A "floating pressure drop" type flowbench - By David Vizard

[Hotz]

VERY VERY VERY GOOD RICK

[FPV_GTp]

Hi , some interesting reading , David Vizard.... love him hate him which ever it maybe you have to give the guy some credit in the cylinder development industry. A guy that share information and educates the young up and coming generation of racers and technicians.

cheers

[Tony]

O/k so I build my Vizard ultra high tech floating pressure drop flow bench, using my mom's vacuum cleaner.

And I test my heads at 3Am when the temperature is only five degrees out in my shed. I also notice that the mains voltage is twenty volts higher than it usually is.

So I VERY CAREFULLY measure the pressure drop and record the value within +/- ten thousandths of an inch on my water manometer.

I then fit much larger valves and hog out nearly a quarter inch of metal out of my inlet ports, and do another test in the afternoon a month later, when the temperature is 104 degrees. Everyone has their air conditioners running flat out, and I notice the mains supply voltage is twenty volts less than it usually is.

I know that I can truly rely on these results, because the super repeatable Vizard back to back comparison method cannot possibly ever introduce any errors.

[AceR]

I've looked at the Floating bench and as long as you calibrate it with a base setting before you use it then I can't really see a problem.

[Tony]

I've looked at the Floating bench and as long as you calibrate it with a base setting before you use it then I can't really see a problem.

How do you do that exactly ?

[AceR]

when the temperature is 104 degrees. Everyone has their air conditioners running flat out, and I notice the mains supply voltage is twenty volts less than it usually is.

Well I don't do this for a start

[Flash]

Well my first flow bench was a DV, shop vac floating depression bench.

I never did any porting with that design. The # were NEVER the same, even when i did a back to back test. aka midnight, two days in a row.

Even having the heater turn on while i was testing made a differance!

It's a grate idea, and if you had a real nice voltage requlator, that keep the voltage steady, 100% of the time............How much is one of them units?

And how much is a PTS bench to build that can and will compansate for voltage, let alone humidity and temp

[AceR]

Well I guess the PTS is $50 more for a start because that's what the plans cost. To me DIY is also about self design or open source..
If someone wants to give me the PTS plans for the same price as the DV plans cost me ($0)then I'd build that one as well..
So how do you compensate for a voltage drop?

[Tony]

So how do you compensate for a voltage drop?

That is dead easy, compared to compensating for ambient temperature changes, and changes in the winding temperature of your vacuum cleaner motor.

Do you realize that as your motor heats up it draws less current and delivers less air ?
And the characteristics of that vacuum cleaner motor are what you are actually using as a measurement standard.

When your motor output varies, depending how hot it is, your airflow readings change.
But Mr V never mentions any of that....

Kind of like trying to measure precise piston size and bore diameter with a rubber band.

[AceR]

So how do you compensate for voltage drop tony? You still haven't told me..
And are you trying to tell me that other benches don't get airflow variations from heat related wiring resistance?