PTS Flowbench Forum

I'm planning to build my first flowbench and I'm contemplating the airsupply. I noticed there seems to be a strong tendancy towards using multiple vacuum motors, but I was considering using something like leaf blowers instead. It seems to me something like the Toro in my garage moves ALOT more air at higher pressure than my shop vac...

Would something like this:
http://www.amazon.com/dp/B000H1Y4EK/ref ... B000H1Y4EK

be suitable? How many would be reasonable to do flow testing on 16valve sport compact cylinder heads?

Thanks!

I looked into it and found that they will not build enough useable pressure. They are designed for maximum air movement at a very low pressure differential. The smarter guys on the forum can probably explain it better then I can.

Think of it like this..........

Your air compressor can pump up bulk air pressure, but has very low airflow.
The fan that blows air around your living room can shift a lot of air, but the developed pressure is just about zero.

A leaf blower is just a fancy fan, and is just not capable of developing enough pressure to be of any use for any type of useful automotive flow testing.

For a flow bench, we require not only a very high airflow, but also a very high developed pressure, usually between 1psi and 2psi.
That requires a LOT of blower drive horsepower.

There are three practical ways to get a suitably powerful air supply for a flow bench.
1/ Multiple vacuum cleaner motors.
2/ A large diameter high pressure centrifugal industrial air blower
3/ A fairly large supercharger

Whatever you end up using will need to be typically in the 5Hp to 10Hp range (or more), and will require a surprisingly large amount of electrical power to run it.

Greetings, PTSrs,

FWIW, I just picked up a new woodworking dust collector with the following specs:
2 HP, 120 volt, 60 Hz, 20 amp peak, single-phase motor
3450 RPM
1550 CFM air suction capacity

Any idea what sort of flow bench air supply this would be for a flow bench testing heads in the 200-250 CFM range? If it won't pull 28", what might it generate?

TIA,

jack vines

Packard V8 wrote:Greetings, PTSrs,

FWIW, I just picked up a new woodworking dust collector with the following specs:
2 HP, 120 volt, 60 Hz, 20 amp peak, single-phase motor
3450 RPM
1550 CFM air suction capacity

Any idea what sort of flow bench air supply this would be for a flow bench testing heads in the 200-250 CFM range? If it won't pull 28", what might it generate?

TIA,

jack vines

Interesting question Jack.
The power required to compress air against some resistance is a fairly basic thermodynamics question.
There is a formula to work out the theoretical power required.
Let's assume your dust collector blower has an efficiency of 50% (not unreasonable).
That suggests 1Hp of actual work is being done by this blower, assuming the motor is fully loaded.
300 x Hp, divided by CFM = developed pressure in Psi.
so 300 divided by 1550 = 0.19 Psi.

That is around 5.4 inches of developed pressure.

At 3,450 Rpm and that pressure, I would guess your rotor diameter is about 8.5 inches ?

That is my wild completely off the wall estimation.
It may be very slightly more pressure than that, but not a whole lot more. It may even be less..........

Sounds like a pretty good thing for a woodworking shop, but not so hot for a practical flowbench.

If you block the flow right down to 250 CFM, you are still stuck with around maybe only six inches of developed pressure.