Vehicle warm-up behavior - ScanGauge observations

the warm-up really drives me nuts. Partly because as folks say, short commutes (unless they come right after each other while the engine is still warm from a previous trip) are destined to be in the 30s and 40s for "no good reason". I'm really confused... what's "the point" of warming up the ICE? If the battery is full, and you're driving moderately such that the battery could handle the load, what does it matter if the ICE isn't "warmed up"? What's gained?

Since our cars are basically drive-by-wire, and that wire is talking to a CPU that in turns powers the car, it seems like a software update could be use to "tune" the algorithms that govern the ICE/electric decision making.

One added thought... given it's current "warm up" requirement, there would be nothing gained by convering a Prius C to a "plug in" IMO because 99% of the time my battery is *already full* and my ICE is still churning away because I'm starting a trip with a cold ICE engine. Would would having plugged my Prius C overnight have accomplished? One bar more of charge on a battery that the car's CPU isn't letting me use anyway????

 

^^^showing my Gen3 ignorance here, but for Gen2 we could get a after-market EV button. Is this not an option for Gen3?

 

...sort of amazing, Prius is...if they gave preference to fuel efficiency over emissions we'd all actually be doing ~55 MPG all the time.

 

Is there any evidence that the warm-up lowers overall mileage? The thermistor hack was posted 6 years ago...has anybody tried it? There is a lot of anguish over having to replace an HV battery...I wonder what replacing an engine would cost.

 

Are you questioning if the engine running vs the engine not running will change the MPGs?...

 

We got the block heater install by the dealership at time of purchase, and use it regularly. I only wish Toyota would put these in at the factory, in all the vehicles. It's a relatively expensive, hard to access hassle to do the install later.

 

Especially PiP could optionally keep engine block toasty warm as a side benfit since you are plugging-in the wall anyways give a slip stream of electric to the engine block, perhaps after the main charging is completed.

 

I am questioning whether anyone has any real evidence that shortcutting the warm-up procedure results in better mileage. It could be that a proper warm-up will result in quicker, higher mileage than would otherwise be attainable. Not running the engine would make it difficult to warm it up.....

 

ah, that makes sense. I was wondering where you were going with that, lol. My thinking on it is, why do I need to warm it up, if I don't need to? Why not let me stay in EV until I need the engine and then start the warm up, instead of just automatically doing the warm up.

 

That makes sense, but may not give the best overall mileage. Pulse and glide is not really intuitive, but it works. That being said, if you press the EV Mode button within a few seconds of starting the car you can get into EV before the warm-up.

 

For a max of 9mph because the engine isn't warm...

 

It's hard to work a block heater effectively in a Prius Plug-In.

First off, the block heater typically has an independent plug-in, dangling through the front grill. We use ours on a timer, and start-up times are pretty predictable, so...

But with the PIP it's hard to see a good strategy for using block heater. If the vehicles running EV mode for 10~12 miles, much of the raised coolant temperature is going to be dissipated, if and when the engine does start.

Unless you can delay EV? Run the engine (prewarmed somewhat by block heater) for the first leg, then EV for the remainder?

 

The thermistor hack might put your expectations to the test.

 

My commute today, 37F temp, no heater on but heated seat on for driver. I started the car and left in about 45 seconds driving in normal mode. I hit every green light (6) so speeds were from 30-45mph. The car takes a beating until it gets warmed up... If I go 7-12 miles I see 53-59mpg according to the end of trip summary. http://i391.photobucket.com/albums/oo354/kenscott30/Mobile%20Uploads/image.jpg


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I think some of you are frustrated that Toyota's goals and your goals are not always the same.

Toyota is trying to build the cleanest internal combustion powered car ever. They do it well.
Once the engine is warm, Toyota has found that the less gas you use, the less emissions are produced, so the Prius is very frugal once warm. If you bought your Prius solely for micro-economics, this is the phase where Toyota and you have the same goals.

However, Toyota clearly feels that when starting up, the quicker the catalytic converter attains operating temperature, the less the Prius will pollute. This may, or may not be a priority to you, the owner. It is almost a certainty that the thermistor hack is causing pollution the stock Prius would not emit.

Now it gets hazy, bureaucratic deals were cut with CARB. If the Prius had been focused on MPG when in start-up, but lost years of HOV access, would owners be better off? (just an hypothetical example, the example I read in the committee meeting is this. The safety bureaucrats wanted a much stronger desire to go backwards in Reverse than HSD could achieve, so owners could tell they were in Reverse. Toyota offered to make the car beep in Reverse if they did not have to redesign the HSD. So a million owners hate a beep that saved the HSD, we would be using IMA or something. That beep we all hate may save us 5 MPG, as IMA was not as good.)

But yes, if you only analyze what happens to MPG in the first 5 miles, Toyota made the wrong choice.

 

In my situation I do a lot of crawling on my short commute to work. I always let the initial warm-up to 103f take place. I installed the temperature hack and often after 103, I will use it to keep the ice off. If my traction battery is a bit low I will force the ice on when I am moving. If the soc it's up, I will just crawl with no ice. This hack had helped me improve mpg on my short trips

 

1) That warm-up logic was written by some of the most knowledgeable people on the planet with regards to the Prius engine and its peculiarities. It is unlikely in the extreme that you could improve them. And any change will be a trade-off, what are you prepared to give up?

2) Engine block heaters trade energy from electricity for energy from gas. Often at a terrible exchange rate, especially if you leave them plug in all night. Work the numbers for yourself, but for me, it would have been twice as expensive and more polluting to use a block heater.