I went down the TEG rabbit hole again today in my mind and did a little reading. This is an especially tantalizing quote from an article with some good images and research summaries, too:
"The Honda system used a simple design of a thin flat rectangular box with TEGs placed on the top and bottom surfaces. Liquid cooling was used in this design. The system consisted of 32 30 mm × 30 mm TEGs and produced a maximum of approximately 500 W. The claimed fuel consumption reduction is 3%."
SOURCE: B. Orra, A. Akbarzadeha, M. Mochizukib, and R. Singhb, "A review of car waste heat recovery systems utilising thermoelectric generators and heat pipes,"
Applied Thermal Engineering, Vol. 101 (2016), 490-495.
https://www.sciencedirect.com/scienc...01128X#bib0060