<VV> Ultravan's new SuperTrapp, Vacuum/Boost gauge and O2

[Craig Nicol]

Dan wrote:
We're taking it out camping this weekend so I'll try to get some averages.
Problem is wind resistance and prevailing wind speed which will have a big
impact on throttle position for a given rpm when driving one of these
whales.  Off the top of my head, I remember seeing the first of the four
red(lean) segments lit on the SafeGuard AFR gauge along with several of the
yellow segments (12:1) @ 3,000 rpm.  On the gauge there are 3 green(rich)
segments beginning at 11:1, 4 yellow segments and 3 red segments ending at
13.5:1.  I did notice that it tended to lite the red segment once I leveled
off to my cruising altitude :)

And Don wrote:
<snip>
With the new O2 sensor, I now realize that I'm running a bit lean in the
upper rpm range. It's fine at idle and cruising below about 2500 but as the
engine speed increases, it leans out a bit. I'm running 53 main jets but am
now thinking of increasing them to 54's given the new information.
<unsnip>

Craig replies:
Boy, there's no way I'd ever call 13.5 "lean".  From all of my reading and
experience, I understand that 12.5 - 13.5 is the "Max Power" range or
"Rich". Any thing lower than 12.5 is over-rich.  14.8 is, of course,
stoichiometric and that makes a catalytic converter happy and keeps NOX
production and HC down.  Above that, say 15.5 to 16.5 is the AFR for best
economy, and numbers above THAT are considered "LEAN".   If you need to
maximize power even at cruise and aren't worried about fuel economy, I'd say
that you're carbs are jetted acceptably rich as they are right now. If it
were me, I'd be looking for a cruise in the high 14 range.

Craig Nicol