Engine temps and ambient temps
 

I'm curious what ambient temp is the threshold where a hybrid like a gen 2 Prius can stay warm enough in city driving, so that it does not need to run just for the sake of keeping itself warm enough.

Does anyone have data on this?

I realize since I am in central TX, engine warming mods are not an area to put time into, and can be risky.

But I think i'm still going to install my own temp sensor on the engine block and see how it reacts. We do have some cold days in the winter where a simple adjustable lower grill block could be beneficial. I drove 2 miles this morning where we had a low near 50, and I got 28mpg. The nice thing about here is that most of the year it will only take a minute or two for the engine to warm up.

rather than install a temp sensor, just get a bluetooth OBDII adapter, grab an old android phone and use Torque or other app. You can get a wealth of data from the computer. It has coolant and other temperatures there for you to read.

Yeah, you've just got to be able to read the sensor you've already got.

All depends on what kind of grill block you're running, the driving you're doing, and how much heat you're taking for the cabin. My Prius has a full grill block and still only gets to 150-160F driving around town when it's 30F out (this is usually with some cabin heat and pretty short trips). Doing 80MPH in the 30s gets coolant temps of ~203F, which is definitely on the higher end. Coolant temps are even high going more reasonable freeway speeds, so I take out half of one of the pieces of pipe insulation in the top grill (leaving 3/4ths of the top still blocked) if I'm going to be driving far in the 30s+. At 20F or lower, it'll stay at around 190F doing 80MPH with the full block.

With your higher winter temps, I wouldn't do a full block unless you're only doing short trips. Lower grill block should be fine, though, I was able to run one most of the year when I was in El Paso. Definitely get a Scangauge, Ultragauge, or bluetooth adapter with Torque app to monitor the coolant temps to stay safe when blocking the grill.

The *problem* with 'grill blocks' in a Prius is NOT with the engine coolant temperature, but rather with the co-located, solid-state, electronics controller for the traction battery.

Do you get a temp for that from OBDII?

I run a near full block on my Prius year round. In winter it is a full block. Its never been a problem.

You can, but you need to use X-Gauges with a Scangauge or custom PIDs with Torque. You can also use a mini-VCI adapter that plugs into a laptop, which is the same thing the dealer uses, so it's great for troubleshooting and certain maintenance procedures.

I'm just using an Ultragauge in my Prius, so I just have to hope for the best when it comes to the inverter temp. I have the snorkel removed from the airbox, so my intake temp should be pretty close to the under hood temp. The highest I've seen was 90 or 100F for the intake with the full block. I'll have to bring my laptop and mini-VCI with me on my next trip and see how the inverter temps look.

It's extremely rare that it's cold enough to need to use cabin heat. Maybe if it's below 40 degrees. There won't be many mornings that cold.

My typical usage is a lot of city driving and 5-13 jobs each day where the car will sit for 15-40 minutes typically. A fair bit near an hour, so the engine does cool down a bit on cooler days. Today the engine ran (in my mind) excessively when exiting a parking space/lot.

I'll buy a bluetooth obd2 reader, sounds like a good idea. I wanted engine rpms too.

Hobbit curates a pretty good article about the stages of operation for the Prius: http://techno-fandom.org/~hobbit/cars/five-stages.txt

That might help explain why it'll kick on the engine, even in times where you might think it shouldn't need to.