Starting up my prius, properly?

Most of the advice that I have seen on the forums indicate that it is just best to start the car and then go. If you are moving, you are at least getting some mileage. Just sitting there doesn't gain you any mileage, although the FE at first will be low.

I usually don't even wait for the ICE motor to start when the car is cold. I just push "On" with my foot on the brake, wait for "Ready" to appear a few seconds later, and then drive away; if I don't take off too fast, the ICE won't even run at first (unless I have the climate control turned on, and it's calling for heat for the passenger compartment).

 

Upon cold startup, the gasoline engine will run with retarded ignition timing for a short duration. At this point the engine can't produce much power so if you are movng around, this will require traction battery power.

If you need to climb uphill upon startup, you may find that it is more efficient to let the engine warm up for a minute or so, so that it can produce the necessary power. If you are just going to creep out of your driveway at a slow pace then its probably OK to proceed immediately upon startup.

 

My take:

Let it warm up unless your able to slowly accelerate below 15mph without climbing any grades. If your merging into neighboorhood traffic or there are cars behind you, then let it warm up first before driving it.

Driving the car before its warmed up WILL use battery power (and battery cycles) much more quickly then if the car is warmed up.

 

Actually, faster seems to be better while the car is in forced warmup mode. I'd suggest a constant 45-55mph for the first 5 minutes.

 

Yeah, there is no clear agreement on this one, is there?

First, if you're worried about some sort of damage, don't be. There is nothing you can damage with any approach.

The issue is whether one technique or another gets better fuel economy. Because, as Patrick describes so well, the car prefers the electric motors for propulsion in that first minute or so, high-power driving (i.e., steep hills or rapid acceleration) will deplete the battery to some degree. (Nowhere near enough for any damage, and besides, the car protects the battery very well from adverse effects of operational extremes.) The battery later needs to be recharged, and the ICE needs to run longer and/or harder to recharge it.

Either way, in the grand scheme of things, the impact on overall fuel economy likely is small. Unless you're a fuel economy nerd like some of us , I wouldn't worry too much about it.

FWIW, my approach is what you propose here unless I have a steep hill or heavy traffic to contend with at the start.

 

Use up to half throttle when cold. Drive right after the ready light comes on, that is what ready means. An engine under light load will warm faster and better than at idle, and it will produce less pollution overall.

 

Interesting thoughts. My thoughts?

If the engine is running you should be moving for max. efficiency possible.
Yes, if you use battery power then have to recharge (all automatic, of course), that power is probably about 50% as efficient as power directly from the engine (power loss during battery discharge/recharge as well as loss in the electric components), but that is still -infinitely- more efficient than sitting idling!

With -any- internal combustion engine, you shouldn't apply full power when cold. It causes higher wear. So start off slowly for the first minute or two. By then the metal in the pistons/cylinders will be warming up. Then full power comes with minimal wear. That being said, I doubt you could rapidly "wear out" the engine by taking off cold on an interstate. You just wear the engine a little faster than normal.

Don't worry about "wearing out" the battery. NiMH batteries like to be used! They deteriorate faster if left unused in my experience.

 

Tony, I was wondering if this same advice relates also to the 2010? You mention the engine heating up the catalytic converter. Will the 2010 be more efficient in the early stages?

 

the only reason I wait to warm up is for the defroster for the big foggy windshield to clear so I can pull out on to pacific coast highway and not get hit , then its a downhill glide to my favorite diner for some food

 

I let it warm up between 30s-1min. I guess I'm just old school. I know that its mainly unnecessary for most modern cars these days. But at the very least I want to give the car some time to let the oil pressure get up to norm and let various other fluids circulate their pathways. Things are brittle and prone to wear when they're cold. And I'm never in a rush to go anywhere.

 

Yes, that's why my UK Prius leaves the engine running idle and uses more electric power when starting off with a cold engine. There's definite resistance to accelerating harder. It will, but you have to press the pedal quite a long way to get the car to do it.

The North America cars, with the coolant thermos, may be a bit different, because they throw hot coolant back through the engine to warm up quickly. However, that can only warm the engine rather than getting the oil pressure up. Still, with the car having to use the motor to move off - the engine doesn't provide enough torque and can't provide any power or torque below 1000rpm - I don't think there's any reason to warm up before moving off.

 

Unless your oil pan is empty, oil pressure will be up before the spark plugs even ignite.

The Toyota hybrid is even easier than your normal car as it spins the engine up to normal idle RPMs before lighting the spark plugs off, where your typical car can only crank the engine over a couple hundred RPM and has to rely on combustion to spin the engine up the rest of the way.

There really is no reason to wait before driving off.

I've got some good used oil analysis (UOAs) to prove it, too.

 

Actually the plugs fire, the injectors don't squirt. Oil pressure is at its highest when the engine is cold. Oil works better though when warm. Oil warms up quicker under light engine load.

 

Yes, the 2010 has a heat exchanger on the exhaust system which reduces the amount of time it takes for the engine to warm up. It also uses advanced EGR to allow for a leaner burn.

Tom