Pressure Sensor for Flow Bench

John A. Hess johnhess at cris.com
Tue May 12 12:23:40 GMT 1998


Pardon me if this is a dumb question;  but, what does a diy_flowbench have
to do with diy_efi?


garfield at pilgrimhouse.com wrote:

> On Mon, 11 May 1998 09:01:33 +1200, "Tony Bryant"
> <Tony.Bryant at psc.fp.co.nz> wrote:
>
> >As, it happens, I'm also building a DIY FlowBench. May I enquire:
> >
> >1) What are you using for (a) blower(s)?
>
> Not sure this is gonna be much help to ya in Kiwilandia, but both
> SuperFlow and QuadrantSci use multiples of what is refered to in the
> trade as ' 5.7" vacuum motor/blowers', made by a number of suppliers,
> especially Ametek, w/air-sealed bearings & double-insolated. They make a
> line of two-stage blower/turbines that for example, are rated at
> 102cfm/90"H20, 120VAC at 9.2A [Ametek (used to be Amtek-Lamb) part #
> 116025-13], which sell from a big US electrical supply house like
> Grainger for about $70US ea. I have looked inside SuperFlow boxes and
> talked to the designer of the QuadrantSci stuff, and in both cases what
> they do is of course use multiple blowers in an array, and stacked in
> pairs in series electrically, which you CAN do with AC/DC motors, so you
> now have a pair of said blowers drawing 9.2A/pair across 240VAC. Put say
> 4 pairs of these puppies together and you're up to a goodly 36A @
> 240VAC. Not maxing out your shop feed, by any means, but still alot of
> power at 5KVA. And yes, you'd better believe it's gonna be noisy! Not to
> mention the  "local warming phenomenon", heh.
>
> >2) Can you publish your thyristor speed controller circuit, or at
> >least give us some rough details?
>
> Sure, got it directly outta
>         http://www.teccor.com/thyristor/an1003.pdf
> Look for the "double-time-constant" circuit examples. To get me up to
> 12A @ 240VAC (25% safety margin above the 9A I expected), I used a
> Teccor Q6025J6 Triac and an HT-32 (SGS-Thomson also make the exact same
> part they call a DB3) Diac. Both of these devices are available cheap
> from DigiKey:
>         ftp://ftp.digikey.com/Catalog/V3/PAGES/201-250/211.pdf
>
> This is only good for driving a single PAIR of these blowers, so you
> need to invent/rig either a tandem mechanical or electrical way of
> controlling the pairs of blowers. If you don't wanna build these up
> yerself, and plan on a manual control for the blowers, Dayton Electric
> makes a similar knob-controlled circuit for fan & blower control
> packaged with an integral heat sink. They charge around $100US for them!
> All for a circuit that contains about $12-15 worth of parts. (Hey, all
> it takes is 2 middlemen, and that's what it's gotta be marked up to).
>
> For my purposes, controlling these pairs of thyristors/blowers via
> computer, I'm gonna use some mosfet devices in place of the pots. Thas
> all. (I gotta look at this 5HP 3-phase Paxton blower Bob MacKnight
> recently posted on, tho; it sounds too good to be true, buy hey, greater
> wonders I've seen happen via "surplus" stuff, so who knows!).
>
> >I'm currently using a hotted up garden leafblower, but I'm only
> >getting 10" @ 100 CFM. (Its also very loud).
>
> Well, that just showTaGoYa what kinda power you have to apply to move
> that much air at that much vacuum/pressure. Your garden blower can't be
> drawing much more than 10-12A @ 120VAC (hmm, not sure what the mains are
> in Nz, but just using US figures for ducks). Multiply that by a factor
> of 6-8 to get what's needed to do 20" @ 300cfm. Or compare that to the
> power both SuperFlow and QuadrantSci spec for their bigger benches. It's
> LOTS of AMPS @ 240VAC. Go see at:
>         http://www.superflow.com/products/products-flowbench-sf300.htm
> and you'll see 240VAC @ 33A or
>         http://www.quadsci.com/products/engair/flwbnch/flwbnch.htm
> where you will see 240VAC @ 29A, that's because they're using motor
> control of the blowers, instead of 'bypass', they get some better
> numbers than the SuperFlow chaps, especially at lower flow rates.
>
> >I'm using the PWM circuit out of the back of the Motorola Thyristor
> >book, but it's kinda pulsey in this application.
>
> Hmm, never looked in there. Not familiar.
>
> >And a mechanical pressure sender (a modified carb
> >secondary vaccum modulator, hooked to a pot) as the feedback to the
> >motor controller.
> >
> >I'm using an uncalibrated flap style MAF (I will calibrate on some
> >known heads)
>
> Alright, yer my kinda guy. It may not be "accurate" or "calibrated" but
> for just comparative flow bench studies, which is the real meatNpotatoes
> of the issue anyways, as long as the pressure is repeatable and the flow
> delta is measurable, that's all that matters. With a small investment in
> better pressure measurement, ala the stuff that
> "Jack" <goflo at pacbell.net> mentioned earlier:
>         http://mot2.indirect.com/senseon/mpxl5010.html
> for the sales pitch and
>         http://mot2.indirect.com/books/dl200/pdf/mpxl5010rev2.pdf
> for the datasheets, for a 0-40"water range, where IF you can operate at
> around 20"water, the linearity and accuracy of this device will be just
> wunnerful for your/our porpoises. And it's "cheap", too!! (North
> American Price List says $13-15 each).
>
> The main thing to get outta all this, I s'pose, is that we're REALLY
> movin a whole lotta  AIR to duplicate what a large ICE does whilst
> breathing. So whether you go for a 5HP single-piece blower motor, ala
> Bob McK's recent post ($350 surplus, so figure $3K new), or you add up a
> bunch of smaller blowers like the big boys do (around $500 total, new),
> you're still talkin about a lot of power to cover the pumping losses for
> that much air flow.
>
> Anywho, Tony, good to see there's at least one other wacko like meself
> thinkin alone these lines. I bought/borrowed/read every article/paper I
> could find about the older "fixed, knife-edge orifice and manometer"
> style FB's ala SuperFlow, but after chatting with the designer of the
> QuadSci stuff (whose name is "Oz", oddly enough), I was thoroughly sold
> on this newer approach via electric control of everythang. Maybe just
> the geek in me, but them knife-edge orifices ain't no easy pie to
> calibrate, and have to be moved in and out mechanically, and besides, I
> like to avoid the black magic whenever I can.
>
> Just some poop and some thots, dude.
>
> Cheers,
> Gar






More information about the Diy_efi mailing list