Flowing Heads [Archive] - CamaroZ28.Com Message Board

MaxRaceSoftware

04-03-2004, 02:26 AM

Only relative on the same port though. Your velocity(both avg and peak) for a given depression will vary from one port type to the next, right?

Some more questions though:

1) Do the majority of flowbenches in use have mechanical gauges, or full computer setups to record and calculate.

2) Can a typical computerized flowbench output the the discharge coefficient for a given port? I'd think so, but its not something you ever see anyone talk about.

-brent
==========================================

For a given test depression, the theoretical air velocity fps follows equation, but like you stated in your post, the actual air velocity in different locations inside port will be different, and be different for various port shapes

Air_Velocity_FPS = (Test_Pressure ^ .5) * 66.2

where FPS = feet per second
^ .5 = same as square root
Test Pressure = inches of water depression

for 28 inches H2O Test Depression ;

350.3 fps = ( 28 ^ .5 ) * 66.2

if port were ideal, then for every square inch area , air velocity
would be at 350.3 fps
but in real Cylinder Head flow tests, air velocity varies inside port
at given test pressure

2) Can a typical computerized flowbench output the the discharge coefficient for a given port? I'd think so, but its not something you ever see anyone talk about.
===========================
yes,...but you don't actually need a computerized flowbench , you can calculate the discharge coefficient from flow data and calculator manually

you don't actually see many people talk about discharge coefficient , but my software calculates this everytime i flowtest a head. ( Curtain Area Discharge Coefficient and Valve Area Discharge Coefficient )

http://www.maxracesoftware.com/Flow_Max_Intake_1.jpg

racer7088

04-04-2004, 02:13 PM

28 inches of water is about 2 inches mercury is about 1 PSI. This means that the flowbench works to reduce the air pressure under the head to one PSI LESS than the air outside the head when intake testing and one psi MORE than the outside air on exhaust tests that are flowing in the opposite direction.

Many veterans established this pressure drop as a standard when seeing a majority of heads run best when the intakes were ported to maximize flow per unit cross section at this pressure drop. Now exhaust and even intake can be flowed at higher or lower drops to test for other phenomenon as well by just changing the pressure drop but this number or 28 inches is usually quoted as flow comparisons between heads.

MaxRaceSoftware

04-05-2004, 10:38 AM

Buick Motor Division uses 40 inches H2O during developement of Buick V6 for NASCAR and DragRacing

Chevy Race Shop uses 41 inches

Ford uses much higher

many flowtest much higher than 28 inches , but publish or tell people they flow at 28 inches

a live engine between peak Torque and peak HP points
is between 90 to 120 inches

28 inches is barely enough test pressure to simulate real engine
primary reason why 28 inches does not correlate 100.0 % PerCent to real HP/Torque numbers

28 inches became popular by Smokey U.
and SuperFlow's 300 FlowBench where 28 inch mark was about eye level

now on SuperFlow 600 bench, the 36 inch mark is where the 28 inch mark was. and on SF-600 the 28 inch mark is awkard being many times having to struggle to look around backside of cyl head on flowbench for 28 inch readings

i flow test all heads 36 inches to 48 inches when i can ,
then Software converts back to 28 inches

every once in awhile , a cylinder head will look great at 28 inches
but take a dive in flow numbers as you increase test depression
to 36 inches or higher

then there other times while flowtesting exhaust ports , they might all flow exactly the same at 28 inches but one port will "CONTINUE" to flow a bunch more air at 48 inches
and some ports will not increase at the same rate

Your test depression sets your theoretical air velocity thru ports
the higher the test depression, the higher the air velocity.
if airflow is too slow thru ports, it can stay attached to bad turns or bad shape ...at higher air velocity, flow will unattach and choke off flow

racer7088

04-06-2004, 01:01 AM

There are a lot of engines that will lose hp and definitely area under the curve if you make them big enough to stay smooth at 36 inches. Can't say that the shape that still is small though even at 36 or 40 won't make peak power much later but this doesn't seem to translate a lot of times to any gains but still turbulence must stay in control but it's a balance between size and velocity I guess. Exhaust however certainly flows at more than 28 inches in reality especially in the first part of blow down! You can certainly learn something there!

Zero_to_69

04-06-2004, 01:16 AM

OldSS,

THis is much better than any Google search. I only have to click
one link :D

Seriously, I've tried sifting through search engines. It's tough to
distinguish who/what is right and wrong.

It's nice to have all the brains in one pile to fight it out.

MaxRaceSoftware

04-06-2004, 01:37 AM

There are a lot of engines that will lose hp and definitely area under the curve if you make them big enough to stay smooth at 36 inches.
=============================================

Erik, i think you misunderstood my Post ?

i'm not making port any larger when flowtesting at 36 inches or higher ..instead flow testing at just higher air velocity .

Example=> 041x SBC NHRA cast iron heads
1.940/1.500 valves
165.0 CC intake ports (NHRA Legal CCs)

same exact castings , same exact valve sizes and intake port volumes

but "Port Shapes" are different

flow one port shape at 28 inches it looks great
flow very same port at 36 inches or higher, it takes a dive

change port shape (still holds same 165.0 cc) and now port
flows same at 28 inches but now doesn't take a dive in flow but keeps on increasing flow with every increase in test pressure
beyond 28 inches

change port shape again, now intake port flows more at 28 inches and continues to flow more at any test pressure above 28 inches (still with same 165.0 cc ports )

The last 2 examples make more HP/Torque
and run faster down DragStrip !
than 1st example when same head looked great at 28 inches but took a dive at 36 or higher test pressures

all examples at 165.0 cc ports

165.0 cc is very small intake port nowdays

i'm not using the higher than 28 inch flow test pressures to make a large port flow smoother ????

but instead, using higher test pressures to find out if port shape, roof and short turn shape are correct and able to properly handle real live engine intake port velocities

racer7088

04-06-2004, 07:13 AM

MaxRaceSoftware,

OK I understand you better then! You can make any port less turbulent with size but that won't usually help you but obviously a more stable port of the SAME size almost always will like you are saying. I thought you were saying that you develop the port around 36 or 40 inches. I know of only a few guys that do that and the biggest teams in NASCAR and Pro-Stock don't on intake right now because they can always make power higher by making a port stable at that airspeed but again at 36 inches average airspeed in a port is higher than it is in a real engine untill way on the backside of teh power curve so you'll be able to make power higher but you'll still actually lose overall power. I'm not talking any instantaneous drop as measured but real average airspeed. At some point the ports really do sort of mimic steady state flow which is why the flowbench has worked so well over the last few years if you know what to look for.

From what I've seen when people laugh at flowbenches and dynos they usually don't know how to operate either correctly so they think the results are less than useful even though it's these two tools that have gotten engines to where they are right now in the hands of true engine builders. I know you aren't one of those guys but just noting that. If you are even in the situation of seeing 3 inches HG or 40 inches of water on something you are running out of air bigtime!

MaxRaceSoftware

04-06-2004, 01:19 PM

If you are even in the situation of seeing 3 inches HG or 40 inches of water on something you are running out of air bigtime!
========================================

Yes on Dyno or RaceTrack ... 3+ inches Hg of intake manifold vacuum is definetly a restriction and TQ/HP killer !!

7+ inches Hg intake manifold vacuum will lose 90 to 120+ HP easily

usually, anything above 1.1 or 1.2 inches Hg. manifold vacuum
during Engine Dyno tests will start to show TQ/HP Losses as
Carb starts to act like restrictor plate

from memory, i don't think i've ever seen an engine make its "Best" peak HP at 1.5" inches HG ....usually Peak HP RPM point almost always occurs between .7 to 1.2 inches Hg manifold vacuum

racer7088

04-06-2004, 08:11 PM

MaxRaceSoftware,

No I meant maximizing flow around 28 inches or 2 in hg across the head only. I would want to see almost 0 manifold drop or as low as possible. I want high pressure dense air in my manifold!

I meant that flow around 28 inches is a fair predictor of hp with a good port because that will usually develop sufficient airspeed to cause turbulence that if fixed will return more power and airflow through the engine. Fixing turbulence at 36 inches say and up sometimes only results in a bigger port with maybe a longer power band with less average power so you have to watch out.

If like you said you had ports of equal sections and volumes but one was stable and kept going to higher drops it should be a better head for sure. I'm only saying that if you have to make it appreciably bigger to kill turbulence at these higher drops sometimes you don't make any more power and can sometimes drop power.

MaxRaceSoftware

04-07-2004, 09:43 PM

Just for additional information
-and not for argument sake-

typically, an engine will make its "BEST" Peak HP at
.7 tenths to 1.2 inches Hg. of plenum vacuum

also, like in a resrictor-plate example or like a 2-Barrell resricted Class Rule engines....an engine can make Peak HP at for instance
7.0" inches Hg. of intake manifold plenum vacuum, but it won't be the "Best" possible Peak HP/TQ its capable of.

however, if the restrictor-plate or 2-Barrell Carb was removed and replaced with higher CFM unit.....you would discover that
at end of all your Dyno testing , the "BEST" Peak HP amount would usually always occur between .7" to 1.2" inches Hg.
never yet have seen an engine make its very "BEST" possible Peak HP at 1.5" inches Hg its capable of

Here is Dyno test results a few days ago on Chevy BBC 540 cid engine

RPM-------TQ---------HP-------Vacuum
5500----726.9-----761.2--------0.7
5600----726.8-----774.9--------0.7
5700----721.1-----782.7--------0.7
5800----734.1-----810.7--------0.7
5900----728.2-----818.0--------0.8
6000----728.8-----832.6--------0.8
6100----726.0-----843.2--------0.9
6200----724.6-----855.4--------0.9
6300----719.0-----862.4--------1.0
6400----713.3-----869.3--------1.0
6500----707.1-----875.1--------1.0
6600----704.1-----884.8--------1.0
6700----705.3-----899.7--------1.1
6800----697.4-----902.9--------1.2
6900----686.2-----901.5--------1.2
7000----679.2-----905.7--------1.2
7100----660.5-----892.8--------1.2
7200----649.4-----890.2--------1.3
7300----638.9-----888.1--------1.3
7400----629.5-----886.9--------1.4
7500----621.4-----887.4--------1.4
7600----610.9-----884.1--------1.5

best peak HP was at 7000 rpm = 905.7 HP and 1.2 inches Hg

7000=905.7 HP and 1.2 inches
7600=884.1 HP and 1.5 inches
--------------------------------------
21.6 HP difference in this example

the above is typical of results i see when vacuum is hooked up to plenum area in the intake manifold ...its also very possible to make "Best" Peak HP at lower than .7"inches Hg with
great carb booster signal/ plenum shape and size

Vacuum inches Hg------inches Water
1.5"-----------------------20.43

.7"------------------------9.53

1.0------------------------13.6195 @ 20 deg C

1.2"-----------------------16.34

2.0"-----------------------27.24 (almost 28 inches H2O)

7.0"-----------------------95.34"

A misconception about Flow Testing heads is to look at your Intake Manifold 's Plenum vacuum and think that you should flow develope your Cylinder heads at only or around that value in Inches of Water test depression.

but Peak Intake Port depressions are much higher than this
inside each individual runner near max piston velocities,
even though at the same time you only recording 0 to 2.0 inches Hg inside Intake Manifold Plenum

if 28.0 inches of test pressure was the "actual only direct correlation" to actual live engine operating conditions between Peak Torque and Peak HP points ....then there would be absolutely no chance on earth of a port going into Sonic Choke
....also there would be hardly any chance of any engine making more than 106.81 PerCent Volumetric Efficiency

All the millions of dollars and time spent in Research/Developement by Detroit, Japan, Germany, etc
all the SAE Papers and articles published on Sonic Choke and Inlet Mach Index subjects would be useless !

Books like ;
1-Scientific Designs of Exhaust and Intake Systems"
by Phillip H Smith page 237 chart 13:5 ....would not apply

2-The Internal Combustion Engine in Theory and Practice
Vol 1 by Charles Fayette Taylor
page 173 Z-Factor ...would not apply

3-Dynomation ....would be wrong

4-Engine Expert-Alan Lockheed ....would be wrong

5-David Vizard ...would be wrong

6-Buick Motor Division (V6 Race effort) ..would be wrong

7-Chevy Race Shop ...would be wrong

8-Ford ...would be wrong

9-Darrin Morgan (Reher-Morrison)...would be wrong
Darrin states some of Chevy Indy Racing League (Chevy IRL)
Cylinder heads were Flow developed at 150 inches of water
...also states in same interview he is planning to go to 50 to 60 inches test depression when flow developing cylinder heads

From my personal experience....i've fixed a lot of Cylinder Heads
that other HeadPorters missed when they only Flow tested those heads at only 28 inches or less .

36",48,50 or 60+ inches of Test Pressure
you use these higher test pressures to find out
if flow will stop gaining or reduce as you do your Flow Tests in Valve Lift increments on the FlowBench

maximum intake port velocities inside intake ports will be
usually 600 to 700 feet per second before going into Sonic Choke

Flow_Velocity_FPS = ( Test_Pressure ^ .5) * 66.2

where Test Pressure can be FlowBench Test depression or can be Pitot Velocity Probe pressure ...all in inches of water

^.5 = same as square root

66.2 = factor

FPS = feet per second

28 inches = 350.3 fps....approx 1/2 of Port Limiting Velocity in live engine ......also = 106.9 % Volumetric Efficiency

600 fps = 82.15 inches of water ...also = 120.16 percent Ve
700 fps = 111.81 inches of water...also = 127.44 percent Ve

.55 Mach = approx 616 fps ..also = 121.25 percent Ve
616 fps= 86.59 inches of water

MaxRaceSoftware

04-07-2004, 09:49 PM

MaxRaceSoftware,

No I meant maximizing flow around 28 inches or 2 in hg across the head only. I would want to see almost 0 manifold drop or as low as possible. I want high pressure dense air in my manifold!

I meant that flow around 28 inches is a fair predictor of hp
============================================

racer7088 (Erik) ...i definetly agree with you that 28 inch Flow numbers are a very good indication of potential HP to expect ;

heres a little more info ;

Peak_HP = Flow_CFM * .257 * Number_of_Cylinders

is estimated potential Peak HP to expect
you multiply .87 percent times cam's theoretical max lift , round off to nearest .050" in Flow Test, then see what CFM is at 28 inches

example=> .700" Lift cam
.700 Lift times .87 percent = .609" Lift
Flow head at .600" Lift , then take CFM at 28 inches and calculate HP potential with above formula

.257 Factor = for beginning engine builders and engines near 10.0:1 Comp Ratio

.285 Factor = would be for Professional engine builders with wet sump pans, lightweight rotating assemblies, low tension great sealing rings, deep oil pans, etc.
excellent use of inertia/wave tuning with 9.5 to 11.5:1 Comp Ratios or
11.5 to 13.0:1 CR ranges without fully utilizing inertia/wave tuning effects

.300 to .310 Factor = Current ProStock Technology with dry sump, unlimited carburetion, Hi Comp Ratio, ultra lightweight rotating assembly, etc, max use of inertia/wave tuning, etc, 14:1 to 17:1 Comp Ratios
(usually no better than .3200 efficiency or no worse than .2980 eff %)

all factors are just baselines

major errors will be from no 2 FlowBenches or Dynos read the same

and there are people with bogus FlowBenches and bogus Dynos out there ..that makes above Factors appear to be incorrect

but if dyno or flowbench is honest,
those Factors will be very close to reality

but its still bench racing
just gives you a ballpark guesstimate of what to expect.

---------------------------------------------------------

Darrin Morgan of Reher-Morrison
has SpreadSheet online at his website

in that SpreadSheet, Darrin's HP prediction is
1324 HorsePower which is 165.5 HP per Cylinder

which is about .2982 Factor

pretty close to .3000 Factor i came up with for Pro Stock technology

Reher-Morrison
1.025 " max approx Lift range times .87 percent
equals = .892" lift, rounded to .900" Lift

at .900" lift heads flow 555.0 CFM at 28 inches

.2982 Factor

SBC

04-07-2004, 10:06 PM

Erik

You make a good point about increasing size.

I just want to emphasize that shape is a better method and area to work on to control intake port turbulance ( which you did not disagree with).

The shapes I use work at 7" 28" 45".

MaxRace has more Time dragging air thru ports than I do!

MaxRaceSoftware

04-07-2004, 10:22 PM

I just want to emphasize that shape is a better method and area to work on to control intake port turbulance ( which you did not disagree with). SBC
-----------------------------------------------------------------

SBC,

yes you use the "Port Shape" not the "size"
to correct turbulence or flow separation

you use the higher test pressures "ONLY" to verify that
the "PORT SHAPE" is correct !!

the reason to flow test at higher test depressions than 28 inches
is to find out what "SHAPE" will work at the "Live engine's"
port velocities

MaxRaceSoftware

04-07-2004, 10:31 PM

700 fps Sonic Choke ?

I thought the speed of sound is roughly 1120 fps depending on the air temperature?
=========================================

1120 fps => yes, you are roughly correct for mean sea level
and Standard Temperature and Pressure conditions (STP)

but also the speed of sound is "zero" in vacuum !!

so at a point or certain amount pressure differential, the actual speed of sound is

much less in live running engine on Intake side

its been known for many decades or almost a Century now, by many researchers like

Ricardo, Heywood, MIT, Ford, GM, Chrysler ,Honda etc along with many SAE papers on

Sonic Choke conditions in Intake and Exhaust ports

recently many engine builders and headporters have used terms like
1-Port limiting Velocity
2- Inertia Block
3-Flow separation

to describe Sonic Choke conditions

Common sense tells you that its "not possible" to run the engine higher and higher in

RPMs to Infinity and continue to make infinte power with infinte port velocity !

Sonic Choke occurs in all engines at a certain port velocity
and sets the point where power will ultimatelty fall off
and where pumping losses skyrocket

in larger Short Turn radius heads with straighter shot at valves like ProStock

technology ..Sonic Choke can be delayed to near .70 of speed of sound (STP referrence

point)

in heads like older 23 deg valve angle with more abrupt turn into bowl area ..Sonic

Choke conditions will occur near .50 to .60 speed of sound (STP referrence point)

if all Ports could be made perfectly straight , then Sonic Choke conditions could be

delayed to .80 to 100 percent of speed of sound

supposedly research papers have shown Wankel engine design to approch .80+ speed of

sound port velocity before Sonic Choke condition occur

FlowBenches are steady-state flow measuring devices

4 Stroke engines are "Batch Processors"
"Inertia Block" with pressure differentials induce Sonic Choke conditions

Zero_to_69

04-07-2004, 11:05 PM

Holy F...

This thread has more "over the head factor information" than the
Caramilk secret!

#1. Sonic Choke in a nutshell = The point where intake runner
velocity is so high, that acoustic tuning is no longer possible?

#2. Flowing a head at 36 inches of water is dynamically outside
of *most* street/strip engine capabilites.

My Meaning: To enable enough air flow through the runner to
maintain a 36 in. H20 reading would require massive amounts of
air movement dictated by large engine displacement, RPM, etc.

Such engines would have poor low RPM efficiency (VE), but would
begin to create decent port velocity at high RPM.

Perhaps a Pro-Mod engine would fit this category?

#3. If manifold vacuum increases to more than 1.2 in./hg. this means
that the carburetor or Throttle Body is too small. The pistons
drawing down are creating a differential of pressure between
the intake valve and throttle blade.

< 1.2 in./hg. means venturi or Throttle Body is too big

= ~ 1.2 in./hg. means venturi or Throttle Body is just about right

> 1.2 in./hg. means venturi or throttle body is too small

Yes, No, maybe so on all assumptions?

MaxRaceSoftware

04-07-2004, 11:53 PM

#2. Flowing a head at 36 inches of water is dynamically outside
of *most* street/strip engine capabilites.

My Meaning: To enable enough air flow through the runner to
maintain a 36 in. H20 reading would require massive amounts of
air movement dictated by large engine displacement, RPM, etc.
========================================

Zero_to_69....you were doing OK until you got there !! :)

"Scientific Design of Exhaust and Intake Systems"
by Phillip H Smith was written/published => 1962

in Morrison Pressure Indicator charts in book
you can calculate that even way back then ,
on the 2000 to 3500 RPM engine examples Smith
talked about ...that max intake port depression
correlated to well over 36 inches of water (84 inches +)

and thats with old low rpm. small valve , small port engine pure street technology of 1950's to early 1960's

a 14 cid lawnmower 1 cyl engine can have much higher than
36 inches of water max intake port peak flow depression
at or near max piston velocity to max cyl volume
-------------------------------------------------------------------------------

#2. Flowing a head at 36 inches of water is dynamically outside
of *most* street/strip engine capabilites. -Zero_to_69

Zero_to_69......the car you drive...its engine will have more than
36 inches of water depression between peak torque and peak hp points

bone stock car's engine cruising down highway at 21.0" inches Hg. = 286.01 inches of water depression in intake manifold plenum

MaxRaceSoftware

04-07-2004, 11:58 PM

Zero_to_69

Here's a little more Info :)

Post from another website ;

Quote =>

In the gas industry laboratory where I used to work, where precision gas flow measurement is required for revenue purposes, positive displacement flow meters are always used. These either use a bellows that fills and empties, or a partly submerged turbine where inverted buckets on a paddle wheel fill and empty as the thing slowly rotates. These are highly accurate and have low pressure drop and work right down to zero flow.

For laboratory (high) air flow references we used sonic nozzles. What you do is have an accurate calibrated nozzle, and increase the depression across it until the flow goes sonic. Any further increase in pressure differential across the nozzle gives no further increase in flow beyond that point.

You connect up the sonic nozzle to a monster vacuum pump and open the valve. You hear the air rushing into the hole with a mighty roar. As you open the valve further the roar gets louder, then suddenly it goes dead silent ! ! As the air rushing in gets to the speed of sound, no sound can escape back out. Fascinating stuff.

You then know exactly how much air volume is rushing down that hole, and you can put your test piece in front of it and know the flow will not change from the exact sonic nozzle calibration figure as long as it remains sonic.

Zero_to_69

04-07-2004, 11:59 PM

Hey, two out of three isn't bad! :)

I'm having a tough time understanding this "Inches of Water"...

One of these days, I'll grasp it. After a few more replies here
and chapters of Dr. Morrison's/ Dr. Smith's book, I might surprise myself and
some of you as well!

I'm on chapter six at the moment. Getting even more interesting
as I flip every page.

Thanks for the guidance,
Tino

MaxRaceSoftware

04-08-2004, 12:27 AM

I'm having a tough time understanding this "Inches of Water"...

like OldSStroker said =>

GOOGLE is your friend. Visit him. :)

you probably benefit from Freeware Units Conversion software
or Conversion Charts

Pressure Conversions

1 psi = 27.7296 inches of water at 20 deg C

1 psi = 2.0360 inches Hg (Mercurcy) at 0 deg C

1 inch of Mercury (Hg.) = 13.6195 inches of water

do searches for rest of units you are interested in ?

Zero_to_69

04-08-2004, 12:47 AM

It's not the unit conversion that I need to grasp, it's how the
numbers are related to head flow.

For example, the flow bench construction and measurement points.

In my head, I see a flow bench with a cylinder head bolted to it.

A valve and a dial gauge

The intake port of the head is fitted with a standard flow device.

The chamber is sealed to the bench to a calibrated cylinder.

Air is sucked through the intake port, through the chamber at a
valve lift of x.xxx inches.

The manometer reads 28 inches of water ... or when the air flow
is sufficient to pull 28 inches of water, the data is reported.

IE: 200 CFM @ 0.500" valve lift @ 28 inches of water

IF we were to increase the flow of air through the flow bench until
the manometer read 36 inches of water, I would suspect the rate
of air flow to increase to maybe 250 CFM (same valve lift).

Or...if the valve was slightly closed at the same rate of air flow (250 CFM):

The manometer reading would go higher if the intake port could flow
the air (IE: 40 inches of water).

The manometer reading would fall if the intake port choked air
flow.

That's the picture in my head at the moment and maybe that's
the reason I can't grasp the concept.

I would have no issue reading web links if I knew they were credible.

I could read something over my level of comprehension and think
it was correct just because it sounded cool. I'd rather make mistakes
here and be corrected before I flap my mouth in the real world :D

racer7088

04-08-2004, 12:57 AM

A 28 inch tall and one square inch base water column weighs one pound. So does an identical 2 inch column of HG (Mercury). When you create a one PSI drop you can support that much water in a manometer. You are reducing the pressure under the head or in the cylinder under the head to one PSI LESS than what is in the intake port so air rushes in to equalize with this and it is measured in terms of flow at that particular pressure drop.

One PSI drops generally correlate with about 145 cfm/ in^2 which is right at 350 FPS average velocity in a straight pipe and less or more at the valve and over the short turn in areas of mismatched velocities and turbulence. Most all out ports are developed around 100 M/S average velocity on intake to develop peak power or are sized similar to that when initially sized. At higher average velocities than this power tends to drop off. I used to live with two engine designers at Ilmor now and I know about how they size stuff there too but again they test stuff at different drops too to uncover turbulence issues that can hurt the port a little at peak instaneous depression. The weird thing is that sometimes fixxing this by going much bigger than the cross section to create the approximate 100 M/S velocity will actually hurt the engine if it involves significantly bigger cross section to slow the air down there locally.

MaxRaceSoftware

04-08-2004, 01:07 AM

Zero_to_69 ,

picture of screen with flow test inputs

http://www.maxracesoftware.com/Flow_Max_Intake_1.jpg

basically,

you start flow tests with valve open
for example, at .200" Lift (or whatever starting point)

you adjust intake flow control knob to increase test depression to 28.0 inches of water ..on vertical manometer

you then look at inclined manometer which is calibrated in percent ...for flow percent reading of a certain orfice flow

the percent reading is multiplied times orfice CFM @ 100.0 percent
to get Flow CFM

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

then again read Flow PerCent Scale (inclined manometer)

usually, everytime you increase valve lift, the vertical manometer level drops

and when you adjust back upwards to 28 inches you see PerCent of Flow (inclined manometer) increase likewise if flow is also increasing

link to picture of flow steps
http://www.maxracesoftware.com/FlowMax_1.gif

http://www.maxracesoftware.com/flow_bench_pictures.htm

this head had small short turn shape problem
which was later corrected
which netted better flow at all lift points

try SuperFlow..and download SF-600 or any other .PDF file
FlowBench manual

just because you don't have a FlowBench doesn't mean you can't download any of their manuals which show you how to flow heads (Basics 101)

racer7088

04-08-2004, 01:10 AM

The monometer simply shows how much pressure drop is being applied to that port to make it flow what it is flowing.

The higher the pressure drop the higher the flow rate will be as it is related to the square root of the difference in the new to the old pressure drops.

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.

If you increase the pressure across this port even more eventually the port starts to back up from the chaotic and disorganized flow that results from turbulence and now at this point even though you are putting more "suction" or pressure drop on the port it is now flowing LESS than it was in true and in mass airflow than it was earlier with the lower drop across it!

All these pressure drops are caused by the shortblock which is essentially the supercharger or "blower" underneith the heads that make them flow what they do. WIth more cubes and/or higher rpm the pressure drop on a head is increased and you can keep turning more and more rpm untill you cross that airspeed limit in the heads we are talking about where true mass flow drops and then you are on the downside of your powerband and have to shift because spinning the engine higher is not allowing you to burn any more fuel and air.

Zero_to_69

04-09-2004, 03:55 PM

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! :D 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 knob 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?

MaxRaceSoftware

04-09-2004, 07:23 PM

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

racer7088

04-09-2004, 10:47 PM

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?

racer7088

04-09-2004, 10:57 PM

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.

Zero_to_69

04-10-2004, 10:13 AM

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! :D

racer7088

04-10-2004, 02:19 PM

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.

MaxRaceSoftware

04-11-2004, 05:02 AM

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 .

racer7088

04-11-2004, 10:10 AM

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.

MaxRaceSoftware

04-11-2004, 02:17 PM

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 ?

racer7088

04-11-2004, 03:29 PM

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!