yea also I bet your scion already recycles its heat to some extent due to newer emissions components, so you may have cooler exhaust headers to begin with, also I found that using purely plastic always produced results for me, but then again I wouldnt run plastic over my valve cover
plastic has less extremes too, it doesnt get as cold or hot, so less transfer of energy
get something similar your intake piping i used plumbing hose once and that worked, its clear and has thread in it, it absorbs alot of heat and heats air on the way in
Stay tuned. I'll get an old blanket and insulate the WAI aluminum tube before I write off WAIs. I'm not going to hunt around for replacement plastic tubing, though. Unless I see better results, I'm never going to recover my current $13.65 in costs , let alone any additional experimental cost. I need to get my wife's okay and a suitable old blanket before I can do this, unless I run across some fiberglass insulation they're throwing away at her HVAC shop.
Two nights ago I drove my wife to dinner (~20 miles each way), with the WAI attached. IAT didn't go over 69?F! I was P&Ging, but thought the WAI must have come loose. I rechecked yesterday, and it's still tight. Temps that night might have been in low-mid 40s. If I'm leaking enough heat that I can only warm my IAT 25? above ambient, it makes sense.
One minor factor I haven't mentioned. Scion xBs have hot water lines to the throttle body (I think to prevent carburetor icing). That occurs after the IAT thermister reads the IAT. I'll have to read up about that system, to see if it's regulated, its purpose, etc. I'm wondering about inserting some extra hose and really wrapping the throttle body with a lot of it. If I actually succeed in lowering the air density after the MAF, I might actually burn richer and get worse mpg.
I wonder (if you felt like doing A-B-A-B testing again) if skipping P&G would help bring your IAT up. That might tell us if WAI could be useful in an xB but not useful with P&G in an xB.
I don't think you'll go rich/lean from any of this, even if you mess with the throttle body heater doohickey; I imagine that's well within the margin of error properly measurable by the O2 sensors, and if it's not then you'd probably throw a code.
Icing is not a problem because MFI has no venturi. Most MFI system run the IAT as cold as is conveniently available and the high powered engines do some extra work to ensure that the IAT is as cold as possible. Depending on where the water goes it may mean is that Scion is way ahead of you and has already designed the WAI into the system which makes it less likely that adding your own WAI will produce further improvement. You can check how well the Scion WAI is working by measuring the temperature of the runners near the head. They may also do heat the air for more consistent emissions.
Improving MPG with a WAI is not as straight forward as you would hope.
adding extra warmth at that point of your air intake system(throttle body) would probably change the mixture of air/fuel in an uncontrollable way, probably not by much but if you over heat it too much after your temp sensor(maf or iat) you are taking a long run chance of breaking something possibly.
a good question is how long do cars last that you screw with in what way?
after thinking about it for a moment im convinced that would cause a lean condition
P&G is my normal non-test driving style, because I get ~10 mpg better FE with P&G.
My bread and butter WAI tests were done with steady state cruise control. After I completed my ABA cruise control testing, I added A and B P&G runs, and a second B cruise control run, as additional tests.
I'm not overly concerned about a blanket catching fire under the hood. I'll have a fire extinguisher handy, and nothing should approach 400 degrees. I'll make sure it's not a synthetic fabric. Or better yet, I may just buy some fiberglass insulation material and toss what I don't use up in my attic after I'm done with the testing.
Ok, that makes sense...I would have posted suggesting you do steady-state cruising for the original tests if I thought you were P&Ging them, and the reason I didn't is that you must have mentioned cruise in the posts about the tests.