Home made flow bench - worth it?

[Tom Slick]

I've been fooling around with die grinders and heads / manifolds, and I really want to know if I should just put them back in the toolbox or if my efforts are worth anything. I want to know if small stuff is worth the time and I think I may be curious enough to spend some money to find out. The very small and wanting to bloom science part of me needs to know.

Flow Performance LLC offers a 1000.00 air flow bench that seems to fit my needs. It's compact, adaptable, and feeds a PC. I don't know anyone that uses one, but the DIYPorting site sure makes it look sexy.

I'd like to hear y'all's opinions on this, if anyone has used one or has another suggestion, whatever flys through your mind when you hear this. Thanks -

[oj]

Re: Home made flow bench - worth it?

I made one many years ago and learned quite a bit from it. The biggest thing i learned is that what is true for one head likely isn't true for another, so the generalities are so vague that they are impractical. Another thing, contrary to all scientific evidence, the highest flowing heads and terrific numbers probably won't translate to horse power.
I reached the conclusion flow benches are used more to justify a porters bill than anything else because some of the very best portwork i have seen have come from shops that don't even use a flow bench. Head porting is one of those art forms that is done more intuivitively than scientific basis.
Before making that kind of investment, get yourself a big powerful shop vac, build a box to act as a chamber/plenum and connect the vacuum to the box and have the box open to the cyl - just like a flowbench. A couple magnehelics and a chart to calculate air flow and you'll be in business. If you get some of those smoke sticks then you can watch the air go thru. Mess with valve lift, add some duct seal to change port shape, get a pitot tube connected to a magnehelic and use it as a probe to go around the mouth of the intake runner - make a dwg like a clock refferenced to the intake runner mouth - and record where the air moves thru it. You'll find dead spaces, you'll find air loves a corner and that the radius makes a difference. Check the exhaust side of a sbc and hold a string up in front of the port while air is pushing out (reverse the air flow thru the shop vac) and you'll see the string get sucked back into the port on the bottom side while the exhaust is pushing out! Lots of information for a curious mind and if you have desire to explore further then buy the flow bench.

[DanStokes]

Re: Home made flow bench - worth it?

I'm with OJ on this one. We had a nice Superflow bench at EPA and while it was cool and all it really is just a big shop vac and an incline manometer, which you can make easily. Or use a Magnehelic as OJ mentioned. Flow benches can teach you a lot but as mentioned they don't show HP.

Dan

[Tom Slick]

Re: Home made flow bench - worth it?


Interesting on the both the manometer and magnehelic - do you have pic / drawing example? I'm having a tough time visualizing it. The low side would go to the pitot tube and the high side stays atmospheric? What range would you recommend I start with? Dwyer seems to have a large variety.

I think I am beginning to understand the concept of velocity meaning more than total flow. This stuff fascinates me. Thanks guys.

[oj]

Re: Home made flow bench - worth it?

I tried to post some pics but the program yelled at me - if you think they'd be handy shoot me an email: [email protected]

I did this decades ago and am struggling to recall proper. I remember the pitot tube was made for me by dwyer, it didn't have a bend so i could use it like a probe. I believe i used it both ways, with 1 hose and both hoses. I have a number of gages, the gage panel held at least 4 gages and i had a couple portable ones that i'd move around and used probes with them. Some of the gages are direct readout in feet per minute as well as inches of water.
I also have the original box i used for carbs, a large hole in top and it had a carb adapter plate screwed over it to set a carb on and a hole in the side for a shopvac. The things i learned about airflow thru a holley 20-30 years ago i use to this day when building circle track carbs.
I also remember measuing the square inches of the mouth of the intake runner etc to get to cfm and there was a slide calculator from dwyer.
Hope this helped, as i said if you want a pic of some of this stuff shoot me an email and i'll be able to fix you right up. oj

[horsewidower]

Re: Home made flow bench - worth it?

I hope you don't mind if we use this as a catch all for homemade flow ideas.

Here is a place I frequent:

http://www.flowbenchtech.com/forum/

Vizard did a couple of articles on his vacuum cleaner/homemade manometer method. Used to be over at gofast.com back when that was an active place. Its also detailed at one of the car mags, you'll have to do a search.

I'm a noob at flowing heads, also, but my rather shallow take is that CFM sells heads and velocity is what actually determines a well performing head. I'm sure its not that simple, and there is a sweet spot in CFM/velocity that makes best horsepower. Mixture motion is also very important.

Bob

[TC]

Re: Home made flow bench - worth it?

I hope you don't mind if we use this as a catch all for homemade flow ideas.

Here is a place I frequent:

http://www.flowbenchtech.com/forum/

Vizard did a couple of articles on his vacuum cleaner/homemade manometer method. Used to be over at gofast.com back when that was an active place. Its also detailed at one of the car mags, you'll have to do a search.

I'm a noob at flowing heads, also, but my rather shallow take is that CFM sells heads and velocity is what actually determines a well performing head. I'm sure its not that simple, and there is a sweet spot in CFM/velocity that makes best horsepower. Mixture motion is also very important.

Bob

To me FlowBench's are only good to get each runner flowing the same. Because the highest flowing head is not always the head that makes the most HP. That was demonstrated in a HotRod article a couple of months back in an LS1 cylinder head shootout, where the ProComp head with it's smaller intake runner and valve size and flow numbers made the most peak HP. And this was up against the best heads in the business........

[JeffMcKC]

Re: Home made flow bench - worth it?

I hope you don't mind if we use this as a catch all for homemade flow ideas.

Here is a place I frequent:

http://www.flowbenchtech.com/forum/

Vizard did a couple of articles on his vacuum cleaner/homemade manometer method. Used to be over at gofast.com back when that was an active place. Its also detailed at one of the car mags, you'll have to do a search.

I'm a noob at flowing heads, also, but my rather shallow take is that CFM sells heads and velocity is what actually determines a well performing head. I'm sure its not that simple, and there is a sweet spot in CFM/velocity that makes best horsepower. Mixture motion is also very important.

Bob

To me FlowBench's are only good to get each runner flowing the same. Because the highest flowing head is not always the head that makes the most HP. That was demonstrated in a HotRod article a couple of months back in an LS1 cylinder head shootout, where the ProComp head with it's smaller intake runner and valve size and flow numbers made the most peak HP. And this was up against the best heads in the business........

The problem is this is a very false test. It did not change camshafts with each head. What it did show is bolting a good head on will not always make more power if the rest of the engine is left alone.

Low flow heads a camshaft can be off and it wont show up but on a good flowing set of heads the camshaft being off can kill the power very easy

The flow bench hearing is as much a tool as anything and getting the correct port velocity so it can make the turn.

Flow is not everything. Make the port right and the flow is the flow.

[TC]

Re: Home made flow bench - worth it?

Check this place out, $997 and you got a flow bench.....

http://www.flowperformance.com/system.html

It's basically the MegaSquirt of flow benches. ;)

[Tom Slick]

Re: Home made flow bench - worth it?

Check this place out, $997 and you got a flow bench.....

http://www.flowperformance.com/system.html

It's basically the MegaSquirt of flow benches. ;)

See my first post. lol.

...

Thanks guys for the input - that's exactly what I was hoping for here. That's a lot to start with - much better than guessing, and it looks like I can get a lot of information for not all that much outlay. Perfect!

[Tazracing]

Re: Home made flow bench - worth it?

OK I can see how this "might" be usefull in a N/A engine to read air speed, as air volume doesn't mean all that much, when compaired to air speed,
BUT tom slick, you are building a turbo'd bbf the way air travels in the port is totally different when pushed instead of pulled

when pushed instead of pulled, volume of the port would move more air, as u ram it through it. and are not rely'n on the piston to suck in the cyl. fill
why think of spending 900ish on this when the engine your building you say will have maybe 1200.oo in it..
I get the , learning usefullness that it might bring, but u'r bypassing most airflow issues by slapping a turbo on the inlet side..
so I'm kinda lost, with a turbo you'd want to move volumes of air. I'd think knowing where you'd hit water in the heads used would be more meaningfull, as air speed will come from the turbo, not the piston intake stroke (push instead of pull)

[Tom Slick]

Re: Home made flow bench - worth it?

The bbf is not the only engine I'm working on... there are many in line behind (beside) it. I am a visual / hands on learner, so a meter is a tools to indicate if I'm on the right track or not. I know what I "think" will work, and I'd like to back that up with measurements to tell me if I'm wrong or right.

You're still looking for the easiest flow boosted or not. With boost being a meaure of restriction, I'd think I would rather have 10 pounds than 12 with the same setup. That is saying if I were topped at 12 before and I improve the flow paths, and now it only makes 10, it's likely making more power now at 10 than it was at 12, and the charge should be cooler.

[horsewidower]

Re: Home made flow bench - worth it?

Mark, that's not correct.

A turbo changes the density of the air, not the volume. And the atmosphere is pushing the air into a NA engine, just like a turbo is pushing air into a blown engine. A 250 cfm head will only pass 250 cfm in each instant without going into choke.

What I want to do is try the vaccum cleaner system. Only I want to connect it to the bottom of the cylinder bore, using some plumbing products, slap the head on with a head gasket and read the manometer installed at the spark plug hole. When I really get going, I could also attach the intake manifold and see how that changes things. I think it'll be very fun, from a comparative stand point. I just won't have CFM #s, which might be an advantage to begin with. The fixation on CFM wouldn't be present.

[Tazracing]

Re: Home made flow bench - worth it?

Mark, that's not correct.

A turbo changes the density of the air, not the volume. And the atmosphere is pushing the air into a NA engine, just like a turbo is pushing air into a blown engine. A 250 cfm head will only pass 250 cfm in each instant without going into choke.

What I want to do is try the vaccum cleaner system. Only I want to connect it to the bottom of the cylinder bore, using some plumbing products, slap the head on with a head gasket and read the manometer installed at the spark plug hole. When I really get going, I could also attach the intake manifold and see how that changes things. I think it'll be very fun, from a comparative stand point. I just won't have CFM #s, which might be an advantage to begin with. The fixation on CFM wouldn't be present.

got it(I think) thanks

[JeffMcKC]

Re: Home made flow bench - worth it?

http://www.1320techtalk.com/viewforum.php?f=1&sid=013e1d54c2e9ddbd81ce491aa1b64b00

Chads site may be of some help to you guys, he is a pretty active guy in theory, and seems to be easy to give up info.