Fuel Consumption During Typical Warm-Up

exactly.

 

Watching ScanGauges in my first Subaru and Prius, I noticed that initial fuel burn rate (GPH) varies with temperature. In freezing weather, the 2.5l Subie might start as high as 1.o gallon/hour, but less in warmer weather. The rate would then gradually fall as the engine warmed, settling to 0.3 gallon/hour.

The only time I observed the Prius while scraping frost from the windows, it started at about 0.8 GPH. Then, and a few other times in warmer weather, it declined to about 0.2 gal/hr before finally warming up enough to allow the ICE to auto-stop.

ScanGauge can be used to check the total fuel burned during warmup. Sorry, I don't have anything accurate for full warmup for any particular car, but have seen figures in the 0.04 to 0.08 gallon range for partial warmup in different weather in the two cars.

This question sounds like a good excuse for additional testing.

 

It's very interesting that you have the thermistor hack on a PiP.
I wonder if any other PiP's have that?
There's a new PiP owner in VA who might want to hear about that.

 

Do you want the consumption of a warmup cycle with the car standing idle or is the typical consumption of a trip with one brief warmup cycle sufficient?

I checked the latter one a few times by watching the trip overview on shutdown. In my experience a typical warmup during driving consumes between 50-200ml depending on driving conditions and temperature. That are roughly 0.01-0.05 gallons.

I will record the next few warmup I encounter and update accordingly.

hope this helps,
/jr

 

what was the ambient temp?

 

Calculate it like Jeremy did! Put PiP into READY mode, set cabing heat so the ICE warm-up starts, turn off the ventilation to prevent further ICE start, and take the car for a short all EV ride. When you power off, take note of the MPG and distance traveled to calculate gallons burned.

 

Which ties up nicely with one to two eggs - apparently a large hen's egg is about 70 ml.

So, different ways to look at it. Daily commute, one warm up each way, to remove condensation etc and put a bit of heat into the car will use maybe 1 1/2 litres a week. Here in the UK that's going to cost about £2, so a bit over $3. Not really a lot, but if you bought the car primarily for ecological reasons, wasting that much fuel a week probably isn't what you want.

 

i don't mind using fuel when necessary, it's the times the ice comes on for no apparent good reason that makes me crazy, one egg, or two.

 

Considering that the Prius hybrid is miles ahead of the competition, I think it's fair to assume that ICE running time is already optimized.

 

There are quite a few threads & articles explaining the optimization... light-weight components, extremely-thin synthetic oil, exhaust gas recirculate, longer pumping cycle, battery-assist to reduce load, etc.

The engine now only takes a teaspoon or two of gas during warm-up, when it's warm out. In the winter, it takes more but you end up sending some electricity to the battery as a tradeoff.

 

As i said in another thread... My problem with ICE warm up is when I just want to move the car 20 feet from on the driveway outside, into the garage, and turn it off. ---I press "on", press "EV", and within the time it takes to shift into drive to move into the garage, the ICE is purring for its warm up cycle, and the display says it moved itself out of EV into ECO mode. I move the 20 feet into the garage, and the ICE is still running, doing its warm up -thing- and I can either sit n wait for it to finally shut off, or, just shut it off. But all that gasoline, was just wasted as I already had a full battery! Again, we live 3 blocks from the Pacific Ocean, it is always high 60's, very low 70's here, and this "warm up" happens every time we move the car,,, anywhere, regardless of state of battery charge... I would love to add the "thermistor hack", but would need to find a way to do it that could be easily undone, for Toy repair shop visits, as I do NOT want to mess with the warranty... Any suggestions?

 

Yep! my 05 did the same thing thats just the way it is. Sorry, if the car is warm you might be able to move it with out warm-up if you have enough charge, thats about it.

 

A third gen Prius keeps the engine off for 20 seconds at startup, without EV Mode being selected. If that was 60 seconds, would be enough for most car moving chores I think.

@Beachnut: when the car starts up, I see no reason to leave it idling just for warming up. Is that what you mean?

 

that's one of the great things about the pip. stone cold ice, move it here, move it there, go down the street and come back, whatever, no ice! sometimes i think it would be great if the lift back had just a little more battery to do this.

 

I believe the old saying is, "never look a gift horse in the mouth."

The Prius does a remarkable job of saving fuel, so it doesn't seem right to assume that we could somehow improve on it by reducing the engine running-time. The ICE runs for a reason, and when it does, it barely sips the fuel.

 

I agree that things can always be improved. Wait for the Gen IV.