Randall Young wrote:
>
> I must still be missing something. The Superflow 1020 is rated for 65" of
> water at 165 cfm. My calculator says that's less than 2.5 psi. According to
> Eaton's charts, a model 112 blower will produce almost 200 cfm at 2.5 psi on a
> little more than 3 hp.
>
> I guess the problem must be that 1000cfm that Superflow talks about.
>
> BTW Keith, you forgot to account for phase angle and motor efficiency. 75A @
> 220v is more like an honest 15hp output.
Doing coal-cleaning research in Massachusetts, we had a Roots blower
good for, I think, about 1000 scfm, and ran it, with the speed reduced
somewhat by gearing, on a 20hp 3-phase, 480V motor. Probably good for
550-600 cfm with some restriction (typically, in a 3" delivery pipe, it
would be about 30-35 inches of water). I'm not disputing the figures
given above, but relating these to describe the running characteristics.
Quite simply put, the noise would drive people out of the building,
particularly the whine from the air inlet.
For anyone contemplating a full-race engine, it's probably much cheaper
to simply farm out the port work and flow bench testing; the equipment
to do the job like the professionals is neither cheap nor a snap to
install, nor easy to live with unless one has the power source outside
in an insulated box.
For most amateur work, or if one wants to learn the principles, not so
much pressure is required. The ability to measure accurately with less
air is more important. And, most importantly, the top people in the
field aren't charging what they do just because they have expensive
equipment. One is paying for their expertise in knowing _how_ and
_where_ to change a port or a chamber. And for most of the people
contemplating doing this work at home, that part is a steep learning
curve.
Moreover, for most streetable small engines, the most carefully-flowed
ports will produce a 3-5% gain in hp, at the highest flow rates, over
ones done by hand with some care. For a NASCAR engine running 650-700 hp
at 7600 rpm, 3-5% is a whopper of a change. For an 1147cc Spit, it might
be worth a tenth or two off the 0-60 times.
Not to discourage anyone from buying what they really want, but
professional flow benches are likely in the $15-20,000 range, with air
source. A decent homemade one can be done for $200-300, with some
creative scrounging, and with another $300-400 for PC-based data
acquisition, and even then, that investment wouldn't be warranted unless
it would be used many times. After all, following all the
recommendations in Kastner's competition guides produces about 160-165
hp on most Triumph two-liter engines with some reasonable amount of
reliability, and the tips in those guides require, at most, a small
lathe, a good grinder, a steady hand and attention to detail.
Cheers, all.
--
Michael D. Porter
Roswell, NM
[mailto: mporter@zianet.com]
`70 GT6+ (being refurbished, slowly)
`71 GT6 Mk. III (organ donor)
`72 GT6 Mk. III (daily driver)
`64 TR4 (awaiting intensive care)
`80 TR7 (3.8 liter Buick-powered)
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