I don't think the guy that figured this out would mind me sharing. He posted the plans on the H.A.M.B. site.
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One more graph,this is for a 95 Mustang MAF. 1 CFM = 2.08KG/HR @ Std air density(59 degrees F @ 1 atm pressure).So the chart is reading approximately twice as high as CFM. Close enough to do a baseline and see improvement.
mafcha1.jpg
http://www.topplocksverkstan.se/flodesbanken.html
Here is another one for you guys. Unfortunately everything is written in Swedish with a few exceptions, but has a lot of pictures and quite a few formulas too. If you need any translation let me know.
This guy, Erland Cox, is very recognized in porting cylinder heads and has an immense knowledge in engines. He does not mind sharing it and has very good English if you need to contact him with questions.
BTW this is not an advertisement
Jim, I didn't see a recommendation for the power of the shop vac. I've got one that could suck the chrome off a trailer hitch, but it might be more than is needed for this flow bench. Otherwise, this seems like a clever little setup.
The Mustang MAF looks like it is sensitive in the 100-200 CFM range (200Kg to 400Kg), so that should work well. I wonder if the Rover MAF would work?
Paul,I imagine the port would only flow so much so the bigger the shop-vac the better.How about a RV sewer gate valve and vacuum gauge at the shop-vac. You could adjust to the standard 28" vacuum.The Rover, if Hotwire MAF would probably work if you could figure out the voltmeter connections.The first two pics are the guy's idea. The third one might confuse as it is a real schematic of a flowbench.
Here is a diffuser that could be put in after the elbow made of soda straws for more consistent MAF readings.
Flow_Bench_Build_18re.jpg
Now THAT is clever. I assume that, to prevent it from being a restriction, you stuff something like a 5" pipe with these straws and adapt that back down to either 3" or 4" or whatever plumbing you were using.
What about cutting the straws to different lengths or staggering them to help muffle standing wave effects?
I'm not sure, but it makes sense after the elbow to straighten and smooth the flow. Here is a picture of a 90 Ford MAF.
Flow_Bench_Build_14re.jpg
Cool project, man. I was considering building one too after reading "Practical Gas Flow". Good book...
Popular Hot Rodding magazine had a series of article where they gave instructions for a homebuilt flowbench. I have the pages scanned somewhere, if someone is interested I can find them for you.
Anybody actually build one ? You can buy a somewhat expensive "kit with black box" included. Somewhere I read you'll need qty. (11) vacum motors ! Why not use a cheap "Rootes" ? 6V71 at swapmeet-$40. Long term satisfaction of making it work-priceless. roverman.
> Why not use a cheap "Rootes" ? 6V71 at swapmeet
That would be suitable for a constant depression (flow drop) type flow bench.
The budget flow benches I've seen are variations on Vizard's varying pressure
drop design:
http://www.gofastnews.com/showthread.php/980-porting-school-2-super-cheap-flow-bench.html
http://www.gofastnews.com/showthread.php/1037-Porting-School-3-Budget-Bench-Calibration
Vizard has a good article on this design in one of his books. Basically
he noted that since the pressure drop across a valve varies rapidly with
valve opening, a constant depression flow bench isn't necessarily better
than a bench that permits the pressure to vary. The latter design requires
much less flow to operate, permitting simple shop vacs to power the benches.
I've got a Beam vacuum unit in my garage that powers a whole house vacuum
system. I plan to tap into it for my home made flow bench. I've picked
up an old manometer but need to finish up a few other projects before
completing the build.
Dan Jones
Would not a Rootes with changable restricting orfices, gate valve retriction or cangable blower driven speeds make suitable for various pressure drops ? Seems like this blower could make pretty high vacum for more engine- like flows on exhaust port. roverman.
"I've got a Beam vacuum unit in my garage that powers a whole house vacuum
system. "
Great idea, Dan!
Hmmm....I have a pretty big vacuum unit for my Skat Blast cabinet that may work, as well. ;)
> Would not a Rootes with changable restricting orfices, gate valve retriction or
> cangable blower driven speeds make suitable for various pressure drops?
You wouldn't need to do it that way. On a standard flow bench, pressure drops
as soon as you open the valve. At each lift increment, you increase the suction
of the pump to maintain a constant pressure drop. In the Vizard bench, you don't
attempt to maintain a constant pressure drop. You let the flow/pressure drop
change as it would in the engine. The Rootes would work but would require a rather
sizeable electric motor to run which would defeat the low cost nature of the
approach.
Dan Jones
Ok, I'm seriously considering a "Flow Performance" flowbench kit. Not cheap but digitalized,(electronic manometers), that runs with windows 98 +. I have a 3 hp industrial vacum, maybe adequate ? Anybody ? Thanks, roverman.
Yea, Now if I just had some TA heads to plop on it. roverman.
Hi Roverman,
Last year I shipped a Flow Performance kit to my friend in Belgium. He uses it for his MGA twin cam heads and he loves the performance of the kit. A bit expensive but he says it is well worth it.
Werner
Werner, Ok so $1,000. US. is expensive ? I suggest pricing a comparable flow "Superflow", for a better definition of ex$$pensive ! Cheers, roverman.