I think you are giving up on heating the HHO too soon Steve.
If you place your coil directly in the exhaust gass streem behind the tailpipe it should work well.
Then through a UV pool bacteria killer to try get some monatomic H and perhaps O3 ...
Or perhaps this info may be helpfull:
http://www.rexresearch.com/leach/leach.htmRemember how a wet face-cloth is air proof?
Any wet ?cotten? type fabric should do to seperate H and O in a cell if you just want to radiate just hot H2 and not the O2.
Then the O2 and Air can cool the mix to 50C again.
'Aanhouer wen!'
