[gudfart]

I was driving around in Constant AWD (with a near full battery) and missed an opportunity to put gas in. I figured even if the gas engine stopped I had enough battery to get to my preferred gas station, no problem. Well the engine stopped and the car went into turtle mode. It locked itself out of Pure even though the range estimate was 33 miles. Hybrid was available but with a limited speed of 45mph. I drove and filled up the tank. When I restarted it was in another turtle mode, full speed available, "diminished performance", Pure still locked out and no electric drive despite 30 miles of range. I drove around a few blocks then shut it down to restart. This time when it started the turtle was gone but it still wanted to run the engine. I assume it was to ensure the engine either had gas through the lines or to go through a warm-up cycle or both. Who knows just speculation. Electric came back shortly after.

I can't find a warning about the consequences of doing this in the manual so I don't feel too dumb. Just a FYI for anyone else with the 22.5 ER/Sensus unicorn: if the engine has no gas on the interstate you'll probably be limited to 45 😬

an edit to add I put just over 18.2 US gallons in the 18.8 tank

 

[capndavey]

And now I know exactly what will happen when my wife does the exact same thing 😅

 

[allpurposeben]

I’ve wondered what would happen in this case. When mine was delivered it was showing single digit gas range but 20 miles of battery.

 

[gudfart]

I’ve wondered what would happen in this case. When mine was delivered it was showing single digit gas range but 20 miles of battery.

My range went in 10s; 50,40,30,20,10, then -- for longer than I care to admit. Like I said it's a Sensus car so literally YMMV

 

[DFrantz]

Makes sense to me, I wouldn't have thought to try it. The sensors are looking for a properly running motor, and if it ran out of fuel it may well have run lean or just gotten low pressure there for a short period and the sensors all got pissy and then limp mode to prevent damage.

 

[gudfart]

And now I know exactly what will happen when my wife does the exact same thing 😅

Emphasize to her the 45mph limit! Ironically I came up on a dead Taycan in the middle lane of the interstate on the same trip!

 

[VolvoFaRmeR]

That's what happens when a car runs out of gas. Low fuel rail pressure, lean fuel mixture, a spike in turbo exhaust temp and a variety of other things are sure to put the car into "limp" mode to protect itself. I'm sure that doesn't do the fuel pump any favors either. Most certainly is not a "flaw" or a "glitch", but rather the car trying to protect itself and not leave you stranded as well.

 

[gudfart]

That's what happens when a car runs out of gas. Low fuel rail pressure, lean fuel mixture, a spike in turbo exhaust temp and a variety of other things are sure to put the car into "limp" mode to protect itself. I'm sure that doesn't do the fuel pump any favors either. Most certainly is not a "flaw" or a "glitch", but rather the car trying to protect itself and not leave you stranded as well.

I can see the logic for turtle mode in a T8 if it's in Hybrid or you have zero battery but at least allow the use of Pure and the top speed of Pure which is 87mph. I can also see the logic in limiting the speed to extend the range but I'd rather have something safer like a 70mph limit or even 60, not 45. I even tried Individual mode which I have programmed as Pure and it stayed in Hybrid which is dumb since the gas engine couldn't be used. Overall I think it's a lack of safe programming for this situation. My beef isn't having the gas engine turtled, it's the car not looking at the battery and allowing normal operation.

 

[DFrantz]

I can see the logic for turtle mode in a T8 if it's in Hybrid or you have zero battery but at least allow the use of Pure and the top speed of Pure which is 87mph. I can also see the logic in limiting the speed to extend the range but I'd rather have something safer like a 70mph limit or even 60, not 45. I even tried Individual mode which I have programmed as Pure and it stayed in Hybrid which is dumb since the gas engine couldn't be used. Overall I think it's a lack of safe programming for this situation. My beef isn't having the gas engine turtled, it's the car not looking at the battery and allowing normal operation.

It would have to be programmed to cut the engine off prior to running out of gas and it isn't. So far as the cars computer is concerned the motor might get damaged. In constant awd mode it would have been trying to keep the ERAD and transaxle spinning at the same speed too. It's a good question to have (and good to know the answer), but yeah, it's clearly not designed to be operated without gas. Of course... being that low... you could have manually switched it to pure.

 

[gudfart]

It would have to be programmed to cut the engine off prior to running out of gas and it isn't. So far as the cars computer is concerned the motor might get damaged. In constant awd mode it would have been trying to keep the ERAD and transaxle spinning at the same speed too. It's a good question to have (and good to know the answer), but yeah, it's clearly not designed to be operated without gas. Of course... being that low... you could have manually switched it to pure.

I now agree it's not designed to be operated without gas lol The engine shuts down constantly in hybrid so I didn't give it much thought that it's different; thankfully it didn't brick. Considering how bad the range estimate is, I can see it can't predict zero fuel and instead has to react to something like low pressure.

In hindsight Pure would have been prudent but then we wouldn't know the answer to these mysteries! I probably helped answer some questions for Volvo 😛