Thanks Erik and Larry for the mental pictures.

I would have loved to check out those JPEG's and GIF's but I'm
getting a Server Timeout error.

"The thing is, that the port or whatever you are actually flowing also can go turbulent and flow only a LITTLE MORE or the SAME or even LESS at a higher pressure drop very easily instead of continuing to flow more and more."

That would simply mean, everything has a limit? The shape, design
and tuned charateristics of the unit under test can only handle
so much before the result turns nasty.

I guess it would be analogous to jamming a hotdog through a dime hole! Too much velocity, not enough runner volume?

"you open valve to .300" Lift ....as you do..the test depression on vertical manometer drops
so you turn flow control **** till you again are back to 28 inches"

I see how that works. Sucking the juice up through a straw with
your mouth. Switch the straw with a paper towel roll...now you
need a bigger mouth to maintain the velocity and manometer reading
of 28 inches.


In summary 100 CFM at 0.200" @ 28" is the same **velocity** as 400 CFM at 0.500" at 28 "?

Maybe **velocity** is the wrong term in my above example?

Would an engine tuner use these numbers to spec a camshaft
with piston acceleration and cam lobe profile to ensure a smooth even flow across the entire valve opening event?

 

Zero_to_69 , it would worth the effort to find someone in your area with FlowBench and bring a cylinder head for that guy to Flow Test right in front of you ....it would be a great experience

if you can't...heres a little more info ;

New_Flow_CFM = (( New_Test_Pressure / Old_Test_Pressure) ^ .5) * Old_CFM

250.0 CFM @ 28 "= ((28/10)^.5)*149.4 CFM @ 10 inches of water

Zero_to_69....try out the Flow Conversion formula for different Test Pressures....with it you can convert any flowbench CFM numbers at one test pressure to another test pressure
========================================



"The thing is, that the port or whatever you are actually flowing also can go turbulent and flow only a LITTLE MORE or the SAME or even LESS at a higher pressure drop very easily instead of continuing to flow more and more." - Zero_to_69

Yes, thats correct.

but you can see that effect happen at any test pressure
between for example, 10 to 60+ inches of water

if the port shape is bad enough, this can happen at 10" or less

if port shape is a little better , but still not great shape,
it can happen at 28 inches or less or any pressure instead of 10 inches

Analogy => picture mentally that each air molecule is an Indy
Formula 1 Car .....how many accidents or spinouts on Track's Corners or Turns would occur if all those Indy cars were going around the Track at 60 MPH ???

How much would you learn in testing your Indy Car at 60.0 MPH
How much would you learn in testing your Indy Car at 120.0 MPH
How much would you learn in testing your Indy Car at 240.0 MPH

How many cars would make it thru Turns at 60.0 MPH ?
How many cars would make it thru Turns at 120.0 MPH ?
How many cars would make it thru Turns at 240.0 MPH ?
How many cars would make it thru Turns at 480.0 MPH ?

60 mph = 1.767 inches of water
120.0 mph = 7.068 inches of water
240.0 mph = 28.27 inches of water
480.0 mph = 113.09 inches of water

Intake Port sonic choke limit (with fuel in mixture)= .50 to .70 Mach

.50 Mach = 381.8 mph or 71.56 inches of water
.60 Mach = 458.18 mph or 103.04 inches of water

so you need your theoretical Indy Car to go around the Race Track between 381.8 mph and 458.18 mph or higher

if you straighten out the Indy Track into one long DragStrip
you won't have anywhere near flow separation problems
(Spinouts/Crashes) ...more cars side by side and grouped together .....and straighter , gentle turn ports (ProStock Technology trends) , can increase or handle higher port velocities => which leads to higher Volumetric Efficiency, TQ/HP
better fuel economy (BSFC) , less or no dead areas in ports


now the FlowBench is a Steady-State flow device
and flowing "Dry Air"
so you do all your port shaping and flowtesting
at a certain test pressure (velocity fps or MPH)

your port shape looks great on the FlowBench

but all that was Dry Flow

now you add extra 1000 Lbs to your Indy car (wet flow = heavier Fuel Molecule)
and still want it to go around same Track corners or turns
at the same MPH as before
..now with fuel inside intake port, that great looking Short Turn Radius shape or Port Shape that looked great, is now causing
flow separation...now in real "Live Track" racing conditions your
Race Car crashes / spinsout in Turns choking off the rest of cars trying to make it around the Turn (Less Flow or No Flow increase)


What you are trying to learn from Flow Testing at higher test pressure/velocities ..is to come as close to simulating
live engine flow dynamics as possible .

you are trying to determine if there is a possible chance of flow separation at higher velocities

you are trying to take the "Sensisitivity" out of the Short Turn radius ....because later in real live engine conditions there will be an Air/Fuel Mixture replacing just the AIR you were using in your FlowBench Tests

if you have a Short Turn Shape or Port Shape that has Dry AirFlow barely staying attached....when you introduce real live wetflow Air/Fuel Mixture inside ports or if in that Live Engine
air velocities are very much higher than when you did your Flow Tests....you will have a very good chance of being fooled by your FlowBench numbers.


its been known for many years by many people that the Inlet Mach Numbers below are good indicators of Live Engine conditions

Intake Port sonic choke limit (with fuel in mixture)= .50 to .70 Mach

.50 Mach = 381.8 mph or 71.56 inches of water
.60 Mach = 458.18 mph or 103.04 inches of water

you would want to find a way to spot check or flowtest your heads on intake side at between 70 to 100 + inches of water
or at least make effort to FlowTest or Spot Check Flow as high
as your FlowBench will go to make sure flow will stay attached to your port shape

then just use Conversion Formula to correct back down to 28 inches or whatever number you want for Industry flow comparisons

you have to remember there will be Fuel in that Intake port

you have to take Short Turn sensitivity out as much as possible
to account for Mixture
the Mixture thru Intake Ports will be traveling
at 382 to 535 mph (.50 to .70 Mach) ( 71.56" to 140.3 " H2O)
around Short Turn Radius and in Port

 

Larry,

That was great and I agree with every part to a point. Like I said if you did it with "port shape" it's gonna be ALL GOOD. But I can take any head you did and make it stable up even higher by just making it a bigger version of what you did but keeping the same seat and valve. Basically I just slowed down the port speed at the amount of air the valve seat is passing.

On the bench it will now stay stable to higher valve lifts and pressure drops. It will also have better wet flow up there if it were really able to run at that drop in the first place because fuel depending on droplet size can only turn so hard before it all goes to the long side.

However at some point this larger port will be slow enough to lose inertial filling to some extent or filling past BDC (compared to the smaller version that goes turbulent earlier) when the piston and pressure drop turn the corner and the only thing filling the cylinder is the inertia left in the column of air and fuel.

So what I am saying is that the flow bench could fool you even by flowing at high drops if your stabilizing the ports by size rather than shape. After all size is part of shape in a way.

Now if you straighten the short turn and raise the entrance etc. and get way more speed before seperation at the same cross section you have certainly made gains in filling and wet flow because you can run more port velocity instead of less.

Larry, how high would you want a 23 degree to stay stable at or even expect you could make it stay stable at without losing serious velocity through sheer runner size. What I mean is that what port velocity do you usually see max power at at least in average port velocity? This is what I look at since most of the real race stuff is in the same ballpark of cam duration say 270-280 degree roller stuff?

 

By the way it's very cool to have someone that understands this stuff as well as you do on here! I love seeing what other people say about this stuff and believe me I've talked to a FEW as I'm sure you have too, maybe many more possibly. I just can't get enough of any of this knowledge or even different viewpoints.

Sometimes it's just semantics but I think you have basically the same ideas on this as I do although like I said I am looking at the pressure drops in general that will give me optimum power with a given valve and cam duration and LSA. You can only do so much with port shape on most heads without welding etc.

I count myself fortunate to know so many that work in PS and NASCAR head shops that do pass along a lot of info through all my connections at SAM and TAMSCC. I know they all think you can go too big but there's a semi gray area of velocity vs cam durations that I don't see tons of agreement over right now. Some of the NASCAR stuff is a little big on purpose to reduce the power off of certain tracks turns and pull a little further down the straightaways.

 

Awesome explainations guys.

Reading Larry's response, I can certainly understand how a fuel
injected head would increase volumetric efficiency as the wet flow
path is much shorter.

It must be cool to hook up with NASCAR techs. Send me some of
those heads please!

 

Zero to 69,

The object of FI is to get higher velocity with the same or better wet flow especially with the newer cars with the injectors rolled up way into the head like the LS1 etc. This is also big with emissions reductions during idle etc.

The nascar head is compromised by having to hook up to one centrally mounted carburetor. Heads like the SB2 are totally designed around that central carb. With FI you can make the head and runners more symmetrical. Some alcohol powered sprint cars run an injector right in the intake port too since they run double the fuel that gas engines do and this helps eliminate a lot of their problems. Alcohol doesn't vaporize as easy either so the droplets stay droplets further from where they are introduced until they absorb sufficient heat to vaporize so wet flow is a huge problem with these heads otherwise.

 

Larry, how high would you want a 23 degree to stay stable at or even expect you could make it stay stable at without losing serious velocity through sheer runner size. What I mean is that what port velocity do you usually see max power at at least in average port velocity? This is what I look at since most of the real race stuff is in the same ballpark of cam duration say 270-280 degree roller stuff?
=========================


"average port velocity"=>
it depends where and how you are measuring velocity and what Formula you are using , but 300 to 360 fps, with anything under 240 fps usually always hurts HP/Torque

Erik, i had a pair of LS-1 CNC'd Chevy heads ported by another
Company on one of Alan Futral's customer's car that the DragStrip times were off from what the FlowBench numbers showed . Alan took heads off the engine and brought them over to my Shop to Flow Test.....we 1st Flow Tested heads at 28 inches just like the original Flow Sheet ......the numbers i got were approx same numbers at all Lift points on Intake and Exhaust.....so far there was nothing showing up that was wrong with heads . so i repeated Intake flowtest , but this time at 36 inches....when i got to .500" Lift w/36" the intake flow took a 5 percent dive....at .600" lift to .700" Lift they were bad, above .700" Lift flow started to come back slightly

i reset Valve Lift back to .500" Lift and flow tested starting at 28 inches again....when i got to 31 inches flow took a dive
at 36 inches ..even more loss ...at 48 inches,still same loss

all i did was redo Short Turn curve ....again heads flow tested at 28 inches ...flow numbers were very close to were they were originally ...but this time increasing test pressure to 36 inches flow kept increasing ...didn't take a dive from .500 lift to .800 lift
even if flow tested to 48 inches

on car at DragStrip ...car was immediately 3 MPH faster and 2.5 tenths faster than best run before

if the original HeadPorter would have just "spot checked" the flow at 36" or higher, he would have caught the problem

this is not your typical everyday flow problem...but it does exist !!
if you never spot check a head above 28 inches , you will never know this problem might exist .

 

I agree with what you are saying about this LArry 100 per cent. I was just saying that I wouldn't develop the port around much over 28 inches. Checking for turbulence at the high drops is certainly good practice.

I've seen people develop a head around 36 inches and then lose overall power to a head that flowed the same at 36 but more at 28 which seems weird but is true. One had a smaller port and larger valve and used a smaller cam and was on a smaller engine. Basically the other was a largish port with a smaller valve that did not go turbulent as easy but had no velocity and only caught up to the other head at 36 inches. This head lost 30 overall hp and pulled out to about the same rpm but didn't fall off as fast. It was slower.

Then you have the case like you said where you have two ports or even the same port and you find and fix turbulence at the higher drop and you pick up. Again I agree with that pretty much always. I guess what I am saying is that you sometimes see people that are into the really high drops run heads that are too big especially on the street. Also they may not ever see the higher drop in reality depending on the rpm and size engine they have.

That's why like I said I have seen similar crossections vs hp vs rpm and engine size that seem to be very consistent. Then you try to make the shape as stable as possible but when you get bigger power starts dropping somewhat.

Using higher pressure drops to find turbulence though and fix it is all good just like people want the head to go to a higher valve lift then they are really using for the same reason....to see if the head will back up at higher airflow speeds through the port.

 

Erik ,

Which FlowBench do you own ??

SuperFlow SF-600 or SF-1020 ?


are you "specializing" in Porting certain type heads ?

and what name Brand cartridge rolls you've found work the best
and what grit and type "finish" are you putting on ports ?

Do any Pitot Probe velocity profiling of Intake and Exhaust ports ?

What have you found or shoot for as far as Pitot Velocity Pressure in ports ?

any particular "hot spots" in ports you should watch out for
while doing Velocity Probe profiling ?

have you ever ported NHRA Super Stock heads ?
anything thing particular to watch out for ?

 

Well none as I'm about to buy one right now and was looking at a completely different model but the only one's I'ves used are the SF 600 and 1020 and even the old 400 with only the manometer and no Flowcom. That's what we have at SAM and what all our race stuff has been developed on including all our NMCA stuff and LSx stuff that's been seen in the heads up racing like that and in the magazines. I will probably stay with the 600 at my own shop just to have a standard machine or people won't believe the numbers.. When your selling things it's just that way, good or bad.

I will not be specializing in any particular type ports but will probably be doing mostly LS1 stuff and Ford late model inline and then of course the old 23 degree chevy stuff including LTx heads. I am trying to do some of my own LSx and Ford ports that are better than what is out there right now but only time will tell. The only reason our stuff is so fast is heads. We have had several guru ported LSx heads that were total jokes and after getting rid of them and using normal ported heads that flow a LOT and yet still go turbulent at 28 inches and .700 lift went from 10.50s and 128 to 9.60s at 142 on one famous car on this board. Of course we did pick up 50 cfm peak at 28 inches. Another ported LS6 head that goes turbulent at .670 but moves superstar numbers at 28 made over 750 hp recently and will be seen very shortly. Believe me it won't slow down and it pulls to 8000 rpm on a 420 inch motor. It makes within a few percent of what it did from 7000-8200. It could certainly use some straightening out but there's only so much metal in those heads.

Yes I have used velocity probes to see where air is fastest and slowest. I've used strings and pencils and clay and all sorts of things. I certainly agree like I said with you about finding where air is too fast and in danger of seperating badly. Obviously the hot spots are the short turn and corners of the short turns and certain ares of the valve job and chamber too. Sometimes the straight walls have more effect and sometimes the other wall can do strange things depending on how the runner comes in to it but that is way specific to the heads. I am not that concerned about the velocity numbers per se but more about the distribution. What they really are in the running engine depends on how big the engine is and the rpm and teh rod ratio and the cam timing. On a large engine with a small head I am more worried.

We have a 400 inch LS1 that is totally our own creation too that is going to run here pretty soon and the heads are very nice on that too. I think we may be able to get into the 9.0 range NA if all goes well and LS1tech series weight even possibly but It should sure run under 9.20 even in normal air.

I really have no idea at all about all the super stock tricks for heads as I've only seen a few and really just don't know anything about how much goes into them but I know its a hell of a lot. I'm not into all those cheater NHRA classes and spray welding and acid porting etc. and redoing such a small port. I know on these you certainly have to work on port shape almost exclusively since you are locked in at a certain port volume or you'll get kicked out! I respect people that go through all that BS to make a teeny "stock type" port run for sure but I would never want any part of it myself. I'd rather do heads that were meant to make power but I know you have to learn a lot messing with some of the SS stuff big time. With these tiny ports you have to control the ever present extreme turbulence!

 

Larry,

Rereading this I hope you aren't mad at me because so far I agree with everything you say. I have just seen people make ports too big when trying too hard for ultimate stability and then the powerband goes out further but does not make more and often makes less overall. This is all I am saying. The same size port that stay stable longer is a better port almost every single time! A bigger port that stays stable longer is a given but it may or may not make you faster.

 

Larry,

Rereading this I hope you aren't mad at me because so far I agree with everything you say.
=========================================

No way in a million years !

whats great about Posts on Internet Forums..is you get a lot of different views .....you look for those little "nuggets of Truth"



from your previous post..are you looking at another Brand FlowBench other than SuperFlow ?

 

At PRI they had a "SAENZ" bench that was basically a 1020 with a flow com and an automatic valve opening fixture from Audi and it was only a bit more than the flow com equipped SF600. It could really pull some vacuum on even a fairly big head for testing like you are talking about. I am unsure though if we had good numbers that others would believe them though so we may just go with the SuperFlow stuff for credibility. It's all realtive but people are very knowledgeable nowadays and they won't believe anything high if it's not from a SuperFlow and even then of course people post bogus numbers all the time unfortunately.