I remember a little while back there was a thread about how some hypermiling (specifically engine off coasting) was potentially bad for emissions. I can't seem to find the thread but I think it had something to do with the catalytic converter not being kept hot enough during engine off coasts..?
I wanted to give my experience today as a data point for the discussion about whether or not hypermiling may lead to increased emissions. I just bought a 94 Civic VX, which has a little under 113000 miles on it. I have started doing EOC's during my commute to and from school since having the car, and the previous owner did some as well.
To register the car, I needed to do an emissions test and it passed no problem, despite having done engine off coasts.
Here are the raw numbers:
At 2217 rpm.
HC: Limit= 82/ Reading=29
CO%: Limit= 0.45 / Reading= 0.03
NO ppm: Limit= 636 / Reading = 13
At 644 rpm.
HC: Limit = 200 / Reading = 115
CO%: Limit= 1.00 / Reading= 0.56
NO ppm: Limit: N/A / Reading = N/A
For anyone wondering about EOC and it's potential effect on emissions, here is one data point to consider. Although it is not applicable to every car/ situation, but is something else to consider.