes, obviously the ICE cuts in... but won't the ICE be put under strain immediately if you're asking for big acceleration right as you exit EV mode? Or does the ICE actually spin up and pressurize the oil before firing? I don't know that answer.

 

i imagine the motor generators will still spin up the ICE before applying spark.

 

Yes. The ICE is spun by MG1 to a certain rpm then fires.

My opinion for the original question is that it does not harm the system but it is not wise use of EV switch.
We'll see a lot of rebounds to charge the battery back to the normal level degrading our mileage number.

Ken@Japan

 

no oil issues. that was addressed by someone some time ago. that is all i remember.

seems that a worse situation is having an engine turning with unburnt gas in the engine which happens everytime you crank a normal car. the gas breaks down the oil coating inside the engine increasing wear.

besides, we must remember that the fuel pump doesnt control the oil flow. the engine turns all the time at high speeds without gas being burned.

 

actually the engine does spin before the valve timing changes to create compression. until it spins up to a set RPM, no gas is injected, no compression is created.

 

If you look at the energy flow when you first start the car cold, you will see more use of the battery for the first minute or so than you'd otherwise expect. The car WANTS to run the engine gently at first. In the scenario you describe in the OP, it's harder for the car to go easy on the engine.

I don't think this will really HURT the engine, but I do think it's inefficient, and I don't think it's good for the engine.

This is why, in an earlier thread, I urged you not to drive a long distance in EV mode first thing in the morning. As stated there, I prefer to park at 3 or 4 bars of SOC in the evening, and then let the engine run to warm up when I start it in the morning.

For ANY car it's good to drive gently for the first few minutes. I think this is true of the Prius also. The fact that you CAN leave the engine off until you hit a high-speed street, just gives you one more way to abuse the EV switch.

 

the ice is spun up by the motor generators before spark is applied. this gets the oil circulating. the engine won't be running without oil in the head. the engine won't start without being spun up- remember there is no "starter" per se to turn the engine over like there is in a conventional car.

if you're going to accelerate above 30 or so, kick it out of EV and let the engine warm up if you're really worried about it.

 

Daniel you are back. I agree EV at night and ICE in the morning!

 

but the engine won't apply power until it's been spun up. you won't feel it do anything until it's good and ready to do so. there is no load applied until the engine has (a) been spun up to the specified rpm and (b ) had spark applied to fire off the cylinders. i'd imagine in the programming it starts a sequence somewhere between 30-33 mph depending on the circumstances that preps the engine for startup.

ah heck. why am i doing this on my own? i'm gonna wait until DH gets back downstairs and we'll ask him.

always best to err on the side of caution, i say

 

I thought the EV mode was standard on the japanese Prius. if that is the case, I don't think you should be worried about the engine kicking in at anytime. them engineers probalby got that this down pat.

 

ok. i asked DH and this is what i got.

in a conventional car, when you start the car there is a moment where the engine builds oil pressure. maybe a second or so.

MG1 spinds the engine to speed much faster, less than a second. it also build oil pressure much quicker. the motor won't start feeling the "stress" of acceleration like that until your oil pressure has been up to par and teh motor is already turning over at at least the baseline speed.

you may not think that when you're accelerating in EV and ICE kicks in during aceleration that the motor actually spins up before applying power. but there is no possible way for it to start without being spun up first. so there is no other option.

the difference in engine feel when it's kicking in is simply the PSD adding power of the motor into the electric that's already powering the car. that's the last part of the sequence of your car switching from EV to electric and gas.

also, cam timing (therefore valve timing) is different during warmup.

don't worry. your prius is plenty smart and can handle itself just fine.

hope that answers everything... whew!

 

another thing is that the thermos is pumped to the cylinder head from the start so the ICE isn't stone cold, once the computer says start the ICE MG1 spins it up with out fuel or spark till it gets to approx 1000 rpm then applies fuel and spark to a partially warm engine. Harm it I doubt it. The cam timing is held in the retated position to force a hotter ehaust to warm the cats till O2 sensor say's were warm and starts the leaning of the exhaust to bring it to normal operating temp and S4.