I started using a piece of cardboard between my battery and the intake a few years ago, and it seemed to gave me about a 2 miles per gallon increase. (Though after building this, I received criticism that this will not help with gas mileage, but will help with performance!)
Now it was time for me to relocate my battery so now I have to make a Hot air block from scratch. I made this one from metal, and I expect better performance than my cardboard version.
This is the finished hot air block and my new battery box
I was using the stock battery mount location, with a normal tie down, but it kept having issues and getting loose. So then bought a replacement tie down, but that also came loose. I wanted to relocate the battery to the trunk, but I have way too many wires added in over time (inverter, fuel pump, 2x amps, and more). So I decided to relocate to about the same area under the hood, but lower and out of the way.
2 years ago I bought a s80 case (USDM) when I rebuilt my y21 JDM transmission, because of cracks in the y21 housing. Then after 1 year of use, a metal plate on the freeway hit my transmission and caused a hole. The aluminum was brittle and filled with stress cracks in the housing, so when I TIG welded the hole, it caused issues.
I decided to go to the junk yard and get a s80 case from an integra. I found a 1995 3 door RS 5spd and pulled the transmission. (read about it here) I did not know it at the time, but after I got home, I found it impossible to find a large oil cap. I tried Honda and Acura dealers, and even used JDM engine suppliers, but no one had any for sale. The USDM 1994-1995 Honda Del Sol VTEC model is the only USDM car with that oil cap. The part is discontinued and not available. I needed a way to cap my new rebuild, so I tried to change the breather vent tube (oil fill hole) from the USDM s80 case to the JDM s80 case.
I have a b16 SIR2 that came with a y21 LSD transmission, but the case leaked and I replaced it with a more common s80 about 2 years ago when I rebuilt it. I added carbon lined synchros, new bearings, new rubber, new gaskets, measured and replaced as need, full rebuild.
I was driving on the freeway about a year ago and a piece of plate steel was pulled up by the wind, and busted a hole in my s80 transmission case. This is an article about how I got a replacement housing from the junk yard.