Prius P&G - "Failed Glides"

[kayakwill]

I have just started using the P&G technique on my commute with fantastic results. I don't yet have my SGII (group 15 buy), so I don't have all the indications yet. I'm having more frustrating moments than I'd like when I can't initiate a glide - particularly on colder mornings. As an example, this morning the temperature at a brisk 42 degrees, I was fine in P&G after warm up - 40mph-30mph, and HSP&G 50mph-45mph for 7-8 miles. At that point I'm going through a small town with 25mph limit, trying to get into glide with no success - either charging, or on the ICE. Then back to 35mph limits with another 10 minutes of successful P&G, then additional failed glides. This is the very frustrating part, because without the failed glides, I'm able to get over 100mpg for this stretch, but this morning only able to do 65-75mpg. Occasionally this happens in the afternoon also, but seems much rarer in warmer temps.

I'm hoping I won't have to live with this - particularly all that way through the winter.

Help!!

[JimboK]

Ahh, the nuances of the Prius warmup sequence. You most likely were still in stage 3 and had not reached stage 4 -- the final warmup stage. Either stage requires an ICE temp of at least 70C; below that and you're still in either stage 1 or stage 2, neither of which allows a glide. Stage 3 will continue indefinitely, near as I can tell, until you come to a complete stop, allow or induce the ICE to run (by, for example, stepping on the go-pedal enough to light it with your foot on the brake), and sit long enough for it to shut off on its own -- generally about 7+ seconds. Meanwhile, S3 glides can begin at speeds above 34 MPH but not below.

Read this for more.

EDIT: As you approach the lower speed zones, begin your glide before you drop below 34 MPH and allow it to continue as long as possible before you either have to stop or have to get back on the go-pedal. Then if you stop, provoke the S4 "idle check" (as some call it) ASAP. Sometimes I've even gone as far as pulling off the road to provoke it if I know I have some low-speed P&G opportunities ahead and won't be able to safely and legally push it higher than 34 MPH. But that was mostly before the days of the EV switch. The switch becomes, as Dan calls it, an "engine veto" switch in low speed S3 glides.

[kayakwill]

Thanks Jim. This is very helpful. Sounds like I need to install an EV switch next - is the Coastal EV switch the one to get?

[JimboK]

I steer folks away from Coastal for any purchase because of a very spotty customer service record. And their EV mod has a 2-second delay, which I would find frustrating. You might consider a "home-grown" approach like this. If you don't feel that ambitious, Sigma Automotive sells one too. More expensive than Coastal's model, IIRC, but I would choose to pay the extra money for better assurances of prompt delivery and support.

A word of caution: At least one Prius owner had a warranty claim for a bad hybrid battery initially denied because of his EV switch. Toyota later relented after he agreed to remove it. I think it's bogus for Toyota to deny it -- they include the button on European Prii, for cryin' out loud -- but in this one case it didn't stop them from trying and putting the owner through some grief.

[Mr. Kite]

I had similar issues shortly after getting my HiHy. It was very frustrating. Now I know about it and it is still frustrating at times. I hate having to do things that waste fuel so I can get to a stage where I can save fuel. My commutes are often short, so being in Stage 3 can really ruin my fuel economy.

Is there any logical reason why Toyota has designed such a transition from Stage 3 to Stage 4?

[xcel]

Hi John:

___Toyota was lowering the Prius’ emissions vs. increasing FE in the warm-up and S4 guarantees solid SULEV-2 capability.

___Kayakwill and John, you have to be watching coolant temps so you know when to pull an idle check. As low as 157 degrees F is when you are ready but any glide falling back below and you have to go through the final stage all over again IIRC

___Good Luck

___Wayne

[Mr. Kite]

Originally Posted by xcel

Hi John:

___Toyota was lowering the Prius’ emissions vs. increasing FE in the warm-up and S4 guarantees solid SULEV-2 capability.

___Kayakwill and John, you have to be watching coolant temps so you know when to pull an idle check. As low as 157 degrees F is when you are ready but any glide falling back below and you have to go through the final stage all over again IIRC

___Good Luck

___Wayne

I do watch the coolant temps on my ScanGauge very closely during warmups. I understand the whole emissions vs. increasing FE thing, but I still do not understand why the transition to Stage 4 is the way it is.

If my coolant temp is already at 85 C, why do I need to come to a complete stop, restart my engine, then wait 7 seconds before I can enter Stage 4 (full-hybrid mode)? It makes no sense to me.

It just seems silly to me that I sometimes hope a light turns red, or I kill my momentum and pull over on the side of the road, or I restart my engine at a stoplight so it can idle for 7 seconds just so I can save gas

Last week, I had to drive to the bank from work. The trip was just long enough and I used Stage 3b enough that my temp was only 71 C when I got to the bank. After leaving, the temp was already back in the low 60s. Well, shortly after leaving, all the lights were green (this shouldn't be a bad thing), so I was stuck in Stage 3. I had to go over one hill and then I would have a long coast to my turn. The only light is right at the top of the hill and is only activated by the occasional traffic coming out of a neighborhood. Of course, I want to get to 35mph so I can get in Stage 3b. Normally I wouldn't worry about that, but I have to go faster so I can save gas. Anyway, as my luck would have it, the light turns red just as I'm about to get to 35mph. The light was so short that I didn't even have time to get into Stage 4.

I just want to know--is there a real reason for the non-linear transition to Stage 4 mode, or is it just some arbitrary hurdle?