Porting School #2 - Super Cheap Flow Bench

[Horsewidower]

Seems that the paragraph dealing with exhaust could apply to flowing boosted applications. Gonna have to think about how to do that.

[MaxRaceSoftware]

David .... who does your Art Work / Graphic Illustrations
for your Articles ??

what Software Programs are you or they using ?

very nice Illustrations in all your Articles !

[havok91]

More than one hundred? Looking forward to each and every one.

[Dusty]

Unfortunately David does his own illustrations. While we are all still sleeping he is up drawing on his computer.

[DavidVizard-GFN]

Originally Posted by FlowSpecialist

For those that are interested it was David who spotted the mistake I'd made in my own first flowbench design some 20 years ago where I'd copied someone else's mistake without thinking about it properly and had a pressure tapping in the wrong place. That enabled me to go on and refine the design and eventually achieve an accuracy against calibrated orifice plates of under 0.3% over the full scale of flow and for that as well as many other things over the years I'm greatly indebted to him.

Dave

Dave,
thanks for the thanks here. I really appreciate that you remembered all those years back ( boy we were a lot younger then!!!!)

DV

[DavidVizard-GFN]

Originally Posted by MaxRaceSoftware

David .... who does your Art Work / Graphic Illustrations
for your Articles ??

what Software Programs are you or they using ?

very nice Illustrations in all your Articles !

All the illustrations done with Corel Draw and Corel Photo Paint. Takes time but I guess the compliments indicate it's worth it. Anyway I think you guys deserve the best!

DV

[Travis Gibson]

[deleted at request of author]

[ThePinnacle]

Mr Vizard,

It's an honor to be able to participate in this forum with you. Your books kept me sane when I was overseas for a year in the military. This forum and the tech articles on here are great.

I liked this cheap flow bench so much I went out and built one




I fabbed up an adapter for my head from 4" schedule 40 pcv pipe and a piece of wood. A little epoxy holds the tube in place, and instead of nuts, I just used epoxy to form threads in the wood. The bolts thread in and hold very nicely.




a rubber drain pipe adapter takes the pvc down to my vacuum hose size

Manometer is just clear 3/8" hose zip tied to a piece of metal




This set up works great. I'm working on my 3.8 turbo buick heads and managed to quantify the difference between my porting and a stock head.

Unfortunately the 3.5 hp vac I bought wasn't giving me enough vacuum to make me happy so I took it back to the store and bought a 6.5 hp monster made by RIGID. Now even at max lift flow on the stock head I'm still showing 21 inches of vacuum whereas with the old vacuum it would drop down to 6 inches or so. The ported ports got down into the high 4" range.
So now I'll have to redo all my measurements

I have a question for you though... How important is it to have some sort of radiused entry to the port? I seem to see some flow bench photos using one, and others not using one. I can certainly see that it would be important if I wanted to test the effects of port entry changes... but if I am just concerning myself with the throat and bowl area, is it really going to matter much?

Also (I'm sure you must have mentioned this somewhere) when flowing the exhaust, is it as simple as reversing the flow and reading the pressure as you would on the intake?

Would it be possible to flow an MPFI intake manifold in this fashion? I was imagining just using the blower on the throttle body and measuring pressure before the throttle body. Only thing that concerns me is that if I just put my probe on the wall of inlet that it might skew my pressure readings because of a potential draw on the probe... then if I face it into the air stream I get a ram effect.. and if i face it with the air stream I would think I get more draw again. Your thoughts?

Anyway thanks again
Pablo

[ThePinnacle]

Well things aren't going as well as I'd like with this bench.

It's not consistent, and the manometer reading can (depending on circumstances unbeknown to me) fluctuate pretty wildly. This makes getting an accurate reading very hard. When I do manage to get a reading I've found that the same port (with no changes) can fluctuate as much as 15% at low lift and 5% at high lift.

This makes the ability to see improvements from port changes next to impossible.

What am I doing wrong? I saw in porting school #3 the mention of a voltage monitoring/regulating device for the vacuum. Is the lack of this causing my problems?

Any advice would be appreciated.

[MorGo]

I don't see where you take the vacuum signal? It can be very critical for consistent and true readings.