The Dyno Dip

[Jon Pennington]

Matt Davis said:

> http://www.b15sentra.net/mdavis/albums/hosts/DYNOSEAF.jpg

> Could that be what causes the  engine to do that Dip at that rpm range?

Well, I don't see timing on *that* graph, but I wonder if you're looking
at effect, rather than cause.  If it's as Mike said (uh, usually he's
right ;)), it's a resonant/harmonic thing, where the MAF sensor indicates
A# of air flowing, and the ECU sends F# of fuel to compensate.  But
there's a tumbling thing going on somewhere between the MAF and the moment
the valve closes, and the engine doesn't actually *get* as much air as the
MAF indicated was available, which would explain the rich dip.  I think it
would be cool to see an OBD-II-sourced line that draws the actual timing
curve through the band as well, just to be sure.

Other wierdass sidenote; why do all of the charts I see on roller SRs have
wildly lean fuel mixtures below 3500 RPM?

--
-=|JP|=-        "Stays Fresh Longer!"

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