[Shotimes] Power adder discussion

[Ron Nottingham]

OK, folks...  To dispell a couple of myths about turbochargers...

First, turbochargers, when properly sized (this email will assume proper
sizing), WILL produce more torque at a lower rpm than any centrifigal
supercharger.  Sorry to rain on some peoples parades, but test after test
after test has shown that a turbo will outperform an S/C across the board
(for a few tests. check out Hot Rod, SCC, Turbo, and countless others,
either from this past year, or even from several years ago).

Second, "turbo lag" is really a misnomer (sp?).  Well, "turbo lag" comes
from a couple of major factors.  One being turbo size and the other being
static compression ratio.  The larger the turbo, the more time it takes for
an engine to spool it up.  The lower the compression ratio, the longer it
will take the engine to produce enough exhaust gases to spin the turbo.
Back in the early days of turbo cars, generally a large turbo and a low
compression was used, which is why many early cars had "turbo lag" and had
that explosive bang of power (check out an early 911 turbo).  Now, with many
turbo engines sporting around 9:1 CR (most early systems used 7.5:1 or
less!), and properly sized turbos, "turbo lag" is a non-issue, except when
trying to pull from higher gears when the engine is out of the power band.

With proper engine and ECU tuning and a properly sized turbo, you will not
have "turbo lag".  Sure, off idle up to 1800-2200 rpm it will feel sluggish,
but what small engine doesn't?  An engine driven centrifigal S/C will not
produce it's highest boost pressure until the engine is spinning near
redline (ok, recent advances in centrifigal s/c's have some tricks like gear
drives inside that make them spin faster at lower rpms, and use blow off
valves like turbos).  A turbo will generally produce max psi by 2800 rpm on
average, then use wastegates, blow off valves, etc to limit boost pressure.

Well, this is all the time I have, as my wife is in the hospital
(complications with her pregnancy, baby is fine, she is fine, just having
early contractions) and I have to go into work tonight, and I need some
sleep.

Ron N. - Dalton, GA
90 SHO
89 325i
88 325
"It takes a man to suffer ignorance and smile"
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