grill blocking

In gen 2 Prius inverter cooling is at bottom of radiator.

It needs to be very hot before blocking the upper grill will cause any problems. But if you use AC for cooling you should not block the grills as hotter the ac condenser gets more the ac has to work (thus taking more energy and ultimately burning more fuel).

I had no problem blocking the upper grill at 22c or 72F. I also have the lower grill blocked 80% when I have the winter tires on.

 

Take a look at my post on here about hypermiling. -> "'Hypermiling' for Dummies" Gen 3 Guide? | PriusChat
I have photos of my grill block and detalis of my 18 months of working with the blocking from all louvers blocked to what I have now which I’ve had in all kind of weather up to 100 F without problems. I’ve driven in excess of 5,000 miles with the grill blocking shown without any problems of over heating or other issues. It seems the bottom two louvers are just excess inlet and really not needed. The top louver significantly increases engine temp (likely the ECU loop and top of the radiator which is hottest).

I get SIGNIFICANT”Y better mileage with the air dam - like high 50’s to 80’s!
It allows the ECU to rest the engine quite a lot - especially with the accelerate - lift off - return for drive foot technique.

 

I'm more cautious, with my third gen, which has inverter rad behind upper opening: one tube (50%) on the bottom grill once the weather starts getting below 7C, and if it's consistantly sub 0C weather, I'll put in a second tube (100%). I've heard 50% block of upper is ok in extreme cold, but opt to always leave it open, both due to the caution and because it's more awkward to block.

I'd really think twice about 100% grill block of the lower, year 'round. IIRC the inverter radiator is behind the lower grill, on second gen? Too, year 'round block like you're doing seems a little cavalier, to second-guess the toyota engineers that much.

I appreciate there's some overkill in their design, but I think you're pushing it, driving in hot summer weather with grill block. And: if you're using AC at the same time it doesn't make any sense.

 

I have a UltraGauge monitor I use to keep an eye on things for the past 18 months. I’ve never seen the engine temp over 200 F even when it’s 100F outside with the AC on. I definitely was initially worried about the year-round block and engine temps which is why I always drove with the UltraGauge monitoring my engine temp. The blockade is easy to pull off if absolutely had to which is another reason I have no concerns with keeping it on.

As for Gen II having their inverter radiator on the bottom, as I understand it that is correct which is also why I opted for the bottom blockade over the upper blockade (e.g. two upper or two lower).

as of overkill on their design, my guess is the Toyota engineers opted for more engine work to reduce charge/discharge on the HV battery to it would last the required 10 yrs/100,000 miles. After all, there’s no such requirement on the ICE except the 36,000 mile warranty.

 

Engine blocking has gotta be degrading AC performance. AC works by pulling heat out of the cabin with low pressure refrigerant, then compressing it, basically "wringing the heat out", in the big radiator (aka condensor) at the front. You block that up, you're effectively hobbling it.

And I can't think of any good reason to grill block in front of the Inverter radiator: it's not like an engine, more efficient when warmed up: heat is the enemy, if I'm not mistaken.

I would think driving in winter, temperatures below 7C, you've definitely got more grill opening then needed. But 100F summer temps? I'd pull it all off.

One more scenario: if you're doing a serious hill climb, say going up a ski mountain, even in the dead of winter, I'd still pull it all off.

If you're driving in summer, in 100F, and your temp monitoring indicates you're around 200F, I'd speculate that's because your cooling fans are running full time to compensate.

Don't sell Toyota short, their engineers are cautious yes, but they know their stuff. The grill openings are more-n-likely slightly more than adequate in blistering summer heat. Maybe...

 

I know AC design as I have a Masters in Mechanical Engineering with subjects on thermal and fluid design.

I’m your fans rarely run as when they do they can be subtly heard inside the cabin.

As for high torque tasks such as hill climbing, have had any problems at all driving almost 2,000 miles from Pennsylvania to Florida with the two rows blocked.

 

And putting blocking in front of the condensor when the AC is running is sensible?

 

It’s only on the lower areas - heat rises and the engine temp NEVER goes above 200 F, as monitored by theengine coolant sensors. As for the refrigerant dealing with 180 F or 200 F, the difference is insignificant. Same goes for the engine but NOT for the ECU logic. The ECU changes it’s behavior drastically above 140F to rest the engine almost all the time except with higher torque requirements.

 

That is odd. I have a ScanGuage-II, and I have seen it hit 202-204 F numerous times during the life of my car. Same with its 2010 predecessor.

As one example, do you ever climb steep forest roads (usually dirt or gravel) that require lower speeds with much less airflow over the radiator and engine?

I do use grill blocking below room temperature, and in cooler years (Pacific Northwest) have even kept it in place until mid-summer. But in certain conditions, it just must come out, though I normally remove just a single foam strip at a time.

And even after the grill is clear, under certain conditions, the coolant temperature will rise to 204 F and trip on the fan at ambient temperatures well below 100 F.

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In colder conditions, the grill block also helps intercept flying sand and gravel from hitting and flattening radiator fins, which can reduce cooling ability in the future. Most of that is applied to the road for ice and snow, so aligns with the season when grill blocking would normally be used.

 

I often drive up steep hills and rarely does the coolant temp climb above 196 F except for a few minutes at the most even when I went to Florida through the mountains.

Marc

 

What time of year was this?

I would think Toyota's engineers designed the amount of grill opening to be sufficient for any outside air temperature. Accordingly, it would seem logical that the opening amount is overkill in the cold of winter, and some degree of grill block is warranted, and safe.

But in summer, most anywhere, but especially down south, and/or steep mountain grades, any amount of grill block is not smart: these are the extremes the engineers designed the full amount of grill opening for.

 

Mendel, I agree they should have designed the grill opening with tighter design standards. However, based on my engineering training, I'm guessing they cared less about the engine wear than the hybrid battery use. The hybrid battery use and thus life is based on the level of charge/discharge and the number of cycles. By reducing the number of charge cycles (e.g. using the engine (ICE) more), they can then meet the stringent 10 or 15 year battery life requirements in most US states. There is no such requirement for ICE life or miles per gallon. Thus, as long as they hold the record MPG value (45 - 52 mpg), they really don't need (nor likely care nor want to) change anything.

I'm told in the new 2017/2018 Prius, there is now a thermostatic gill block - Voila!

 

8/100 or 10/150

 

Yes the Gen 4 Prius comes with what are referred to as shutters in the grill.

 

I don't recall saying that, lol.

This is my flogging horse day I guess: in the heat of summer, with AC running, and/or hill climbs, any amount of grill block is asking for trouble.