Finally got to pull a grill block today!

wow... wish the weather was good enough to pull some of mine. had a few days in the 70's and actually had water temps hit 210º once, but that lasted a day...its like 55 right now...

 

Pulled mine this past weekend. Hated to do so as the mileage just kept going up...56 mpg on short trips with highway/interstate interspersed. Mileage is trending back toward 53 since I pulled the blocks. It's too bad that Toyota doesn't have grill slat thermostat controls for the coolant and inverter. This would improve warm up and mileage on short trips even in warm weather.

The grill blocks made a big difference this winter. Earlier this fall/winter without blocking when the temps dipped below 30 F I observed mileage on various trips at those temps hitting around 42 mpg ave.--and only days before I was hitting 50 mpg on the same routes with temps in the 50's. After completing the grill block of all but the bottom-most slot, mileage improved to the high 40's again. The last two tanks with the grill blocked were 50 mpg.

 

I was 100% blocked until this heat wave. I have to say, at $2 a gallon the economic benefit of the block seems pretty minimal - might be outweighed by the risk of damage if you are not monitoring temps and you forget to pull it when the weather turns hot all of a sudden like it did last weekend. I know that is heresy around here.

 

BMW already do automatic grille blocking louvres - they call it 'Active Aerodynamics' as part of their EfficientDynamics theme. It may be patent-encumbered.

The exhaust heat recirculation on the new Prius will help a bit, but it won't stop the engine being cooled unnecessarily when it's off.

 

That's a patent fight that should be easy to win. It's hardly novel. WWII aircraft of various types (and likely before) had similar arrangements. Open up the ports to cool the engine, close them for speed.

 

its too bad that more people cannot apply your alarmist stand to the possibility of Global Climate Change

 

The problem as I see it is the inverter. Since I have no way to monitor the inverter temp (haven't bothered with the Scangauge since my understanding is that it doesn't report it either) I have to unblock everything when the outside temps start pressing 80 F. Plus if the wife is driving she's not going to reliably watch/catch things like that, so even with a gauge I would still have to unblock it for her.

I'm not really worried about engine coolant as fans and such will begin running to take care of that even though I can't monitor it directly at present. However, the inverter is a black box to me...

This should be done automatically with an electronic control scheme and shutters. Various temp. points could be used, much like the present limitations on stage operation of the hybrid system.

 

I never truly "fully blocked" because I left one set of slats open on the very bottom. This seemed to keep the outside temperature reading live.

When we had a day or two in Jan./Feb. break new records in the 78 F range I worried a bit, but since we weren't doing any extended driving and didn't use the defog/defrost (obviously) I didn't pull any blocks until it hit the 70's again in mid-March. Then I pulled half my lower grill blocks, but that turned out to be too soon, as the weather did a head fake and turned unseasonably cold for 3 full weeks. When April finally warmed I pulled the remaining lower and upper blocks.

And this brings me to an important question: Would it make more sense to remove the upper grill blocks first rather than the lower? And perhaps then only on the driver's side next to the inverter? Is the primary cooling of the inverter coming from the top grills on its side of the car?

 

we had water temps (only have scangauge on the 06) hit 215º the other day albeit very briefly, so we pulled the top blocks. even then the fans did not come on... come to think about it maybe this should be a guideline as to just how much cooling a Prius needs

the only time i have ever heard the fans come on in 5 years was with my 2004. this was in the middle of my return trip from Montana. i was on I-90 doing 65-70 mph, OAT was 101º. AC was set at 70º. did not have any monitoring system so dont have any Pri temp stats.

i pulled into rest stop. got out to take a leak, took about 5 steps and the fans kicked on. they were very loud causing me to jump a bit. i went back to pop the hood cause i was concerned over the loudness (assuming that they probably temperature controlled variable speed or something) fans went off within 5 seconds of me opening the hood. as far as heat from the engine... pretty moderate compared to other vehicles i had been around.

well, was only gone a few minutes and while walking back, i heard the fans kick on again, they ran somewhat less than a minute and shut off. i sat there for at least 5 minutes waiting to see if they kicked back on and they did not.

my conclusions: its apparent to me that a seemingly minor increase in efficiency greatly reduces the need to eliminate dangerously high "waste heat" from the system therefore making the cooling system less of a dangerous situation that we equate to regular vehicles.

for anyone driving the northern tier states in the dead of winter thru town screaming for heat, they might agree

 

inverter is the lower i believe and if there was a definitive answer as to the degree of cooling the inverter needed i missed it. with the vents, apparently it does need some, but as far as what the upper safe temperature limit would be and at what driving conditions would those conditions begin to be met i wish i knew. there has been a lot of discussion on it, lost track of any conclusions if any since all i saw was speculation. now having been in Detroit, that is the one question i wish i would have asked.

 

That's what I would expect. Driving on the highway there will be quite a bit of air circulation, even blocked. Once you stop the circulation stops, both of the air and the fluid. But the temp of the internal thermal mass that is the engine block is still greater than the coolant temp and will continue to transfer into the coolant.

The only times I've had vehicles over heat were: 1. Bad radiator cap on a truck on the interstate, it was boiling off coolant and I could smell it as I monitored the gauge. 2. Running AC full out on an old K-car with typical high ring blow-by, mid-July, hot sunny & sticky, crawling in bumper to bumper construction after 100 miles at interstate speed. Never had it happen again.

At an autocross in Texas some years ago I helped a new Mustang owner out after his car overheated after a few high rpm, low speed laps. I simply told him to take it out on the highway at a moderate cruise speed with the heater going full blast (windows down.) What he needed was some airflow across the heat transfer surface (radiator and heater) while the engine was running low load. It worked. Sitting was the problem.

 

agreed 100%... but what i have not expected is

1) the other day we hit 215º in water temp, that was at street speeds with 100% grill blocking

2) driving 5 years over 2 diff Pri's and taking SEVERAL trips at freeway speeds some easily covering over 100 miles at a time and never having the fans come on in any of those instances.

with the grill blocking we drove from Olympia WA to Salem Or about 200 miles and when we parked it, no fan, that was also 100% grill blocking...now all this is on a 2006, a vehicle i have never heard the fans on...now it makes me wonder

1) maybe the fans have been on and are much quieter than my 04...

2) or they are not functioning properly and i am causing yet to be determined damage to the engine

 

Lower first. The inverter uses the bottom third of the radiator, which is behind the air conditioning's condenser - A/C gets first crack at cool air. The engine uses the top two-thirds. The engine/inverter radiator is the full width of the car between the headlamps.

I don't know the inverter failure temperature, but the service manual says that the MG1 and MG2 Inverter Temperature parameters can range from -50 to +205ºC (i.e. it's a one byte 0-255 value offset by -50), and that in street driving they should range from 25ºC to 80ºC.

If the MG1 or MG2 inverter, or DC/DC converter, get too hot, the car logs a DTC - P3221, P0AEE, or P3226 respectively - and the Master Warning Light comes on. Oddly the fail-safe chart says 'Normal Driving' rather than 'Limited Driving', so it clearly doesn't shut down the overheating part.

The car has two fans to pull air through the radiator if it's necessary. It looks like they can be driven at least semi-independently - one relay (FAN NO. 3 or NO. 3 FAN) controls whether the two are connected together. The service manual says that the fan should start to run when the engine coolant temperature is over 93ºC and switch off below 83ºC. The engine's thermostat is supposed to open at 80 - 84ºC and fully close below 77ºC.

The diagram seems to suggest that one of the fans has five blades, and the other has seven!

I suspect the engine cooling is an aspect that, like the brakes, is overengineered for the worst-case scenario, making it way, way overengineered for the normal scenario, causing the problems that we see with the engine cooling down too much and not staying in the closed-loop fuel control range.

 

Check this Damper control here
DIY Zoning: Dampers
May be we can make out own damper like these ones.
1. Take the output from any of the fan( or all of the FANs with diodes) so that when FAN kicks to cool down it open the slots.
a. Have the low powered relay powered by Fan circuit( just tap from Fan wiring) that will operate the servo. Power to operate servo comes from another main relay/battery. ( or it could simply a Magnetic relay).
b. Directly connect the servo( it uses very little power) from Fan circuit.

2. Or keep a temp sensor with a relay that will operate based on outside temp and control the servo.

Just some ideas. Somehow I am not comfortable with idea we constantly keep an eye on the temps and blocking and unblocking the slots.

 

ok then mine aint working because it does not and has never run in those temperature ranges. to be honest with ya, as much as i battle low coolant temps in the winter time, i think i would be upset if the fan did run the coolant temps down to 180º F

 

This is a good and simple idea. Based on what I am reading, hardly anyone has ever heard their fan run and if they did they were startled. I would think then that the fan doesn't run that much. And by blocking the grill up to the point that the fan runs (although intrinsically safe) would force the fan to run more then it was potentially designed to run.

I am reading this thread with interest because I did some grill blocking this weekend (pimping my ride) with the foam pipe insulation stuff from Home Depot. I got the SGII so I can see the Water Temp (FWT) but I can't see the invertor temp. Nor the state of charge (SOC) of the HV batteries.

Some on this thread said that certain sections of the grill are kinda aimed at the invertor intake air. Perhaps this section can be ducted directly to the invertor and controlled separately (or always left open). Can the invertor ever be too cold?

But in a perfect world, the dampers to the radiator, etc should open prior to the fan starting (why use the fan if you don't have to?).

I haven't got to drive the Prius to work yet with the blocking mods, but we have cool rainy weather for a few days so this should be a good test. I got the top two slots blocked and in addition lower slots 2 and 3 blocked.

Quickly, what temperature does the EBH heat the engine to? Does it run all night or do you plug it in and it can heat the engine while you make coffee and brush your teeth? Does it make a difference when the temp only reaches 50F at night and the Prius is in the garage (unheated but warmer)? I think I need one.

I am just trying to get better mpg's and I think this is an area to concentrate on.