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#1
03-21-2017, 11:44 PM
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Port flow with boost
Did a little looking around to see if port size would really matter much.
Found a online calculator Put in 80 degree air, 30 psi down to 0 psi thru a 2" orifice and the flow was 2057 SCFM Multiply by 8 cylinders and get 16,456 SCFM Got to believe its the valve opening that makes the difference A 15 to 0 pressure drop thru a smaller 1.5" orifice still flows 741 SCFM X 8 = 5928 SCFM http://www.tlv.com/global/TI/calcula...h-orifice.html Last edited by v869tr6; 03-22-2017 at 12:13 AM. |
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#2
03-22-2017, 06:19 AM
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And then getting the spent Gases out the Exh, lol!
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#3
03-22-2017, 06:46 AM
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Flow in cfm, I believe,will be the same at 1 psi of boost or 20 psi of boost, it's just the density of the air that's been changed. In effect, at 15 psi of boost you have crammed (just example figures) 1500cfm into a 750cfm space.
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#4
03-22-2017, 09:50 AM
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Correct Taff. It is the density or MASS FLOW (number of molecules of good oxygen) in a given air space per engine combustion event.
Tom V.
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
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#5
03-22-2017, 10:16 AM
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Quote:
Depends on the device used to create that pressure. Blower vs. Turbos two completely different animals for Port cross section. Blowers mechanically linked to the crankshaft so the more pressure you make the more horsepower it robs from the motor to make it. The turbo is linked by air and air is compressible............. It's not as simple as to break it down as a (boosted application. )
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John Marcella Marcella Manifolds Inc. john@marcellamanifolds.net ph. 248-259-6696 |
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#6
03-22-2017, 10:20 AM
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I was told that it is not what you put in a intake port with a added booster motor, it is how well you can get it out the exhaust. You will get more out of a boosted motor improving the exhaust path then the intake path. Cylinder head Intake flow is good but if you restrict the out flowing gasses all bets are off. It is more about valve train and how it stays together at top RPM and Exhaust flow. So correct me if I am wrong this is not my expertise.
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 Bob C.Quickest, Fastest, Best selling Pontiac Aftermarket Block IA II and Tiger Heads Boss Bird Funny Car Best pass to date 08/06/2016 6.027@231.64 Allpontiac Big Chief Aluminum Engine Block http://www.AllPontiac.com |
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#7
03-22-2017, 10:27 AM
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Quote:
We increased the flow on the exhaust side with different cam timing, increased the flow with larger stepped headers, increased the flow with Clocked Collectors, (better scavenging) and the engine made more power for sure. His engine was a typical 9000 rpm 347 cid engine. He had good valvetrain parts and a excellent engine builder Ronnie Crawford. Tom V. ps He used a Belt Driven Vortech Supercharger.
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
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#8
03-22-2017, 10:38 AM
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Quote:
Density ratio is derived from pressure ratio, compressor efficiency, ambient temp, barometer, compressor discharge temps (if used intercooler discharge temp and flow losses), and intake manifold temps. There are precise calculations for this. Compressor efficiency alone could make a considerable difference.... at @ 15 psi(2.0 pressure ratio) a change from 60% to 70% comp eff could increase density ratio from say @1.47 to @1.54. Seems small but its significant. At 800 hp and 60% compressor efficiency improving to 70% compressor efficiency could net @ 40 or more hp. in approximate rough estimator terms... 790 cfm at no boost could equal @ 1160 cfm at 1.47 density ratio 15lbs boost or @1216 cfm at 1.54 density ratio 15 lbs boost. Its not uncommon to have density ratios much closer to pressure ratio!!! |
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#9
03-22-2017, 11:15 AM
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Turbos and Belt driven centrifugal devices with have higher efficiency numbers usually in the 70+% range. Screw Superchargers can also get there. Roots stuff in the 55% range. All that being said, if you have a Vortech Supercharger with 76% efficiency and a good density ratio and you match it against a F-3 Centrifugal supercharger (from the other guys) the F-3 will win simply because it moves much more air even at a lower efficiency number. Same applies to a 6-71 vs a 14-71 boosting device. Tom V.
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
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#10
03-22-2017, 01:06 PM
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The point I was trying to make is that with boost, the ports in a head are going to get the job done until the amount of flow thru the valves has reached a very high level.
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#11
03-22-2017, 03:06 PM
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You read any of the good Boost Books by Friends of mine like Hugh MacInnis, Corky Bell, etc and they all say that the valve diameter is the choke point for a boosted engine. Corky lives in Texas. A super Guy who really knows how to explain boost to people. His books are well worth the money. (Little plug for him)
4 Valve engines give you a lot of equivalent valve area in a small package. When Mahovitz can run 5.88 at 250 mph with a 281 cid Cobra 4 valve engine that should make it clear for you. For ANY typical Pontiac Engine with boost as you said the ports should be ok. Tom V.
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
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#12
03-22-2017, 04:56 PM
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Quote:
I am off in either the second or third decimal place. What did you use for ambient temp and get for compressor discharge temps? Thanks, Stan
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Stan Weiss/World Wide Enterprises Offering Performance Software Since 1987 http://www.magneticlynx.com/carfor/carfor.htm David Vizard & Stan Weiss' IOP / Flow / Induction Optimization - Cam Selection Software http://www.magneticlynx.com/DV Download FREE 14 Trial IOP / Flow Software http://www.magneticlynx.com/DV/Flow_..._Day_Trial.php Pontiac Pump Gas List http://www.magneticlynx.com/carfor/pont_gas.htm Using PMD Block and Heads List http://www.magneticlynx.com/carfor/pont_pmd.htm |
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#13
03-22-2017, 05:06 PM
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In simple terms, a pound of air mass will make between 9.5 and 10.5 HP.
So if we call it 10 HP per pound of air mass, the 40 HP mentioned is 4 pounds of air mass. 100 pounds of air mass will make 1000 HP so 4 pounds of air mass change from the efficiency calculation is a 4% change. You can easily have a 2% error in Air Mass Calculations on a Test Stand (depending on the test conditions and how the data was taken). So basically most quoted efficiency data reported is taken with a grain of salt. Just saying. Tom V.
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
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#14
03-22-2017, 06:15 PM
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Can some of you that have a dyno sheets that shows both BSFC and Air/Fuel ratio, please do a little math and report back your results?
60 / (BSFC * Air Fuel Ratio) Thanks, Stan
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Stan Weiss/World Wide Enterprises Offering Performance Software Since 1987 http://www.magneticlynx.com/carfor/carfor.htm David Vizard & Stan Weiss' IOP / Flow / Induction Optimization - Cam Selection Software http://www.magneticlynx.com/DV Download FREE 14 Trial IOP / Flow Software http://www.magneticlynx.com/DV/Flow_..._Day_Trial.php Pontiac Pump Gas List http://www.magneticlynx.com/carfor/pont_gas.htm Using PMD Block and Heads List http://www.magneticlynx.com/carfor/pont_pmd.htm |
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#15
03-22-2017, 09:22 PM
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No dyno sheets, all that was left at work.
Have you ever read anything Stan from this website? : https://www.turbobygarrett.com/turbo...mass_flow_rate Mass Flow Rate is the mass of air flowing through a compressor (and engine!) over a given period of time and is commonly expressed as lb/min (pounds per minute). Mass flow can be physically measured, but in many cases it is sufficient to estimate the mass flow for choosing the proper turbo. Many people use Volumetric Flow Rate (expressed in cubic feet per minute, CFM or ft3/min)) instead of mass flow rate. Volumetric flow rate can be converted to mass flow by multiplying by the air density. Air density at sea level is 0.076lb/ft3 What is my mass flow rate? As a very general rule, turbocharged gasoline engines will generate 9.5-10.5 horsepower (as measured at the flywheel) for each lb/min of airflow. So, an engine with a target peak horsepower of 400 Hp will require 36-44 lb/min of airflow to achieve that target. This is just a rough first approximation to help narrow the turbo selection options. How do their calculations compare with your stuff? Assume you would want to specify engine info and boosted or NA to help with different testing. Tom V.
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
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#16
03-22-2017, 09:43 PM
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Stan I was rough estimating from an old chart in MacInnes1st edition turbo book along with using 10 hp per lb air mass. Think I rounded some on cfm to lbs/min airflow as well. (.07 maybe?)
Actually the OP was port flow. VE is in play here(its KING). Better flow capability creates greater VE opportunities. Short answer... overall if head is a good match to NA requirement(high ve capable in range you can best use it) it will be a good match boosted. |
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#17
03-23-2017, 07:46 AM
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A straight shot to the back of the valve is still important I believe, as even boosted airflow loses some energy/efficency as it negotiates the bends in a port.
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#18
03-23-2017, 11:12 AM
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Quote:
Tom V.
__________________
"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
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#19
03-23-2017, 11:44 AM
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I do not do engine / hp simulations. But I can calculate mass air flow in a number of different units and time frames. Besides the lbs/min below I could have also done CFM, m^3/min, m^3/s, kg/s, kg/hr, m^3/hr http://forums.maxperformanceinc.com/...=799164&page=2 Quote:
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Stan Weiss/World Wide Enterprises Offering Performance Software Since 1987 http://www.magneticlynx.com/carfor/carfor.htm David Vizard & Stan Weiss' IOP / Flow / Induction Optimization - Cam Selection Software http://www.magneticlynx.com/DV Download FREE 14 Trial IOP / Flow Software http://www.magneticlynx.com/DV/Flow_..._Day_Trial.php Pontiac Pump Gas List http://www.magneticlynx.com/carfor/pont_gas.htm Using PMD Block and Heads List http://www.magneticlynx.com/carfor/pont_pmd.htm |
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#20
03-23-2017, 12:17 PM
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Agree those are just simple conversions to your programs to load the proper Kyle's Converter type value into the appropriate formula using U.S customary units, Imperial units, Metric units, whatever.
Once you load any basic formula for air flow you can switch between units. Tom V.
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
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