So I have a 2013 Prius V here on Vancouver Island and yes I know we really don't have winter. I have read the article called a Hybrid Owners Winter Survival Guide in which they go into the various methods of grill blocking to keep in engine heat. I have installed the block heater and I'm sure that makes a differance as you just start the car after a couple of hours and go with pretty much instant heat. Now back to the article they give a chart which indicates various operating temperatures combined with ambient air and grill blocking. In the article it indicates that 90C or over is to hot. I did purchase a OBDll ELM327 bluetooth scanner device and downloaded the Torque App. Even without blocking the grill it indicates temperature as high as 95C when pulling the Malahat out of Victoria. And even on the rest of the trip it is close to the 90C if not over. So what gives? Or are these scanner things and apps not that accurate??? Or is 90C the normal operating temperature. Ah the days of a guage with it clearly marked on the guage where the temp should be.
91°C (195°F) is the normal operating high. When the temperature outside drops, it's more of a challenge reaching that. So, we block the grille to help reduce the loss of heat.
I will admit that I've never see an official document that outlines the maximum coolant temperature for the Prius engine. Hopefully, someone can link an official source. I have seen the coolant temperature as high as 198F (92C) during extended hill climbs in the summer when the OAT was 102F(39C). I think the car will take care of itself as long as you don't impede airflow while operating it as outlined in the owners manual. Now regarding cold weather... Living on the west side of the Cascades, I block the lower grill 100% when the high temps are consistently below 60F(15C). The engine seems to reach 103F (39C) within the first 1/2 mile (>160F/71C by 1.5 miles) with temps in the low 40's on surface streets with speed limit of 35mph or less. The engine does seem to retain heat better without having to restart itself to warm up during city/slow EV driving.
AFAIK grill blocking doesn't affect the warm up time, the thermostat stems the flow through the radiator until the engine is up to temperature. Grill blocking will help maintain the heat once its up there. On a different note, one thing that I've always wondered about is, does engine braking cool the engine on a petrol car ? I would think it does on a diesel engine as there is no throttle plate so it's drawing in fresh air through the air intake, but on a VVT petrol engine does it even draw in any air ?
Actually, engine braking on a big diesel retains heat rather than cooling it. Sudden gulps of cool air are bad for red-hot pistons in a diesel. The diesel engine brake closes the intake valves and just cracks open the exhaust valve, retaining heat. I'm not sure what the ICE in the Prius does with the valves, but it does alter valve timing. In either case I doubt it offers any "cooling".
Thank for the info, logically it makes more sense to close the valves, it sort of holds the pistons back more on the suck and squeeze strokes.
Thought I'd weigh in regarding blocking the radiator: I'm in Saskatchewan and we had more than a week where the temperature didn't get any warmer than -27C (coldest was -35C). I did plug in the block heater, but aside from that I didn't do anything else and it had no trouble pumping heat inside (this is a 2014 Prius V).
