Head flow, Positive boost vs. Flow Bench - Moparts Forums

Register Log In Moparts Forums Unlawfl's Race & Engine Tech Head flow, Positive boost vs. Flow Bench

Print Thread

Head flow, Positive boost vs. Flow Bench #552637 12/13/09 01:13 PM 12/13/09 01:13 PM
Joined: Aug 2005 Posts: 760 Southington Ct. T turbobitt OP super stock
turbobitt OP super stock T Joined: Aug 2005 Posts: 760 Southington Ct.	Here is a question that is bothering me. How does flow bench under vaccuum relate to positive boost pressure flow ? Example, if my head flow flattens out at .600 lift on a flow bench, could I expect a different reaction under boost pressure ? Would flow increase ? Allan G. 1970 Challenger w/572 Hemi street car and my pride and joy. 1986 T-Type with 272 Stage 2 Buick V6 engine - True 8 second street car. Just updated the engine and put down 928 HP @ 35# boost to the ground on chasis dyno. 1976 Cee Bee Avenger Jet Boat - 460 Ford powered.

Re: Head flow, Positive boost vs. Flow Bench [Re: turbobitt] #552638 12/13/09 01:58 PM 12/13/09 01:58 PM
Joined: Aug 2003 Posts: 43,141 Bend,OR USA C Cab_Burge I Win
Cab_Burge I Win C Joined: Aug 2003 Posts: 43,141 Bend,OR USA	Quote: Here is a question that is bothering me. How does flow bench under vaccuum relate to positive boost pressure flow ? Example, if my head flow flattens out at .600 lift on a flow bench, could I expect a different reaction under boost pressure ? Would flow increase ? Allan G. Thank about that You can force more air thru a hole under pressure,same thing as liquids when you turn up the pressure on a water hose Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)

Post deleted by Defbob [Re: Cab_Burge] #552639 12/13/09 02:19 PM 12/13/09 02:19 PM
A Anonymous Unregistered
Anonymous Unregistered A

Re: Head flow, Positive boost vs. Flow Bench #552640 12/13/09 04:03 PM 12/13/09 04:03 PM
Joined: Aug 2005 Posts: 760 Southington Ct. T turbobitt OP super stock
turbobitt OP super stock T Joined: Aug 2005 Posts: 760 Southington Ct.	I undestand the relation between HP and boost. Just wondering if I should consider more lift on my cam. AG. 1970 Challenger w/572 Hemi street car and my pride and joy. 1986 T-Type with 272 Stage 2 Buick V6 engine - True 8 second street car. Just updated the engine and put down 928 HP @ 35# boost to the ground on chasis dyno. 1976 Cee Bee Avenger Jet Boat - 460 Ford powered.

Re: Head flow, Positive boost vs. Flow Bench [Re: turbobitt] #552641 12/13/09 04:12 PM 12/13/09 04:12 PM
Joined: Jan 2003 Posts: 9,990 Frostbitefalls MN (Rocky&Bullw... gregsdart master
gregsdart master Joined: Jan 2003 Posts: 9,990 Frostbitefalls MN (Rocky&Bullw...	Maybe another way to look at the situation is absolute pressure. 0 being a total vacuum, 14.7 psi is normal atmospheric pressure at sea level, 30 psi (14.7 plus 15.3 psi boost) about two atmospheres of pressure. Horespower will rise about the same as absolute pressure, if the efficiency of the blower/intercooler is high enough. The valve lift can remain the same, heads can remain the same, the extra pressure will put more air in the cylinder. 8..603 156 mph best, 2905 lbs 549, indy 572-13, alky

Re: Head flow, Positive boost vs. Flow Bench [Re: turbobitt] #552642 12/13/09 07:06 PM 12/13/09 07:06 PM
Joined: Jul 2005 Posts: 8,647 ELYRIA,OH B blownzoom440
blownzoom440 B Joined: Jul 2005 Posts: 8,647 ELYRIA,OH	i have read where going .050 past peak flow will keep the port in peak flow window longer.mine is.

Re: Head flow, Positive boost vs. Flow Bench [Re: turbobitt] #552643 12/13/09 07:37 PM 12/13/09 07:37 PM
Joined: Oct 2007 Posts: 4,206 New York polyspheric master
polyspheric master Joined: Oct 2007 Posts: 4,206 New York	Can't really answer the question, because some of the blower discharge is expanded into volume at low pressure (only slightly higher than normal low vacuum in the manifold), but some may still be under higher pressure between boost pressure and zero, depending on manifold volume and boost level. A 3-71 producing 5 psi into a 500" RB with a tunnel ram manifold will get the entire flow as CFM at zero to low vacuum, a 14-71 producing 30 psi into a 300" LA with a simple base plate to the manifold will have over 20 psi. Flow benches don't test density. HP will not increase linear to boost regardless of blower efficiency, because there is heating and expansion just due to the temperature rise in the engine. The Wallace calculator simply multiplies existing power by (14.696 + your boost input) � 14.696, and it's wayyy too high (yes, the same mistake appears elsewhere, even on blower manufacturer sites - and still wrong). Read my article: http://victorylibrary.com/mopar/blower-c.htm Boffin Emeritus

Re: Head flow, Positive boost vs. Flow Bench [Re: turbobitt] #552644 12/13/09 08:04 PM 12/13/09 08:04 PM
Joined: Aug 2003 Posts: 43,141 Bend,OR USA C Cab_Burge I Win
Cab_Burge I Win C Joined: Aug 2003 Posts: 43,141 Bend,OR USA	Quote: I undestand the relation between HP and boost. Just wondering if I should consider more lift on my cam. AG. Anything you can do to improve the airflow into and out of the motor will normally make more HP and torque. When it comes to boost and intake manifold temps, lower air temps makes the air a lot denser than hotter air temps. My message is a inter cooled motor will make a lot more power with the same amount of boost as a roots blown motor with no intercooler or alcholol or water injection to cool the inlet air temps. down Same thing on any supercharged or blown motor. I'm hoping my next boosted motor will be turocharged instead of a crank driven supercharger You have to drive the air compressors and that eats up a certain % of the power gained from the boost, not so on a turbo motor Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)

Re: Head flow, Positive boost vs. Flow Bench [Re: turbobitt] #552645 12/13/09 10:23 PM 12/13/09 10:23 PM
Joined: Feb 2007 Posts: 1,025 Las Vegas, NV dodgeboy11 super stock
dodgeboy11 super stock Joined: Feb 2007 Posts: 1,025 Las Vegas, NV	Flow would increase, but you're thinking about it wrong. The motor doesn't know it's boosted mechanically or not. Vacuum is often used incorrectly. The engine doesn't see vacuum, it sees reduced pressure. N/A the engine sees atmospheric pressure. If you add 1 bar under boost, that's a total of 2 atmospheres. So the flow bench would have to have the pressure drop increased. I've done it out of curiosity and a port that went turbulent at 28in did indeed flow more air at 35in. I don't know what the numbers are exactly, but more pressure will force more air through the same size hole UNTIL you've got the port saturated. Which is why I go for volume on engines I know are going to be boosted.

Re: Head flow, Positive boost vs. Flow Bench [Re: dodgeboy11] #552646 12/13/09 10:49 PM 12/13/09 10:49 PM
Joined: Oct 2006 Posts: 365 Motor City S Shaker223 enthusiast
Shaker223 enthusiast S Joined: Oct 2006 Posts: 365 Motor City	My car has run a best of 117mph in the qtr @ 3,500lbs. The stock slant six intake flows around 110-120cfm and the exhaust flows around 90cfm. Using various formulas this calculates to around 450 FWHP. This is at 29psi. Increasing from 22psi to 29psi of boost netted 7mph in the qtr. I can't wait to see what a good flowing head and camshaft will do! 11.02 @ 120 mph - Slant 6 & Turbo http://www.youtube.com/watch?v=EAxRmoDgsdY Chassis Dyno http://www.youtube.com/watch?v=wd6hFGzLJMc

Re: Head flow, Positive boost vs. Flow Bench [Re: Shaker223] #552647 12/13/09 11:23 PM 12/13/09 11:23 PM
Joined: Feb 2007 Posts: 1,025 Las Vegas, NV dodgeboy11 super stock
dodgeboy11 super stock Joined: Feb 2007 Posts: 1,025 Las Vegas, NV	I expect it to drop your boost numbers and increase your mph:)

Re: Head flow, Positive boost vs. Flow Bench [Re: dodgeboy11] #552648 12/14/09 12:31 AM 12/14/09 12:31 AM
Joined: Aug 2005 Posts: 760 Southington Ct. T turbobitt OP super stock
turbobitt OP super stock T Joined: Aug 2005 Posts: 760 Southington Ct.	Quote: Flow would increase, but you're thinking about it wrong. The motor doesn't know it's boosted mechanically or not. Vacuum is often used incorrectly. The engine doesn't see vacuum, it sees reduced pressure. N/A the engine sees atmospheric pressure. If you add 1 bar under boost, that's a total of 2 atmospheres. So the flow bench would have to have the pressure drop increased. I've done it out of curiosity and a port that went turbulent at 28in did indeed flow more air at 35in. I don't know what the numbers are exactly, but more pressure will force more air through the same size hole UNTIL you've got the port saturated. Which is why I go for volume on engines I know are going to be boosted. Im looking at different lobe profiles that have more lift at the same duration. My goal would be to increase flow at boost without sacrificing low end performance at vaccum or no boost. Allan G. 1970 Challenger w/572 Hemi street car and my pride and joy. 1986 T-Type with 272 Stage 2 Buick V6 engine - True 8 second street car. Just updated the engine and put down 928 HP @ 35# boost to the ground on chasis dyno. 1976 Cee Bee Avenger Jet Boat - 460 Ford powered.

Re: Head flow, Positive boost vs. Flow Bench [Re: dodgeboy11] #552649 12/14/09 01:54 AM 12/14/09 01:54 AM
Joined: Dec 2006 Posts: 506 Texas Afghanistan Iraq etc. D DakFink mopar
DakFink mopar D Joined: Dec 2006 Posts: 506 Texas Afghanistan Iraq etc.	Quote: Flow would increase, but you're thinking about it wrong. The motor doesn't know it's boosted mechanically or not. Vacuum is often used incorrectly. The engine doesn't see vacuum, it sees reduced pressure. N/A the engine sees atmospheric pressure. If you add 1 bar under boost, that's a total of 2 atmospheres. So the flow bench would have to have the pressure drop increased. I've done it out of curiosity and a port that went turbulent at 28in did indeed flow more air at 35in. I don't know what the numbers are exactly, but more pressure will force more air through the same size hole UNTIL you've got the port saturated. Which is why I go for volume on engines I know are going to be boosted. THIS ANSWER RIGHT HERE IS ABOUT AS CLOSE TO ANY I HAVE HEARD COME FROM PROFESSIONAL TURBO RACERS ABOUT HEADS!!!! I've had the privilege to hear and pay attention when questions about building Turbo Motrs were brough up and HEADS was always the HOT TOPIC!! Everyone of them said your heads is where it's at! Buy the best flowing heads you pocket $$$$ can stand and go from there. The turn radius and stagnant port flow that N/A guys worry about doesn't apply as much to Boost. Look for Port Volume and Flow the more the better. I wish more people would flow their heads like dodgeboy11 did, especially when they know they are being set-up for Boost.

Re: Head flow, Positive boost vs. Flow Bench [Re: dodgeboy11] #552650 12/14/09 11:04 AM 12/14/09 11:04 AM
Joined: Oct 2006 Posts: 365 Motor City S Shaker223 enthusiast
Shaker223 enthusiast S Joined: Oct 2006 Posts: 365 Motor City	Quote: I expect it to drop your boost numbers and increase your mph:) Believe me...I realize the stock cam and head are an obstruction!! I've always wondered bow much of the boost was making it into the cylinders with a .380"(after lash cam) 11.02 @ 120 mph - Slant 6 & Turbo http://www.youtube.com/watch?v=EAxRmoDgsdY Chassis Dyno http://www.youtube.com/watch?v=wd6hFGzLJMc

Moderated by Al_Alguire, Hotwheelsjr, moparts, not_a_charger, RangerDan440, tboomer

Hop To

Powered by UBB.threads™ PHP Forum Software 7.7.1