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cylinder head porting with DIY flow bench


PatAllen

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Instead of poluting the forum with random post about this project i decided to start a blog about it.

Initial idea was to make the flow bench that i found plans on the web 10 years ago, which is almost like a FS600.

Then i came up on some DIY flow bench that uses shop vacs, software to calculate cfm,...

So i made mine.

It came up prety good, works well, and seems accurate enough.

I tested various stock head i have and theirs flow numbers are very close to some known ones given by Metric Mechanics when they where "public".

flow numbers and head identification here:

http://www.bmw2002faq.com/component/option,com_forum/Itemid,50/page,viewtopic/t,313512/

post-119-13667639902594_thumb.jpg

2006 530xi, 1974 2002 Automatic summer DD
1985 XR4TI, 22psi ±300hp
1986 yota pick-up, 2006 Smart FT diesel

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later i found a Neway valve cutter, specificaly to test 30 deg back cut on the valves.

Result shows some improvements, especialy at mid to high lift

stock one base flow is 58cfm at 0.1" and 217 at .5"

back cut one is 63 cfm at 0.1" and 223 cfm at 0.5"

mid flow went from 140 to 167 cfm at around 0.3".

post-119-13667639906578_thumb.jpg

2006 530xi, 1974 2002 Automatic summer DD
1985 XR4TI, 22psi ±300hp
1986 yota pick-up, 2006 Smart FT diesel

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most recent work where spent on making the head flow equal, which is not easy at all.

Port #3 realy flow more than all others and #2 doesnt flow well at all.

Intake manifold got port matched, but it didnt showed any real cfm improvements there.

The short side radius just under the carb seems to impede flow a lot. I dont know if i will mess this one up, it may be made this way to make a lot of turbulence to help atomise the fuel ?

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post-119-13667639912771_thumb.jpg

2006 530xi, 1974 2002 Automatic summer DD
1985 XR4TI, 22psi ±300hp
1986 yota pick-up, 2006 Smart FT diesel

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my suspicions are valid, this manifold flow unevenly, which just makes plenty of sens since its unequal lenght.

stock

runner 1-4=±210cfm

runner 2-3=±220cfm

with port match

1-4=±230cfm

2-3=±240cfm

Note that at theses levels my flow bench is quite unstable but shows unit of flow differences, which is more than enough to make conclusions.

I i had to do this again, i would port-match deep only #1 and 4 and only round the edges on 2-3, this would make them flow all around 230cfm i think.

I have a lot of thoses manifold, maybe i will try it anyway.

Next is to bolt it up to the head and see what it does.

To come: flow comparision in between a stock Tii exhaust manifold and a non-Tii one (egr type), a E21 and a E30 efi one.

post-119-13667639923649_thumb.jpg

2006 530xi, 1974 2002 Automatic summer DD
1985 XR4TI, 22psi ±300hp
1986 yota pick-up, 2006 Smart FT diesel

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This is real nice work. Can you elaborate a bit more on how you built it?

nothing real fancy at first, i used the common plans on the internet BUT instead of using tube manometers (one for test pressure and one for flow loss) and the need to constantly adjust test pressure and calculate flow loss, i used tiny electronic map sensors meant for medical instrumentation (±0,3psi), and made my own software. This is the trick.

So i can use a smaller shop vac motor and the overall assembly is portable, it actualy sits over a speaker enclosure.

I found several other plans but this one is very neat

http://dtec.net.au/Flowbench%20Design%20Guide.htm

I have all the same hardware and a calibrated orifice in mine for about 255cfm but went a slight different route. I only use one of the sensor and read differential presure from atmosphere, and calibrated the readout with 10 different known flow orifices. It behaves like a car with a map sensor that extrapolate an equivalent air flow from a differential pressure. It works. Basically i can make it say wathever i want but since the readout is calibrated with known flow orifices, it is accurate. It has 16 bits a/d resolution. The very first test i did with it is a test with a stock e21 2.0 head and compared my readouts with MM ones, it was well within ±5cfm and steady. As long as the readout it steady, even it is says 0-500 units, if the next day it says the same thing its good enough to see if you improve or not the air flow.

2006 530xi, 1974 2002 Automatic summer DD
1985 XR4TI, 22psi ±300hp
1986 yota pick-up, 2006 Smart FT diesel

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Pat, "the short side radius under the carb......"? Do you mean the left fender side of the manifold plenum?? Those of us who have capped the smog port there probably have even more messed up flow there. Yes? Are you thinking of filling the tight radius to reduce the kink? With what? Am I making any sense? If it would improve flow numbers a LOT of us who have stripped the smog equipment from '74-'76cars could benefit from your info. Hint. Hint.:)

CarlkkinMadCity

'74 ex-malaga 8 yr. driving restoration

4-spd, recaros, front bbk, I.E. bars+.s.exhaust. heater refurb(thanks Kieth), total motor rebuild 175 mi ago

(thanks Steve P., Jeff I.)

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Pat, "the short side radius under the carb......"? Do you mean the left fender side of the manifold plenum?? Those of us who have capped the smog port there probably have even more messed up flow there. Yes? Are you thinking of filling the tight radius to reduce the kink? With what? Am I making any sense? If it would improve flow numbers a LOT of us who have stripped the smog equipment from '74-'76cars could benefit from your info. Hint. Hint.:)

i mean everything that is just under the carb, it has to do a 90deg sharp turn to reach the runners...simply make that 90deg bend smoother, it is hard because no good cutter on a dremel reach there, only an inverted flute on a milling would do it "correctly" and most important, evenly.

I spent a lot of time yesterday, i took all the junk manifold i have and made a very interesting find. On all of them (6) the runner #2 ALWAYS flow more, and the #1 always less. By measuring cross sectional area of each runners, and by also measuring lenght, it makes perfect sens that it is. I dont know why BMW made it this way. It just makes a very uneven flow.

Runners #2 and 3 should never be grinded off with a dremell the red neck way, maybe just the sharp edges can be debured to match the head port, but not much. Runner #1 needs severe modification to make it flow like #2, and #4 flow a bit more, but still need deep porting to flow like #2 and 3.

i have to find a way to reach deeper in the runners to remove some material so they will flow all evenly.

So far i was able to make 1-3-4 flow around 218 and #3 flow 226 untouched. crap.

2006 530xi, 1974 2002 Automatic summer DD
1985 XR4TI, 22psi ±300hp
1986 yota pick-up, 2006 Smart FT diesel

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picture of runner 1-2

i just barely deburred the edges of runner #2 to match the port, otherwise it will flow too much, #1 is still under work to reach flow numbers of #2

post-119-13667640044215_thumb.jpg

2006 530xi, 1974 2002 Automatic summer DD
1985 XR4TI, 22psi ±300hp
1986 yota pick-up, 2006 Smart FT diesel

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The different intake lengths will resonate at different RPMs so even if the steady state flow rate is the same there will be differences under running conditions.

The most attractive thing about the duel side drafts is the equal intake lengths.

Patrick Owens

www.OopsClunkThud.com

BMW 2002 US manufactured on April 17th, 1969, colour was Granada, paint code 023.

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The different intake lengths will resonate at different RPMs so even if the steady state flow rate is the same there will be differences under running conditions.

The most attractive thing about the duel side drafts is the equal intake lengths.

i am well aware of that, but given the helmholtz equations, the differences in cross sectional area (once i will get finished) and the fact that they will flow equaly in term of cfm's and the relative small difference in lenght make this irrelevant. I have a book with a complete section (bout 50 pages) just about unequal intake design and it is quite interesting what they end up with to "correct" this kind of issue. They even did try a completely uneven intake design so each cylinder will resonate at its own frequency thus broading the torque curve.

On such M10 motor, considering the lenght of each runners, the "uneven" original manifold will resonate from 2800rpm to 3200rpm, quite narrow ...not much to get worried at at this point.

2006 530xi, 1974 2002 Automatic summer DD
1985 XR4TI, 22psi ±300hp
1986 yota pick-up, 2006 Smart FT diesel

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The different intake lengths will resonate at different RPMs so even if the steady state flow rate is the same there will be differences under running conditions.

The most attractive thing about the duel side drafts is the equal intake lengths.

i am well aware of that, but given the helmholtz equations, the differences in cross sectional area (once i will get finished) and the fact that they will flow equaly in term of cfm's and the relative small difference in lenght make this irrelevant. I have a book with a complete section (bout 50 pages) just about unequal intake design and it is quite interesting what they end up with to "correct" this kind of issue. They even did try a completely uneven intake design so each cylinder will resonate at its own frequency thus broading the torque curve.

On such M10 motor, considering the lenght of each runners, the "uneven" original manifold will resonate from 2800rpm to 3200rpm, quite narrow ...not much to get worried at at this point.

Great stuff Pat! Keep it up. A lot of motorcycles use different length intakes to broaden the torque curve. Air cooled Ducatis from the 90s for instance use a velocity stack on one cyl. that is 4 inches longer than the other cyl.

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