BP4W DIY Porting - Flow bench analysis
Jun 8, 2019 8:44:25 GMT
niklas, martiny, and 3 more like this
Post by schercheeroo on Jun 8, 2019 8:44:25 GMT
*******************************************************
Introduction
*******************************************************
Objective
Measure the effect that basic porting modifications have on the flow performance of a Mk2 non VVT cylinder head's intake port.
Overview
Perform two simple DIY porting operations to a Mazda MX5 BP4W cylinder head and make a flow assessment and comparison of intake port flow before and after modifications.
The flow assessment will be made with a late Mk2 European intake manifold (aka square top or flat top manifold) fitted to the cylinder head.
Modifications were made to block off the manifold’s EGR system.
The test results will be compared to a small data base compiled from flow test results found at sabre heads website.
*******************************************
Contents
*******************************************
Basic engine and intake port geometry
Cylinder head porting equipment
Documentation of modifications undertaken
Cylinder head flow test equipment
Cylinder head flow test procedure
Cylinder head flow measurement data and analysis
Assessment of flow performance before and after modifications
Analysis of existing cylinder head flow data from around the web
Summary and conclusion
Recommendation
Acknowledgements
*************************************
Basic engine and intake port geometry
**************************************
Bore (mm) 83
Stroke (mm) 85
Rated Speed (rpm) 7000
Camshaft geometry (BP4W)
Max Lift (mm) 8.51 (includes 0.21mm lash for solid lifter)
Duration (CA°) 245
Number of inlet valves per cylinder 2
Inner seat diameter [ISD] (mm) 29.5
Seat angle (°) 45
Valve head diameter (mm) 33
Inner seat area (sq. M) 0.001367
Mid Port area [Pm] (sq. M) 0.0014577
Port entry area [Pe] (sq. M) 0.0010555
**************************************************************
Cylinder head porting equipment
**************************************************************
A) Air die grinder
B) Permanent marker
C) Ball end carbide burr
D) Mandrel for Sanding roll (6mm diameter rod with slot for emery cloth)
E) Parallel sided square ended carbide burr
F) 80 grit emery cloth
G) Large washer
H) Calibrated profilometer
**************************************************************
Documentation of modifications undertaken
*************************************************************
Two modifications were undertaken:
The first modification was to the intake port’s short side radius (SSR) and bowl area.
The machining of the factory valve seats leaves a sharp edge on the short side radius and leaves heavy machining marks in the bowl area where the valve seat cutter removes material from the port. The flow coefficient can be improved if the machining marks are removed from these areas.
Modification procedure:
1) The sharp edge on the SSR was broken and smoothed with a sanding roll
2) Using a ball end carbide burr and sanding roll, the machining marks left in the bowl area when the valve seat was cut were blended and smoothed.
3) Measurements were taken by inserting a calibrated profilometer into the port to determine whether the correct degree of smoothing had been achieved
Time taken to perform modifications: 40 – 80 minutes (10-20 minutes per cylinder)
The second modification was removal of material from the combustion chamber to deshroud the intake valve:
Modification procedure:
1) A large washer was turned to 36mm in diameter
2) The washer was fixed concentrically to the head of the valve
3) The valve was placed into the valve guide and lowered into the chamber
4) A witness mark was made where the washer contacted the chamber wall
5) A parallel sided square ended carbide burr was used to remove material where the washer contacted the chamber wall
6) An scrap valve was used to protect the valve seat while the cutting was being carried out
Time taken to perform modifications: 40 – 80 minutes (10-20 minutes per cylinder)
Total time spent on modification: 80 - 160 minutes (+ set up time)
*************************************************************
Cylinder head flow test equipment and test conditions
**************************************************************
The flow bench uses a sharp edge orifice plate as the metering element with pressures measured at P1 (Barometric pressure), P2 (Pressure at cylinder head adaptor exit), P3 (upper plenum pressure) and P4 (lower plenum pressure). The air flow is created by an air pump driven by a three phase motor.
Test conditions
7 kPa delta across the test piece (P1-P2)
Intake manifold fitted (throttle removed)
Radius fitted to entry of intake manifold (in place of throttle body)
Cylinder head adaptor geometry
Bore (mm) 83 (1x Bore)
Length (mm) 127.5 (1.5x Stroke)
**************************************************************
Cylinder head flow test procedure
**************************************************************
Measurements taken at 1mm valve lift increments
Data collected over 10 seconds (averaged figure)
Valve opened to lift of L/D = 0.3 (10mm) (L/D = Ratio of valve lift to valve head diameter)
**************************************************************
Cylinder head flow measurement data and analysis
**************************************************************
Flow coefficient (Cf)
Cf = A measure of port flow efficiency. Compares actual port flow performance with that of a theoretically unrestricted port. Referenced to inner valve seat diameter
Modifications to the intake port has increased the Cf at maximum valve lift by 3%
Mean flow coefficient (mCf)
mCf = The area under the Cf curve. Calculated as the integral of flow coefficient over one intake cycle.
BP4W mCf = Has not been calculated
BP4W SSR mCf = 0.494
BP4W SSR + Deshround mCf = 0.506
Deshorunding the intake valves increases the mCf by 1.1% more than the SSR porting modifications alone.
Alpha K (Ak)
Ak = A measure of how effective the port is at filling the cylinder.
A good Alpha K number for a typical 4 valve chamber at a peak valve Lift is in excess of 0.16. An exceptional number is in excess of 0.22. Referenced to engine bore size
Modifications to the intake port has increased the Ak value at maximum valve lift by 0.6% when compared to the standard port.
Time area
Chart displays flow area (Af) (i.e. annular ring or curtain area created when valves are lifted off the seat) over time the valve is open in seconds at an engine speed of 7000 rpm.
The lower three curves show the effective flow area (Aef), that is the flow area multiplied by the flow coefficient at that specific valve lift.
The area under the curves has been calculated:
BP4W (Af/s) 0.00000227
BP4W (Aef/s) 0.00000103
BP4W SSR (Aef/s) 0.00000106
BP4W Deshroud (Aef/s) 0.00000108
The port SSR modifications have increased the time area by 2.51%
The port SSR and deshrouding modifications have increased the time area by 4.29%
Mach index (Mi)
The Mach index is useful for cylinder head analysis as it considers not only the camshaft profile and effective flow area, but also air flow due to piston motion.
The Mi calculation gives the ratio of the local sonic velocity to the air speed within the intake port. The calculation returns a pseudo Mach number that is the integrated value over one intake cycle.
The Mi gives an indication of the intake ports breathing ability with a lower value indicating a more efficient port.
Empirical data (presented by Charles Fayette Taylor) has shown that volumetric efficiency starts to fall away at ~0.5Mi, with 0.6 Mi as the reference not to exceed value.
The chart below shows the Mi / engine speed of the standard and modified ports.
The BP4W achieves 0.5Mi at 7640 rpm and 0.6Mi at 9170rpm
The BP4W with SSR modifications achieves 0.5Mi at 7820 rpm and 0.6Mi at 9380rpm
The BP4W with SSR and valve deshrouding modifications achieves 0.5Mi at 8000 rpm and 0.6Mi at 9600rpm
Port velocity
If the port is too large the port velocity will be low, resulting in poor in cylinder burn due to less in cylinder motion as a consequence of the slower incoming air charge.
To asses port velocities the port is split into the entry portion (Pe), mid portion (Pm) and the throat (measured at the ISD). The guidelines used are calculated as mean gas velocity at peak power speed (7000 rpm). Good design practice guidelines for a high performance engine are 100-110 meters per second , 90 to a 100 m/s and 70 to 80 m/s at the Entry/mid port/ and port throat respectively.
The velocities presented are the same for all cases as no significant amount of material has been removed from the in the valve seat, mid port or port entry during the porting operations.
**************************************************************
Analysis of existing cylinder head flow data from around the web
**************************************************************
A data set of 4V/cylinder flow data has been compiled using data found at sabre-heads.co.uk
The comparisons made are Cf @ L/D = 0.25 and Ak @ L/D = 0.25
The data is displayed with the ratio of Valve flow area / bore area on the x axis.
The MX5 1600 cylinder head and MK1 MX5 (BP05) cylinder head data are displayed for comparison.
The Honda k20 (Type R) cylinder head is generally considered to be a well developed high performance engine. The k20 data is highlighted here as a performance yardstick.
The data review shows flow coefficients range from low 0.5s to high 0.6s. The standard 1800cc MX5 cylinder heads display a mid level flow performance when compared to the wider population.
The modified MX5 BP4W head has a flow coefficient in the upper half of the population presented here. There appears to be no correlation between Cf and valve area / engine bore area (R squared = 0.0). Therefore we can assume valve size and engine bore has little or no effect on port efficiency and that port flow efficiency is independent of basic engine geometry. It is more probable that the shape of the intake port will determine the flow efficiency.
The data review shows Ak valves ranging from 0.14 to over 0.19. The standard 1800cc MX5 cylinder heads display a mid level performance when compared to the wider population.
The modified BP4W cylinder head does not show much improvement, this is almost certainly due to the valve size limiting the overall airflow. There is a clear positive correlation between Ak and flow area/bore area. Therefore we can assume that increasing valve size will increase the Alpha K value. That is the cylinder filling effectiveness can be improved by fitting the largest valves possible.
**************************************************************
Summary and conclusion
**************************************************************
A simple set of DIY porting modifications have been made to a BP4W MX5 cylinder head.
A flow assessment and comparison of the intake port flow performance before and after modifications has been made.
Modifying the SSR and bowl area of the port has been show to improve the flow coefficient by 3% over the standard BP4W cylinder head.
The porting modifications have improved the Alpha k value by 0.6% over the standard BP4W cylinder head.
The flow coefficient curve shows no difference between the port with just SSR modifications and the SSR with valve deshrounding modifications at the maximum valve lift value.
This is not unexpected as the valve is unlikely to be shrouded when the valve is at maximum lift. However, the flow coefficient curves do show that the port with SSR and deshrounding has better flow efficiency up to around L/D of 0.24. This is demonstrated by mean flow coefficient values of 0.494 and 0.506 of the port with just SSR modifications and SSR + deshrounding respectively.
The flow improvement of the modifications can also be observed when comparing the effective flow area / time metric. The SSR modifications alone improve the value by around 2.5%, with the chamber deshrouding modifications improving the effective flow area / time by a further 1.8% (around 4.3% improvement over the standard cylinder head).
The flow improvement of the modifications can also be seen in the change to the Mach index. The standard cylinder head has a mach index of 0.458 at rated speed. Modifying the SSR and bowl area decrease the Mach index to 0.448 at the rated speed. Further improvements can be made by deshrouding the valves which decreases the Mach index to 0.437 at the rated speed.
A comparison of the MX5 cylinder head performance has been made to a small population of 4V heads. The standard BP4W head display an average level of flow performance and when comparing the flow coefficient and Alpha K valves to the data set available. When modified the cylinder head flow coefficient can be improved to slightly better than average. However the Alpha k value is still low relative to the population. This is most likely due to the intake valves being undersized for the size of the cylinder. The modifications have only managed to realise a 0.6% increase in Alpha k bringing the final result to a mediocre value of 16% at maximum valve lift.
The flow analysis above indicates that the BP4W cylinder head’s flow performance can be improved with a couple of simple hand porting operations.
The expected performance increase would be in the order of up to 2.5% if the modifications were limited to in port modifications and up to 4.3% if the intake valves are also deshrouded.
**************************************************************
Recommendation
**************************************************************
The porting operations detailed above could be used as a low cost, low effort method to realise a power increase of around 4.3%.
It is debatable whether this level of power increase would be worth pursuing if the engine is intended to be turbocharged as a 4% power increase can easily be achieved with an increase in boost pressure. The potential power gain may be worth pursuing if the intended application is supercharged or naturally aspirated.
Further flow performance could be realised with valve seat modifications or an increase in valve size.
**************************************************************
Acknowledgements and references
**************************************************************
www.sabre-heads.co.uk/
www.sciencedirect.com/science/article/pii/S1110016817302582
www.mx5nutz.com/forum/index.php?showtopic=122108
www.mx5nutz.com/forum/index.php?showtopic=383971&page=2#entry4506893
mighty5s.com/thread/3246/cylinder-heads-flow-bench-analysis
web.archive.org/web/20140729045855/http://www.auto-scape.com/?p=305
Introduction
*******************************************************
Objective
Measure the effect that basic porting modifications have on the flow performance of a Mk2 non VVT cylinder head's intake port.
Overview
Perform two simple DIY porting operations to a Mazda MX5 BP4W cylinder head and make a flow assessment and comparison of intake port flow before and after modifications.
The flow assessment will be made with a late Mk2 European intake manifold (aka square top or flat top manifold) fitted to the cylinder head.
Modifications were made to block off the manifold’s EGR system.
The test results will be compared to a small data base compiled from flow test results found at sabre heads website.
*******************************************
Contents
*******************************************
Basic engine and intake port geometry
Cylinder head porting equipment
Documentation of modifications undertaken
Cylinder head flow test equipment
Cylinder head flow test procedure
Cylinder head flow measurement data and analysis
Assessment of flow performance before and after modifications
Analysis of existing cylinder head flow data from around the web
Summary and conclusion
Recommendation
Acknowledgements
*************************************
Basic engine and intake port geometry
**************************************
Bore (mm) 83
Stroke (mm) 85
Rated Speed (rpm) 7000
Camshaft geometry (BP4W)
Max Lift (mm) 8.51 (includes 0.21mm lash for solid lifter)
Duration (CA°) 245
Number of inlet valves per cylinder 2
Inner seat diameter [ISD] (mm) 29.5
Seat angle (°) 45
Valve head diameter (mm) 33
Inner seat area (sq. M) 0.001367
Mid Port area [Pm] (sq. M) 0.0014577
Port entry area [Pe] (sq. M) 0.0010555
**************************************************************
Cylinder head porting equipment
**************************************************************
A) Air die grinder
B) Permanent marker
C) Ball end carbide burr
D) Mandrel for Sanding roll (6mm diameter rod with slot for emery cloth)
E) Parallel sided square ended carbide burr
F) 80 grit emery cloth
G) Large washer
H) Calibrated profilometer
**************************************************************
Documentation of modifications undertaken
*************************************************************
Two modifications were undertaken:
The first modification was to the intake port’s short side radius (SSR) and bowl area.
The machining of the factory valve seats leaves a sharp edge on the short side radius and leaves heavy machining marks in the bowl area where the valve seat cutter removes material from the port. The flow coefficient can be improved if the machining marks are removed from these areas.
Modification procedure:
1) The sharp edge on the SSR was broken and smoothed with a sanding roll
2) Using a ball end carbide burr and sanding roll, the machining marks left in the bowl area when the valve seat was cut were blended and smoothed.
3) Measurements were taken by inserting a calibrated profilometer into the port to determine whether the correct degree of smoothing had been achieved
Time taken to perform modifications: 40 – 80 minutes (10-20 minutes per cylinder)
The second modification was removal of material from the combustion chamber to deshroud the intake valve:
Modification procedure:
1) A large washer was turned to 36mm in diameter
2) The washer was fixed concentrically to the head of the valve
3) The valve was placed into the valve guide and lowered into the chamber
4) A witness mark was made where the washer contacted the chamber wall
5) A parallel sided square ended carbide burr was used to remove material where the washer contacted the chamber wall
6) An scrap valve was used to protect the valve seat while the cutting was being carried out
Time taken to perform modifications: 40 – 80 minutes (10-20 minutes per cylinder)
Total time spent on modification: 80 - 160 minutes (+ set up time)
*************************************************************
Cylinder head flow test equipment and test conditions
**************************************************************
The flow bench uses a sharp edge orifice plate as the metering element with pressures measured at P1 (Barometric pressure), P2 (Pressure at cylinder head adaptor exit), P3 (upper plenum pressure) and P4 (lower plenum pressure). The air flow is created by an air pump driven by a three phase motor.
Test conditions
7 kPa delta across the test piece (P1-P2)
Intake manifold fitted (throttle removed)
Radius fitted to entry of intake manifold (in place of throttle body)
Cylinder head adaptor geometry
Bore (mm) 83 (1x Bore)
Length (mm) 127.5 (1.5x Stroke)
**************************************************************
Cylinder head flow test procedure
**************************************************************
Measurements taken at 1mm valve lift increments
Data collected over 10 seconds (averaged figure)
Valve opened to lift of L/D = 0.3 (10mm) (L/D = Ratio of valve lift to valve head diameter)
**************************************************************
Cylinder head flow measurement data and analysis
**************************************************************
Flow coefficient (Cf)
Cf = A measure of port flow efficiency. Compares actual port flow performance with that of a theoretically unrestricted port. Referenced to inner valve seat diameter
Modifications to the intake port has increased the Cf at maximum valve lift by 3%
Mean flow coefficient (mCf)
mCf = The area under the Cf curve. Calculated as the integral of flow coefficient over one intake cycle.
BP4W mCf = Has not been calculated
BP4W SSR mCf = 0.494
BP4W SSR + Deshround mCf = 0.506
Deshorunding the intake valves increases the mCf by 1.1% more than the SSR porting modifications alone.
Alpha K (Ak)
Ak = A measure of how effective the port is at filling the cylinder.
A good Alpha K number for a typical 4 valve chamber at a peak valve Lift is in excess of 0.16. An exceptional number is in excess of 0.22. Referenced to engine bore size
Modifications to the intake port has increased the Ak value at maximum valve lift by 0.6% when compared to the standard port.
Time area
Chart displays flow area (Af) (i.e. annular ring or curtain area created when valves are lifted off the seat) over time the valve is open in seconds at an engine speed of 7000 rpm.
The lower three curves show the effective flow area (Aef), that is the flow area multiplied by the flow coefficient at that specific valve lift.
The area under the curves has been calculated:
BP4W (Af/s) 0.00000227
BP4W (Aef/s) 0.00000103
BP4W SSR (Aef/s) 0.00000106
BP4W Deshroud (Aef/s) 0.00000108
The port SSR modifications have increased the time area by 2.51%
The port SSR and deshrouding modifications have increased the time area by 4.29%
Mach index (Mi)
The Mach index is useful for cylinder head analysis as it considers not only the camshaft profile and effective flow area, but also air flow due to piston motion.
The Mi calculation gives the ratio of the local sonic velocity to the air speed within the intake port. The calculation returns a pseudo Mach number that is the integrated value over one intake cycle.
The Mi gives an indication of the intake ports breathing ability with a lower value indicating a more efficient port.
Empirical data (presented by Charles Fayette Taylor) has shown that volumetric efficiency starts to fall away at ~0.5Mi, with 0.6 Mi as the reference not to exceed value.
The chart below shows the Mi / engine speed of the standard and modified ports.
The BP4W achieves 0.5Mi at 7640 rpm and 0.6Mi at 9170rpm
The BP4W with SSR modifications achieves 0.5Mi at 7820 rpm and 0.6Mi at 9380rpm
The BP4W with SSR and valve deshrouding modifications achieves 0.5Mi at 8000 rpm and 0.6Mi at 9600rpm
Port velocity
If the port is too large the port velocity will be low, resulting in poor in cylinder burn due to less in cylinder motion as a consequence of the slower incoming air charge.
To asses port velocities the port is split into the entry portion (Pe), mid portion (Pm) and the throat (measured at the ISD). The guidelines used are calculated as mean gas velocity at peak power speed (7000 rpm). Good design practice guidelines for a high performance engine are 100-110 meters per second , 90 to a 100 m/s and 70 to 80 m/s at the Entry/mid port/ and port throat respectively.
The velocities presented are the same for all cases as no significant amount of material has been removed from the in the valve seat, mid port or port entry during the porting operations.
**************************************************************
Analysis of existing cylinder head flow data from around the web
**************************************************************
A data set of 4V/cylinder flow data has been compiled using data found at sabre-heads.co.uk
The comparisons made are Cf @ L/D = 0.25 and Ak @ L/D = 0.25
The data is displayed with the ratio of Valve flow area / bore area on the x axis.
The MX5 1600 cylinder head and MK1 MX5 (BP05) cylinder head data are displayed for comparison.
The Honda k20 (Type R) cylinder head is generally considered to be a well developed high performance engine. The k20 data is highlighted here as a performance yardstick.
The data review shows flow coefficients range from low 0.5s to high 0.6s. The standard 1800cc MX5 cylinder heads display a mid level flow performance when compared to the wider population.
The modified MX5 BP4W head has a flow coefficient in the upper half of the population presented here. There appears to be no correlation between Cf and valve area / engine bore area (R squared = 0.0). Therefore we can assume valve size and engine bore has little or no effect on port efficiency and that port flow efficiency is independent of basic engine geometry. It is more probable that the shape of the intake port will determine the flow efficiency.
The data review shows Ak valves ranging from 0.14 to over 0.19. The standard 1800cc MX5 cylinder heads display a mid level performance when compared to the wider population.
The modified BP4W cylinder head does not show much improvement, this is almost certainly due to the valve size limiting the overall airflow. There is a clear positive correlation between Ak and flow area/bore area. Therefore we can assume that increasing valve size will increase the Alpha K value. That is the cylinder filling effectiveness can be improved by fitting the largest valves possible.
**************************************************************
Summary and conclusion
**************************************************************
A simple set of DIY porting modifications have been made to a BP4W MX5 cylinder head.
A flow assessment and comparison of the intake port flow performance before and after modifications has been made.
Modifying the SSR and bowl area of the port has been show to improve the flow coefficient by 3% over the standard BP4W cylinder head.
The porting modifications have improved the Alpha k value by 0.6% over the standard BP4W cylinder head.
The flow coefficient curve shows no difference between the port with just SSR modifications and the SSR with valve deshrounding modifications at the maximum valve lift value.
This is not unexpected as the valve is unlikely to be shrouded when the valve is at maximum lift. However, the flow coefficient curves do show that the port with SSR and deshrounding has better flow efficiency up to around L/D of 0.24. This is demonstrated by mean flow coefficient values of 0.494 and 0.506 of the port with just SSR modifications and SSR + deshrounding respectively.
The flow improvement of the modifications can also be observed when comparing the effective flow area / time metric. The SSR modifications alone improve the value by around 2.5%, with the chamber deshrouding modifications improving the effective flow area / time by a further 1.8% (around 4.3% improvement over the standard cylinder head).
The flow improvement of the modifications can also be seen in the change to the Mach index. The standard cylinder head has a mach index of 0.458 at rated speed. Modifying the SSR and bowl area decrease the Mach index to 0.448 at the rated speed. Further improvements can be made by deshrouding the valves which decreases the Mach index to 0.437 at the rated speed.
A comparison of the MX5 cylinder head performance has been made to a small population of 4V heads. The standard BP4W head display an average level of flow performance and when comparing the flow coefficient and Alpha K valves to the data set available. When modified the cylinder head flow coefficient can be improved to slightly better than average. However the Alpha k value is still low relative to the population. This is most likely due to the intake valves being undersized for the size of the cylinder. The modifications have only managed to realise a 0.6% increase in Alpha k bringing the final result to a mediocre value of 16% at maximum valve lift.
The flow analysis above indicates that the BP4W cylinder head’s flow performance can be improved with a couple of simple hand porting operations.
The expected performance increase would be in the order of up to 2.5% if the modifications were limited to in port modifications and up to 4.3% if the intake valves are also deshrouded.
**************************************************************
Recommendation
**************************************************************
The porting operations detailed above could be used as a low cost, low effort method to realise a power increase of around 4.3%.
It is debatable whether this level of power increase would be worth pursuing if the engine is intended to be turbocharged as a 4% power increase can easily be achieved with an increase in boost pressure. The potential power gain may be worth pursuing if the intended application is supercharged or naturally aspirated.
Further flow performance could be realised with valve seat modifications or an increase in valve size.
**************************************************************
Acknowledgements and references
**************************************************************
www.sabre-heads.co.uk/
www.sciencedirect.com/science/article/pii/S1110016817302582
www.mx5nutz.com/forum/index.php?showtopic=122108
www.mx5nutz.com/forum/index.php?showtopic=383971&page=2#entry4506893
mighty5s.com/thread/3246/cylinder-heads-flow-bench-analysis
web.archive.org/web/20140729045855/http://www.auto-scape.com/?p=305