SC'd runner length

[Jody Shapiro]

I'm curious to the list's thoughts on this one...

For a naturally aspirated engine, tuning the intake runner length is
important so as to optimize volumetric efficiency gains.  By tweaking the
runner length, the air harmonics can be optimized for a given RPM range.
Without getting into the mathematical calculations, let's just go with the
general rule of short intake runners are tuned for higher-frequency intake
air oscillations and will boost VE at high RPM.  Likewise, long intake
runners are tuned for lower-frequency intake air oscillations and will
boost VE at low RPM.

The L98 small block chevy is known for its low-rpm torque at the expense
of high-rpm HP (245 in stock form).  It had the long intake runners which
helped it increase VE at low RPM (off the top of my head, the number 19"
or 21" runners is coming to mind - someone correct me if I'm wrong).

The LT1 which came out in 92 came with much shorter intake runners (again,
the number 11" is in my head, correct me if I'm wrong) and compromised
low-rpm torque in exchange for high-rpm HP.

SBC's "in-between" include the Mini-Ram intake manifold from TPIS for the 
L98 motors (short runners like the LT1) and the new LS1 engine for the 97
Vette which has runners longer than the LT1 but shorter than the LS1.

OK, so now that I've over-explained where I'm coming from...  :)

How important is intake tuning on a forced-induction motor?  In
particular, for a centrifugal supercharger which really isn't producing
any boost low in the RPM range, wouldn't it be advantageous to use an
intake manifold with longer runners to boost low-rpm torque and since the
ramming/tuning effect is potentially "useless" at higher rpm because the
supercharger is forcing air down the runners?

Thanks,
-Jody

--
97 Blue Z28 M6 (Memphis #1997)
  Eibach's, !CAGS, !DRL, Crane HI-6, T-Rex, Kenny Brown SFC's,
  MBA plate, 1LE shaft, Vortech 7lb S-Trim
  To be installed: AutoMeter FP & Boost Gauges
Best ET (stock): 13.941/101.18   Best MPH: 13.999/101.61
http://www.bit-net.com/~jshapiro/z28/