Archives

I just posted a 3-page write-up on the Gen3 warm-up stages, their significance and detection over at PC. It is based on Ken@Japan's work and the Gen2 material, and will be refined as more is reported. Here is the link to Ken's thread in which I posted:

http://priuschat.com/forums/gen-iii-2010-prius-technical-discussion/76501-gen3-warming-up-stages.html#post1068435

Nice work KS

Awesome stuff KS.

However, I've noticed that my recorded lower thresholds of 46C, do not match the values noted on the PC post (40C). I also noticed a few additional behaviors related to a definite restriction state that completely inhibits EV mode at ambient temps below -18C, even when the engine reaches S4 temps.

Unlike the Gen2, it appears the G3 factors in the ambient temp more aggressively. I am still in the process of building my state transition table, but when I am done I will post in the usual hybrid winterizing article.

Cheers;

MSantos

Thanks, guys.

msantos, luckily humans don't go where it's -18C! :) Actually, that's not all that cold, eh? 0F.

I agree there is more to the story than presented and the presented stuff is not 100% yet.

When you say lower theshold, are you referring to the S4 section where the ICE restarts, or to the various mentions of 40C in the early stage transitions?

No EV at lower than 0F would seriously hurt here in MN, too. :(

Sean, EV-mode is not used much anyway.

If he is referring to engine-off glide, that would be huge, but I didn't take it that way. Cannot say for sure that I've had mine S4 in <0F yet. Ok at 5F, I'd say, for gliding.

But EV-mode is a mere novelty anyway, most of the time.

If it is anything like the add on for the second gen, it is incredibly useful as a way to ensure the engine is off. AER is too limited to make EV Mode useful as propulsion, but as a way to "FAS" it is quite valuable.

What say you, Manuel? Is a full glide still available under 0F?

EV less useful for FAS in Gen3 with its 10 or 25 mph max speed. Plus the Gen3 may be more inclined to cut the engine outside of EV and the engine stopped limit is up from 42 to 45 mph. I glide forever with engine off and not using EV.

Hi Sean;

In lower temps, engine off glides are still possible once the car reaches a higher warm-up stage. This is true for soft glides (induced with the accelerator pedal) or forced glides (induced by switching to N).

However, below -18C, EV only operation is actively suppressed even when you know you should be able to do it.

The other thing I noticed mine doing more often, is that getting a lower IGN operation (13-16) is much easier than it was during the warmer temps. The car prefers to keep the ICE ON longer (when you would expect it to do EV) and the affinity to remain in IGN range (high MPG regimen) is quite high. So despite the loss of the EV feature you can still get into an HCH-II like, high FE mode that can cut the FE losses dramatically. We're talking 65-75 MPG zones of steady state low speed cruising (15-45 MPH).

Auto-stops also get to be a hit and miss sometimes at ambient temps below -18C, even when the car is well warmed up.

Cheers

MSantos

The IGN timing sounds like a serious win — thanks for the added info!

Too bad there is no way to force engine off whenever you want it…

...
When you say lower theshold, are you referring to the S4 section where the ICE restarts, or to the various mentions of 40C in the early stage transitions?

I was referring to the multiple references of 40C in the early transitions. 46C (114.8F) is the lowest transition temperature I've recorded.

Cheers;

MSantos

...
Too bad there is no way to force engine off whenever you want it…

Hi Sean;

Yes, that's true. Not being able to force an ICE shut off does suck a bit though... However, even though I can do it in the HCH-II, I have been choosing against it when the temps are really low simply because the price you pay for a FAS is so darn high and in so harmful in several different ways.

What I am trying to say is that with HSD we are forced to let it do its thing and take it for what it is. But while we can FAS with other hybrid systems (like the Gen 4-5 IMA) it does not mean it is the best option either. In the big scheme of things when it is that cold, it just is... and letting the systems do their thing often produces the better results in the long run.


Cheers;

MSantos

Manuel, I've also found that engine off coasting is almost useless when the temps are low enough simply because glide distances are almost nil with all the extra friction in play... but being able to force engine off at stops still makes a huge dent in fuel usage. That's the one I'd really like to be sure I could do in a Prius in really cold temps.

Hi Sean;

The problem with FAS on a 2010 Insight or HCH-II (especially nasty on the HCH-II) is that when at temps below 15C (59F) the warm-up stage is reset back to stage 1 for 10-15 seconds after Power-off.

This will happen even when the engine is fully warmed up. So for short stop lights a FAS is not helpful at all since the fuel consumption is going to be higher after power-up and in the process you've dinged your 12V battery quite a bit too.

The other problem in colder temps is that the ICE temp drops like a rock in just 30 seconds so much so that even keeping the ICE ON and in N can slow but not stop the free-fall. The Gen 3 Prius also drops the ICE temp like a rock when it is very cold, so an ICE OFF condition does not help the Prius either. This I verify on a daily basis with a grille fully blocked on both cars.

Cheers;

MSantos

Hi Manuel -- I see the same with my tiny aluminum block in the Insight-I... but I still find it useful early in the drive when the block hasn't really warmed up anyway. Such as trying to get through the first 10 lights on my route every morning (which occur in the first 3mi). Light timing is (as always) the most powerful tool in the arsenal... but if I have to stop I'd rather cut my losses. Later in the trip it is typically a different story.

Too bad there is no way to force engine off whenever you want it…
A thermistor hack (http://priuschat.com/forums/gen-ii-prius-modifications/36342-another-thermistor-hack.html) will let the engine off if you want.
I will write up it soon for Gen3 Prius.

Yoshi@Japan, aka Ken@Japan

Hello, Yoshi!! Good to hear from you again. :)

I wasn't aware that a thermistor hack would work in the 3rd generation. Very cool! :thumbs_up:

Hi,
I just posted yet another thermistor hack for Gen3 (http://priuschat.com/forums/gen-iii-2010-prius-accessories-modifications/76906-yet-another-thermistor-hack-gen3.html) on the PriusChat forum.

Enjoy,
Yoshi@Japan, aka Ken@Japan

As always, thank you for your hugely helpful contributions to the knowledge base. :D