I've got a piece of "super insulation/radiant barrier," made up of heavy duty aluminum foil bonded to both sides of 1/4 inch thick plastic foam. The piece is about 36 in. by 48 in. I'm thinking about using it as a radiant heat reflector/thermal blanket over the top of the ICE in my Gen II. The goal is to help retain heat as the temps drop and help keep FE/MPGs up. Here's a view of the engine bay: I won't cover the electronics package on the right, as I don't want/need it kept warm. By cutting the sheet in half, I can extend the blanket about halfway down between the ICE and the radiator and keep well away from the serpentine belt on the far passenger side of the ICE. By feeling over the top and behind the ICE, I can cover it, and maybe extend the insulation /barrier half way down the back side. Here's a picture of the insulation/barrier in place: I can work the two pieces of insulation around the various bits of piping and wiring at the front of the ICE, and between the ICE and electrical boxes going to the rear. Here is a view looking down between the ICE and the radiator with the insulation in place: As I'm not going to try to mold the insulation tightly to the block/head, there will still be an airspace and some moving air between the insulation/barrier and the block. I expect that the only real contribution to heat retention will be to reflect radiant heat back to the block when I'm stopped in traffic with the ICE off and block temps plummet. I'm thinking the insulation/barrier will stay in place due the many bends and curves created in working it into place. I use grill blocking already. I'm using a ScanGaugeII, so I can monitor ICE temps. My questions are: * Have any of my fellow Gen II Prianistas experimented with something like this? * If so, did you see any noticeable/measurable FE/MPG results? * Did you encounter any problems, or incur any damage? I welcome constructive comments, suggestions, concerns, etc. (I know what you're thinking.... No, there isn't enough left over foil/foam/foil to make an insulated aluminum foil hat. )
If possible you might want to place this under the air cleaner box. Heating the intake air reduces thermal efficiency of the combustion process and, therefore, requires more gas to produce less HP. This is why performance engines use cold air intake (hood scoop or under bumper intake) - the cooler air is denser, producing better performance.
I imagine this would be an effective upgrade for Prius owners who live in cold climates, especially in cases where the engine runs simply to maintain heater temperature. However, I have significant concerns about the effect of heat retention in places where temperatures exceed 100 degrees F. Fundamentally, my question is: At the top range of normal environmental temperatures, could this modification have negative consequences related to overheating?
The hood already has a layer heat retaining material. You may be better off covering the bottom of the engine/transaxle block. They are openly exposed under the car. I am thinking about heat shielding them as well as the cat converter with fiber glass insulation. I wonder if it can handle the temp of the cat converter. I am also concern about the cat getting too hot and possibly causing damage. Anyone with knowledge about it? Is this a bad idea? I am not concern about overheating the ICE and transaxle because they have active cooling with coolant through radiator.
I have been looking for some foil-backed foam material such as this for similar purposes. Where did you get this material?
KjF, I got my scrap piece from a friend. However, you can get it, or something like it, at Lowes: Reflectix at Lowe's: 16" x 25' Double Reflective Foil Insulation
While cooler air can make more power, hotter, less dense air can actually improve fuel economy since being less dense, allows you to open your throttle body more (and the throttle body is a huge restriction). So without actually testing it, I'd say don't worry about it.
I thought of that, but it's against the "easy-in, easy-out" nature of this project as initially conceived. That said, on a 30 mi. trip earlier today, I monitored both OAT (Outside Air Temp) on the MFD, and IAT (Inlet Air Temp) on the ScanGauge for the first time. Outside air was 55 defF, Inlet Air varied beteen 62 and 88 degF., with a peak of 92 when stopped with the ICE off. The SG booklet says that IAT will be "a few degrees" above OAT. That seems like more than a "few," but since I've got no base line to compare against, I'm going to have to do some data gathering on this. I'm also going to check and see how easily the air box is to remove/replace. If it's quick and easy, I may try this. Thanks. Sorry. My OP is less than perfect; I didn't make it clear that I am considering this only for cold weather use this coming winter. I pulled and poked at that when I opened the hood. I didn't see any obvious stuff to suggest that it would act as a radiant heat reflector. I toyed with the idea of putting the stuff I got behind it, but decided it was too far from the block itself. As I drove around today watching various temps on the SG, I thought about this as well. The oil sump is pretty much hanging out in the breeze under there. Wrapping it would seem to be a good idea, although I'm not in a position to get under there easily, if at all. You would also probably need a thin gauge, well attached aluminum shield to protect from rocks, pebbles, small road debris, etc. Keeping the shield in place in heavy snow/slush would be problematic. For those interested in further reading, here is a thread I found over at EcoModder: Insulated Engine? - Fuel Economy, Hypermiling - EcoModder.com Buried in that thread is this jewel of a link: Randall's Insight - MIMA Honda Insight Modified Integrated Motor Assist Holy Cow! a permanent, zippered closure, multi-layered ICE Cozy sewed of some unnamed fabric/foil/insulation laminate. Hot stuff!
I've made two out and back trips of about 30 miles with the radiant heat reflector/barrier in place. It is too early to quantify any benefit it may provide. It appears that initial ICE warm up is hastened, WT cools more slowly at ICE-off stops and no-arrows glide, and steady-state running block temps are somewhat higher. I'm holding off putting numbers to these conditions as I collect more data over a longer period of time, maybe a week or so. Some casual observations: For the first time, I've been simultaneously monitoring three temps: Outside Air Temp (OAT) on the MSD, ICE cooling Water Temp (WT), and Inlet Air Temp (IAT) on my ScanGaugeII. Fascinating stuff. In the discussion that follows, OAT is between 55-57 degF. Inlet air Temp is a strange beast. I don't know where it is measured, but it is subject to great variability: * it appears to be located close to or in the engine block, head, or intake manifold because after turing the car off, over a period of ~30 min. temps rise dramatically up to 110 deg in one case. As the car sits, WT slowly falls, IAT slowly rises. When the two roughly match, they then fall roughly together. The same thing happens when you sit ICE-off at a light or in a long, no-arrows glide. * it appears to react to large volumes of air passing it because with the ICE running over 2 or 3 minutes, the temp begins to drop. In general driving around, IAT runs from 5 to 55 degF above OAT. The higher differentials are reached as the car fully warms up, this is well beyond the Stage 4 warm up period, at least 20 minutes from start up. Also, higher differentials occur in roughly steady state driving at freeway speeds. I haven't puzzled out what meaningful information I can learn from further observation of IAT. However, I do wonder how to make head or tail about the earlier postings about high IA temp with lower density air and conversely low IA temps and higher density air. With the 55 degF swings that i've see in very gentle driving in moderate OATs, there must be a whole lot of computer based compensation going on in real time. I suppose this is one reason why computer controlled fuel injection is so vastly superior to a carburetor.
Time for a preliminary assessment of this proposed cold weather thermal retention enhancement. I've been doing my regular ~28 mi. round trip commute and weekend errands runs with the radiant barrier in place on my Gen II for 13 days now. Temps have been between 43 and 63 degF. I'm also running a full upper grill block, and all but the lowest slot on the lower grill blocked. The radiant barrier seems to be having a positive FE/MPG effect. :rockon: On my commutes, I'm seeing an apparent 2-3 MPG gain. On the stop, park, and go weekend errand runs, the gain may be as much as 5 MPG. In addition, I am seeing an apparent 5-10 degF higher coolant temps across the board. I am being intentionally fuzzy about the possible gains. What with driving safely and using hyper-mileing tactics, I haven't been able to record hard coolant temp data despite having a ScanGauge to read coolant temps and get trip and daily MPG numbers. I have made numerous runs over very familiar routes, and I am seeing both MPG numbers and coolant temps that are higher than I would have expected to see without the barrier. And that friends is about as good as I can do. FWIW, I plan on keeping my reflector in all winter. I'd like to encourage the members who have the more sophisticated monitoring gear and data recording capabilities to give the barrier a try and get some good, hard numbers so we can know for sure if this is worth adding to our cold weather bags of tricks... er, thermal retention enhancements.
