Idle Warm Up - When Should We

power up and go! gently at first if your route will allow. keep it under 20-25 until warm up is over depending on outside temp. of course, that's the ideal situation. some have to get right onto main roads with traffic. but, in any case, you don't want to sit in the driveway idling. all the best!

 

Ken1784 from Japan indicates their tests show it IS better to sit and idle through stage 1a (about a minute) IF you must make demands on the engine. This is because the retarded timing in that stage inhibits the ICE from making power.

My commute is flat and slow, so I can give a gentle pulse and then glide my way through stage 1a. I feel this beats sitting and idling in my scenario.

For every non-hybrid, you always want to go as soon as you start since mpg at a stop is zero.

edit:
The crux of the findings from Japan (IRRC) was that by sitting for a minute, the small amount of power from the ICE can charge the pack, but driving during this time is done by drawing from the pack, precluding that charging.

 

Move as quickly as you can.

The worst gas mileage you get is when you are not moving. Prius or any vehicle. Moving warms your engine up quicker. Idling with modern fuel injected engines is mostly just a waste.

In the 70's 80's and even 90's there might of been some advantage to letting an engine warm up at idle. But with modern engines, computer controlled fuel injection, and synthetic high quality oils...I vote MOVE......

 

This seems to be the key factor in your commute. Therefore I say let 'er warm up in the driveway through the first stage.

 

I have to go down a short hill and then straight up a large long one at 50+mph. on a cold day i allow the 50 second warmup to happen before moving, on a warm day i go straight away, but do force the ice on (press the pedal before engaging D) as soon as i start. If i don't warmup and use EV, i drop out a quarter of the way up the hill, down to two bars, and the ice starts and instantly goes nuts. pretty sure that's bad

 

Either a great strength of mine, or a great weakness but I can admit when I'm being stupid. I don't understand.

Seems to me that the "minute" for warm up, is going to pass whether you are moving or sitting still. So maybe with a Prius that initial minute if moving results in it drawing from the battery pack...but since ultimately balance of charge is maintained automatically why wouldn't you want to be moving? The battery charge will be maintained and balanced eventually in any case, The Prius is designed to keep it within a range regardless of driving style.

With any car, I wouldn't recommend instantaneous start up and hitting a freeway...or instant start and heading up the side of a mountain. BUT if you can move, and keep it under 40..for a minute or so, why not move?

 

Agreed, the best way to warm up a modern engine is not to let it sit idly by. If possible, warming up the engine by moving is a much better alternative than sitting. Moving, though it will drain more battery that will eventually be refilled as you drive, allows the vehicle to not only warm faster, but also more efficiently.

 

Yeah, it's weird. But I've come to accept that in some situations one should 'sit & charge' a Prius for 50 seconds, so the ICE can provide power thereafter and reduce draw on the pack which must be replaced later. If you do avoid the pack all day, you may want to go EV as you near home in order to make room in the pack for next A.M.'s idle charge.

In a 2010, warmup is skipped if already warm enough, in which case go immediately. And again, I take off because I can glide through stage 1a with only nominal draw from the pack for pulses, so moving makes sense. For those who start uphill or high speed/acceleration, the first 50 seconds of the ICE are worthless for propulsion and the draw from the pack is high. It that case, put the ICE into the pack and wait, then use the ICE for power.

 

Your SOC is 60%, and you start the car. You start moving immediately, the engine is running, but all motive power is coming from the battery. Two minutes later your SOC is 50% and your engine now starts providing motive power and must return SOC to 60%, resulting in reduced economy for the next two minutes.

Your SOC is 60% and you start the car. You wait until the first minute of warmup is complete, and your SOC is 62%. You move off, using a blend of electric and ICE for motive power. a minute later warmup is finished, SOC is 58%. your car returns you to 60%, giving reduced economy for 30 seconds.

Which used more fuel? the consensus seems to say the first option.

 

Personally, I've found I do pretty well by just going immediately, since my first minute is about 5% backing slowly, 60% at ~8 mph in a driveway, and then 35% at ~18 mph on a short residential street. Shortly after I turn off that street, I can get the first engine stop, indicating I'm into S2. Driving that route is fairly easy on the battery; current from the battery is typically only a couple amps, especially in the driveway.

On the other hand, if your initial route is pulling straight out of the driveway and accelerating to 35 mph immediately, you might be better off idling. The best way to find out is to test it yourself! Try recording your mileage for two weeks or so, alternating tactics every other day, and you might get enough data to cancel out the noise from the rest of your commute.

 

We know an aggressive battery power usage will worsen the total fuel economy, so I would recommend to stay one minutes during the S1a.
Anyway, following is copy of my post.
-----
If your road is downhill for the first 1 minute, you can start immediately after READY on.
If your road is uphill for the first 1 minutes, wait for 1 minute to finish the S1a stage, then go.
If your road is flat, it's your decision. You can start immediately and drive slowly to save battery power, OR you can wait for 1 minutes then start your driving at normal speed.
-----

More aggressive approach are...

• install engine block heater
• install thermistor hack

Ken@Japan

 

Hmm..just for the record, I'm not saying I'm right or wrong. I'm honestly saying I don't know.

Seems to me, both scenario's are simple P.O.V.. You can "count" the minute but you are only counting the reduced economy of the 30's seconds as "reduced economy" and not the "minute of not moving" which is the warm up. So even in the "wait" scenario, you have 90 seconds of reduced economy, 60 seconds of which includes making no gains towards your destination...which I think should be factored.

Again, maybe I'm being stupid...seriously, but it also seems to me that arriving at your destination ASAP is also a benefit because you will then be shutting your engine off and not using your ICE or Draining your battery.

With The Prius isn't the simplification simply that you can A: choose to warm it up before a short trip..inwhich it will be potentially slightly more efficient (higher MPG's) for the actual driving duration of that trip (BUT you "wasted" a minute or more not moving with the ICE running) or B: You can rely on the system as designed to warm itself up AS you are moving...and potentially arriving that much sooner thus turning off your engine and NOT either draining a battery pack and/or burning fossil Fuel.

In either case it's a pretty close call. I understand that while it warms up The Prius is less efficient, and likely to draw more from the battery pack, which I also understand will eventually be paid back from a working ICE engine. I'm still unclear as to why, having that working ICE engine "pre-heated" while not moving is more efficient than letting it warm up as it IS moving.

Part of this is based on comparisons to MPG's and a fully ICE vehicle...but I'm also basing it on my understanding of the genesis of The Prius warm up cycle, which in my admittedly limited understanding- includes the idea that The Prius warm-up cycle exists not so much with the aim of making The Prius more efficient from a MPG standpoint, but of creating the best scenario for limiting emmisions. My understanding is The Prius "slowly" warms up the engine...not so much with an aim to it being the most efficient way to maintain MPG's but to keep emissions reduced.

But hey, I'm really open to either scenario. I've got to think the difference is pretty minimal in either case, bottom line is starting out, and short trips with any vehicle are less efficient, and that includes Prius.

If I have to abandon my ICE instincts....which do tell me to move as soon as possible? Then so be it. I've learned a lot the past 2 years. Can we simply say, "The Prius Moves in Mysterious Ways" and leave it at that?

 

Because with a cold engine the 10kw of powered required to move you along uses (say) twice the fuel required by a warm engine outputting 10kw. and yes, that's reduced fuel economy -and- higher emissions. so Prius tries his best to not use the power during warmup, and sap it from the battery (to reduce emissions) and later on replaces that used electrical energy from a warmed up low emission engine.

The design of the control system -allows- you to get in and drive it straight away, but i still don't think it's best in all situations (instant high load from hills or high speed, or extremely low temperatures).

With the Volt, if the battery is depleted and you don't recharge, the next morning you'll see it run on battery and do a gentle warmup of the ICE, and it will probably be two or three minutes before it's providing full motive power from the ICE - it has a much bigger battery and a more powerful motor to play with...