Blocked grill for winter - overheat?

Grille Blocking

Efficiency & Emissions are both dependent upon warmth. During the winter, colder temperatures require the engine to run more to provide that. By blocking the grilles, warmth can be retained longer. With less cold air hitting the radiator and passing through to the engine compartment

(along with an accompanying aerodynamic improvement), the overall amount of fuel consumed can be reduced. Discreet Look
Unless you’re specifically looking for it, you may not even notice the

upper-grille is blocked entirely and the lower-grille partially.
Blocking Method

There are a variety of different methods available for grille blocking, some more cosmetically appealing than others. Squeezing

half-inch foam pipe insolation between each grille slot is a quick and inexpensive method that works surprisingly well. The only tool you need is a knife to cut notches in a few places to allow the foam to insert flat. The tight fit holds the foam in place.
Partial Blocking

Once the daytime high temperature in your area drops below 50 F degrees (10 C), it is safe to block the

upper-grille entirely and the lower-grille partially.
Full Blocking

For those experiencing in harsh climates, such as Minnesota, there can be a benefit from blocking the

lower-griller entirely. You’ll want to monitor temperature of the coolant though. Also, note that outside temperature won’t be displayed correctly, since that will inhibit the sensor.
Temperature

Use an aftermarket add-on device, like ScanGaugeII, to monitor the engine coolant temperature. The normal operating range of 186 F to 194 F degrees (85.5 C to 90 C) is what to expect. At about 204 F degrees (95.5 C) the radiator fan will turn on. Above that is when you should be concerned. The heater will trigger the engine to restart at 145 F degrees (62.8 C).



PG32,

The above is copied from the iconic Prius User Guide.

You can download the guide here: John's Stuff - Toyota Prius and more

It appears 204 is about as hot as you want to get, according to the guide. Normal seems to be 186 to 194.

Ron

 

I don't have a Gen2, but that temperature seemed to be the point where my first Gen3 turned on its electric fan. (The second hasn't been here long enough to characterize.) As long as the fan is cycling on and off, I think the engine ought to be OK. If it begins staying on full time, or the temperature runs higher, then some grill block needs to be removed. If I didn't have an engine monitor showing coolant temperature full time, then I'd leave that last strip out.

I have never blocked the grill in front of the inverter (top in a Gen3, the opposite of your Gen2), as colder is always better for its life expectancy. I'm not yet willing to mess with that inverter. The resulting extra air flow into the engine compartment (combined with my lower speed & engine load) has meant that my coolant temperature stays in the low 190s in ambient temperatures well above freezing.

 

Any chance this was the first time it ever reached this temperature? The first time always seems to put out some smell.

Hmm, 2007. Probably not the first time to this temp, so maybe something was happening.

 

Interesting... I'm planning to build a louvered grill block that can be adjusted while driving, so I too am looking forward to knowing what the most ideal operating temperatures are in winter.

Right now I have nothing blocked and I think the ICE is running way too cold at freeway speed and costing me MPGs whenever outside temperature gets down below 40' F.

So I'm looking forward to any links to other threads that gives insight into ideal ICE and inverter operating temperatures.

So thanks for starting this thread!

 

Adjust the grill blocking to where the operating temp stays between 186 and 194, and you will be good to go. Better too cool than too hot. Too hot, and you are going to fry something.

Use a Scangage 2 to monitor the coolant temp.

Ron

 

Leaving the bottom 2 slots open with my 2004 and the rest blocked entirely, I never saw temperatures that high. It would spike to 193 climbing hills with the normal "hot" measuring 191.

I took a similar approach with my 2010 and am now with the plug-in, blocking the bottom entirely and leaving the top open. That spikes to 198 with a normal at 195.

I'd be concerned hitting the 200's, though those using gauges more informative than my basic ScanGuage (monitoring engine coolant) usually say it's fine.

 

OP, how did your mileage change with the high coolant temp?

 

In the 1970's I had an AMC Jeep CJ5 that came from the factory with a 225◦ thermostat. I drove it & drove it & drove it ... 'till the locking hubs were ready to fall off and never had an issue. Temps will get hotter than that when you pull a grade leaving Vegas on a hot August summer.

As for the Prius, while driving around town on a regular winter commute (mid 40's mid 50's here in So Cal) I don't give a 2nd thought to doing a full grill block. Even in the summer time, if the daytime temps stay below 80, I leave the whole shebang installed. Hotter, I pull half out only, until it hits the 90's. What the heck, it only takes 20 seconds to install or remove. This easy attitude about not worrying about over heating the Prius actually came from reading other's posts who'd already figured that out. Although others may fret and disagree ... if I were in Michigan winters ... I'd REALLY not worry about it. but that just me (and a bunch of others).
.

 

I agree that the low 200F range coolant temperatures reported by others are no biggie, but without knowing the other temperatures like MG temperatures, we don't really know how much of a problem there might be. F8L has observed some "interesting" MG temperatures. Unfortunately, AFAIK, we don't know what the design temperature for the MG units is. Another member keeps mentioning the old 10C temp rise effect from high school chemistry that doubles the speed of most chemical reactions and cuts the insulation life in half, rule of thumb. That is fairly valid, but if the design life of the windings is forever at 180F, then there is no significant insulation life benefit to running them at a lower temperature.

A continuous 225F isn't good for cooling system component life, a particularly rubber and plastic, but as your Jeep demonstrated, it doesn't always cause early failures.

 

The issue isn't just the life of wire insulation, but also of the semiconductor junctions in the power electronics.

 

Back before Prius came along one of the best ways to improve MPG was to get your engine to run cooler by using a lower temp thermostat as well as lower temp spark plugs. But as near as I can tell that's not relevant at all anymore when it comes to Prius technology... They've already optimized the engine for temperature and the only real advantage of grill blocking is to warm up a cold engine faster.

PS: If there are MPG advantages to grill blocking beyond warmup please post some link to threads that explain this.

 

I can't see using any grill blocking at ambient temperatures warranting Air Conditioning use. I mean: the A/C is relying on that big frontal radiator for cooling.

 

True, a failure of each basically trashes an MG. So the same goes for them.

Until we know the acceptable temp of the semi-conductors if you want them to last the real life of the car, we are just speculating. The temperatures F8L reported for MG temperatures under some blocked conditions might be reason for concern. I wouldn't want to run mine at those temperatures for long periods of time, but that's just speculation on my part.

 

Reliable computer controlled grill shutters would be a nice feature to have. As the competition catches up to Prius in fuel economy , I expect Toyota to start using them.

Grill shutters that will always fail safe (open), withstand day to day abuse on the front of the car, still work in freezing slush condtions, yadda, yadda, are no trivial design job.

 

Don't know if you have a ScanGage or not, but a lot of factors come into play concerning MPG at certain speeds. Hobbit, who is IMO one of the pioneers on this board figured out the that the throttle position figure along with RPM and vacuum vary considerably from speed to speed as well as road grade's and temps, elevation and so forth. He did seem to find certain sweet spots where economy seemed to be better at certain conditions.

Bottom line IMO is to drive safely, conservatively, without impeding the flow of traffic and be happy with the MPG you are getting.

Glad to hear you got the blocking tweaked and are running it a little cooler.

Ron

 

This won't help you with the lack of a place for the the readout , but you can buy right angle OBD-2 cables that don't stick out as far and don't look as bad as the cables with normal straight out connectors.

Google right angle OBD-2. There are several sources.