grill blocking a 2005 prius and over heating

[moonmonkey]

hey just starting mods on my prius. its a 2005 so 2nd gen. i am a little scared to do major blocks on the grills like i did on my echo, because of the extra electrical stuff under the hood. i live in florida so its hot-ish 6-7 months out of the year. i had a scan gauge on my old car and monitered the coolant temps,but on this car,arnt there more things to worry about? anybody have a full upper block in hot weather? looking for some guidance,dont want to damage my "new to me" ride.

[Weather Spotter]

start slowly, and see what happens. there should be a engine temp gauge (or get one). I bet that you can do a 50% block and be fine. In my MI heat (95-100 max) I get away with 100% closed for the first 10 miles then I give it 1/4 of total grill area open and that keeps the fan off except on long trips where it comes on every 10 min or so.

[Daox]

I live in Wisconsin, but I run with my lower grill completely blocked off and don't have any problems with my 04 Prius. I honestly can't say how much my coolant fan comes on, but I really don't think its much at all. I watch coolant temp constantly with the scangauge and its rock solid around 188F. With as efficient as the Prius engine is you really don't need a ton of cooling for it.

[Diesel_Dave]

It all depends on the vehicle and how you use it. I've recently run my truck in 102+ deg F heat with BOTH an upper and lower grille block and never had the fan kick on at all. But here's what I've got going for me:

1) I was running the truck unloaded. The truck's rated to tow around 7 tons and the cooling system's been designed to handle that level of cooling load.
2) I was doing engine-off-caosting pulse & glide. I've found that that significantly reduces the amount od cooling capacity required. I've looked at how long it takes for my engine to get up to full operating temp. EOC P&G vs. "normal" driving takes nearly double the time to get up to full operating temp. That means the required cooling capacity is roughly cut in half.
3) I've removed the EGR system, which cuts the heat rejection by 20%+.

So, it all depends. My advice would be start slow and keep an eye on things. If you want to monitor under-hood temps you can also get and indoor-outdoor weather thermometer and put the probe under the hood.

[Rokeby]

I drive an '08 Gen II Prius. For the last 4 years, I've had the upper grill blocked year
'round. I do monitor coolant temps with a ScanGuage though. in a long term high
ambient temp environment like Florida, I wouldn't recommend grill blocking without
a SG or other means to monitor coolant temps.

When grill blocking, there are two things to consider. The first is obvious; ICE
coolant temps. This can be monitored. The second thing is HV inverter temps. The
inverter has a separate cooling circuit that uses the lower driver's side area of the
radiator. If you have any concers about inverter cooling when you block the lower
grill you should leave about 1 ft of the grill on the driver's side open.

For me, lower grill blocking is a seasonal thing. Effectively there are four lower
grill openings. I begin blocking the lower grill when the highest daytime air temps
fall below 70 degF. I put in one plastic pipe insulation block at 70 degF, the second
at 60 degF, etc. In my experiecnce this is pretty conservative. I see the highest
coolant temps at ~193-198 degF which I understand to be good for high MPG
driving. I can't remember ever hearing the radiator fans coming on.

My cool weather daily 32 mi round trip commute with 2 people in the car is pretty
tame. ~2/3 urban streets with speed limit of 35 MPH, 1/3 highway at 50 MPH. My
summer 20 mi round trip solo commute is even tamer; 100% urban streets at 35
MPH.

Of course, YMMV... and don't forget the ScanGuage.

[moonmonkey]

any easy way to moniter hv inverter temps? or would it be something home made? and also is the scangauge for a prius different than a ice only car?