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I'm tempted to install the EV Button in my Prius as an engine kill switch during engine warm up. As I've understood it, the reason for Toyota programming in an always-on stage of operation for the Prius, had something to do with Emissions (heating up the cat-converter).

So if I have a 30 minute commute and use the Engine-Veto button to reduce the amount of gas I consume, wouldn't I also reduce my Emissions?

Conversely, if a heated cat-converter reduces emissions, wouldn't the 10 minutes that it forces the engine to run counter act the 5-10 minutes of "clean" operation it produces. Keeping in mind that on my 30 minute commute with P&G, my engine really only runs for 15-20 minutes without an EV switch, and with it, could probably be reduced down to 10-15 minutes.

Dan,
I got my button about one year ago. Here's what I've found.

You can not engage the button when the engine is warming up. So when you say, "as an engine kill switch during engine warm up" this will not work. The Prius is too smart for that.


About that CatConv, I don't know. I don't know what the proper operating temp is and I don't have a ScanGauge.

Another thing: I have used the button a lot and abused it on more than a few occasions. If you extend its range, you will discharge your battery to a level your Prius won't like. It will immediately run the engine to recharge the battery. And it will do this ignoring anything you attempt to stop it. If you are sitting still, the engine will run. If you are moving, your mileage will be horrific. Trust me, it's no fun.

I'm not trying to talk you out of the button, just trying to provide the reality of the situation. It's a great little device and I use it to move around parking lots and to shuffle cars.

You can not engage the button when the engine is warming up.

Depending on outside temps, you may be able to engage it as early as stage 2 (http://www.techno-fandom.org/~hobbit/cars/five-stages.txt), which is still in the first 5 minutes of operation.

I have used the button a lot and abused it on more than a few occasions. If you extend its range, you will discharge your battery to a level your Prius won't like. It will immediately run the engine to recharge the battery. And it will do this ignoring anything you attempt to stop it.

Yes, this is awful! The one time I tried to EV an entire trip of less than a mile, I started from only 4 bars. Once it hit 2 bars the EV auto-disengaged and I was doomed to a completely unnecessary warmup/charging cycle. Don't abuse it. ;) Use it as a kill-switch when you are already attempting to glide, or for trolling around parking lots and such. It's not meant to get you X miles on EV only.


Having said this, I don't have much in the way of insight with regard to the question in the OP. I leave that to people who know more about this, and am also curious about the answer. :)

I don't think there's any way that it would harm emissions. Here's my take:

Used to move the car around the parking lot, driveway, etc. it is a very good thing from an emissions standpoint because it reduces the number of cold starts and the associated burst of stupid-high emissions. Score 1 for the EV button.

Used properly during driving (i.e. to shut down the engine but not to draw excessively from the pack for propulsion) I don't think it's any worse than a normal stealth/glide situation. The car simply won't let you use it when it isn't ready. You get the dreaded "BEEP BEEP BEEP" and the ICE just keeps on running. My understanding is that the EPA banned it from the US because they didn't know how to account for it in mileage testing, not because it could be an emissions problem. Apparently they resolved that and the new Highlander Hybrid will get the EV button from the factory.

About that CatConv, I don't know. I don't know what the proper operating temp is and I don't have a ScanGauge.
A question I've been meaning to ask - what triggers autostop on the Toyota, Honda? Is it when the cat is warmed up or the coolant?


Another thing: I have used the button a lot and abused it on more than a few occasions. If you extend its range, you will discharge your battery to a level your Prius won't like. It will immediately run the engine to recharge the battery. And it will do this ignoring anything you attempt to stop it. If you are sitting still, the engine will run. If you are moving, your mileage will be horrific. Trust me, it's no fun.Now you know what it's like to drive the Insight in either hypermiling or hyperdrive mode. Anyone that tries to drive the Insight like a racing car will drain the battery down quickly. On the other extreme, pulse and glide will do it because shutting off the engine denies it a change to recharge from regenerative braking.

For the long-time EV-equipped Prius owners: How much benefit do you think you're actually getting FE-wise? I think a couple of folks on PriusChat (Evan and possibly Tony) have commented that the benefit is marginal at best, and for that reason I've chosen not to install one up until now. The recent discussions here have prompted me to rethink it, but I'm still not convinced. I've gotten pretty good at pedal-feathering EV mode, and I can pretty much get a fully warmed ICE (and during stage 2 warmup) to cut off when I want it to in low-speed situations: parking lot movement, between closely spaced red lights, extending low-speed glides, etc.

What's the consensus?

A bit OT, but I think I'm interested in the debat.

Just to clairify, I see the EV button as serving two functions:
Electric Vehicle - run off pack
Engine Veto - to kill the ICE
I will NEVER use EV for 1, with the exception of moving the car from the front of my driveway to the back (25 feet). My only interest in EV is 2.

Depending on outside temps, you may be able to engage it as early as stage 2 (http://www.techno-fandom.org/~hobbit/cars/five-stages.txt), which is still in the first 5 minutes of operation.Thanks for the link locutus. I'd seen it before, but hadn't seen the sidebar and addition that Ken@Japan put in. So I think I get it now. To summarize, and jump in if I'm off track, for me to get to work with the least reduction in SoC and least operation of ICE, I should do the following:


Stay home if it's below freezing (it's ok, they close Houston when it freezes anyway) since Engine Veto won't work.
When I get in the car, push start and let the ICE kick on and run for 57 seconds.
After the initial minute of warm up, while in park, the ICE cuts out, now hit EV
Backup out of driveway, then turn off EV. Now I'm in Ken's stage 1a and EV is enabled.
Pulse to desired speed, hit EV and feather gas, this should give me a ICE-off glide in stage 1a
Disengage EV before coming to a complete stop, since stage progression at stop can be hendered in EV mode.
Once on the Highway do what I can to draft and keep MPG high
Upon exit of the highway, if I haven't progressed to S4, use Engine Veto (EV) to kill engine on glides in stage 2 or 3.
Continue to disengage EV before stops to allow "natural" progression to S4


So this is what I'm reading as "possible" from the analysis. There seems to be some disagreement as to whether Engine Veto (EV) can be obtained before S4. Is it commonly accepted that this best case that I outlined above never happens, rarely happens, or happens from time to time? If Engine Veto (EV) before stage 4 only works 1-2% of the time, I'm not likely to do the surgery. A success rate above 20% and I'd consider it.

I can pretty much get a fully warmed ICE (and during stage 2 warmup) to cut off when I want it to in low-speed situationsDon't forget, black arrows don't always mean ICE-off. Found out this morning as I coasted with black arrows, my iFCD started dropping when I slowed to 15 mph. The arrows were still black (or gone really) but my iFCD was < 99.9.

OK.. now back OT:
it is a very good thing from an emissions standpoint because it reduces the number of cold starts and the associated burst of stupid-high emissions.But if I never use it as an Electric Vehicle (EV) switch, and only and Engine Veto (EV) switch, I would think I'm actually maximizing the number of cold starts with stupid-high emissions. My justification is the fact that I could reduce the ICE-on time from 20min down to 10min. Less ICE = Less Emission, yes? And on the nonEV prius, aren't you just as dirty when your attempting to drive in S1 and S2 when the ICE is always on, as you would be if you only fired it up for load, and killed it on idle?

As for the EPAMy understanding is that the EPA banned it from the US because they didn't know how to account for it in mileage testingI'd heard that too, but failed to believe they could be that stupid. My nievity led me to believe that: <pureFantacy>
the agency suggested the button be removed to reduce overall emissions
related to continual cold starts resulting from it's use
</pureFantacy>I guess I didn't apply the EPA-IQ reduction factor.

But if I never use it as an Electric Vehicle (EV) switch, and only and Engine Veto (EV) switch, I would think I'm actually maximizing the number of cold starts with stupid-high emissions. My justification is the fact that I could reduce the ICE-on time from 20min down to 10min. Less ICE = Less Emission, yes? And on the nonEV prius, aren't you just as dirty when your attempting to drive in S1 and S2 when the ICE is always on, as you would be if you only fired it up for load, and killed it on idle?


I don't think you have to "never" use the EV switch to run off the pack, as Toyota originally gave use the feature for specifically that purpose. Remember that we're not talking about going for a mile and running the pack down to nothing, just using a little juice to back out of the garage, move the car a few hundred feet...stuff that doesn't deplete the pack appreciably. Given the choice between that and a cold start, you would be MUCH better off on all fronts if you take the small hit to the SoC. Remember that cold start is when most of your smog forming emissions (NOx, hydrocarbons...the things other than CO2 and water) are formed.

That said, I really don't think the the Prius will allow you more than one true cold start for a trip. Even in stage 2 the engine has warmed up appreciably and fuel should be vaporizing properly. The catalytic convertor should have had time to warm up, too. Finally, consider that a Prius doesn't start up like a normal car. The engine spins to idle speed then it starts injecting and igniting fuel. So it would bypass the enriched condition that is present while a normal engine cranks away.

Of course there could be other important puzzle pieces. This was a good question to ask and I wish we had more hard information to go on. Maybe it exists somewhere...

Dan, nice post and summary. :flag: A few thoughts:

Just to clairify, I see the EV button as serving two functions:
Electric Vehicle - run off pack
Engine Veto - to kill the ICE
I will NEVER use EV for 1, with the exception of moving the car from the front of my driveway to the back (25 feet). My only interest in EV is 2.


"Engine Veto" is definitely my top use, but as brick mentioned, NEVER using EV to run off the pack isn't true. Of course the obvious use of very short trips or trolling around parking lots, but also things like when your glide is going to come up short of a stop and you need a little EV to get there (assuming you're not in S4 or otherwise ICE-off yet). It's a tradeoff of the hit of reigniting the ICE for a few seconds vs conversion losses in drawing from the pack. I wish I had more hard data on where that break-even point is.

Stay home if it's below freezing (it's ok, they close Houston when it freezes anyway) since Engine Veto won't work.


:D Don't I wish. My experience so far is that it works sporadically rather than not at all from about 10 degrees up to freezing, then below 10 pretty much not at all. (I got it to work at some points today at about 12 degrees.)



When I get in the car, push start and let the ICE kick on and run for 57 seconds.
After the initial minute of warm up, while in park, the ICE cuts out, now hit EV
Backup out of driveway, then turn off EV. Now I'm in Ken's stage 1a and EV is enabled.



I don't know about this one, I'd have to see some data. It seems like you would want to be moving during that time to get some low MPG but >0. 57 seconds seems like approximately the length of time that stage 1 lasts anyway....?




Disengage EV before coming to a complete stop, since stage progression at stop can be hendered in EV mode.
Continue to disengage EV before stops to allow "natural" progression to S4



If you're sure you will have to come to a complete stop this is a good idea. ;) Stage progression from 3 to 4 is the only one that's hindered I think.

If Engine Veto (EV) before stage 4 only works 1-2% of the time, I'm not likely to do the surgery. A success rate above 20% and I'd consider it.


If it's above freezing I can hit it in stage 2 almost all of the time. Sadly, "above freezing" was so long ago I don't remember if that was more like "most all of the time" or "without exception". :(


Don't forget, black arrows don't always mean ICE-off.


Yep, this is my primary use of the EV button - to "enforce" this. ;)

Should I change the title from "If I had a Prius" - sounds too much like O.J. Simpson's latest book. :eek:

Seriously, I think my commute could use the EV mode:

back out the driveway, going uphill three feet
go 100 yards down the alley
turn sharp left 15 yards
turn right, go another 15 yards
turn on the street
20 more yards, crest the hill
100+ yards downhill to the stoplightWould the EV switch help for that kind of start?

You should see me trying a Pulse & Glide on that. :D

I think you're thinking too hard...
.
The EV is useful for those times when the engine *would*
shut itself down in stage 4 but can't yet, because you're
still in 2 or 3a. I.e. when you back off your foot. If
it doesn't shut down, *and* the battery is warm enough to
allow EV, you can coerce the ICE to not churn away your
fuel dollars while you're coasting up to that next light.
.
Then, you toggle back OUT of EV mode next time you know
you're able to get a good, efficient burn from the ICE.
The car doesn't know your upcoming terrain, but you do.
.
That's it. Just helps you do real P&G that much earlier.
.
_H*