The Dyno Dip

[Jon Pennington]

Matt Davis said:

> I am looking for general information from people who know something
> about the engines characteristics. What i am looking for is the reason
> why on a Dyno graph that all sr20's Seem to have a SURGE of power @ 3600
> Rpms.

The long-runner intakes (low port and roller) each do this, but the roller
seems to do it in a more exaggerated way.  I don't think it's so much of a
surge as a dip.  A highport motor has a similar high-slope climb as the
RPMs head for 4000, but lowports and rollers seem to hit some sort of a
weird turbulent harmonic *or* something is going nutty at the
ECU/emissions system that causes a DIP at a similar but later part.

I have heard from a Puerto Rican (IIRC) G20 owner that installing an OBD-I
ECU from a Brazillian Primera GT got rid of this dip, which seems to
support my THEORY.  I bet that with some serious ignition tracing and
maybe EGR/AIV disabling, we long-runner types could get rid of it, too.

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

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