Grill block on/off experiment: 71 mpg v. 62 mpg

Cool, mainer.

You could probably keep some partial blocking on if you're comfortable, 40°F is still rather cool. It was 55°F here today, and with my top grill half blocked and bottom 3/5 blocked (Gen II Prius), coolant was still in typical ranges even with 2400-2500 RPM moments in the drive.

 

71 mpg!

That`s something I can only dream about!
But with just 3000 miles my ICE is not broken in yet.

 

It's getting warm here in So Cal 60-90F. I got top 50%, bottom 100%. Since I'm using Enginer my coolant temp rarely hit 190F even at 85-90F. I'll remove a strip of insulation next month. There are too many stop and go traffic here so I never hit as high of mileage as you without plugin.

 

Let's see, modifies the car for better gas mileage, does experiments to determine MPG, adjusts driving habits to get better gas mileage, gets mileage 40% better than EPA, I hate to tell you, but you are a hypermiler. It isn't an insult you know.

 

I see Ford is also installing shutters on their new models.

 

I just unblocked half the lower grill on my car. We keep getting sporadic days of 70-80 degrees here, with 60s the norm. Granted, my typical drive is only 5 miles each way, but with the chance I might need to take a longer drive, I didn't want to risk any potential damage. I will probably keep the half lower blocked until we get to the upper 60s consistently here.

Are there any recommendations on when to remove based upon temps? I know it can make a difference with trip length (shorter trips, probably not a big deal until it's really warm out). I think I'm at a good spot right now. I had it full blocked on saturday when I drove 100 miles r/t and got 56 mpg with temps around 55 degrees.

 

A Hybrid Owner’s winter survival guide - CleanMPG Forums

 

I remember Ken@Japan and his acquaintances where working on an automated louver system for the Prius. After having the bumper skin off myself, I wouldn't think this would be particularly difficult to do (at least for the lower grill). Just need a good metal or plastic fabricator...

 

I am confident you will be there soon.

 

I did a similar winter experiment, but instead of blocking the grille I wrapped the motor block with foil faced fiberglass insulation. Warmup occurred in a few minutes instead of twenty, and mileage improved dramatically, while the radiator was still able to cool the engine if needed. Of course the insulation all got wet and I took it off, but the point of it was very worthwhile. I might wrap the block again with waterproof insulation next winter. Maybe I'll try reflectix bubble wrap, which might melt, or high density fiberglass board cut to fit and wrapped with weldguard tie wired on. A good formed, water and fireproof block wrapper would be a great product for an aftermarket manufacturer to develop.

 

I thought the same thing when I saw the ads for the new Ford Focus with the grill shutters.

 

71 MPG! You drive like a maineac.

 

I'm running at 191f un blocked? Is this std for Gen3?

 

Yes. Unblocked, mine runs around 194° - 195° depending on load, speed, outside temperature and how far I've been gliding with the engine off.

 

I've recently blocked my engine, I see the temp getting up to 195 F, what's the "danger zone" for too much heat?

 

Excellent results. :cheer2:

Did you block both the upper and lower air intake grills or just the top one? Do you have a way of monitoring the coolant temperatures? What kind of tires are you using and what tire pressure settings are you using? The Prius FE tends to be better when its travelling downhill so when FE is quoted for only one way (not a round trip) - gravity can be a factor so knowing the starting elevation and ending elevation helps one assess how much gravity affected your MPGs.

Both Ford and Chevy have active air intake/grill shutter technology but they are only available on a few cars. The president of Toyota say that their R&D is looking to increase the thermal efficiency of their next generation ICE over 10% ( 35% -> 45%) so its likely that some type of dynamically control air intake cooling system is on the table for future Toyota designs.

Fortunately, manually grill blocking is an inexpensive option for us today. Along with upping the tire pressure - grill blocking is one of those inexpensive mods that one can do which have a significant fuel efficiency payoff. Last winter, grill blocking helped me keep my 2010 Prius fuel efficiency over 50 mpg so this year I started grill blocking early in the fall in an attempt to increase my overall fuel efficiency.

From your description, what you refer to as a *Modified Pulse and Glide* (MPG) is often referred to as *Driving with Load* (DWL) within hypermiling circles (see the FAQs on Cleanmpg.com).

Walter Lee
(aka "HyperDrive 1" on Cleanmpg.com mileage logs)
2010 Toyota Prius type 3, blue ribbon/dk grey, oem floormats
Yokohama Avid S33(D), (front 50psi rear 48 psi)
ScangaugeII ( Fwt, GPH, SoC, RPM)
Grill blocking (50% top 100% bottom)
Odeometer +18000 miles, overall FE = 61 mpg

 

IIRC 170-189F fully warmed up, 190-204F is hot but not dangerous, >205F is dangerous ( the ICE thermostat is fully open at this point so additional cooling would be from the coolant pump working harder to do the heat exchange). I would take off the grill blocking if the coolant temperatures started climbing over 200F. However, more importantly, once the Prius engine coolant temperature rises over 168F there is no additional benefit to grill blocking except possibly a warmer defroster and passenger cabin in the winter time.