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Author: Subject: DIY Flowbench?
greggors84

posted on 7/2/07 at 02:37 PM Reply With Quote
DIY Flowbench?

Has anyone had a go at making one?

Im not worried about accurately measuring the flow with digital manometers, just to see before and after effects and see what works as regard to increase in flow.

I was just thinking about a cylinder that sealed around the combustion chamber, a hoover attached to one end and a cheap manometer attached to the cylinder.

For the manometer I was just thinking about a U shaped tube filled with water and a tube going to the cylinder attached to one end.

Would any hoover give a constant enough suck, or would it be better to dismantle one and just attached a pipe to the motor. Got a few lying about from the garage so wouldn't be too hard to find a donor.

As said Im not looking for accurate flow measurements, just something so i can see if a certain manifold or porting method flows better.

Would there be an easy way of adjusting the scale of the manometer? Thinner u tube, thinner tube going to the cylinder?

Sorry for all the Qs, just wondered if anyone has any knowledge. Also does anyone have the PPC article about a DIY flowbench? Wasnt sure if they used a digital manometer?

Cheers

[Edited on 7/2/2007 by greggors84]





Chris

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02GF74

posted on 7/2/07 at 03:13 PM Reply With Quote
search the tools/fab section - pretty sure there was one posted, up to 1 yr ago.

wondering whether a cheap version would be to seal the valve stem, remove the valve and time how loing it takes to pour 1 litre of water into the port and out the other end - there has to be more to it than that????


[Edited on 7/2/07 by 02GF74]

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tks

posted on 7/2/07 at 03:44 PM Reply With Quote
mhhh

whats needed is

just digital pressure sensors

like the one megasquirt uses..

these will be needed to be placed over the space where you want to measure the pressure drop.

the dropped pressue will tell you about the resistance.

Tks





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greggors84

posted on 7/2/07 at 04:22 PM Reply With Quote
Thats not a bad idea using a manifold air pressure sensor connected to a voltmeter as a manometer.

As for placement you would just have in the side of the cylinder attached to the combustion chamber, then the less the vacuum in the cylinder the higher the flow.

As for water, I dont think i could time it accurately enough to work out any change.





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Stuart Walker

posted on 7/2/07 at 04:49 PM Reply With Quote
Water flow bench:

We built one of these at uni, and I'm currently doing my final year project /dissertation using it, testing flow through Crossflow standard and race heads, and a pre-crossflow and MAE race head.

The guy who did the initial study and designed the prototype version of the bench worked out that a water bench gives equally accurate results at much lower cost and complexity than an air bench, assuming you don't need very very very accurate results.

From what you said I think its a bit more involved than you are looking for, but might be of some use? I have some pictures and diagrams I'll find and post up, but I can't put too much of it on here or I think I could get into trouble!

Stu

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Stuart Walker

posted on 7/2/07 at 04:54 PM Reply With Quote
schematic... Rescued attachment schematic.JPG
Rescued attachment schematic.JPG

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Stuart Walker

posted on 7/2/07 at 04:54 PM Reply With Quote
and the rig... Rescued attachment Copy of PB250012.JPG
Rescued attachment Copy of PB250012.JPG

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greggors84

posted on 7/2/07 at 05:16 PM Reply With Quote
So do you measure the amount of water flowed over a time? Or the pressure it takes to push the water through?

Its probably harder for me to build one of those at home rather than one with a vacuum cleaner motor.





Chris

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Stuart Walker

posted on 7/2/07 at 05:44 PM Reply With Quote
Yep, might be pretty difficult to make at home.

We measure the mass of water passed through the inlet port over a given time, for a given valve lift and at a set constant pressure. Then we compare this to the amount which would pass through a perfect orafice of the same size, and find the "bulk flow coefficient", which basically tells you how efficient the port is compared to perfect.

Stu

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BenB

posted on 7/2/07 at 05:56 PM Reply With Quote
PPC did an article on flow benching DIY stylee a while back by D. Vizard.... all over my head I'm afraid but I'm sure they'd flog you a reprint....
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Confused but excited.

posted on 7/2/07 at 06:05 PM Reply With Quote
Only a univerity would consider that a cheap option!
If you Google 'DIY flowbench' you will find all sorts of cheap projects.





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NS Dev

posted on 7/2/07 at 06:14 PM Reply With Quote
hmmmm indeed!!!
If you look at Bill Bleidenstein's first flowbench, it was a column of oil tins stacked up and brazed together, clamped to a head and filled with water. They pulled a plug out and started a stopwatch!

Air one is easier diy to do properly, basically a vacuum cleaner to supply the suck and an orifice plate with two manometers (water columns or map sensors or whatever) to measure the flow. As you say it only has to be repeatable, not absolutely accurate.

Make an mdf box sealed thoroughly with silicone bathroom sealer, as a plenum to sit under the part to be flowed, and connect that to the vac via the orifice plate, job done.





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MikeR

posted on 7/2/07 at 09:48 PM Reply With Quote
So when are you doing yours then Nat? Sure those heads on the grasser could do with some porting
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greggors84

posted on 7/2/07 at 11:04 PM Reply With Quote
Would you need the orifice plate? Would the port not be the orifice to cause the pressure difference needed to measure the flow?





Chris

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NS Dev

posted on 8/2/07 at 10:37 AM Reply With Quote
Yes but to get some actual flow numbers an orifice plate will give consistency.

You "should" find that the pressure drop across the head is pretty small, thus not giving much on your manometer.

Certainly give it a go though without, as long as your vacuum cleaner stays constant you will see if you are making improvements!





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NS Dev

posted on 8/2/07 at 10:39 AM Reply With Quote
quote:
Originally posted by MikeR
So when are you doing yours then Nat? Sure those heads on the grasser could do with some porting


LOL best get the car together first!!!!

may well get some spare heads and see what I can do though in the future, 300ish hp prob won't be enough!





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greggors84

posted on 8/2/07 at 01:23 PM Reply With Quote
quote:
Originally posted by NS Dev

You "should" find that the pressure drop across the head is pretty small, thus not giving much on your manometer.




Thats why I was asking about changing the scale of the Manometer, i guess I could experiment with different ID tubes to see if that gives a better scale.

Will pop over to my parents this weekend, I think my mums got a new dyson, so will disect the old one!





Chris

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Confused but excited.

posted on 8/2/07 at 09:05 PM Reply With Quote
Changing the manometer tube diameter will have no effect, as you are measuring pressure.
If you want to increase the amount of travel of the meniscus ( surface of the liquid in the manometer) for any given change in pressure, simply incline the tube, so that for a given vertical change in level, you get an increased movement of liquid in the tube.





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greggors84

posted on 8/2/07 at 11:05 PM Reply With Quote
That makes sense!

Shouldnt be a problem now as hopefully I should be able to use MAP sensors. I need to get my hands on the PPC article to see how they did it.





Chris

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NS Dev

posted on 9/2/07 at 10:20 AM Reply With Quote
This link may be useful to you, as it gives the specs of bosch sensors:

bosch sensors pdf





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