2010 Prius Grill Blocking strategy

Hello all,

On the NHW20(Gen2), we used to block upper grill all year around because the HV inverter/motor coolant radiator is located at the bottom, therefore it's better to leave open the lower grill, especially during hot summer.

On the ZVW30(Gen3), I confirmed the HV inverter/motor coolant radiator is located at the top.
I believe we have to leave open the upper grill on the ZVW30 for better cooling of the inverter coolant during hot summer.

edit on Nov 5th: add a copy of table on post#10.
following is my personal recommendation.
[table="head"]temp in Celsius|temp in Fahrenheit|lower blocking %|upper blocking %
below 5|below 41|100|50
5 - 18|41 - 64|75|50
18 - 30|64 - 86|75|0
above 30|above 86|50|0
[/table]

Ken@Japan

With the 2G I believe over 90% of cooling air came from the bottom. With the 3G, since the upper opening is not much bigger, would not most of the cooling air still come from the bottom? Didn't I see a JDM nose/grill piece that eliminates the top opening?

Wayne

One of the aero kits (ironically named it actually has a negative impact on CD) designed for the 2010 def eliminates the upper grille...it's a full upper block for sure. Something to look into if planning to add a grille block, full or partial. A couple weeks ago someone posted pics of the aero kits on here and one had a full upper block.

The majority of air underflow on a vehicle always (unless deflected with a belly pan) flows vertically after clearing the frontal area of the vehicle. This is the entire reason for a belly pan as mods attempt to force air under and past the underbelly rather than air getting trapped in the vehicle after clearing/flowing through the grille.

I agree that the most of grill opening is required for the engine coolant radiator during heavy load in hot weather.
We know we see mpg improvement to block the grill during light load in cold weather.

I believe the temperature of the inverter coolant is "cooler is better", between ambient temp and 50C(122F) vs 88C(190F) engine coolant temp, therefore I would like to suggest to leave open for the inverter coolant radiator area during hot summer.

I've never seen such for the 2010 ZVW30 Prius.
Would you please post a link or picture if you found any?

Thank you,
Ken@Japan

I have never seen anyone on PriusChat address this, but yes, for the electronics "cooler is better" with regard to the lifetime of the semiconductor devices used in the inverter. Solid state diffusion is a time and temperature related phenomenon - higher temps = higher diffusion rates.

Since I live in a climate that is quite hot (>100°F or >38°C) for much of the summer, I do not block the grille on my NHW-20 even in winter. I need all of the "cool" time I can get.

Here's the thread on this site (specifically post #2) that I saw the upper grill block aero kit from Modellista. After looking at it again (I had not viewed it since seeing it a few weeks ago) it is not a full upper grill block but def smaller than on the 2009 and stock 2010 model. Perhaps the aero kit took the new inverter location into account to allow free flow directly on the inverter.

http://priuschat.com/forums/2010-toyota-prius/61877-2010-prius-modellista-aero-kits.html

I would be interested to hear/read/see comments from the Prius Team and/or Toyota engineers in regards to changes made to the location of the inverter. Perhaps it was moved to decrease crash casualties of the most integral parts of the hybrid engine. On the other hand, it may have been simply moving the equipment around to accomodate other equipment under the hood. Anyone have a source addressing this?

While the "physical modding for mpg" community has just begun to be accepted into the mainstream on this site and others...I highly doubt auto engineers take this into account when designing vehicles. The Prius is already slippery in terms of CD and if the engineers would have had future mods in mind during the design of the vehicle they would have already put in place full belly pans, more aero antenna and rear wiper, etc. Guess they left that up to us "modders."

I will note, the 2010 Prius, while having a lower Cd than the 2009 model really has no significant improvement in CdA than the 2009 model due to the larger frontal area on the 2010 model.

Wayne,

It looks to me as though the Gen2 upper grill is larger than the Gen3 upper grill, while it looks like the lower grills are about the same. I haven't measured this at it, and I base my statements only on the "look" of things when I had my 2007 side-by-side with my 2010.

I'm also able to see the upper grill openings.
I believe it's enough to cool the inverter radiator temp down.

Again, my suggestion is not to block the upper grill completely, 100%, during hot summer.

Ken@Japan

I think you can block 100% of lower grille and 50% of upper grille on such condition.
If you're going to attack [ame="http://en.wikipedia.org/wiki/Pikes_Peak_International_Hill_Climb"]Pikes Peak hill climb[/ame], it's another story.

Anyway, following is my personal recommendation.
[table="head"]Celsius|Fahrenheit|lower blocking %|upper blocking %
below 5|below 41|100|50
5 - 18|41 - 64|75|50
18 - 30|64 - 86|75|0
above 30|above 86|50|0
[/table]

Ken@Japan

I applied blocking to the lower grill. I used 2 - 3/8" think pipe insulation for 3/4" pipe, 3' long sections as mentioned in another poster. I attached them with zip ties. Not real fancy looking (see attached photos) but they should do the job (100% blockage). I am mainly interested in blocking the road crud from getting in the engine compartment but I am sure it will have warm up, retention.

Using 1/2" instead, you can squeeze one into each slot. It looks really nice that way (uniform & small, making them difficult to see) and nothing is needed to keep them in place. The catch is you have to cut few small notches in the foam for fitting around the vertical plastic.

Photos of that for the Iconic are in that User-Guide. Eventually, they'll be photos of the 2010 blocked. But it looks pretty much the same as the other Prius anyway.
.

Will any of this Gen III grill blocking interfere with the outside air temperature sensor?

You might see some artifacts at slow speed, below 20 mph, but it's not a big issue.

Ken@Japan.

Do the full 100% lower. Recently at 36F here on the highway the engine temp was about 4F lower than with no block in the summer. No harm will come to you or your Prius. Honest.

Wayne

Is that the little thingy about 1" long on the end of a string of wire just in back of the lower grill in front of the radiator? If so, I wonder what effect that would have on the engine feedback?

Pardon my ignorance, but what is the advantage of blocking the grill?

Good question. I mainly do it to keep the road crud out of the engine compartment. They sand/salt the roads intensely up here and it all ends up on the engine... a mess.
Also to reduce the cooling off of the coolent so the engine doesn't have to run as much (new to me for the Prius, in theory).