I've wondered how to counteract the loss of MPG due to warming up the engine. It's easy to dismiss this line of thinking, based on the fact that the gas must heat the engine no matter what you do. But I wondered whether it would make any sense to go ahead and drive "hard" while the engine is cold (accelerate in the high power range). The loss of efficiency will count toward heating up the engine, so really you're recovering all of that loss of fuel. On the plus side, you'll get up to speed faster, and not be accelerating for as much time, which could boost MPG. Does that make any sense? Has anybody experimented with this? If it works, it seems this should be added to the recommended driving techniques. With my extremely short commute, I think I'll start doing this.
I've had the same thoughts before. When I see the engine is still running to warm up (but able to provide torque to the wheels), I try to run the HSI bar above the midline, based on the thought that using the ICE to provide power will also generate the waste heat it currently seeks and desires. Yes, I know the Prius has no emotional capability. Since it is going to run anyways, I don't see an obvious downside.
Say, post your results for everyone to see. Should be easy enough to test, using both acceleration techniques of hard and easy.
Have you ever considered the engine life? For me, I won't let high load on the cold engine. Ken@Japan
The question was about MPG. Of course engine life is a concern. But even in my old Yaris I didn't warm up the engine because I didn't want to waste gas. I did actually did a pulse and glide the first few blocks, not knowing it was something other people did. I figured coasting while the engine warms up is better than being parked while the engine warms up. If log the MPG on my Prius as an experiment, maybe I should include a run where I let the engine warm up while parked.
My wife and I have had our Prii for about a year now and since start of 2011 we have let the engine heat up before driving. The results are at http://www.fuelly.com/driver/jaquimo/prius/annual and http://www.fuelly.com/driver/jaquimo/prius-2/annual. It is autumn here now and I think during winter the difference will be even more pertinent.
Being in CA and having pretty warm weather, I wouldn't think you would need to worry about warm up and engine wear so much. The Prius seems to bypass its rich mixture (sluggish) if you request power early on but return if it has not reached its operating temp.\ Try your experiment... we would like to see the results.
live in Central Indiana. I tend to just get in and drive it. I'm still trying to get the hang of P&G'ing.......at least I think I am. not really sure what it is. guess my next stop? google......
During warm up I try to keep ICE on, without doing P&G if I can. So it will get warm earlier. Warm ICE (>75°C / 167°F) = more efficient ICE. But until ICE coolant is below 65°C (150°F) I just give light loads, and I keep engine below 1350 rpm if I can. I think this could be good for ICE life and limit wear. I don't know if driving "hard" with cold engine could improve overall fuel economy, but I care more about ICE life, and I won't start this experiment. In addition I always use 0W-20 100%synth motor oil: this ensures a good lubrication even during very cold warm ups, and good fuel economy. And when outside temp is below 15°C (60°F), partial lower grill blocking is highly recommended.
I've done a few runs of "drive hard" versus "take it easy / P&G" on my 2 mile commute. Actually, the commute involves a stop at a coffee shop, but I digress. So far, it looks like the "take it easy" driving gives better mileage, but there are large variations for both types of driving. I've also been keeping track of the state of charge of the battery before the drive. This seems to have a significant influence on the MPG. It makes me wonder whether it would be a good idea to somehow charge the battery to 100% before driving. There must be some info out there about this. Are there chargers for the existing 200V battery? Does this void the warranty? Is there a way to make it undetectable, so the warranty doesn't get voided? TIA. By the way, I got to wondering whether a solar panel would do the trick! That would be way slick. I go to work around 11AM, so it would get some charge before I leave. As an electrical engineer, I could design whatever voltage converter is required.
I second that as well regarding gentle vs hard driving on a cold engine. The experiments conducted as below: Method 1 ======= - Putting the car on EV mode, drive it out of car park - Drive it hard from rest to 80km/h, usually into the PWR zone of HSI. Battery level runs down to 5/8 bars. Versus Method 2 ======= - Just drive it; letting the engine warmed up by idling. By the time I got out of the car park, it is probably warm enough to be throttled without relying too much on battery alone. It is giving you false impression of bad MPG number first up but it will eventually gets better. I also concluded since the car is being warmed by idling and battery is charged (7/8 bars), acceleration load is being balanced between engine and battery, therefore get better MPG as a result than method 1. This is true even for the current wintery condition in Melbourne.
One thing that hasn't really been mentioned here is that during the first warmup stage (1a) the ICE runs, but doesn't actually provide any power to drivetrain or generator... even if you move the HSI past the midline the car is still running on electric power only and hard acceleration in this stage will drain your battery very quickly. The car can be in this mode for up to a minute or so, depending on how warm the ICE is to start with. I've seen people suggest that it's best to just sit and wait for the ICE to finish stage 1a before moving. The theory is that since the ICE isn't providing any benefit assisting with motion or even charging the battery it's just 'wasted' gas and if you start driving in this stage you're just draining the battery and will need to use even more gas to recharge it later. Having an engine block heater, particularly in cooler weather can definitely help here as it will allow the ICE to come out of stage 1a much quicker. Here's a link to the Gen III warmup stages... http://priuschat.com/forums/gen-iii...-discussion/76501-gen3-warming-up-stages.html
I discovered this today with my new scangauge. The engine ran at 1280rpm regardless of my driving, while warming up from "cold." I thought maybe I was crazy or it wasn't updating the rpm correctly. But it does make sense to avoid warming up the engine too quickly.
Well, so far I've discovered I can boost the MPG by driving around 40MPH while the engine is warming up (as opposed to 25MPH in stop-n-go traffic). I am gentle on the throttle, and there is no point in attempting pulse & glide since the engine will be idling anyway. Once it starts to get warm, then of course gliding is possible.
Not sure it should be a big concern at least as long as temperatures are above freezing. Modern synthetic oils esp 0w20 flow at temperatures -35C and below. Most of the time issues with OHC engines are not due to mechanical wear.. the weakest point is the valve seals. They harden up after many heat up/cool down cycles even nitrile rubber turns into glass. After that oil starts flowing through valves into cylinders, burn and case damage. If you wanna double life of your engine, replace seals at ~120-200K miles/6-8 years with the best money can buy.
My commute is also 2 miles (with no coffee shop on the way) with six sets of traffic lights and a 300ft variation in elevation along the way. I find that I get the best MPG when I reverse on to the driveway (at which point the ICE starts up) then idling for the minute or so it takes for it to shut down again. I must include that I am in no way a hypermiler though, with a current displayed MPG of 46.5 on my commute (around 75 degrees when I set off) and a lowly 38 when it's colder (20-40 deg). Even 38 still felt great to me after ditching a bimmer for the Prius, since that was giving me 12-14 mpg over the same journey.
No matter what you do and no matter what kind of car you drive, mpg will suffer on short trips. Which is depressing, so I avoid it. I hate seeing 20-30mpg in a car that will give 50-60mpg normally. For a 2 mile commute I'd bicycle (maybe 10 minutes?). Or walk (30 minutes at a brisk walk). As long as weather is good and assuming I didn't need the car for a longer trip during the workday (or for getting kids to school, etc). Either has added health benefits to me. And (in urban areas) no hassles with parking. In the Boston area bicycling is often faster than driving, and eliminates traffic frustrations. When I'm working in Boston I commute by bicycle from Medford to Cambridge (where parking is nearly impossible), perhaps 4-5 miles, unless it's raining hard. Takes 15-20 minutes. If I were commuting like this regularly, I'd consider factoring the bicycling/walking mileage into my mileage spreadsheet for the car, which would help offset the mpg "hit" on the days when I MUST take the car to work.
