Re: Brake dancing on CB

[QSHIPQ@aol.com]

In a message dated 97-11-20 23:54:20 EST, you write:

<< I've been reading the Bell book and am puzzled at how some of his
> conclusions seem to differ so markedly with those BTDTs posted here.  For
> instance, he says there's no point in having the exhaust system any larger
> than the turbo outlet (in the case of our cars, roughly 2.25") yet those
> running 3" downpipe/exhaust systems claim significant performance
> improvements.  Likewise, the boost levels he recommends for 92/93 octane
> pump gas are quite a bit less than what many of us are running (presumably
> with no ill effect) and he likes big turbos for maximum power and not small
> turbos for maximum throttle response ... what gives here?
 ____ >>
I tend to look at his book more as a good baseline for the theory, he does
make some statements that many could and do take issue with.  Some of the
leeway he was given on "opinion" might be considered liberal at best.  The
biggest blunder, and Randall pointed this out already, is the single vs dual
turbo argument, "don't send a boy to do a man's job" conclusion.  The 911t
has never been compared to a 300tt, but the latter bad "boy" gets the credit
for effectively killing the 944t here. And, the 993 might just put some
correction to that whole paragraph... "unless the boy is kicking 'dads' ass",
then the Nicholson line comes to mind "Where do those japanese get those
wonderful toys".  Recommending boost levels in reference material should be
on the conservative side, IMO, tho there are several of us that have had
experience with higher boost levels with no ill effects.  I would hold off
judgement of that until we actually disconnected the rear driveshaft and put
numbers on a dyno.  We can "calculate" a lot of numbers, but I believe that
the actual "gains" might be closer to confirming Bell's proposed.

Regarding the exhausts, same thing.  His numbers are pretty good basis for
velocity of exhaust vs HP.  Again, some dyno stuff might show his numbers
more valid than originally thought.  Very few of us, when looking to upgrade
to a performance exhaust, see doing a freeflow 2.50 exhaust "upgrade" when 3
sounds really good, and must be better.  We don't have a dyno comparo to say
the 3 is better than a good 2.5, but we do have plenty of btdt that 3 is
really good.  The guy that did my 3in system in PDQ goes as high as 4in
("good to 1100 dyno HP"), has been doing race exhausts for 25years.  He
laughed when I told him that I wanted 3in, cuz he indicated that the GN strip
cars he does often, only use 3in ("up to 650HP"), and we know the flow is
mucho higher than our puny 136ci.  He said that my gains on 3 vs 2.5 are
prolly a wash, but as long as the check was good....  Still, given the size
of the stock exhaust on an audi, I might want to ask how the chart on page
133 was derived.  That seems to look fine and dandy for the pipe, with no
muffler and no cat and no specified length...  "adequate" might prove very
"in-" when you add those factors back in.  One can look at the downpipe of an
audi turbo right at the flange and tell why bigger might be better there.  I
do take some acception to the turbo outlet "theory" as well cuz tho that may
be a general rule, an RS2 turbo for instance, has a smaller outlet than a
stock k26 yet has some very high velocity figures associated with them.

His guru status, and ease of read and calculation, is a VERY good basis for
conversations on this List.  Many of us that nerd the long complicated
numbers for s*its and grins (Dave, Dave et. al. and I guilty as charged) can
look thru Corky's book and understand immediately where he made some jumps,
but bottom line, many of his time saving graphs and charts when calculated
the "long" way, look to be very valid, whatever assumptions he takes.  His
book, should be in any enthusiasts library, even the nerds, cuz it takes some
pretty complicated theory and makes it really simple.  

Many here have picked this up and use it AS THE reference material for
discussions here.  I really have no problem with that, it establishes a
BASELINE for performance threads, something many of us have been advocating
here for years.  To me, other reference material, easily puts some of the
more blatent mis-statements up for challenge.  But considering some of the
assumptions many automotive and physics "experts" have expounded here, the
book is a valuable tool for establishing facts vs fiction in go faster theory
and practice.

Few can argue that Bell is one of the most respected experts in the field of
turbocharging.  Going forward here with his book tucked under the arm, really
raises the appreciation that we indeed can go forward, beats spinning wheels
anytime, btst.  Minor corrections to his content and context hardly slows the
spirit of that progress. 

Happy he came out with it

My .02

Scott Justusson
QSHIPQ@aol.com
'87 5ktqwRS2
'87 5ktq
'86 5ktqw
'84 Urq