Blow through intake manifold flow testing

[MadBill]

No, my point is that it's the pressure difference that causes the flow. The air doesn't know suck from blow. In fact those terms are only meaningful if you're using atmospheric pressure as a reference, and depending on weather and where your flow bench is located, that could be anywhere from 30+" Hg. down to under 20".
If you go up 2000 ft. and blow 28" H2O into the plenum, you get exactly the same upstream and downstream pressures and the same flow as you would by sucking 28" at the lower altitude.

[gruntguru]

Charlie, I tried the same thing as you several years ago on 3 or 4 intakes and made notes on each test. Then I turned them around with the air being pulled in as it normally would be. Every test in the blow through method gave higher numbers. I think this is due to the way the air acts at the runner entrance areas, but I am not sure.

When you blow through the manifold, the pressure is 1 atm + 28" = 1.069 atm. So the air density entering the runners is about 7% higher and the mass flow will be 7% higher.

[MadBill]

But most flow benches measure volume, not mass and as I wrote, just changing altitude can cause the same density change yet we don't calibrate our benches to a sea level reference.

[gruntguru]

Yes but where is the orifice plate measuring volume flow located? Is the density at the orifice plate different for the two tests described?

[Carnut1]

Sorry guys, busy week already. So just to get an idea what each runner pulls this will work but if you are really looking hard bolt it on the head. I am having trouble with what flowing the manifold in the reverse direction will help with as far as from clay radius to runner to plenum. Some interesting point were brought up. Thanks, Charlie

[juuhanaa]

I got to try my first single plane manifold using a shop vac

https://youtu.be/-p5eMrrYY04?feature=shared

One vacuum source that is branched into several ports equalizes the velocitys. I dont know what its about but ive seen it before.

I think blowing from one source to several branches makes the air flow out where there is the least resistance.



-juhana